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  • 刊频： Monthly, 1993-
  • NLM标题： FEMS Microbiol Ecol
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  • 1.

    【2hr】Modification of Escherichia coli–bacteriophage interactions by surfactants and antibiotics in vitro

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    机译 表面活性剂和抗生素体外修饰大肠杆菌与噬菌体的相互作用
    摘要：Although experiments indicate that the abiotic environment plays an important role in bacterial interactions with their parasitic viruses (bacteriophages or phages), it is not yet clear how exposure to compounds present in nature alters the impact of phages on bacterial growth and evolution. To address this question, we exposed Escherichia coli K12 MG1655, in combination with three lytic phages, to various substances that natural and clinical microbial populations are likely to encounter: bile salts (present in mammalian gastrointestinal tracts), sodium dodecyl sulfate (SDS, a common surfactant in cleaning and hygiene products) and four antibiotics (present at variable concentrations in natural and clinical environments). Our results show that bile salts and SDS can reduce the detrimental effect of phages on bacterial growth. In some cases these compounds completely mitigated any negative effects of phages on bacterial growth and consequently bacteria did not evolve resistance to phages in these conditions. The proportional effects of phages were unaffected by antibiotics in most combinations, excepting three cases of phage-drug synergy. These results suggest that accounting for interactions between phages and environmental factors such as surfactants and antibiotics will improve understanding of both bacterial growth and resistance evolution to phages in vivo and in nature.
  • 2.

    【2hr】In vitro fermentation of B-GOS: impact on faecal bacterial populations and metabolic activity in autistic and non-autistic children

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    机译 B-GOS的体外发酵：对自闭症和非自闭症儿童的粪便细菌种群和代谢活性的影响
    摘要：Children with autism spectrum disorders (ASD) often suffer gastrointestinal problems consistent with imbalances in the gut microbial population. Treatment with antibiotics or pro/prebiotics has been postulated to regulate microbiota and improve gut symptoms, but there is a lack of evidence for such approaches, especially for prebiotics. This study assessed the influence of a prebiotic galactooligosaccharide (B-GOS) on gut microbial ecology and metabolic function using faecal samples from autistic and non-autistic children in an in vitro gut model system. Bacteriology was analysed using flow cytometry combined with fluorescence in situ hybridization and metabolic activity by HPLC and 1H-NMR. Consistent with previous studies, the microbiota of children with ASD contained a higher number of Clostridium spp. and a lower number of bifidobacteria compared with non-autistic children. B-GOS administration significantly increased bifidobacterial populations in each compartment of the models, both with autistic and non-autistic-derived samples, and lactobacilli in the final vessel of non-autistic models. In addition, changes in other bacterial population have been seen in particular for Clostridium, Rosburia, Bacteroides, Atopobium, Faecalibacterium prausnitzii, Sutterella spp. and Veillonellaceae. Furthermore, the addition of B-GOS to the models significantly altered short-chain fatty acid production in both groups, and increased ethanol and lactate in autistic children.
  • 3.

    【2hr】Shifting the balance of fermentation products between hydrogen and volatile fatty acids: microbial community structure and function

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    机译 改变发酵产物在氢和挥发性脂肪酸之间的平衡：微生物群落结构和功能
    摘要：Fermentation is a key process in many anaerobic environments. Varying the concentration of electron donor fed to a fermenting community is known to shift the distribution of products between hydrogen, fatty acids and alcohols. Work to date has focused mainly on the fermentation of glucose, and how the microbial community structure is affected has not been explored. We fed ethanol, lactate, glucose, sucrose or molasses at 100 me- eq. L−1, 200 me- eq. L−1 or 400 me- eq. L−1 to batch-fed cultures with fermenting, methanogenic communities. In communities fed high concentrations of electron donor, the fraction of electrons channeled to methane decreased, from 34% to 6%, while the fraction of electrons channeled to short chain fatty acids increased, from 52% to 82%, averaged across all electron donors. Ethanol-fed cultures did not produce propionate, but did show an increase in electrons directed to acetate as initial ethanol concentration increased. In glucose, sucrose, molasses and lactate-fed cultures, propionate accumulation co-occurred with known propionate producing organisms. Overall, microbial communities were determined by the substrate provided, rather than its initial concentration, indicating that a change in community function, rather than community structure, is responsible for shifts in the fermentation products produced.
  • 4.

