Antarctica is one of the most ancient, largest glacier reserves and the most pristine environment left on the earth. Industrialization and the release of greenhouse gases have severely affected environment of Antarctica causing melting of polar ice sheets, changes in atmospheric chemistry, and ozone depletion. Antarctica continent experiences arrays of abiotic stress such as low temperatures and sunlight, high solar radiations and low nutrient availability making it unsustainable for most organisms. Over the last few decades, anthropogenically emitted chlorofluorocarbons have led to severe ozone destruction in the stratosphere over Antarctic continent, leading to increased UV radiation at the surface. This creates adverse effects on the resilient biota like seaweed, microorganisms etc.
In a recent study, researchers at NCMR-NCCS, Pune and IITM, Pune used high-throughput sequencing to understand the impact of subtle changes in environmental parameters on bacterial communities in Antarctica. In this study, the surface sediment samples were collected from Larsemann hills near the ‘Bharati‘ station of India located in southeastern region of Prydzy Bay, Antarctica. A total of 10 samples were collected on alternate day spanning across 20 days to generate a robust sequencing data to assess the microbial community composition under poly-extremophilic conditions. Community DNA extraction and amplicon sequencing was performed, NGS analysis, bacterial load estimation, functional prediction and statistical analysis was done. The objective of the study was to understand the bacterial community composition under the poly-extremophilic conditions of Antarctica continent. Researchers also examined the functional adaptations with respect to the survival and nutrient adaptations endorsed by bacterial communities, with the help of imputed metagenomics.
Dominance of Cyanobacteria followed by Bacteroidetes, Acidobacteria, Proteobacteria, Actinobacteria, Firmicutes was observed. Metagenomic imputations revealed higher abundance of gene families associated with DNA repair and carotenoid biosynthesis enabling bacterial communities to resist and function under the high UV radiations. Notable differences in the abiotic factors such as temperature, total radiation, and overhead zone, was observed. Variability among the alpha diversity indices across the study duration was observed. The extreme environmental conditions in Antarctica may confer a high stress condition for the microorganisms, but such perpetual pressures have often been found to cast an emergence of novel mechanism for survival and adaptation. In this study, researchers employed an approach of metagenomic imputation to dissect the adaptive mechanism of these bacterial communities sustaining varied abiotic stress. Also, the abundant acquisition of elements of energy metabolism such as sulfur metabolism, oxidative phosphorylation, nitrogen metabolism and photosynthesis would enable effective survival of the bacterial communities under harsh conditions of Antarctica. The assessment of abiotic factors revealed subtle variations with respect to the time. Substantial changes in the surface temperature and the total radiation was observed. Predominance of bacterial phyla like Proteobacteria, Actinobacteria and Bacteroidetes in soils of Antarctica and, abundance of Firmicutes and lower to rare persistence of Acidobacteria, respectively was observed.
This study showed the changes in the bacterial community composition with subtle changes in the environmental conditions. The study also revealed abundance of the genes responsible for the survival of bacterial communities under the rising temperature, low nutrient, and high UV radiations in Antarctica.
Reference: https://journals.pan.pl/dlibra/show-content?id=120895
Microbe World 