May 21, 2020
Bumble bees damage plant leaves and accelerate flower production when pollen is scarce
Bumble bees rely heavily on pollen resources for essential nutrients as they build their summer colonies. Pashalidou et al. (2020) reports (368: 881-884) in the journal Science that bees may have strategies to cope with irregular seasonal flowering. When faced with a shortage of pollen, bumble bees actively damaged plant leaves in a characteristic way, and this behavior resulted in earlier flowering by as much as 30 days. Laboratory studies revealed that leaf-damaging behavior is strongly influenced by pollen availability and that bee-damaged plants flower significantly earlier than undamaged or mechanically damaged controls. Subsequent outdoor experiments showed that the intensity of damage inflicted varies with local flower availability; furthermore, workers from wild colonies of two additional bumble bee species were also observed to damage plant leaves. These findings elucidate a feature of bumble bee worker behavior that can influence the local availability of floral resources.
May 11, 2020
Cultured macrophages transfer surplus cholesterol into adjacent cells in the absence of serum or high-density lipoproteins
By ingesting dying cells and other cellular debris, macrophages accumulate cholesterol. Some of the cholesterol is esterified and stored in cytosolic lipid droplets, mitigating the toxicity from free cholesterol. Eventually, however, macrophages must unload surplus cholesterol—a process often referred to as “cholesterol efflux.” Cholesterol efflux is an important physiologic process because it would be expected to retard the formation of cholesterol-rich macrophage foam cells in atherosclerotic plaques. Most studies of cholesterol efflux have focused on the ability of ABC transporters to export cholesterol onto high-density lipoproteins. The current study examines another mechanism. He et al. (2020) in the journal PNAS (117: 10476-10483) reports that macrophages unload cholesterol directly into adjacent smooth muscle cells. This mechanism is potentially relevant to cholesterol efflux by tissue macrophages.
May 9, 2020
Aerodynamic imaging by mosquitoes inspires a surface detector for autonomous flying vehicles
Some flying animals use active sensing to perceive and avoid obstacles. Nocturnal mosquitoes exhibit a behavioral response to divert away from surfaces when vision is unavailable, indicating a short-range, mechanosensory collision-avoidance mechanism. Nakata et al. (2020) reports in Science (368: 634-637) reports that this behavior is mediated by perceiving modulations of their self-induced airflow patterns as they enter a ground or wall effect. The authors used computational fluid dynamics simulations of low-altitude and near-wall flights based on in vivo high-speed kinematic measurements to quantify changes in the self-generated pressure and velocity cues at the sensitive mechanosensory antennae. They validated the principle that encoding aerodynamic information can enable collision avoidance by developing a quadcopter with a sensory system inspired by the mosquito. Such low-power sensing systems have major potential for future use in safer rotorcraft control systems.
May 8, 2020
Preclinical validation of a repurposed metal chelator as an early-intervention therapeutic for snakebite
Snakebite envenoming causes 138,000 deaths annually, and ~400,000 victims are left with permanent disabilities. Envenoming by saw-scaled vipers (Viperidae: Echis) leads to systemic hemorrhage and coagulopathy and represents a major cause of snakebite mortality and morbidity in Africa and Asia. The only specific treatment for snakebite, antivenom, has poor specificity and low affordability and must be administered in clinical settings because of its intravenous delivery and high rates of adverse reactions. This requirement results in major treatment delays in resource-poor regions and substantially affects patient outcomes after envenoming. Albulescu et al. (2020) reports in the journal Science Translational Medicine (12: eaay8314) the value of metal ion chelators as prehospital therapeutics for snakebite. Among the tested chelators, dimercaprol (British anti-Lewisite) and its derivative 2,3-dimercapto-1-propanesulfonic acid (DMPS) were found to potently antagonize the activity of Zn2+-dependent snake venom metalloproteinases in vitro. Moreover, DMPS prolonged or conferred complete survival in murine preclinical models of envenoming against a variety of saw-scaled viper venoms. DMPS also considerably extended survival in a “challenge and treat” model, where drug administration was delayed after venom injection and the oral administration of this chelator provided partial protection against envenoming. Last, the potential clinical scenario of early oral DMPS therapy combined with a delayed, intravenous dose of conventional antivenom provided prolonged protection against the lethal effects of envenoming in vivo. The study demonstrate that the safe and affordable repurposed metal chelator DMPS can effectively neutralize saw-scaled viper venoms in vitro and in vivo and highlight the promise of this drug as an early, prehospital, therapeutic intervention for hemotoxic snakebite envenoming.
May 7, 2020
Aerodynamic imaging by mosquitoes inspires a surface detector for autonomous flying vehicles
Although sonar or lidar are used by autonomous vehicles to detect nearby objects, these approaches incur significant equipment and signal-processing costs. Nakata et al. (2020) report in the journal Science (Vol. 368, Issue 6491, pp. 634-637) show that nocturnal mosquitoes exhibit a behavioral response to divert away from surfaces when vision is unavailable, indicating a short-range, mechanosensory collision-avoidance mechanism. We suggest that this behavior is mediated by perceiving modulations of their self-induced airflow patterns as they enter a ground or wall effect. The authors used computational fluid dynamics simulations of low-altitude and near-wall flights based on in vivo high-speed kinematic measurements to quantify changes in the self-generated pressure and velocity cues at the sensitive mechanosensory antennae. They further validated the principle that encoding aerodynamic information can enable collision avoidance by developing a quadcopter with a sensory system inspired by the mosquito. Such low-power sensing systems have major potential for future use in safer rotorcraft control systems.
May 3, 2020
Mechanism of water extraction from gypsum rock by desert colonizing microorganisms
Microorganisms, in the most hyperarid deserts around the world, inhabit the inside of rocks as a survival strategy. Water is essential for life, and the ability of a rock substrate to retain water is essential for its habitability. Huang et al. (2020) reports in PNAS (117: 10681-10687) that the microorganisms can extract water of crystallization from the rock, inducing a phase transformation from gypsum (CaSO4·2H2O) to anhydrite (CaSO4). To investigate and validate the water extraction and phase transformation mechanisms found in the natural geological environment, the authors cultivated a cyanobacterium isolate on gypsum rock samples under controlled conditions. They found that the cyanobacteria attached onto high surface energy crystal planes of gypsum samples generate a thin biofilm that induced mineral dissolution accompanied by water extraction. This process led to a phase transformation to an anhydrous calcium sulfate, anhydrite, which was formed via re-precipitation and subsequent attachment and alignment of nanocrystals. The data of this work not only shed light on how microorganisms can obtain water under severe xeric conditions but also provide strategies for advanced water storage methods.
May 1, 2020
Interleukin-13 drives metabolic conditioning of muscle to endurance exercise
Interleukin-13 (IL-13) is a cytokine secreted by T cells, innate lymphoid cells (ILC2s), and granulocytes. It acts as a central mediator in allergy and antihelminth defense with various effects. Knudsen et al. (2020) in the journal Science Vol. 368, Issue 6490, eaat3987 , report a distinct role for IL-13 in exercise and metabolism. Animals subjected to endurance training showed increases in circulating IL-13, which correlated with ILC2 expansion in the muscles. By contrast, exercise-induced increases in muscle fatty acid utilization and mitochondrial biogenesis were erased when animals lacked IL-13. Activation of signaling pathways downstream of the muscle IL-13 receptor was key to this effect. Intramuscular injection of adenoviral IL-13 could recapitulate exercise-induced metabolic reprogramming. This signaling pathway may have evolved to combat the metabolic stresses of parasite infection.
