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111.
In the process of biogenous weathering of Beacon sandstone in the McMurdo Dry Valleys (Ross Desert), Antarctica, periods of microbial growth, on the time scale of 103-104 years, alternate with sudden exfoliation events. The present study addressed the question of whether microbial growth is continuous between exfoliation events or whether each exfoliation is followed by a period of comparatively rapid growth and then an extended period of steady state. The color intensity (Munsell lightness value) of the rock surface is an indicator of relative age of the crust within the exfoliation cycle, permitting measurement of changes in microbial biomass on a geological time scale. Results indicate that microbial growth is continuous and that exfoliation occurs when the microbial biomass reaches the carrying capacity of the cryptoendolithic habitat. 相似文献
112.
Mineralogy, microbial ecology, and mineral weathering in the subsurface are an intimately linked biogeochemical system. Although bacteria have been implicated indirectly in the accelerated weathering of minerals, it is not clear if this interaction is simply the coincidental result of microbial metabolism, or if it represents a specific strategy offering the colonizing bacteria a competitive ecological advantage. Our studies provide evidence that silicate weathering by bacteria is sometimes driven by the nutrient requirements of the microbial consortium, and therefore depends on the trace nutrient content of each aquifer mineral. This occurrence was observed in reducing groundwaters where carbon is abundant but phosphate is scarce; here, even resistant feldspars are weathered rapidly. This suggests that the progression of mineral weathering may be influenced by a mineral's nutritional potential, with microorganisms destroying only beneficial minerals. The rock record, therefore, may contain a remnant mineralogy that reflects early microbial destruction of biologically valuable minerals, leaving a residuum of "useless" minerals, where "value" depends on the organism, its metabolic needs, and the diagenetic environment. Conversely, the subsurface distribution of microorganisms may, in part, be controlled by the mineralogy and by the ability of an organism to take advantage of mineral-bound nutrients. 相似文献
113.
AbstractThe objective of this study was to establish meaningful relationships between prokaryotic community profiles and water quality parameters in different water bodies (spring, stream, cave, and mine) in the middle reach of the Chesapeake & Ohio Canal National Historic Park (C&O), Maryland. The microbial profiles in the water samples were determined using metagenomic analysis. The relationships between microbial phylogenetic profiles and water quality parameters were investigated using principal component analysis (PCA) and redundancy analysis (RDA). The most abundant phyla identified in most samples were Proteobacteria (55.4%), Bacteroidetes (12.3%), Actinobacteria (10.6%), Firmicutes (2.4%), Planktomycetes (1.8%), Verrucomicrobia (1.5%), Chloroflexi (1.5%), and Acidobacteria (1.3%), which are major bacterial and archaeal groups typically observed in natural freshwater environments. PCA showed that water chemistry was determined primarily by the geology of the site and the type of water source (i.e., spring, stream, cave, or mine). Most samples located in carbonate formations correlated with high alkalinity, inorganic carbon, and calcium, representing the typical karstic geochemistry. RDA shows that pH, electrical conductivity, temperature and nutrients including nitrate, phosphate, and sulfate, were significant determinants of the microbial ecology. 相似文献
114.
Mingsong Kang Ya-Ping Ko Xiaowen Liang Caná L. Ross Qing Liu Barbara E. Murray Magnus H??k 《The Journal of biological chemistry》2013,288(28):20520-20531
Members of a family of collagen-binding microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) from Gram-positive bacteria are established virulence factors in several infectious diseases models. Here, we report that these adhesins also can bind C1q and act as inhibitors of the classical complement pathway. Molecular analyses of Cna from Staphylococcus aureus suggested that this prototype MSCRAMM bound to the collagenous domain of C1q and interfered with the interactions of C1r with C1q. As a result, C1r2C1s2 was displaced from C1q, and the C1 complex was deactivated. This novel function of the Cna-like MSCRAMMs represents a potential immune evasion strategy that could be used by numerous Gram-positive pathogens. 相似文献
115.