    【2hr】Soil and leaf litter metaproteomics—a brief guideline from sampling to understanding

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    机译 土壤和叶子凋落物蛋白质组学-从采样到了解的简要指南
    摘要：The increasing application of soil metaproteomics is providing unprecedented, in-depth characterization of the composition and functionality of in situ microbial communities. Despite recent advances in high-resolution mass spectrometry, soil metaproteomics still suffers from a lack of effective and reproducible protein extraction protocols and standardized data analyses. This review discusses the opportunities and limitations of selected techniques in soil-, and leaf litter metaproteomics, and presents a step-by-step guideline on their application, covering sampling, sample preparation, extraction and data evaluation strategies. In addition, we present recent applications of soil metaproteomics and discuss how such approaches, linking phylogenetics and functionality, can help gain deeper insights into terrestrial microbial ecology. Finally, we strongly recommend that to maximize the insights environmental metaproteomics may provide, such methods should be employed within a holistic experimental approach considering relevant aboveground and belowground ecosystem parameters.
  • 5.

    【2hr】Cyanobacterial diversity of western European biological soil crusts along a latitudinal gradient

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    机译 西欧生物土壤结皮的蓝细菌多样性沿纬向梯度变化
    摘要：Cyanobacteria associated with biological soil crusts (BSCs) have important attributes, such as nitrogen fixation and soil stabilisation. However, research on these organisms has been minimal, and their diversity and distribution throughout temperate Europe is currently unknown. The SCIN (Soil Crust International) project is a multidisciplinary research initiative that aims to achieve improved understanding of the BSCs of Europe, one facet being an investigation into the cyanobacterial communities of BSCs across a latitudinal gradient. Cyanobacteria assemblages were analysed by both morphological and molecular analysis. Two treatments were applied prior to DNA extraction, continued sample wetting and a dry sample process, and 16S ribosomal RNA (rRNA) amplicons were processed by Illumina MiSeq sequencing. The results reveal high and variable cyanobacterial diversity with each site showing a unique assemblage. Many common cyanobacterial genera, for example Nostoc and Microcoleus, were found in all sites but the abundances of different genera varied considerably. The polyphasic approach was found to be essential in recording the presence of important cyanobacteria that a single method itself did not highlight. The wet and dry treatments showed some differences in diversity, but mainly in abundance, this may suggest how cyanobacterial composition of BSCs changes with seasonal variability.
  • 6.

    【2hr】The gut microbiome of the sea urchin, Lytechinus variegatus, from its natural habitat demonstrates selective attributes of microbial taxa and predictive metabolic profiles

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    机译 海胆的Lytechinus variegatus的肠道微生物组来自其自然栖息地，显示出微生物分类群的选择性属性和预测性代谢特征
    摘要：In this paper, we describe the microbial composition and their predictive metabolic profile in the sea urchin Lytechinus variegatus gut ecosystem along with samples from its habitat by using NextGen amplicon sequencing and downstream bioinformatics analyses. The microbial communities of the gut tissue revealed a near-exclusive abundance of Campylobacteraceae, whereas the pharynx tissue consisted of Tenericutes, followed by Gamma-, Alpha- and Epsilonproteobacteria at approximately equal capacities. The gut digesta and egested fecal pellets exhibited a microbial profile comprised of Gammaproteobacteria, mainly Vibrio, and Bacteroidetes. Both the seagrass and surrounding sea water revealed Alpha- and Betaproteobacteria. Bray–Curtis distances of microbial communities indicated a clustering profile with low intrasample variation. Predictive metagenomics performed on the microbial communities revealed that the gut tissue had high relative abundances of metabolisms assigned to the KEGG-Level-2 designation of energy metabolisms compared to the gut digesta, which had higher carbohydrate, amino acid and lipid metabolisms. Overall, the results of this study elaborate the spatial distribution of microbial communities in the gut ecosystem of L. variegatus, and specifically a selective attribute for Campylobacteraceae in the gut tissue. Also, the predictive functional significance of bacterial communities in uniquely compartmentalized gut ecosystems of L. variegatus has been described.
  • 7.