April 29, 2020
The Structure of the Membrane Protein of SARS-CoV-2 Resembles the Sugar Transporter of Prokaryotes
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the disease COVID-19 that has decimated the health and economy of our planet. The virus causes the disease not only in people but also in companion and wild animals. People with diabetes are at risk of the disease. As yet we do not know why the virus is highly successful in causing the pandemic within 3 months of its first report. The structural proteins of SARS include, membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N) and the spike protein (S). The structure and function of the most abundant structural protein of SARS-CoV-2, the membrane (M) glycoprotein is not fully understood. Using in silico analyses Thomas (2020) (Preprints, 2020040512) (doi: 10.20944/preprints202004.0512.v2), determined the structure and potential function of the M protein. In silico analyses showed that the M protein of SARS-CoV-2 has a triple helix bundle, form a single 3-transmembrane domain (TM), and are homologous to the prokaryotic sugar transport protein semiSWEET. SemiSWEETs are related to the PQ-loop family that function as cargo receptors in vesicle transport, mediates movement of basic amino acids across lysosomal membranes, and is also involved in phospholipase flippase function. The advantage and role of sugar transporter-like structure in viruses is unknown. Endocytosis is critical for the internalization and maturation of RNA viruses, including SARS-CoV-2. Sucrose is involved in endosome and lysosome maturation and may also induce autophagy, pathways that help in the entry of the virus. It could be hypothesized that the semiSWEET sugar transporters could be used in multiple pathways that may aid in the rapid proliferation and replication of the virus. Biological experiments would validate the presence and function of the semiSWEET sugar transporter.
April 18, 2020
Emerging North American megadrought induced by human activity
Global warming has pushed what would have been a moderate drought in southwestern North America into megadrought territory. Williams et al. (2020) in the journal Science (368:314-318) used a combination of hydrological modeling and tree-ring reconstructions of summer soil moisture to show that the period from 2000 to 2018 was the driest 19-year span since the late 1500s and the second driest since 800 AD. The changes in temperature, relative humidity, and precipitation can be correlated to human activity. This appears to be just the beginning of a more extreme trend toward megadrought as global warming continues.
April 14, 2020
Early delivery and prolonged treatment with nimodipine prevents the development of spasticity after spinal cord injury
Spasticity, one of the most frequent comorbidities of spinal cord injury (SCI), disrupts motor recovery and quality of life. Despite major progress in neurorehabilitative and pharmacological approaches, therapeutic strategies for treating spasticity are lacking. Marcantoni et al. (2020) in the journal Science Translational Medicine (12: eaay0167) reports in a mouse model of chronic SCI that treatment with nimodipine—an L-type calcium channel blocker already approved from the European Medicine Agency and from the U.S. Food and Drug Administration—starting in the acute phase of SCI completely prevents the development of spasticity measured as increased muscle tone and spontaneous spasms. The aberrant muscle activities associated with spasticity remain inhibited even after termination of the treatment. Constitutive and conditional silencing of the L-type calcium channel CaV1.3 in neuronal subtypes demonstrated that this channel mediated the preventive effect of nimodipine on spasticity after SCI. This study identifies a treatment protocol and suggests that targeting CaV1.3 could prevent spasticity after SCI.
April 9, 2020
Dendritic cell–derived hepcidin sequesters iron from the microbiota to promote intestine healing
Anemia due to bleeding and altered iron distribution is a frequent complication of disorders such as inflammatory bowel disease. Bessman et al. (2020) in the journal Science (368:186-189) reports that hepcidin, the master regulator of systemic iron homeostasis, is required for tissue repair in the mouse intestine after experimental damage. This effect was independent of hepatocyte-derived hepcidin or systemic iron levels. Rather, the authors identified conventional dendritic cells (cDCs) as a source of hepcidin that is induced by microbial stimulation in mice, prominent in the inflamed intestine of humans, and essential for tissue repair. cDC-derived hepcidin acted on ferroportin-expressing phagocytes to promote local iron sequestration, which regulated the microbiota and consequently facilitated intestinal repair. Collectively, these results identify a pathway whereby cDC-derived hepcidin promotes mucosal healing in the intestine through means of nutritional immunity.
April 2, 2020
Susceptibility of cats and dogs to SARS-coronavirus-2
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the infectious disease COVID-19, which was first reported in Wuhan, China in December, 2019. Despite the tremendous efforts to control the disease, COVID-19 has now spread to over 100 countries and caused a global pandemic. SARS-CoV-2 is thought to have originated in bats; with report of intermediate animal sources of the virus as pangolin. Chen (2020) has reported in the preprint server, Biorxive the susceptibility of ferrets and other animals in close contact with humans to SARS-CoV-2. He reports that SARS-CoV-2 replicates poorly in dogs, pigs, chickens, and ducks, but efficiently in ferrets and cats. The virus transmits in cats via respiratory droplets. The study provides important insights into the animal reservoirs of SARS-CoV-2 and animal management for COVID-19 control.
March 28, 2020
Pangolins may be intermediate hosts in the emergence of novel coronaviruses
The ongoing outbreak of viral pneumonia all over the world is associated with a novel coronavirus, SARS-CoV-21. This outbreak has been tentatively associated with a seafood market in Wuhan, China, where the sale of wild animals may be the source of zoonotic infection. Although bats are likely reservoir hosts for SARS-CoV-2, the identity of any intermediate host that might have facilitated transfer to humans is unknown. Lam et al. (2020) in Nature report the identification of SARS-CoV-2-related coronaviruses in Malayan pangolins (Manis javanica) seized in anti-smuggling operations in southern China. Metagenomic sequencing identified pangolin-associated coronaviruses that belong to two sub-lineages of SARS-CoV-2-related coronaviruses, including one that exhibits strong similarity to SARS-CoV-2 in the receptor-binding domain. The discovery of multiple lineages of pangolin coronavirus and their similarity to SARS-CoV-2 suggests that pangolins should be considered as possible hosts in the emergence of novel coronaviruses and should be removed from wet markets to prevent zoonotic transmission.
March 23, 2020
High-salt diet increase infections due to reduced capacity of neutrophils to kill ingested bacteria
A diet rich in salt poses various health risks. A high-salt diet (HSD) can stimulate immunity through the nuclear factor of activated T cells 5 (Nfat5)–signaling pathway, especially in the skin, where sodium is stored. The kidney medulla also accumulates sodium to build an osmotic gradient for water conservation.
Jobin et al. (2020) reports in the journal Science Translation Medicine the effect of an HSD on the immune defense against uropathogenic E. coli–induced pyelonephritis, the most common kidney infection. Pyelonephritis enhanced in mice on an HSD by different mechanisms. First, on an HSD, sodium must be excreted; therefore, the kidney used urea instead to build the osmotic gradient. However, in contrast to sodium, urea suppressed the antibacterial functionality of neutrophils, the principal immune effectors against pyelonephritis. Second, the body excretes sodium by lowering mineralocorticoid production via suppressing aldosterone synthase. This caused an accumulation of aldosterone precursors with glucocorticoid functionality, which abolished the diurnal adrenocorticotropic hormone–driven glucocorticoid rhythm and compromised neutrophil development and antibacterial functionality systemically. Consistently, under an HSD, systemic Listeria monocytogenes infection was also aggravated in a glucocorticoid-dependent manner. Healthy humans consuming an HSD for 1 week showed hyperglucocorticoidism and impaired antibacterial neutrophil function. These findings argue against high-salt consumption during bacterial infections.
Cryo-electron microscopy structure of the SARS-CoV-2 spike
The World Health Organization has declared the outbreak of a novel coronavirus (2019-nCoV) to be a public health emergency of international concern. The virus binds to host cells through its trimeric spike glycoprotein, making this protein a key target for potential therapies and diagnostics. To facilitate medical countermeasure development, Wrapp et al. (2020) report in the journal Science (367:1260-1263) the cryo–electron microscopy structure of the 2019-nCoV S trimer in the prefusion conformation. The predominant state of the trimer has one of the three receptor-binding domains (RBDs) rotated up in a receptor-accessible conformation. The authors also provide biophysical and structural evidence that the 2019-nCoV S protein binds angiotensin-converting enzyme 2 (ACE2) with higher affinity than does severe acute respiratory syndrome (SARS)-CoV S. They also tested several published SARS-CoV RBD-specific monoclonal antibodies and found that they do not have appreciable binding to 2019-nCoV S, suggesting that antibody cross-reactivity may be limited between the two RBDs. The structure of 2019-nCoV S should enable the rapid development and evaluation of medical countermeasures to address the ongoing public health crisis.
