Dr. Shipra Nagar

Summary

Huge algal and bacterial biodiversity in Antarctic sea ice plays a vital role in Antarctic coastal food web. It acts as source of Extracellular Polymeric Substances (EPSs) in water as a response to environmental stress such as low temperatures, high salinity, pH difference etc. EPS is composed of exopolysaccharides (ExP), proteins, lipids and DNA. Amongst these, ExP (40-90%) is main component and exhibit unique properties viz. cryoprotection, anti-desiccation ;trace metal uptake & binding, sequestration of dissolved organic matter (DOM) & nutrients; adhesion, buffering against high salinity & pH; aggregate formation and biofilm production thereby assisting microbial communities to endure extremes of temp., salinity, and nutrient availability. EPS can influence environment substantially by its role in biogeochemical cycles, especially carbon cycle. They are also key to microbial biofilm stabilization by acting as substrate for growth of complex microbial communities. They aid in cryoconite granules formation on glacial surface and are known to be significantly responsible for acceleration in glacial and ice sheet melting. EPS may also aggregate to form particulate organic matter, which may be degraded to dissolved organic carbon and dissolved organic nitrogen by microbes, thereby adding to the pool of DOM in environment. In microbial dominated ecosystems, EPS can represent a major source of biologically labile carbon that fuels the microbial web. Despite significant role of EPS in Antarctic coastal ecosystems, very few studies have been carried out to unravel the chemical structures of constituent ExP. The studies so far carried out in this region have been limited to monosaccharide analysis and quantification of EPS, carbohydrate, uronic acid and protein contents. Hence, it is important to carry out complete structural characterization of ExP from polar microbes for a better understanding of their role in Antarctic coastal environments. The study used microbial cultures of representative samples from such supraglacial ecosystems situated within coastal East Antarctica (Larsemann Hills and Dronning Maud Land), collected as part of the ongoing 'Cryosphere and Climate' project at National Centre for Polar and Ocean Research, Goa, India. It was proposed to profile the compositional structure of EPSs produced by microbes and to characterize their constituent ExP. Elucidation of ExP structure would lead to enhanced understanding of their role in polar environment, viz., biogeochemical processes, food web, their atmospheric processing and relevance for climate. The complete and thorough structural profiling of EPS would provide potentially new insights into structure-activity relationship and behavior of EPS, and its interaction with surrounding environment. Further, study would provide background data necessary for exploring industrial prospects of polar ExP.

Funding Agency

Science and Engineering Research Board, Department. of Science and Technology, India

Programme

National-Postdoctoral Fellowship