    【2hr】Differential utilization patterns of dissolved organic phosphorus compounds by heterotrophic bacteria in two mountain lakes

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    机译 两个高山湖泊中异养细​​菌溶解性有机磷化合物的差异利用模式
    摘要：Although phosphorus limitation is common in freshwaters and bacteria are known to use dissolved organic phosphorus (DOP), little is known about how efficiently DOP compounds are taken up by individual bacterial taxa. Here, we assessed bacterial uptake of three model DOP substrates in two mountain lakes and examined whether DOP uptake followed concentration-dependent patterns. We determined bulk uptake rates by the bacterioplankton and examined bacterial taxon-specific substrate uptake patterns using microautoradiography combined with catalyzed reporter deposition–fluorescence in situ hybridization. Our results show that in the oligotrophic alpine lake, bacteria took up ATP, glucose-6-phosphate and glycerol-3-phosphate to similar extents (mean 29.7 ± 4.3% Bacteria), whereas in the subalpine mesotrophic lake, ca. 40% of bacteria took up glucose-6-phosphate, but only ∼20% took up ATP or glycerol-3-phosphate. In both lakes, the R-BT cluster of Betaproteobacteria (lineage of genus Limnohabitans) was over-represented in glucose-6-phosphate and glycerol-3-phosphate uptake, whereas AcI Actinobacteria were under-represented in the uptake of those substrates. Alphaproteobacteria and Bacteroidetes contributed to DOP uptake proportionally to their in situ abundance. Our results demonstrate that R-BT Betaproteobacteria are the most active bacteria in DOP acquisition, whereas the abundant AcI Actinobacteria may either lack high affinity DOP uptake systems or have reduced phosphorus requirements.
  • 8.

    【2hr】Characterising the microbiome of Corallina officinalis, a dominant calcified intertidal red alga

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    机译 表征Corallina officinalis（一种占优势的钙化潮间红藻）的微生物组
    摘要：The living prokaryotic microbiome of the calcified geniculate (articulated) red alga, Corallina officinalis from the intertidal seashore is characterised for the first time based on the V6 hypervariable region of 16S rRNA. Results revealed an extraordinary diversity of bacteria associated with the microbiome. Thirty-five prokaryotic phyla were recovered, of which Proteobacteria, Cyanobacteria, Bacteroidetes, Actinobacteria, Planctomycetes, Acidobacteria, Verrucomicrobia, Firmicutes and Chloroflexi made up the core microbiome. Unclassified sequences made up 25% of sequences, suggesting insufficient sampling of the world's oceans/macroalgae. The greatest diversity in the microbiome was on the upper shore, followed by the lower shore then the middle shore, although the microbiome community composition did not vary between shore levels. The C. officinalis core microbiome was broadly similar in composition to those reported in the literature for crustose coralline algae (CCAs) and free-living rhodoliths. Differences in relative abundance of the phyla between the different types of calcified macroalgal species may relate to the intertidal versus subtidal habit of the taxa and functionality of the microbiome components. The results indicate that much work is needed to identify prokaryotic taxa, and to determine the nature of the relationship of the bacteria with the calcified host spatially, temporally and functionally.
  • 9.

    【2hr】Water level changes affect carbon turnover and microbial community composition in lake sediments

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    机译 水位变化影响湖泊沉积物中的碳转化和微生物群落组成
    摘要：Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. 13C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions.
  • 10.

    【2hr】Quantification of the effects of ocean acidification on sediment microbial communities in the environment: the importance of ecosystem approaches

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    机译 量化海洋酸化对环境中沉积物微生物群落的影响：生态系统方法的重要性
    摘要：To understand how ocean acidification (OA) influences sediment microbial communities, naturally CO2-rich sites are increasingly being used as OA analogues. However, the characterization of these naturally CO2-rich sites is often limited to OA-related variables, neglecting additional environmental variables that may confound OA effects. Here, we used an extensive array of sediment and bottom water parameters to evaluate pH effects on sediment microbial communities at hydrothermal CO2 seeps in Papua New Guinea. The geochemical composition of the sediment pore water showed variations in the hydrothermal signature at seep sites with comparable pH, allowing the identification of sites that may better represent future OA scenarios. At these sites, we detected a 60% shift in the microbial community composition compared with reference sites, mostly related to increases in Chloroflexi sequences. pH was among the factors significantly, yet not mainly, explaining changes in microbial community composition. pH variation may therefore often not be the primary cause of microbial changes when sampling is done along complex environmental gradients. Thus, we recommend an ecosystem approach when assessing OA effects on sediment microbial communities under natural conditions. This will enable a more reliable quantification of OA effects via a reduction of potential confounding effects.
  • 11.