March 10, 2020
The pneumonia outbreak associated with the coronavirus (SARS-CoV-2) is probably of bat origin
Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease is a pandemic since its origin in China in December 2019. There are many theories on where the virus originated. Zhou et al. (2020) in the journal Nature (579: 270–273) report the identification and characterization of the coronavirus (2019-nCoV), which caused the epidemic of acute respiratory syndrome in humans in Wuhan, China. The epidemic, which started on 12 December 2019, has 200,000 infections and 8000 deaths until 10 March 2020. Full-length genome sequences were obtained from five patients at an early stage of the outbreak. The sequences are almost identical and share 79.6% sequence identity to SARS-CoV. Furthermore, the authors show that 2019-nCoV is 96% identical at the whole-genome level to a bat coronavirus. Pairwise protein sequence analysis of seven conserved non-structural proteins domains show that this virus belongs to the species of SARSr-CoV. In addition, 2019-nCoV virus isolated from the bronchoalveolar lavage fluid of a critically ill patient could be neutralized by sera from several patients. Notably, the authors confirm that 2019-nCoV uses the same cell entry receptor—angiotensin converting enzyme II (ACE2)—as SARS-CoV.
March 9, 2020
Oil and gas companies invest in legislators that vote against the environment
The role of money in politics has long been a focus of research in political science. One explanation for campaign contributions to Congress is to buy influence. That is, companies contribute to the campaigns of those running for Congress with the expectation that those candidates, if elected, will vote in ways aligned with the interests of the companies.
The influence of money in politics has taken on new importance in the United States with the Citizens United versus Federal Election Commission Supreme Court decision in 2010. With the Citizens United decision, the court ruled that the First Amendment to the US Constitution protects independent spending for political communications by for-profit corporations, nonprofit corporations, and labor unions. Large corporations have taken full advantage of this “money as speech” court decision.
Using 28 years of campaign contribution data, Goldberg et al. (2020) in the journal PNAS (117:5111) reports that more a given member of Congress votes against environmental policies, the more contributions they receive from oil and gas companies supporting their reelection. Oil and gas companies contributed more than $84 million to candidates running for the US Congress in 2018. This is more than a twofold increase since the Citizens United decision in 2010, when oil and gas companies contributed approximately $35 million to candidates. While the absolute value of these contributions may seem relatively small, the doubling is noteworthy because it occurred in conjunction with the allowance of unlimited election spending by corporations and labor unions through the establishment of “independent expenditure-only committees,” or Super PACs. Thus, it is important to investigate how this money may influence legislators’ voting behavior on environmental issues.
March 3, 2020
Bisphenol A and bisphenol S used in plastic manufacturing disrupts placenta and effects the placenta–brain axis
BPA (Bisphenol A) is a precursor of plastics including polycarbonates, epoxy resins and polysulfones. BPA-based plastic is clear and tough, and is made into a variety of common consumer goods, such as plastic bottles including water bottles, food storage containers baby bottles, sports equipment, CDs, and DVDs. Epoxy resins derived from BPA are used to line water pipes, as coatings on the inside of many food and beverage cans and in the manufacture of thermal paper used in sales receipts.
BPA is similar to the hormone estrogen. BPA bind to both the nuclear estrogen receptors and mimics the hormone. The mammalian placenta is a target for BPA. Consumer unease with BPA has led to manufacture of substitutes, such as bisphenol S (BPS). Mao et al. (2020) in the journal PNAS (117: 4642-4652) reported using a multiomics approach to study effects of developmental exposure to BPA and BPS on midgestational mouse placenta. BPA and BPS altered the expression of an identical set of 13 genes. Both exposures led to a decrease in the area occupied by spongiotrophoblast relative to trophoblast giant cells (GCs) within the junctional zone, markedly reduced placental serotonin concentrations, and lowered serotonin GC immunoreactivity. Concentrations of dopamine and 5-hydroxyindoleacetic acid, the main metabolite of serotonin, were increased. The data imply that in rodents there could be associated effects on the placental–fetal brain axis. The authors conclude that BPS should be regarded as hazardous as BPA.
February 29, 2020
Bacteriophages could contribute to the bacterial community changes observed in child stunting
Malnutrition is a major health concern in low- and middle-income countries and the leading cause of death in children younger than 5 years. Stunting, a severe and multigenerational growth impairment, globally affects 22% of children under the age of 5 years. The largest concentration of our microbiome occupies the gut. The gut microbiota plays essential roles in host metabolism, immune modulation, and colonization resistance to pathogens. Shifts in gut bacterial composition have been associated with increasing numbers of diseases including inflammatory bowel diseases (IBD), allergies, diabetes, and obesity.
Stunted children have altered gut bacterial communities with higher proportions of Proteobacteria, a phylum with several known human pathogens. Stunted children also harbor an altered gut microbiota, with increased prevalence of Enterobacteriaceae, which may further contribute to their impaired growth and nutritional deficiencies. Indeed, the local inflammation caused by overgrowth of Enterobacteriaceae has been shown to lead to impaired digestive and absorptive functions of the gut, all linked to stunting. Stunted children have an immature gut microbiota relative to their non-stunted age-matched counterparts.
Despite the links between an altered gut microbiota and stunting, the role of bacteriophages, highly abundant bacterial viruses, is unknown. The role of gut phage communities in child stunting remains largely unexplored. Phages are bacterial viruses that are key to the maintenance and function of many ecosystems by supplying bacteria with genes involved in host adaptation, toxin production, and metabolism. Phages control bacterial diversity and abundance and can modify the O-antigen component of lipopolysaccharide (LPS) in gram-negative bacteria, which is particularly relevant to intestinal inflammation. In the gut, phages are abundant, with a phage-to-bacteria ratio close to 1:1 based on sequencing data. Phage communities are distinct between individuals and stable over time compared with gut bacterial ones. Recently, changes in the diversity and abundance of phages have been associated with many diseases such as IBD, diabetes, malnutrition, AIDS, and Parkinson’s disease, highlighting their potential role in human health.
Mirzaei et al. (2020) in the journal Cell Host and Microbiome (27: 199-212) reports whole community bacteria-phage population dynamics from stunted and non-stunted, otherwise clinically healthy, children from Dhaka, Bangladesh. Despite the significant progress in tackling malnutrition, Bangladesh still has one of the highest rates of child stunting in the world, affecting an average of 36.1% of children younger than 5 years. The authors report that these children harbor distinct gut bacteriophages relative to their non-stunted counterparts. In vitro, these gut bacteriophages are infectious and can regulate bacterial abundance and composition in an age-specific manner, highlighting their possible role in the pathophysiology of child stunting. Specifically, Proteobacteria from non-stunted children increased in the presence of phages from younger stunted children, suggesting that phages could contribute to the bacterial community changes observed in child stunting.
February 27, 2020
High dose vitamin C promotes cancer immunotherapy
Vitamin C plays an important role in a number of bodily functions including the production of collagen, L-carnitine, and some neurotransmitters. Collagen, which vitamin C helps produce, is the main component of connective tissue and the most abundant protein in mammals. Between 1 and 2% of muscle tissue is collagen. Wounds, cuts, and grazes may heal faster in people with a higher intake of vitamin C than is usually available from their food. This may be because vitamin C contributes to collagen production. In addition, people with adequate levels of vitamin C are thought to be better able to fight off infections compared to people with vitamin C deficiency. Vitamin C may also help prevent acute respiratory infections, especially in people with malnutrition and those who are physically stressed.
The role of vitamin C as an antioxidant also helps repair tissue and reduce damage from inflammation and oxidation. Vitamin C helps metabolize proteins and its antioxidant activity may reduce the risk of some cancers. Vitamin C is known to directly impair cancer cell growth in preclinical models, but there is little clinical evidence on its anti-tumoral efficacy. In addition, whether and how vitamin C modulates anticancer immune responses is mostly unknown.