Heng Zhang Heng Zhang Zeng-Qiang Gao Wen-Jia Wang Guang-Feng Liu Jian-Hua Xu Xiao-Dong Su Yu-Hui Dong 《The Journal of biological chemistry》2013,288(8):5928-5939
The type VI secretion system (T6SS), a multisubunit needle-like apparatus, has recently
been found to play a role in interspecies interactions. The Gram-negative bacteria
harboring T6SS (donor) deliver the effectors into their neighboring cells (recipient) to
kill them. Meanwhile, the cognate immunity proteins were employed to protect the donor
cells against the toxic effectors. Tae4 (type VI
amidase effector 4) and Tai4
(type VI amidase
immunity 4) are newly identified T6SS effector-immunity pairs.
Here, we report the crystal structures of Tae4 from Enterobacter cloacae
and Tae4-Tai4 complexes from both E. cloacae and Salmonella
typhimurium. Tae4 acts as a dl-endopeptidase and displays a typical
N1pC/P60 domain. Unlike Tsi1 (type VI
secretion immunity 1), Tai4 is an
all-helical protein and forms a dimer in solution. The small angle x-ray scattering study
combined with the analytical ultracentrifugation reveal that the Tae4-Tai4 complex is a
compact heterotetramer that consists of a Tai4 dimer and two Tae4 molecules in solution.
Structure-based mutational analysis of the Tae4-Tai4 interface shows that a helix
(α3) of one subunit in dimeric Tai4 plays a major role in binding of Tae4, whereas
a protruding loop (L4) in the other subunit is mainly responsible for inhibiting Tae4
activity. The inhibition process requires collaboration between the Tai4 dimer. These
results reveal a novel and unique inhibition mechanism in effector-immunity pairs and
suggest a new strategy to develop antipathogen drugs. 相似文献
116.
Arnab Bhattacharjee Jesper S. Oeemig Robert Kolodziejczyk Taru Meri Tommi Kajander Markus J. Lehtinen Hideo Iwa? T. Sakari Jokiranta Adrian Goldman 《The Journal of biological chemistry》2013,288(26):18685-18695
Borrelia burgdorferi spirochetes that cause Lyme borreliosis survive for a long time in human serum because they successfully evade the complement system, an important arm of innate immunity. The outer surface protein E (OspE) of B. burgdorferi is needed for this because it recruits complement regulator factor H (FH) onto the bacterial surface to evade complement-mediated cell lysis. To understand this process at the molecular level, we used a structural approach. First, we solved the solution structure of OspE by NMR, revealing a fold that has not been seen before in proteins involved in complement regulation. Next, we solved the x-ray structure of the complex between OspE and the FH C-terminal domains 19 and 20 (FH19-20) at 2.83 Å resolution. The structure shows that OspE binds FH19-20 in a way similar to, but not identical with, that used by endothelial cells to bind FH via glycosaminoglycans. The observed interaction of OspE with FH19-20 allows the full function of FH in down-regulation of complement activation on the bacteria. This reveals the molecular basis for how B. burgdorferi evades innate immunity and suggests how OspE could be used as a potential vaccine antigen. 相似文献
117.
Microbial diversity was assessed in the soils of non-polluted rice fields of Central Rice Research Institute and Choudwar, and textile effluent contaminated (about 30 years) rice fields of Choudwar about 4 years after cessation of pollution. The soils contained 0.62–1.01 % organic C and 0.07–0.12 % total N, and measured 6.18–8.24 pH and 0.6–2.68 mS/cm Eh which were more in the polluted Choudwar soil. The microbial populations (×106 cfu/g soil) in the soils were: heterotrophs 1.21–10.9, spore formers 0.9–2.43, Gram (−)ve bacteria 4.11–8.0, nitrifiers 0.72–1.5, denitrifiers 0.72–2.43, phosphate solubilizers 0.14–0.9, asymbiotic nitrogen fixers 0.34–0.59, actinomycetes 0.07–0.11, fungi 0–0.5 and Bacillus thuringiensis (Bt) 0.4–0.61 which predominated in the polluted soil of Choudwar. The fungi were scarce in the polluted rice fields. The Bt isolates belonged to three motile and one non-motile group. Two motile Bt isolates were phenotyped as Bt subsp. sotto and israelensis, whereas, the non-motile isolate was Bt subsp. wahuensis. All Bt isolates produced extracellular protease, lipase and amylase enzymes. The microbial guilds had positive correlation among themselves, as well as, with soil physico-chemical characters but the fungi had negative relation and the nitrogen fixers were unrelated with the biotic and abiotic components. 相似文献
118.
