Microbial extracellular polymeric substances in marine biogeochemical processes

Microbial extracellular polymeric substances (EPS) are widely distributed in marine environments; and are found in free dissolved form, colloids, discreet particles like TEP and/or associated with particulate matter, including cell aggregates, detritus, biofilms, microbial mats, etc. The chemical composition of EPS is influenced by various factors, including nutrients, temperature, pH, physiology and age of the culture. Microbial EPS perform various functions, and are involved in diverse marine processes. The unique gelling properties of microbial EPS are considered important in the transport and transformation of organic matter, complexation or dissolved metals and biogeochemical cycling of elements. EPS are rich in organic carbon and therefore are an important source of carbon for different organisms in the food chain. The production of dissolved EPS during the bacterial growth, production of particulate organic carbon from the dissolved EPS and enzymatic breakdown and conversion of particulate EPS into dissolved organic matter within the microbial loop, form an important alternate route of organic carbon cycling in the marine trophic web. In this article, recent findings on EPS and their significance in biogeochemical processes are discussed with respect to their role in marine microbial ecology, marine food-web and other areas of future research.