Study of life history strategies may help predict the performance of microorganisms in nature by organizing the complexity of microbial communities into groups of organisms with similar strategies. ...Here, we tested the extent that one common application of life history theory, the copiotroph-oligotroph framework, could predict the relative population growth rate of bacterial taxa in soils from four different ecosystems. We measured the change of in situ relative growth rate to added glucose and ammonium using both
O-H
O and
C quantitative stable isotope probing to test whether bacterial taxa sorted into copiotrophic and oligotrophic groups. We saw considerable overlap in nutrient responses across most bacteria regardless of phyla, with many taxa growing slowly and few taxa that grew quickly. To define plausible life history boundaries based on in situ relative growth rates, we applied Gaussian mixture models to organisms' joint
O-
C signatures and found that across experimental replicates, few taxa could consistently be assigned as copiotrophs, despite their potential for fast growth. When life history classifications were assigned based on average relative growth rate at varying taxonomic levels, finer resolutions (e.g., genus level) were significantly more effective in capturing changes in nutrient response than broad taxonomic resolution (e.g., phylum level). Our results demonstrate the difficulty in generalizing bacterial life history strategies to broad lineages, and even to single organisms across a range of soils and experimental conditions. We conclude that there is a continued need for the direct measurement of microbial communities in soil to advance ecologically realistic frameworks.
The Fire Bay Formation of Trettin (1998), Clements Markham belt, Ellesmere Island, Canada, includes volcanic rocks described as Silurian in age based on Llandovery graptolites in adjacent clastic ...rocks. New field observations suggest the Llandovery fossils are from packages of the Silurian Danish River and/or Lands Lokk formations that are fault-bounded rather than stratigraphically tied to Ordovician sections that contain a 470.0 ± 0.2 Ma lithic tuff, volcaniclastic units with maximum depositional ages (MDAs) of 466 ± 2 and 462 ± 2 Ma based on detrital zircon, volcanic clasts with ages of 498 ± 6, 478 ± 4, and 477 ± 8 Ma, and Ordovician conodonts and graptolites of Darriwilian and Sandbian age, respectively. Since the Fire Bay Formation of Trettin (1998) lacks a type section and is fault-bounded with ambiguous age relationships, Ordovician volcanic units and fault-bounded clastic rocks correlated with the Hazen Formation are both included in the Fire Bay assemblage following the original interpretations of Trettin and Nowlan (1990). The Fire Bay assemblage records juvenile Ordovician arc magmatism proximal to the Pearya terrane. The adjacent Lands Lokk Formation yields bimodal age peaks at 440-430 and 465 Ma, MDA of 424 ± 3 Ma, and εHf(t) values of -5 to +10. The signature matches Ordovician Pearya units and Silurian circum-Arctic arc sources but there is no evidence for Silurian arc magmatism between the Pearya terrane and Laurentian margin, compatible with Pearya accretion during oblique Ordovician arc collision and Silurian sinistral translation along the northern Laurentian margin.
The growth and physiology of soil microorganisms, which play vital roles in biogeochemical cycling, are shaped by both current and historical soil environmental conditions. Here, we developed and ...applied a genome-resolved metagenomic implementation of quantitative stable isotope probing (qSIP) with an H
O labeling experiment to identify actively growing soil microorganisms and their genomic capacities. qSIP enabled measurement of taxon-specific growth because isotopic incorporation into microbial DNA requires production of new genome copies. We studied three Mediterranean grassland soils across a rainfall gradient to evaluate the hypothesis that historic precipitation levels are an important factor controlling trait selection. We used qSIP-informed genome-resolved metagenomics to resolve the active subset of soil community members and identify their characteristic ecophysiological traits. Higher year-round precipitation levels correlated with higher activity and growth rates of flagellar motile microorganisms. In addition to heavily isotopically labeled bacteria, we identified abundant isotope-labeled phages, suggesting phage-induced cell lysis likely contributed to necromass production at all three sites. Further, there was a positive correlation between phage activity and the activity of putative phage hosts. Contrary to our expectations, the capacity to decompose the diverse complex carbohydrates common in soil organic matter or oxidize methanol and carbon monoxide were broadly distributed across active and inactive bacteria in all three soils, implying that these traits are not highly selected for by historical precipitation.