    【2hr】Evidence for plasmid-mediated salt tolerance in the human gut microbiome and potential mechanisms

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    机译 人类肠道微生物组中质粒介导的耐盐性的证据及其潜在机制
    摘要：The human gut microbiome is critical to health and wellbeing. It hosts a complex ecosystem comprising a multitude of bacterial species, which contributes functionality that would otherwise be absent from the host. Transient and commensal bacteria in the gut must withstand many stresses. The influence of mobile genetic elements such as plasmids in stress adaptation within the ecosystem is poorly understood. Using a mobilomic approach we found evidence for plasmid-mediated osmotolerance as a phenotype amongst the Proteobacteria in healthy faecal slurries. A transconjugant carrying multiple plasmids acquired from healthy faecal slurry demonstrated increased osmotolerance in the presence of metal salts, particularly potassium chloride, which was not evident in the recipient. Pyrosequencing and analysis of the total plasmid DNA demonstrated the presence of plasmid-borne osmotolerance systems (including KdpD and H-NS) which may be linked to the observed phenotype. This is the first report of a transferable osmotolerance phenotype in gut commensals and may have implications for the transfer of osmotolerance in other niches.
  • 12.

    【2hr】All the microbiology nematodes can teach us

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    机译 所有微生物线虫都能教我们
    摘要：Be it their pervasiveness, experimental tractability or their impact on human health and agriculture, nematode–bacterium associations are far-reaching research subjects. Although the omics hype did not spare them and helped reveal mechanisms of communication and exchange between the associated partners, a huge amount of knowledge still awaits to be harvested from their study. Here, I summarize and compare the kind of research that has been already performed on the model nematode Caenorhabditis elegans and on symbiotic nematodes, both marine and entomopathogenic ones. The emerging picture highlights how complementing genetic studies with ecological ones (in the case of well-established genetic model systems such as C. elegans) and vice versa (in the case of the yet uncultured Stilbonematinae) will deepen our understanding of how microbial symbioses evolved and how they impact our environment.
  • 13.

    【2hr】Comparisons of diazotrophic communities in native and agricultural desert ecosystems reveal plants as important drivers in diversity

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    机译 对原生和农业沙漠生态系统中重氮营养群落的比较表明，植物是多样性的重要驱动力
    摘要：Diazotrophs provide the only biological source of fixed atmospheric nitrogen in the biosphere. Although they are the key player for plant-available nitrogen, less is known about their diversity and potential importance in arid ecosystems. We investigated the nitrogenase gene diversity in native and agricultural desert soil as well as within root-associated microbiota of medicinal plants grown in Egypt through the combination of nifH-specific qPCR, fingerprints, amplicon pyrosequencing and fluorescence in situ hybridization–confocal laser scanning microscopy. Although the diazotrophic microbiota were characterized by generally high abundances and diversity, statistically significant differences were found between both soils, the different microhabitats, and between the investigated plants (Matricaria chamomilla L., Calendula officinalis L. and Solanum distichum Schumach. and Thonn.). We observed a considerable community shift from desert to agriculturally used soil that demonstrated a higher abundance and diversity in the agro-ecosystem. The endorhiza was characterized by lower abundances and only a subset of species when compared to the rhizosphere. While the microbiomes of the Asteraceae were similar and dominated by potential root-nodulating rhizobia acquired primarily from soil, the perennial S. distichum generally formed associations with free-living nitrogen fixers. These results underline the importance of diazotrophs in desert ecosystems and additionally identify plants as important drivers in functional gene pool diversity.
  • 14.

    【2hr】Effects and mode of action of chitosan and ivy fruit saponins on the microbiome, fermentation and methanogenesis in the rumen simulation technique

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    机译 瘤胃模拟技术中壳聚糖和常春藤果皂苷对微生物组，发酵和产甲烷作用的影响和作用方式
    摘要：This study investigates the effects of supplementing a control diet (CON) with chitosan (CHI) or ivy fruit saponins (IVY) as natural feed additives. Both additives had similar abilities to decrease rumen methanogenesis (–42% and –40%, respectively) using different mechanisms: due to its antimicrobial and nutritional properties CHI promoted a shift in the fermentation pattern towards propionate production which explained about two thirds of the decrease in methanogenesis. This shift was achieved by a simplification of the structure in the bacterial community and a substitution of fibrolytic (Firmicutes and Fibrobacteres) by amylolytic bacteria (Bacteroidetes and Proteobacteria) which led to greater amylase activity, lactate and microbial protein yield with no detrimental effect on feed digestibility. Contrarily, IVY had negligible nutritional properties promoting minor changes in the fermentation pattern and on the bacterial community. Instead, IVY modified the structure of the methanogen community and decreased its diversity. This specific antimicrobial effect of IVY against methanogens was considered its main antimethanogenic mechanism. IVY had however a negative impact on microbial protein synthesis. Therefore, CHI and IVY should be further investigated in vivo to determine the optimum doses which maintain low methanogenesis but prevent negative effects on the rumen fermentation and animal metabolism.
  • 15.