Magri et al. (2020) in the journal Science Translational Medicine (12: eaay8707) reports that a fully competent immune system is required to maximize the antiproliferative effect of vitamin C in breast, colorectal, melanoma, and pancreatic murine tumors. High-dose vitamin C modulates infiltration of the tumor microenvironment by cells of the immune system and delays cancer growth in a T cell–dependent manner. Vitamin C not only enhances the cytotoxic activity of adoptively transferred CD8 T cells but also cooperates with immune checkpoint therapy (ICT) in several cancer types. Combination of vitamin C and ICT can be curative in models of mismatch repair–deficient tumors with high mutational burden. The authors study provides a rationale for clinical trials combining ICT with high doses of vitamin C.
February 26, 2020
Timing of fungal spore release influence survival during atmospheric transport
Fungi are so widespread and numerous that they make up a large proportion of the biomass in any given ecosystem. Fungi play an important role in energy cycling within, and between, ecosystems. Fungi play a very important part in the decomposition process, because they can break down tough organic materials, such as cellulose and lignin, which invertebrates find difficult to digest. Fungi release digestive enzymes that are used to metabolize complex organic compounds into soluble nutrients, such as simple sugars, nitrates and phosphates.
Fungi disperse spores to move across landscapes and spore liberation takes different patterns. Many species release spores intermittently; others release spores at specific times of day. It is clearly not understood whether timing of release of spores influence the survival of the spores during atmospheric transport.
Oneto et al. (2020) in the journal PNAS (https://doi.org/10.1073/pnas.1913752117) reports using state-of-the-art numerical simulations of atmospheric transport and meteorological data to follow the trajectory of many spores in the atmosphere at different times of day, seasons, and locations across North America. The authors report that spores released during the day fly for several days, whereas spores released at night return to ground within a few hours. Differences are caused by intense turbulence during the day and weak turbulence at night. The pattern is widespread but its reliability varies; for example, day/night patterns are stronger in southern regions. Species with short-lived spores reproducing where there is strong turbulence during the day, for example in Mexico, maximize survival by releasing spores at night. The study suggest the timing of spore liberation may be finely tuned to maximize fitness during atmospheric transport.
February 21, 2020
Vitamin E Acetate in Bronchoalveolar-Lavage Fluid Associated with Vaping
E-cigarettes are devices that heat a liquid into an aerosol that the user inhales. The liquid usually has nicotine and flavoring in it, and other additives. The nicotine in e-cigarettes and regular cigarettes is addictive. E-cigarettes were introduced as an alternate to regular cigarettes. E-cigarettes (the device associated with vaping) heat nicotine (extracted from tobacco), flavorings and other chemicals to create a water vapor that you inhale. Regular tobacco cigarettes contain 7,000 chemicals, many of which are toxic. It is not known what chemicals are in e-cigarettes.
Recent reports point to the harmful effects of vaping on young adults. Lung injuries and deaths are reported associated with vaping. As of January 2020, the Centers for Disease Control and Prevention (CDC) confirmed 60 deaths associated with vaping. The causative agents for the current national outbreak of electronic-cigarette, or vaping, product use–associated lung injury (EVALI) have not been established.
Blount et al. (2020) in the journal New England Journal of Medicine (382:697-705) reports the analyses of the bronchoalveolar-lavage (BAL) fluid from patients with EVALI. Vitamin E acetate was associated with EVALI in a sample of 51 patients in 16 states across the United States. Among the case patients for whom laboratory or epidemiologic data were available, 47 of 50 (94%) had detectable tetrahydrocannabinol (THC) or its metabolites in BAL fluid.
February 17, 2020
Harvesting energy from humid atmosphere
The energy needs are increasing due to increase in portable devices and hence there is a demand for renewable clean energy. Harvesting energy from the environment offers the promise of clean power for self-sustained systems. Known technologies—such as solar cells, thermoelectric devices and mechanical generators—have specific environmental requirements that restrict where they can be deployed and limit their potential for continuous energy production. The vast atmospheric moisture offers an alternative. However, existing moisture-based energy-harvesting technologies can produce only intermittent, brief (shorter than 50 seconds) bursts of power in the ambient environment, owing to the lack of a sustained conversion mechanism.
Liu et al. reports in the journal Nature (2020) that thin-film devices made from nanometer-scale protein wires harvested from the microorganism Geobacter sulfurreducens can generate continuous electric power in the ambient environment. The device produces a sustained voltage of around 0.5 volts across a 7-micrometre-thick film, with a current density of around 17 microamperes per square centimeter. The authors find the driving force behind this energy generation to be a self-maintained moisture gradient that forms within the film when the film is exposed to the humidity that is naturally present in air. Connecting several devices linearly scales up the voltage and current to power electronics. The study demonstrates the feasibility of a continuous energy-harvesting strategy that is less restricted by location or environmental conditions than other sustainable approaches.
February 14, 2020
Tropical snake diversity collapses after widespread amphibian loss
Biodiversity is declining at unprecedented rates worldwide. The global pandemic chytridiomycosis caused by the amphibian fungal pathogen Batrachochytrium dendrobatidis has decimated frog populations around the world. This decline has been called out as a potential catastrophe for amphibian species. What has been less explored are the impacts of amphibian declines on other members of their ecological communities. Using survey data collected over 13 years, Zipkin et al. (2020) in the journal Science (367:814-816) looked at diversity and body condition of a tropical snake community heavily affected by chytridiomycosis. After mass mortality of amphibians, the snake community contained fewer species and was more homogeneous across the study site, with several species in poorer body condition, despite no other systematic changes in the environment. The demise of the snake community after amphibian loss demonstrates the repercussive and often unnoticed consequences of the biodiversity crisis and calls attention to the invisible declines of rare and data-deficient species.
Global ecosystem thresholds driven by aridity
Aridity, which is increasing worldwide because of climate change, affects the structure and functioning of dryland ecosystems. Whether aridification leads to gradual (versus abrupt) and systemic (versus specific) ecosystem changes is largely unknown. Berdugo et al. (2020) in the journal Science (367: 787-790) investigated how 20 structural and functional ecosystem attributes respond to aridity in global drylands. Aridification led to systemic and abrupt changes in multiple ecosystem attributes. These changes occurred sequentially in three phases characterized by abrupt decays in plant productivity, soil fertility, and plant cover and richness, culminating with a shift to low-cover ecosystems that are nutrient- and species-poor at high aridity values. More than 20% of the terrestrial surface will cross one or several of these thresholds by 2100, which calls for immediate actions to minimize the negative impacts of aridification that can potentially lead to widespread land degradation and desertification worldwide.
February 12, 2020
B cells migrate into remote brain areas and support neurogenesis and functional recovery after focal stroke
Neuroinflammation occurs immediately after stroke onset, but whether neuroinflammation occurs in remote regions of the brain supporting functional recovery remains unknown. Ortega et al (2020) in the journal PNAS (https://doi.org/10.1073/pnas.1913292117) reports using advanced imaging to quantify whole-brain B cells in the capillaries. The authors identified bilateral B cell in the remote regions, outside of the injury, that support motor and cognitive recovery in animal models. Poststroke depletion of B cells confirms a positive role in neurogenesis, neuronal survival, and recovery of motor coordination, spatial learning, and anxiety. B cell depletion in animal models demonstrated delayed motor recovery, impaired spatial memory, and increased anxiety. B cell depletion reduced stroke-induced hippocampal neurogenesis and cell survival. B cell diapedesis occurring in areas remote to the infarct mediate motor and cognitive recovery. Understanding the role of B cells in neuronal health and disease-based plasticity is critical for developing effective immune-based therapies for protection against diseases that involve recruitment of peripheral immune cells into the injured brain.
More than 80% of stroke survivors have long-term disability uniquely affected by age and lifestyle factors. Thus, identifying beneficial neuroinflammation during long-term recovery increases the opportunity of therapeutic interventions to support functional recovery.
