CHARACTERIZATION OF EPS PRODUCING MICROORGANISMS IN ANTARCTIC SUBGLACIAL SYSTEMS

Microorganisms produce extracellular polymeric substances (EPS) that form the structural matrix of biofilms. EPSs are high molecular weight polymers comprised of polysaccharides and protein, but can also contain lipids, nucleic acids or other biomacromolecules. Biofilms serve numerous functions for microorganisms including protection and nutrient acquisition. In permanently cold ecosystems like that found in Antarctica, EPS can protect cells from freezing or help access limiting nutrients such as iron. Here we examine the EPS-production of microorganisms isolated from diverse Antarctic ecosystems including a subglacial outflow feature known as Blood Falls and the marine grounding zone of the Whillans Ice Stream. The isolates obtained for this study include: Pseudomonas, Arthrobacter, and Shewanella. We attempted to induce EPS secretion rates at both elevated sugar (sucrose) concentrations (up to 4%) and near environmental in situ conditions. For our in situ incubations we examined carbon source (protein, polysaccharide or complex) as well as concentration. Selective carbon plates were prepared to examine carbon substrate utilization and EPS production. Treatments included (1g and 5g) casamino acids, (0.25g and 1g) yeast and (2ml and 4 ml) lysed Prochlorococcus cells. EPS production was highly variable across the low carbon treatments. The highest number of colony forming units (CFUs) were observed on yeast extract and casamino acids. EPS was visualized with light and electron microscopy across all isolates. After EPS production was verified whole genome analysis was done to determine the genes associated with the EPS production. Data from these growth experiments demonstrate the ability of our Antarctic isolates to generate EPS under laboratory conditions. Future directions include characterization and quantification of EPS produced and to examine a broader range of environment conditions such as temperature and salinity. For example, these organisms may be using the secretion to gain access to carbon sources for metabolism or to protect themselves from lysing during ice formation. Understanding how the microorganisms utilize EPS in the Antarctic system can provide new insight to the interactions between microorganisms and large scale biogeochemical cycles.