Soil moisture is a critical factor that strongly shapes the lifestyle of soil organisms by changing access to nutrients, controlling oxygen diffusion, and regulating the potential for mobility. We identified active microorganisms in three grassland soils with similar mineral contexts, yet different historic rainfall inputs, by adding water labeled with a stable isotope and tracking that isotope in DNA of growing microbes. By examining the genomes of active and inactive microorganisms, we identified functions that are enriched in growing organisms, and showed that different functions were selected for in different soils. Wetter soil had higher activity of motile organisms, but activity of pathways for degradation of soil organic carbon compounds, including simple carbon substrates, were comparable for all three soils. We identified many labeled, and thus active bacteriophages (viruses that infect bacteria), implying that the cells they killed contributed to soil organic matter. The activity of these bacteriophages was significantly correlated with activity of their hosts.
Introduction
Diet and activity are recognized as modulators of nervous system disease, including pain. Studies of exercise consistently reveal a benefit on pain. This study focused on female rats to ...understand differences related to metabolic status and peripheral nerve function in females.
Methods
Here, we investigated parameters of peripheral nerve function relevant to pain in rats selectively bred for high (high‐capacity runners; HCR) or low endurance exercise capacity (low‐capacity runners; LCR) resulting in divergent intrinsic aerobic capacities and susceptibility for metabolic conditions.
Results
LCR female rats have reduced mechanical sensitivity, higher intraepidermal nerve fiber density and TrkA‐positive epidermal axons, increased numbers of Langerhans and mast cells in cutaneous tissues, and a higher fat content despite similar overall body weights compared to female HCR rats. Sensory and motor nerve conduction velocities, thermal sensitivity, and mRNA expression of selected genes relevant to peripheral sensation were not different.
Conclusions
These results suggest that aerobic capacity and metabolic status influence sensory sensitivity and aspects of inflammation in peripheral tissues that could lead to poor responses to tissue damage and painful stimuli. The LCR and HCR rats should prove useful as models to assess how the metabolic status impacts pain.
These results suggest that aerobic capacity and metabolic status influence sensory sensitivity and aspects of inflammation in peripheral tissues that could lead to poor responses to tissue damage and painful stimuli. The LCR and HCR rats should prove useful as models to assess how the metabolic status impacts pain.
Introduction/Results
In 17 patients, chronic idiopathic nausea was associated with orthostatic intolerance (OI) by abnormal tilt table tests (88%) or gastric dysrhythmias (71%). After fludrocortisone ...treatment, there was >26% nausea improvement in 71%, 1–25% in 6%, and no improvement in 24%. In six subjects, EGGs repeated after >50% nausea improvement all remained to be abnormal, suggesting nausea is independent of gastric dysrhythmias.
Conclusion
Association of EGG abnormalities and OI in this subset of nausea patients suggests a generalized disturbance of autonomic regulation.
Climate influences soil microbial composition and function, but the relative importance of a site's historic climate versus its more immediate environmental conditions is unclear. Using quantitative ...stable isotope probing (qSIP), we characterized actively growing soil microbial communities and soil properties in three California annual grasslands that span a rainfall gradient and have developed on similar parent material. The soils were assayed in the wet winter season, when environmental conditions are most similar across sites. Since growing populations might be expected to be most responsive to contemporary environmental conditions, we hypothesized that the structure of growing microbial communities would be more similar across the gradient than that of total communities (i.e., including non-growing populations). In addition, we hypothesized that population growth rates would be slowest in the driest site, reflecting a legacy effect of low soil moisture on microbial growth. Soils along the rainfall gradient differed in pH, texture, and cation exchange capacity, but not in total C, C:N or dominant minerals. The radiocarbon (14C) age of soil C (reflecting turnover time) increased with mean annual precipitation but soil respiration was uniformly modern, reflecting microbial reliance on recent C inputs across the sites. The structure of both total and growing microbial communities differed across sites. Across major microbial phyla, including the Actinobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes and Proteobacteria, bacterial growth rates were consistently lower in the site with the lowest mean annual precipitation. Taxa that were growing at the dry site alone grew more slowly than taxa that grew at multiple sites. These results reflect the influence of climate history and point to the role of environmental filtering at the driest site in shaping its slower growing microbial community, possibly reflecting adaptation to repeated exposure to water stress. Lastly, across taxa, the growth rate of a taxon at one site was correlated with its growth rate in the other sites. This growth rate coherence is likely a consequence of genetically determined physiological traits and is consistent with the idea that evolutionary history constrains growth rate.