February 10, 2020
Helicobacter pylori eradication treatment reduces the risk of gastric cancer
Helicobacter pylori infection and a family history of gastric cancer are the main risk factors for gastric cancer. Whether treatment to eradicate H. pylori can reduce the risk of gastric cancer in persons with a family history of gastric cancer in first-degree relatives is unknown.
Choi et al. (2020) in the journal New England Journal of Medicine (382: 427-436) reports that among persons with H. pylori infection who has a family history of gastric cancer in first-degree relatives, H. pylori eradication treatment reduced the risk of gastric cancer.
February 4, 2020
The 2019 coronavirus may have had its origin in bats
The 2019 novel coronavirus (2019-nCoV) is a threat to the entire planet. As yet, it is not known the origin of the virus. Zhou et al. (2020) in the journal Nature report the identification and characterization of 2019-nCoV which caused an epidemic of acute respiratory syndrome in humans that started in Wuhan, China. The epidemic, which started from 12 December 2019, has caused 2,050 laboratory-confirmed infections with 56 fatal cases by 26 January 2020. Full-length genome sequences were obtained from five patients at the early stage of the outbreak. They are almost identical to each other and share 79.5% sequence identify to SARS-CoV. Furthermore, it was found that 2019-nCoV is 96% identical at the whole-genome level to a bat coronavirus. The pairwise protein sequence analysis of seven conserved non-structural proteins show that this virus belongs to the species of SARSr-CoV. The 2019-nCoV virus was then isolated from the bronchoalveolar lavage fluid of a critically ill patient, which can be neutralized by sera from several patients. Importantly, the authors confirmed that the novel CoV uses the same cell entry receptor, ACE2, as SARS-CoV.
January 31, 2020
Transmission of 2019 coronavirus (nCoV) Infection from an Asymptomatic Contact
The novel coronavirus (2019-nCoV) that originated in Wuhan, China, is a concern as the virus is spreading around the world. The disease caused by the virus is causing severe economic and emotional distress all over the world. Since its identification in late December 2019, the number of cases in China and other countries is on the rise. Rothe et al. (2020) reports in the clinical journal New England Journal of Medicine (DOI: 10.1056/NEJMc2001468) that the coronavirus could be transmitted from asymptomatic person to a healthy person.
January 28, 2020
Any matter containing carbon could be converted into graphene
With atom-thin sheets of carbon atoms arranged like chicken wire, graphene is stronger than steel, conducts electricity and heat better than copper, and can serve as an impermeable barrier preventing metals from rusting. Current strategies to make graphene at industrial scale is expensive.
Most bulk-scale graphene is produced by a top-down approach, exfoliating graphite, which often requires large amounts of solvent with high-energy mixing, shearing, sonication or electrochemical treatment. Although chemical oxidation of graphite to graphene oxide promotes exfoliation, it requires harsh oxidants and leaves the graphene with a defective perforated structure after the subsequent reduction step. Bottom-up synthesis of high-quality graphene is often restricted to ultrasmall amounts if performed by chemical vapour deposition or advanced synthetic organic methods, or it provides a defect-ridden structure if carried out in bulk solution.
Luong et al. (2020) in the journal Nature report that flash Joule heating of inexpensive carbon sources—such as coal, petroleum coke, carbon black, discarded food, rubber tyres and mixed plastic waste—can afford gram-scale quantities of graphene in less than one second. The product, named flash graphene (FG) after the process used to produce it, shows turbostratic arrangement (that is, little order) between the stacked graphene layers. FG synthesis uses no furnace and no solvents or reactive gases. Yields depend on the carbon content of the source; when using a high-carbon source, such as carbon black, anthracitic coal or calcined coke, yields can range from 80 to 90 per cent with carbon purity greater than 99 per cent. No purification steps are necessary. The electric energy cost for FG synthesis is only about 7.2 kilojoules per gram, which could render FG suitable for use in bulk composites of plastic, metals, plywood, concrete and other building materials.
January 23, 2020
How stress turns hair white
Rapid greying of hairis often assumed to be caused by stress. The relative contributions of ageing, genetic factors and stress to greying are not known – due to a lack of mechanistic understanding of the process.
Hair color is determined by cells called melanocytes, which produce different combinations of light-absorbing melanin pigments. Melanocytes are derived from melanocyte stem cells (MeSCs), which are located in a part of the hair follicle called the bulge. The normal hair cycle is divided into three stages: hair-follicle regeneration (anagen), degeneration (catagen) and rest (telogen). Melanocyte production begins early in the anagen phase. As people age, the pool of MeSCs is gradually depleted — and so pigmented hair becomes ‘salt and pepper’ colored, and then turns to grey and finally to white after a complete loss of pigment in all hair follicles.
Zhang et al. (2020)in the journal Nature reported the role of stress in the greying process in mice. The authors report that acute stress leads to hair greying through the fast depletion of melanocyte stem cells. Stress-induced loss of melanocyte stem cells is independent of immune attack or adrenal stress hormones. Instead, hair greying results from activation of the sympathetic nerves that innervate the melanocyte stem-cell niche. Under conditions of stress, the activation of these sympathetic nerves leads to burst release of the neurotransmitter noradrenaline (also known as norepinephrine). This causes melanocyte stem cells to proliferate rapidly, and is followed by their differentiation, migration and permanent depletion from the niche. Transient suppression of the proliferation of melanocyte stem cells prevents stress-induced hair greying. The study demonstrated that neuronal activity that is induced by acute stress can drive a rapid and permanent loss of somatic stem cells, and illustrates an example in which the maintenance of somatic stem cells is directly influenced by the overall physiological state of the organism.
January 22, 2020
Global-scale human impact on delta morphology has led to net land area gain
River deltas are created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. Due to their rich soils and convenient positions for trade and transport, many deltas have become hotspots of socio-economic development. River deltas rank among the most economically and ecologically valuable environments on Earth. Even in the absence of sea-level rise, deltas are increasingly vulnerable to coastal hazards as declining sediment supply and climate change alter their sediment budget, affecting delta morphology and possibly leading to erosion.
Nienhuis et al. (2020) in the journal Nature (577:514–518) reports that human activity has led to net increase in delta land area. The author’s model estimates delta morphology on the basis of a quantitative characterization of three main drivers that shape deltas. These are: sediment delivered by the river; wave action that redistributes sediment along the coast; and sediment transported into or out of the delta by tidal flows. The relative influences of these drivers were used to determine two key morphological metrics; namely, the protrusion of the delta into the sea and the shape of the river channel.
The morphology of deltas all over the world has been affected by river damming and deforestation. Over the past 30 years, despite sea-level rise, deltas globally have experienced a net land gain of 55 square kilometres per year. Humans are a considerable driver of these net land gains – 25 per cent of delta growth can be attributed to deforestation-induced increases in fluvial sediment supply. However for some delta regions, river damming has resulted in a severe (more than 50 per cent) reduction in anthropogenic sediment flux, forcing a collective loss of 15 square kilometres per year of deltaic land. Not all deltas lose land in response to river damming: deltas transitioning towards tide dominance are currently gaining land, probably through channel infilling.
The study also reveals notable regional patterns. The Arctic river deltas have seen almost no change in morphology. Sediment delivery by rivers in North America has fallen overall, leading to large land losses – especially in the Mississippi delta. The largest land gains are in eastern South America and in south, southeast and east Asia, where soil erosion due to deforestation has caused a net growth in delta areas, despite the construction of sizeable dams in these regions. With expected accelerated sea-level rise, however, recent land gains are unlikely to be sustained throughout the twenty-first century.
January 21, 2020
Ozone depleting gases influence extreme Arctic warming
The Arctic is warming at more than twice the average rate of the rest of the planet – a phenomenon known as Arctic amplification – and it is losing sea ice rapidly.
