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      Diversity and activity of microorganisms in Antarctic polar soils

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      One Ecosystem

      Pensoft Publishers

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          Abstract

          The study is focused on microbiological analyses in polar soils in selected monitoring sites in Livingstone Island, Antarctica region. The analyses include determination of the quantity and qualitative composition of the heterotrophic block of soil microflora (non-spore-forming bacteria, bacilli, actinomycetes, micromycetes, bacteria absorbing mineral nitrogen), insofar as it plays a major role in the element cycling and soil formation processes. Aerobic (rapidly and slowly growing) and anaerobic groups of soil microorganisms were investigated and the biogenicity (total microflora) and the rate of mineralisation processes (mineralisation coefficient) were determined. Mostly non-spore-forming aerobic bacteria, followed by actinomycetes, are dominant in determining the biogenicity of the studied polar soils. The rearrangement of the microorganisms in the composition of the total microflora by degree of dominance indicates the participation of all the studied groups of microorganisms in most sites in the initial and final stages of the decomposition of organic matter. The mineralisation of soils is most active in sites with vegetation cover. The established pigmentation in aerobic microorganisms is probably due to their good adaptation and protection under extreme polar conditions, while the absence of oxygen impedes the formation of pigments.

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          Patterns of bacterial diversity across a range of Antarctic terrestrial habitats.

          Although soil-borne bacteria represent the world's greatest source of biological diversity, it is not well understood whether extreme environmental conditions, such as those found in Antarctic habitats, result in reduced soil-borne microbial diversity. To address this issue, patterns of bacterial diversity were studied in soils sampled along a > 3200 km southern polar transect spanning a gradient of increased climate severity over 27 degrees of latitude. Vegetated and fell-field plots were sampled at the Falkland (51 degrees S), South Georgia (54 degrees S), Signy (60 degrees S) and Anchorage Islands (67 degrees S), while bare frost-sorted soil polygons were examined at Fossil Bluff (71 degrees S), Mars Oasis (72 degrees S), Coal Nunatak (72 degrees S) and the Ellsworth Mountains (78 degrees S). Bacterial 16S rRNA gene sequences were recovered subsequent to direct DNA extraction from soil, polymerase chain reaction amplification and cloning. Although bacterial diversity was observed to decline with increased latitude, habitat-specific patterns appeared to also be important. Namely, a negative relationship was found between bacterial diversity and latitude for fell-field soils, but no such pattern was observed for vegetated sites. The Mars Oasis site, previously identified as a biodiversity hotspot within this region, proved exceptional within the study transect, with unusually high bacterial diversity. In independent analyses, geographical distance and vegetation cover were found to significantly influence bacterial community composition. These results provide insight into the factors shaping the composition of bacterial communities in Antarctic terrestrial habitats and support the notion that bacterial diversity declines with increased climatic severity.
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            Functional ecology of an Antarctic Dry Valley.

            The McMurdo Dry Valleys are the largest ice-free region in Antarctica and are critically at risk from climate change. The terrestrial landscape is dominated by oligotrophic mineral soils and extensive exposed rocky surfaces where biota are largely restricted to microbial communities, although their ability to perform the majority of geobiological processes has remained largely uncharacterized. Here, we identified functional traits that drive microbial survival and community assembly, using a metagenomic approach with GeoChip-based functional gene arrays to establish metabolic capabilities in communities inhabiting soil and rock surface niches in McKelvey Valley. Major pathways in primary metabolism were identified, indicating significant plasticity in autotrophic, heterotrophic, and diazotrophic strategies supporting microbial communities. This represents a major advance beyond biodiversity surveys in that we have now identified how putative functional ecology drives microbial community assembly. Significant differences were apparent between open soil, hypolithic, chasmoendolithic, and cryptoendolithic communities. A suite of previously unappreciated Antarctic microbial stress response pathways, thermal, osmotic, and nutrient limitation responses were identified and related to environmental stressors, offering tangible clues to the mechanisms behind the enduring success of microorganisms in this seemingly inhospitable terrain. Rocky substrates exposed to larger fluctuations in environmental stress supported greater functional diversity in stress-response pathways than soils. Soils comprised a unique reservoir of genes involved in transformation of organic hydrocarbons and lignin-like degradative pathways. This has major implications for the evolutionary origin of the organisms, turnover of recalcitrant substrates in Antarctic soils, and predicting future responses to anthropogenic pollution.
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              Dominant bacteria in soils of Marble Point and Wright Valley, Victoria Land, Antarctica

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                Author and article information

                Journal
                One Ecosystem
                OE
                Pensoft Publishers
                2367-8194
                June 12 2020
                June 12 2020
                : 5
                Article
                10.3897/oneeco.5.e51816
                © 2020

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