    【2hr】Patterns of bacterial biodiversity in the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica

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    机译 南极麦克默多干旱谷冰川融水流中细菌生物多样性的模式
    摘要：Microbial consortia dominate glacial meltwater streams from polar regions, including the McMurdo Dry Valleys (MDV), where they thrive under physiologically stressful conditions. In this study, we examined microbial mat types and sediments found in 12 hydrologically diverse streams to describe the community diversity and composition within and across sites. Sequencing of the 16S rRNA gene from 129 samples revealed ∼24 000 operational taxonomic units (<97% DNA similarity), making streams the most biodiverse habitat in the MDV. Principal coordinate analyses revealed significant but weak clustering by mat type across all streams (ANOSIM R-statistic = 0.28) but stronger clustering within streams (ANOSIM R-statistic from 0.28 to 0.94). Significant relationships (P < 0.05) were found between bacterial diversity and mat ash-free dry mass, suggesting that diversity is related to the hydrologic regimes of the various streams, which are predictive of mat biomass. However, correlations between stream chemistry and community members were weak, possibly reflecting the importance of internal processes and hydrologic conditions. Collectively, these results suggest that localized conditions dictate bacterial community composition of the same mat types and sediments from different streams, and while MDV streams are hotspots of biodiversity in an otherwise depauperate landscape, controls on community structure are complex and site specific.
  • 16.

    【2hr】Role of secondary metabolites in the interaction between Pseudomonas fluorescens and soil microorganisms under iron-limited conditions

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    机译 铁限制条件下次生代谢产物在荧光假单胞菌与土壤微生物相互作用中的作用
    摘要：Microorganisms can be versatile in their interactions with each other, being variously beneficial, neutral or antagonistic in their effect. Although this versatility has been observed among many microorganisms and in many environments, little is known regarding the mechanisms leading to these changes in behavior. In the present work, we analyzed the mechanism by which the soil bacterium Pseudomonas fluorescens BBc6R8 shifts from stimulating the growth of the ectomycorrhizal fungus Laccaria bicolor S238N to killing the fungus. We show that among the three secondary metabolites produced by the bacterial strain—the siderophores enantio-pyochelin and pyoverdine, and the biosurfactant viscosin—the siderophores are mainly responsible for the antagonistic activity of the bacterium under iron-limited conditions. While the bacterial strain continues to produce beneficial factors, their effects are overridden by the action of their siderophores. This antagonistic activity of the strain P. fluorescens BBC6R8 in iron-depleted environments is not restricted to its influence on L. bicolor, since it was also seen to inhibit the growth of the actinomycete Streptomyces ambofaciens ATCC23877. We show that the strain P. fluorescens BBc6R8 uses different strategies to acquire iron, depending on certain biotic and abiotic factors.
  • 17.

    【2hr】The green alga Zygogonium ericetorum (Zygnematophyceae, Charophyta) shows high iron and aluminium tolerance: protection mechanisms and photosynthetic performance

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    机译 绿藻（Zygogonium ericetorum）（Zygnematophyceae，Charophyta）显示出高的铁和铝耐受性：保护机制和光合性能
    摘要：Streptophyte green algae, ancestors of Embryophytes, occur frequently in terrestrial habitats being exposed to high light intensities, water scarcity and potentially toxic metal cations under acidic conditions. The filamentous Zygogonium ericetorum synthesizes a purple vacuolar ferrous pigment, which is lost after aplanospore formation. However, it is unknown whether this cellular reorganization also removes excessive iron from the protoplast and how Z. ericetorum copes with high concentrations of aluminium. Here we show that aplanospore formation shifts iron into the extracellular space of the algal filament. Upon germination of aplanospores, aluminium is bound in the parental cell wall. Both processes reduce iron and aluminium in unpigmented filaments. Comparison of the photosynthetic oxygen production in response to light and temperature gradients in two different Z. ericetorum strains from an Austrian alpine and a Scottish highland habitat revealed lower values in the latter strain. In contrast, the Scottish strain showed a higher optimum quantum yield of PSII during desiccation stress followed by rehydration. Furthermore, pigmented filaments of both strains exhibited a higher light and temperature dependent oxygen production when compared to the unpigmented phenotype. Our results demonstrate a high metal tolerance of Z. ericetorum, which is crucial for surviving in acidic terrestrial habitats.
  • 18.

