Microbial community changes along the Ecology Glacier ablation zone (King George Island, Antarctica)

In recent years glacial surfaces have received much attention as microbial habitats of diverse photoautotrophic and heterotrophic cells. Supraglacial ecosystems are annually covered and uncovered by snow. The aim of this study was to investigate the microbial community response to changing environmental conditions in a transect following the receding snow line on the surface of Ecology Glacier (King George Island, Antarctica). Parameters of surface ice and cryoconite holes included chemical composition of ice and sediment, Bacteria diversity by denaturating gradient gel electrophoresis (DGGE), microbial functional diversity (Biolog Ecoplates), and microbial counts (epifluorescence microscopy, colony forming units - CFU). Data demonstrated profound differences between surface ice and cryoconite holes. Changing environmental factors along the transect influenced composition and abundance of the microbiocenosis in both habitat types. Several parameters correlated positively with distance from the glacier edge, including the cell morphotype Shannon Index, chlorophyll a, nitrogen and seston concentrations. Suspended solids content positively correlated with microbial 2 abundance and diversity. Nitrogen and phosphorus were limiting factors of microbial growth as amounts of organic nitrogen and phosphorus positively correlated with the cell numbers, fission rates and photoautotroph contribution. Our findings indicate that microbial community shows a response in terms of abundance and diversity to exposure of the glacial surface as snow-cover melts. To our knowledge this is the first study to recognize a microbial development pattern on a glacier surface in connection with the receding snow line. This may help better understand variability within supraglacial habitats, correct sampling procedures and inform biocenotic development models

Evidence of adaptation, niche separation and microevolution within the genus Polaromonas on Arctic and Antarctic glacial surfaces

Polaromonas is one of the most abundant genera found on glacier surfaces, yet it’s ecology remains poorly described. Investigations made to date point towards a uniform distribution of Polaromonas phylotypes across the globe. We compared 43 Polaromonas isolates obtained from surfaces of Arctic and Antarctic glaciers to address this issue. 16S rRNA gene sequences, intergenic transcribed spacers (ITS) and metabolic fingerprinting showed great differences between hemispheres but also between neighboring glaciers. Phylogenetic distance between Arctic and Antarctic isolates indicated separate species. The Arctic group clustered similarly, when constructing dendrograms based on 16S rRNA gene and ITS sequences, as well as metabolic traits. The Antarctic strains, although almost identical considering 16S rRNA genes, diverged into 2 groups based on the ITS sequences and metabolic traits, suggesting recent niche separation. Certain phenotypic traits pointed towardscell adaptation to specific conditions on a particular glacier, like varying pH levels. Collected data suggest, that seeding of glacial surfaces with Polaromonas cells transported by various means, is of greater efficiency on local than global scales. Selection mechanisms present of glacial surfaces reduce the deposited Polaromonas diversity, causing subsequent adaptation to prevailing environmental conditions. Furthermore, interactions with other supraglacial microbiota, like algae cells may drive postselectional niche separation and microevolution within the Polaromonas genus

The C2H2 zinc finger transcription factors are likely targets for Ni(ii) toxicity.

Ni(ii) ions are able to hydrolyze Naa-(Ser/Thr) peptide bonds in Naa-(Ser/Thr)-Xaa-His-Zaa sequences. We found that various human transcription factors contain such nickel hydrolytic patterns within C2H2 zinc finger (ZF) domains. We demonstrated the hydrolysis on two peptide models, the 3rd ZF of the Sp1 transcription factor and the 1st ZF of the ZNF302 transcription factor. The experimentally studied reaction rates indicate that the hydrolysis reaction is likely to be an element of intracellular nickel toxicity