Ozone-depleting substances, including chlorofluorocarbons (CFCs), are known to warm the atmosphere more efficiently than carbon dioxide. However, most of the research on these chemicals has focused on their effects on the planet’s protective ozone layer – especially over the Southern hemisphere, where they are responsible for the formation of the Antarctic ozone hole.
Polvani et al. (2020) in the journal Nature Climate Change (https://doi.org/10.1038/s41558-019-0677-4) reports that when ozone depleting substances (ODS) are kept fixed, forced Arctic surface warming and forced sea-ice loss are only half as large as when ODS are allowed to increase. They also demonstrated that the large impact of ODS on the Arctic occurs primarily via direct radiative warming, not via ozone depletion. Their findings reveal a substantial contribution of ODS to recent Arctic warming, and highlight the importance of the Montreal Protocol as a major climate change-mitigation treaty. The Montreal Protocol (ratified in 1987) is a treaty to protect the ozone layer by phasing out the production of substances that are responsible for ozone depletion.
January 16, 2020
Use of bacteria in building construction
Building materials using sand, cement or other binders have been employed for construction purposes for a long time. Recent innovations in construction includes the use of 3D printing technology for construction.
Living building materials (LBM) is a new concept wherein microorganisms (eg. bacteria) are used in the manufacture of building materials based on the principle of biomineralization. Biomineralization is the chemical alteration of an environment by microbial activity that results in the precipitation of minerals. Microbially induced calcite precipitation (MICP) refers to the formation of calcium carbonate from a supersaturated solution due to the presence of their microbial cells and biochemical activities. During MICP, organisms are able to secrete one or more metabolic products (carbonate) that react with ions (calcium) in the environment resulting in the subsequent precipitation of minerals. The enzyme urease induce carbonate precipitation in the microorganisms. Some bacterial species like Sporosarcina pasteurii has high level of urease that induce calcite precipitation.
MICP is utilized for soil stabilization, in situ concrete crack repair, fracture sealing of oil and gas wells, bioremediation of metals, and mitigating leakage from geologically sequestered carbon dioxide (CO2). During MICP, the metabolic activity of microorganisms increases the saturation state local to the bacterial cell and promotes calcium carbonate precipitation.
Heveran and coworkers in the journal Matter (2020) (https://doi.org/10.1016/j.matt.2019.11.016) reports LBMs created by inoculating an inert structural sand-hydrogel scaffold with Synechococcus sp., a photosynthetic cyanobacterium. The scaffold provided structural support for Synechococcus, which toughened the hydrogel matrix via calcium carbonate biomineralization resulting in the formation of solid bricks.
When half of a brick is placed in a mold with more of the gel and sand, the bacteria from that half will migrate and colonize the new material, eventually forming another brick. Ultimately, one parent brick – that is initially divided – can be used to produce up to eight more bricks.
Although this technology is in its nascence, potential applications of LBMs range from temporary civil and military structures to paving, façades, and other light-duty load-bearing materials. LBMs are not intended to broadly replace cementitious materials, but instead represent a new class of materials in which structural function is complemented by biological functionalities.
January 14, 2020
Engineered banana lectin, a carbohydrate binding protein, could protect against influenza virus infection
Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death. Many strains of the influenza virus exist. They are constantly mutating and changing. The best way to prevent flu is by getting a flu vaccine each year. The Centers for Disease Control and Prevention (CDC) estimates that influenza has resulted in between 9 million – 45 million illnesses, between 140,000 – 810,000 hospitalizations and between 12,000 – 61,000 deaths annually since 2010. Flu can directly lead to death when the virus triggers severe inflammation in the lungs. When this happens, it can cause rapid respiratory failure because your lungs can’t transport enough oxygen into the rest of your body. There is a pressing need for new anti-influenza therapeutic agents as current therapies are not very effective.
Lectins are carbohydrate binding proteins and found in several foods including beans, banana, cereals, etc. Coves-Datson and colleagues report in the journal PNAS (2020) (https://doi.org/10.1073/pnas.1915152117) that a molecularly engineered banana lectin has broad-spectrum activity against all influenza strains tested, including drug-resistant and currently circulating strains; is safe upon repeated administration in animal models; and, moreover, is efficacious at treating lethal influenza infection via clinically pertinent routes of administration. The authors demonstrate that the lectin binds to the viral hemagglutinin glycoprotein and exerts its primary antiviral effect via inhibition of an early stage of the viral life cycle, viral membrane fusion to the host endosomal membrane. The studies indicate that this engineered lectin, which has a mechanism of action quite distinct from the presently available agents, has potential as an anti-influenza agent.
January 10, 2020
Some species of parrots voluntarily help each other to obtain food rewards
Altruism is the belief that the well-being of others is equally, if not more, important than the well-being or survival of the self. Altruism involves selfless acts or undertakings that put the welfare of others before one’s own. Helping others to obtain benefits, even at a cost to oneself, poses an evolutionary puzzle. Kin selection may explain such “selfless” acts among relatives, only reciprocity (paying back received favors) entails fitness benefits for unrelated individuals. Experimental evidence for both prosocial helping (providing voluntary assistance for achieving an action-based goal) and reciprocity has been reported in a few mammals, including bonobos and orangutans, but no avian species. Brucks et al. in the journal Current Biology (DOI:https://doi.org/10.1016/j.cub.2019.11.030) reports testing two parrot species in an instrumental-helping paradigm involving “token transfer.” Here, actors could provide tokens to their neighbor, who could exchange them with an experimenter for food. The authors found that African grey parrots voluntarily and spontaneously transferred tokens to conspecific partners, whereas significantly fewer transfers occurred in the control conditions. Blue-headed macaws, in contrast, transferred hardly any tokens. Species differences in social tolerance might explain this discrepancy. These findings show that instrumental helping based on a prosocial attitude, accompanied but potentially not sustained by reciprocity, is present in parrots, suggesting that this capacity evolved convergently in this avian group and mammals.
January 4, 2020
Residential neighborhood green space is associated with reduced risk of cardiovascular disease
Diseases of the heart and circulatory system (cardiovascular disease or CVD) are the biggest cause of death globally. According to a substantial body of evidence, people have better physical and mental health in areas of green space–natural areas or urban vegetation.
Green spaces such as parks and sports fields as well as woods and natural meadows, wetlands or other ecosystems, represent a fundamental component of any urban ecosystem. Green urban areas facilitate physical activity and relaxation, and form a refuge from noise. Trees produce oxygen, and help filter out harmful air pollution, including airborne particulate matter.
Dalton and Jones (2020) in the journal PLoS ONE (15(1): e0226524) reports the importance of green space in reducing cardiovascular risk. There is a statistically significant decrease in mortality for people living in greener areas. Greener home neighborhoods may protect against risk of cardiovascular disease even after accounting for socioeconomic status (SES), whilst the mechanism does not appear to be strongly associated with physical activity. Exposure to green space may be protective against incident CVD in older adults. Participants living in the greenest locations had a 7% lower relative risk of developing CVD at follow-up when compared to those living in the least green areas, after adjustment for potential confounding by age, sex, body mass index, prevalent diabetes and SES.
The causes of the association between green space exposure and incident CVD remain largely unexplained, despite a growing body of work in this field. Likely explanations include physiological and psychological benefits of seeing green space, including stress reduction and restoration; the role of green space in creating a sense of attachment to place and community, and reduced isolation and increased social ties; the advantages of exposure to nature for immunological regulation; and, albeit with less evidence, the ‘biogenics’ hypothesis, that natural toxins and compounds can reduce unhealthy cell activity in humans, and reduce the incidence of disease.
December 31, 2019
Steering carbon dioxide electroreduction toward ethanol production
Carbon dioxide (CO2) is an important greenhouse gas, which is released through human activities such as deforestation and burning fossil fuels. When the carbon dioxide concentration goes up, temperature goes up. Similarly, when the carbon dioxide concentration goes down, temperature goes down.