    【2hr】Formation of lipid bodies and changes in fatty acid composition upon pre-akinete formation in Arctic and Antarctic Zygnema (Zygnematophyceae, Streptophyta) strains

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    机译 北极和南极Zygnema（Zygnematophyceae，Streptophyta）菌株中预先形成小net子后脂质体的形成和脂肪酸组成的变化
    摘要：Filamentous green algae of the genus Zygnema (Zygnematophyceae, Streptophyta) are key components of polar hydro-terrestrial mats where they face various stressors including UV irradiation, freezing, desiccation and osmotic stress. Their vegetative cells can develop into pre-akinetes, i.e. reserve-rich, mature cells. We investigated lipid accumulation and fatty acid (FA) composition upon pre-akinete formation in an Arctic and an Antarctic Zygnema strain using transmission electron microscopy and gas chromatography coupled with mass spectrometry. Pre-akinetes formed after 9 weeks of cultivation in nitrogen-free medium, which was accompanied by massive accumulation of lipid bodies. The composition of FAs was similar in both strains, and α-linolenic acid (C18:3) dominated in young vegetative cells. Pre-akinete formation coincided with a significant change in FA composition. Oleic (C18:1) and linoleic (C18:2) acid increased the most (up to 17- and 8-fold, respectively). Small amounts of long-chain polyunsaturated FAs were also detected, e.g. arachidonic (C20:4) and eicosapentaenoic (C20:5) acid. Pre-akinetes exposed to desiccation at 86% relative humidity were able to recover maximum quantum yield of photosystem II, but desiccation had no major effect on FA composition. The results are discussed with regard to the capability of Zygnema spp. to thrive in extreme conditions.
  • 19.

    【2hr】Response of Antarctic cryoconite microbial communities to light

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    机译 南极冰壳微生物群落对光的响应
    摘要：Microbial communities on polar glacier surfaces are found dispersed on the ice surface, or concentrated in cryoconite holes and cryolakes, which are accumulations of debris covered by a layer of ice for some or all of the year. The ice lid limits the penetration of photosynthetically available radiation (PAR) to the sediment layer, since the ice attenuates up to 99% of incoming radiation. This suite of field and laboratory experiments demonstrates that PAR is an important control on primary production in cryoconite and cryolake ecosystems. Increased light intensity increased efficiency of primary production in controlled laboratory incubations of debris from the surface of Joyce Glacier, McMurdo Dry Valleys, Antarctica. However, when light intensity was increased to levels near that received on the ice surface, without the protection of an ice lid, efficiency decreased and measurements of photophysiology showed that the communities suffered light stress. The communities are therefore well adapted to low light levels. Comparison with Arctic cryoconite communities, which are typically not covered by an ice lid for the majority of the ablation season, showed that these organisms were also stressed by high light, so they must employ strategies to protect against photodamage.
  • 20.

    【2hr】Isolation of ‘Candidatus Nitrosocosmicus franklandus’, a novel ureolytic soil archaeal ammonia oxidiser with tolerance to high ammonia concentration

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    机译 分离出一种耐高氨浓度的新型尿素分解土壤古生氨氧化剂“ Candidatus Nitrosocosmicus franklandus”
    摘要：Studies of the distribution of ammonia oxidising archaea (AOA) and bacteria (AOB) suggest distinct ecological niches characterised by ammonia concentration and pH, arising through differences in substrate affinity and ammonia tolerance. AOA form five distinct phylogenetic clades, one of which, the ‘Nitrososphaera sister cluster’, has no cultivated isolate. A representative of this cluster, named ‘Candidatus Nitrosocosmicus franklandus’, was isolated from a pH 7.5 arable soil and we propose a new cluster name: ‘Nitrosocosmicus’. While phylogenetic analysis of amoA genes indicates its association with the Nitrososphaera sister cluster, analysis of 16S rRNA genes provided no support for a relative branching that is consistent with a ‘sister cluster’, indicating placement within a lineage of the order Nitrososphaerales. ‘Ca. N. franklandus’ is capable of ureolytic growth and its tolerances to nitrite and ammonia are higher than in other AOA and similar to those of typical soil AOB. Similarity of other growth characteristics of ‘Ca. N. franklandus’ with those of typical soil AOB isolates reduces support for niche differentiation between soil AOA and AOB and suggests that AOA have a wider physiological diversity than previously suspected. In particular, the high ammonia tolerance of ‘Ca. N. franklandus’ suggests potential contributions to nitrification in fertilised soils.
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