DNA fingerprinting methods provide a means to rapidly compare microbial assemblages from environmental samples without the need to first cultivate species in the laboratory. The profiles generated by these techniques are able to identify statistically significant temporal and spatial patterns, correlations to environmental gradients, and biological variability to estimate the number of replicates for clone libraries or next generation sequencing (NGS) surveys. Here we describe an improved DNA fingerprinting technique that combines terminal restriction fragment length polymorphisms (TRFLP) and single stranded conformation polymorphisms (SSCP) so that both can be used to profile a sample simultaneously rather than requiring two sequential steps as in traditional two-dimensional (2-D) gel electrophoresis. For the purpose of profiling Archaeal 16S rRNA genes from soil, the dynamic range of this combined 1-D TRFLP-SSCP approach was superior to TRFLP and SSCP. 1-D TRFLP-SSCP was able to distinguish broad taxonomic clades with genetic distances greater than 10%, such as Euryarchaeota and the Thaumarchaeal clades g_Ca. Nitrososphaera (formerly 1.1b) and o_NRP-J (formerly 1.1c) better than SSCP. In addition, 1-D TRFLP-SSCP was able to simultaneously distinguish closely related clades within a genus such as s_SCA1145 and s_SCA1170 better than TRFLP. We also tested the utility of 1-D TRFLP-SSCP fingerprinting of environmental assemblages by comparing this method to the generation of a 16S rRNA clone library of soil Archaea from a restored Tallgrass prairie. This study shows 1-D TRFLP-SSCP fingerprinting provides a rapid and phylogenetically informative screen of Archaeal 16S rRNA genes in soil samples. 相似文献
119.
120.
Jason R. Rohr Thomas R. Raffel Neal T. Halstead Taegan A. McMahon Steve A. Johnson Raoul K. Boughton Lynn B. Martin 《Proceedings. Biological sciences / The Royal Society》2013,280(1772)
Exposure to stressors at formative stages in the development of wildlife and humans can have enduring effects on health. Understanding which, when and how stressors cause enduring health effects is crucial because these stressors might then be avoided or mitigated during formative stages to prevent lasting increases in disease susceptibility. Nevertheless, the impact of early-life exposure to stressors on the ability of hosts to resist and tolerate infections has yet to be thoroughly investigated. Here, we show that early-life, 6-day exposure to the herbicide atrazine (mean ± s.e.: 65.9±3.48 µg l−1) increased frog mortality 46 days after atrazine exposure (post-metamorphosis), but only when frogs were challenged with a chytrid fungus implicated in global amphibian declines. Previous atrazine exposure did not affect resistance of infection (fungal load). Rather, early-life exposure to atrazine altered growth and development, which resulted in exposure to chytrid at more susceptible developmental stages and sizes, and reduced tolerance of infection, elevating mortality risk at an equivalent fungal burden to frogs unexposed to atrazine. Moreover, there was no evidence of recovery from atrazine exposure. Hence, reducing early-life exposure of amphibians to atrazine could reduce lasting increases in the risk of mortality from a disease associated with worldwide amphibian declines. More generally, these findings highlight that a better understanding of how stressors cause enduring effects on disease susceptibility could facilitate disease prevention in wildlife and humans, an approach that is often more cost-effective and efficient than reactive medicine. 相似文献