Scientists have considered various strategies to store CO2. Carbon capture and storage (CCS) is a process whereby CO2 is “captured” from the air and then transported to a storage site – which could be, for example, a depleted oil or gas field or a deep rock reservoir beneath the sea. Though the technologies are currently restricted to a few small pilot projects, many view its large-scale development as an essential step to limiting the effects of future climate change.
Electrochemical reduction of CO2 can convert CO2 emission back to value-added fuels and chemicals and store renewable electricity. Reducing CO2 to multi-carbon products has attracted great interest because of their higher energy densities and associated economic values. Liu et al (2019) reports in the journal PNAS (116: 26353-26358) a strategy for steering CO2 electroreduction toward ethanol production by exploiting a surface-bound Ruthenium (Ru) polypyridyl carbene catalyst on an N-doped porous carbon electrode. The authors show the synergistic effects of Ru polypyridyl carbene for CO intermediate production with a porous carbon for C–C coupling that could boost ethanol production at relatively low over potentials. The strategy provides insights on how to improve selectivity and efficiency for CO2 reduction toward multi-carbon products.
December 30, 2019
Decline in prey body size due to resurgence of an apex marine predator
In coastal waters of the northeast Pacific Ocean, marine mammals have increased in abundance over the past 50 years, including fish-eating killer whales that feed primarily on Chinook salmon. Chinook salmon, a species of high cultural and economic value, have exhibited marked declines in average size and age throughout most of their North American range during this time.
Chinook salmon (Oncorhynchus tshawytscha) hatch and rear in freshwater, subsequently migrate to sea to spend 1 to 5 years in the ocean, and finally return to their native rivers to spawn once and then die. In the ocean, these fish often migrate thousands of kilometers and are widely distributed along the west coast of North America, the Gulf of Alaska, and farther west along the Aleutian Islands and into the Bering Sea. In most populations, fish now mature at younger ages, and while the size of younger fish has been stable or increasing, older fish that return to spawn after several years in the ocean are increasingly smaller. The trend toward smaller and younger fish is a pressing concern because Chinook salmon are valuable to commercial, recreational, and subsistence fisheries, and because large fish contribute disproportionally to reproduction.
The successful implementation of the 1972 US Marine Mammal Protection Act had increased the recovery of marine mammal predators. Killer whales (Orcinus orca) are the ocean’s ultimate apex predator and are widely distributed throughout the world’s oceans. Resident killer whales, which primarily occupy coastal waters, have nearly tripled in abundance in the northeast Pacific Ocean since the early 1970s. Their diets are dominated by salmon, especially Chinook salmon, which have the highest energy content of any salmon, and the whales selectively prey on the largest Chinook salmon. Estimates suggest that killer whales consume over 2.5 million adult Chinook salmon every year; these consumption levels by killer whales now exceed the combined annual removals of Chinook salmon by commercial, recreational, and subsistence fisheries.
Ohlberger et al. (2019), reports in the journal PNAS (116: 26682-26689) that fish-eating killer whales are currently having a larger effect than fisheries on phenotypic traits and life-history characteristics of Chinook salmon. The widespread declines in the body size of Chinook salmon over the past 50 years can be explained by intensified predation by growing populations of resident killer whales that selectively feed on large Chinook salmon, thus revealing a potential conflict between salmon fisheries and marine mammal conservation objectives. Further, the direct removal of large maturing fish, primarily via predation, has a larger effect on prey body size than evolutionary changes resulting from selection for faster growth and earlier maturation.
Camponotus ants feed on vertebrate urine to extract nitrogen
Ants eat a variety of food ranging from seeds, fruits, nectar, fungi, invertebrates to flesh of vertebrates. However, the environment influences the feeding habit of organisms including ants.
Petit et al. (2019) in the journal Austral Ecology (https://doi.org/10.1111/aec.12840) has reported the feeding behavior of the Camponotous ants at Kangaroo islands, a resource poor island in Australia. The ants have preference for animal urine. The researchers wondered whether why the ants preferred urine to other food resources. They baited ants with liquid stains of urine (human and kangaroo), urea in water (2.5%. 3.5%, 7.0%, 10.0%) and sucrose in water (20% and 40%) poured directly on the ground, as well as hard baits in plots drawn on sandy soil. Ants were most numerous on 10% urea, followed by 7% urea, 3.5% urea, urine (which contains ~2.5% urea) and 2.5% urea; sucrose was less attractive to them than equimolar urea bait. Ants were attracted to human, kangaroo, and unidentified urine, and they collected bird guano (rich in nitrogen). The remarkable ability of the Camponotous ants to extract nitrogen from dry sand over weeks explains partly its success on sandy soils. Foraging on urine may be an important strategy to address nitrogen limitation on sandy soils and exploit commensally niches in which hosts are kangaroos, wallabies and other vertebrates.
December 28, 2019
How does large humpback whales capture highly maneuverable fish
Predator–prey relationships have been likened to an evolutionary arms race—the prey become more difficult to capture and eat, while the predators perfect their abilities to catch and kill their prey. Just how strong these selective forces are probably depends on the strength of the interactions between the predators and their prey.
The humpback whales are around 15 meters long and weigh around 30 tons and are the largest of the rorqual species of whales. The humpback whales feed in the polar waters and migrate to the tropical and sub-tropical waters to breed and give birth. The diet consists of krill and small fish. But how does species such as humpback whale capture forage fish at speeds that barely exceed their prey where highly maneuverable fish could easily escape. Cade et al. (2019) reports in the journal PNAS (https://doi.org/10.1073/pnas.1911099116) that humpback whales delay the expansion of their jaws until very close to schools of anchovies, and it is only at this point that the prey react, when it is too late for a substantial portion of them to escape. This suggests that escape responses of these schooling fish, which have evolved under pressure from single-prey feeding predators for millions of years before the advent of lunge feeding, are not tuned sufficiently to respond to predators that can engulf entire schools, allowing humpback whales flexibility in prey choice.
December 27, 2019
Serotonin modulates walking in the fruit fly, Drosophila
People with neurodegenerative diseases like Parkinson’s disease and Alzheimer’s disease have walking difficulties. When these difficulties occur, patients walk with slow and irregular steps and find it hard to negotiate turns, climb onto a stepping stool, avoid obstacles in their path.
Howard et al. (2019) in the journal Current Biology (29:P4218-4230) reports that that the serotonergic system in the fruit fly, Drosophila melanogaster, can modulate walking speed in a variety of contexts and also change how flies respond to sudden changes in the environment. These multifaceted roles of serotonin in locomotion are differentially mediated by a family of serotonergic receptors with distinct activities and expression patterns.
Serotonin, a neurotransmitter is predominantly synthesized in the intestine (not in the brain). It is estimated that 90 percent of the body’s serotonin is made in the digestive tract. Serotonin is synthesized by specialized cells in the intestine mediated by the host microbes. Diet influences the rate of serotonin synthesis. A diet rich in the amino acid tryptophan may increase serotonin levels. It is not known if serotonin influences locomotion in humans. Future studies will determine whether serotonin levels could influence locomotion in neurodegenerative diseases.
December 24, 2019
Sleep fragmentation is accompanied by accelerated microglial aging and cognitive impairment in Alzheimer’s disease
People are living longer than the previous generation all over the world. However, the quality of life is declining with old age. Cognitive impairment and dementia constitute a growing public health concern. The global prevalence of dementia is estimated at 35.6 million individuals and is predicted to nearly double in 20 years.
Modern lifestyle and behavior have led to poor quality sleep patterns. Sleep disruption may contribute to cognitive impairment and dementia in older adults. In experimental studies, sleep deprivation is associated with altered expression of genes associated with inflammation and altered immune function. Immune dysregulation may, in turn, contribute to cognition-related disease processes, including Alzheimer’s disease (AD).
Sleep disruption may contribute to cognitive impairment through an immune mechanism. The nervous system comprises a remarkably diverse and complex network of different cell types, which must communicate with one another with speed, reliability, and precision. Microglia, the resident innate immune cells of the central nervous system, may play an important role in AD. It has been shown in animal models that chronic sleep restriction or deprivation can alter the immune signaling in a way known to trigger changes in microglial function and can lead to morphologic microglial activation and inhibiting this can improve cognition.