•Climate strongly influences structure of growing soil microbial communities.•Repeated low water exposure reduces soil microbial growth across taxonomic levels.•Microbial growth rates are consistent between sites across a precipitation gradient.•Genetics and physiology constrain variation in taxon-specific growth rates.
Juxtaposition of the composite Pearya terrane with the northern Laurentian margin at Ellesmere Island, Nunavut, Canada is an understudied tectonic event that has significant ramifications for the ...tectonic histories of other crustal fragments in the circum-Arctic region during the Paleozoic. Two end member models for accretion currently exist: 1) translation and emplacement along a sinistral margin-parallel strike-slip system, or 2) orthogonal collision with the Laurentian margin. Current hypotheses regarding this accretionary event rely upon interpretation of the Kulutingwak formation, an Ordovician sedimentary package often identified as a subduction-related sequence, and the Danish River formation, a laterally continuous unit often cited as a post-accretionary overlap assemblage.Geologic relationships present in the Yelverton Inlet-Phillips Inlet region offer a unique opportunity to understand this accretion event, where the Ordovician Kulutingwak formation separates the crystalline basement of the Pearya terrane from the Silurian Danish River formation. Seventeen igneous and detrital zircon samples were collected from this area for U-Pb and Lu-Hf analysis in order to better characterize the Paleozoic sedimentary packages which underpin current tectonic models. Detrital zircon age distributions from the Kulutingwak formation demonstrate a transition from signatures indicative of the Laurentian margin to those diagnostic of the Pearya terrane in the Late Ordovician. Detrital zircon signatures in the Danish River formation record a dynamic tectonic setting in the Silurian where distinct facies belts with variable provenance signals are preserved. Both units are disturbed by late translation along major northeast-southwest striking structures and included in structural assemblages, exposing the need for additional quantitative data in this complex tectonic system.
SARS‐CoV‐2 is a newly emerged coronavirus that caused the global COVID‐19 outbreak in early 2020. COVID‐19 is primarily associated with lung injury, but many other clinical symptoms such as loss of ...smell and taste demonstrated broad tissue tropism of the virus. Early SARS‐CoV‐2–host cell interactions and entry mechanisms remain poorly understood. Investigating SARS‐CoV‐2 infection in tissue culture, we found that the protease TMPRSS2 determines the entry pathway used by the virus. In the presence of TMPRSS2, the proteolytic process of SARS‐CoV‐2 was completed at the plasma membrane, and the virus rapidly entered the cells within 10 min in a pH‐independent manner. When target cells lacked TMPRSS2 expression, the virus was endocytosed and sorted into endolysosomes, from which SARS‐CoV‐2 entered the cytosol via acid‐activated cathepsin L protease 40–60 min post‐infection. Overexpression of TMPRSS2 in non‐TMPRSS2 expressing cells abolished the dependence of infection on the cathepsin L pathway and restored sensitivity to the TMPRSS2 inhibitors. Together, our results indicate that SARS‐CoV‐2 infects cells through distinct, mutually exclusive entry routes and highlight the importance of TMPRSS2 for SARS‐CoV‐2 sorting into either pathway.
SYNOPSIS
Ideally, preventing SARS‐CoV‐2 spread requires approaches targeting the early steps of infection. This study shows that SARS‐CoV‐2 infects cells through distinct, mutually exclusive entry routes (e.g., pH independent versus pH dependent) and highlights the importance of the protease expression patterns of target host cells for sorting SARS‐CoV‐2 into either pathway.
The host cell surface protease TMPRSS2 determines the SARS‐CoV‐2 entry pathway when it is expressed in target cells.
In the presence of TMPRSS2, SARS‐CoV‐2 uses a fast pH‐independent route to enter and infect cells.
In cells lacking TMPRSS2 expression, SARS‐CoV‐2 relies on a slow acid‐activated late endosomal pathway for infection, and endosomal acidification is required for endolysosomal proteases priming viral fusion.
Proteolytic processing is both sufficient and necessary for SARS‐CoV‐2 fusion.
SARS‐CoV‐2 infects cells through mutually‐exclusive, pH‐independent versus pH‐dependent entry routes, whose distinction is governed by processing protease expression in target cells.
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