Kaneshwaran et al. (2019) in the journal Science Advances (5: eaax7331) reports that greater sleep fragmentation was associated with higher neocortical expression of genes characteristic of aged microglia, and a higher proportion of morphologically activated microglia, independent of chronological age- and dementia-related neuropathologies. Thus, sleep fragmentation is accompanied by accelerated microglial aging and activation, which may partially underlie its association with cognitive impairment.
December 19, 2019
New classes of antibiotics to treat Gram-negative bacteria
Bacteria are classified as Gram-positive and Gram-negative based on the ability to bid Gram stain. Gram-negative bacteria has a more complex cell membrane compared to the Gram-positive counterpart and hence resistant to several antibiotics. There are several Gram-negative bacteria that are pathogenic that are harmful to humans. E. coli, Klebsiella, Neisseria, Pseudomonas, etc., are examples of Gram-negative bacteria that cause illnesses.
The current need for novel antibiotics is especially acute for drug-resistant Gram-negative pathogens. The last class of antibiotics that acted against Gram-negative bacteria was developed in the 1960s.
Imai et al. (2019) reports in the Journal Nature 576:459-464 a new antibiotic named darobactin, which was obtained from the Gram-negative bacteria, Photorhabdus. Photorhabdus is a genus of bioluminescent bacilli that lives symbiotically within entomopathogenic nematodes. Photorhabdus is known to be pathogenic to a wide range of insects and has been used as a biopesticide in agriculture.
Darobactin has an unusual structure with two fused rings that form post-translationally. The compound is active against Gram-negative pathogens and was tested in cell culture and in animal models of infection. The authors demonstrated that the bacterial symbionts of animals contain antibiotics that are particularly suitable for development into therapeutics.
In the same issue of the journal Nature, Luther et al. (2019) 576: 452-458 describe a class of synthetic antibiotics inspired by scaffolds derived from natural products. These chimeric antibiotics contain a β-hairpin peptide macrocycle linked to the macrocycle found in the polymyxin and colistin family of natural products. They are bactericidal and have a mechanism of action that involves binding to both lipopolysaccharide and the main component (BamA) of the β-barrel folding complex (BAM) that is required for the folding and insertion of β-barrel proteins into the outer membrane of Gram-negative bacteria. These antibiotics protected against Gram-negative pathogenic bacteria.
December 11, 2019
Monocrop cannot sustain the long-term nutritional health of bee colonies; but integrating biodiversity into the landscape provides relief to nutritional stress.
Honey bees are responsible for providing the food security of man. The honey bees not only pollinate flowers, but also provide us with honey, bees wax, etc.
Climate change, over use of pesticides and insecticides, bacterial and fungal diseases has an impact on the bee population. In recent years, it is known that the agriculture land use patterns impact the health of honey bees.
An ever-increasing demand for food and biofuels following human population expansion requires more land be dedicated to agricultural production. Global land use has shifted to meet this demand, with natural areas and smaller-scale agricultural enterprises transformed into high-yielding monocultures. Monocultures can have substantial negative environmental effects on soil, water, and air quality, and when coupled with the removal of native, non-crop habitat, this form of agriculture is associated with declines in pollinator populations.
Dolezal et al. in the journal PNAS (2019; 116 (50): 25147-25155) reported the impact of soybean or corn monoculture on the wellness of honey bee population. The authors report that a brief burst of colony growth during soybean bloom, is followed by a longer period of forage scarcity, resulting in decline in several aspects of honey bee health at both colony and individual levels. This decline is reversible when honey bees have access to native, perennial plants (i.e., prairie). The authors conclude that a sustainable pollinator management in landscapes dominated by monocultures can be achieved through reintegration of native biodiversity.
December 5, 2019
Are you tired seeing no improvements in the glucose levels even after regular exercise – blame your microbiome
Metabolic syndrome is a collection of disease risk factors that increase your chance of developing heart disease, stroke, and diabetes. The condition is also known by other names including Syndrome X, insulin resistance syndrome, and dysmetabolic syndrome. More than 1 in 5 Americans has metabolic syndrome. The number of people with metabolic syndrome increases with age, affecting more than 40% of people in their 60s and 70s.
The exact cause of metabolic syndrome is not known. Many features of the metabolic syndrome are associated with insulin resistance. Insulin resistance means that the body does not use insulin efficiently to lower glucose and triglyceride levels. A combination of genetic and lifestyle factors may result in insulin resistance. Lifestyle factors include dietary habits, activity and interrupted sleep patterns.
Exercise is an effective strategy for diabetes management but is limited by the phenomenon of exercise resistance (i.e., the lack of or the adverse response to exercise on metabolic health). Liu and team reported in the journal Cell Metabolism (https://doi.org/10.1016/j.cmet.2019.11.001) that exercise induced changes in the host gut microbiome (all the microbiota of your body’s gut) and it correlated to improvements in glucose homeostasis and insulin sensitivity. The microbiome of responders exhibited an enhanced capacity for biosynthesis of short-chain fatty acids and catabolism of branched-chain amino acids, whereas those of non-responders were characterized by increased production of metabolically detrimental compounds. Fecal microbial transplantation from responders, but not non-responders, mimicked the effects of exercise on alleviation of insulin resistance in obese mice. Furthermore, a machine-learning algorithm integrating baseline microbial signatures accurately predicted personalized glycemic response to exercise in an additional 30 subjects. These findings raise the possibility of maximizing the benefits of exercise by targeting the gut microbiota.
December 3, 2019
Specialized sledge dogs accompanied Inuit dispersal across the North American Arctic
Inuit are the indigenous people inhabiting the arctic regions of Canada, Greenland and Alaska. Domestic dogs have been central to life of the Intuits in the North American Arctic for thousands of years. Aside from this initial peopling of the Americas, the North American Arctic has experienced additional human migration episodes of genetically distinct populations, which were accompanied by potentially distinct dog populations. Investigating whether or not these new groups brought genetically differentiated dog populations with them into the North American Arctic, and the relationship between these dogs and those already present in the region, is crucial for understanding the history of dogs in the Americas.
Recent genetic analyses indicate that the earliest dogs found in the Americas belonged to a now extinct lineage of Arctic dog that was introduced from Eurasia at least 10,000 years ago. The ancestors of the Inuit were the first to introduce the widespread usage of dog sledge transportation technology to the Americas, but whether the Inuit adopted local Palaeo-Inuit dogs or introduced a new dog population to the region remains unknown.
The Inuit emergence in Alaska beginning approximately 2000 years ago brought large-scale changes in life style, subsistence practices and material culture to the North American Arctic. Their subsequent expansion translocated this culture out of Alaska eastward to Greenland, and along the coast of subarctic Eastern Canada around 1000 years ago. The rapid expansion of the Inuit is attributed in part to their exploitation of advanced transportation technologies, including the development and widespread usage of the umiak and kayak for sea travel, and the dog sledge for use on land and ice.
Ameen et al. recently reported in the journal Proceedings of the Royal Society B (2019) (https://doi.org/10.1098/rspb.2019.1929) that the Inuit dogs are distinct from the earlier dogs of the Arctic. The authors analyzed themitochondrial DNA and geometric morphometric data of skull and dental elements of North American Arctic dogs and wolves spanning over 4500 years. Their analyses revealed that dogs from Inuit sites dating more than 2000 years ago possess morphological and genetic signatures that distinguish them from earlier Palaeo-Inuit dogs, and identified a novel mitochondrial clade in eastern Siberia and Alaska. The genetic legacy of these Inuit dogs survives today in modern Arctic sledge dogs despite phenotypic differences between archaeological and modern Arctic dogs. The authors are of the opinion that the Inuit dogs derive from a secondary pre-contact migration of dogs distinct from Palaeo-Inuit dogs, and probably aided the Inuit expansion across the North American Arctic beginning around 1000 years ago.