Advances in extracellular polymeric substances in phycosphere environment

Abstract:

Microalgae releases extracellular substances around the cell to form a unique algal microenvironment called "phycosphere niche" that attracts a large number of bacteria to colonize. The algae-bacteria interactions are very complex involving multiply material exchanges and information communication. Among the algae-bacterial relationship, extracellular polymeric substances (EPS) serve as a bridge for matter flux. Both microalgae and bacteria can produce EPS, and the production process is regulated by many factors. In the phycosphere environment, EPS play important ecological roles, such as participating in the formation of biofilm, affecting the algae-bacterial symbiotic structure and regulating the composition of microbial communities. In addition, as an important member of EPS, transparent exopolymer particles (TEP) mediate the conversion of dissolved organic carbon into particulate organic carbon. This profile made TEP is an important regulator, participating in marine carbon cycle. In this review, we focus on phycosphere niche, and summarise the newest advance in EPS production, composition and effect factors. Meanwhile, the ecological roles of EPS in marine carbon cycle have also been discussed, to provide reference for better understanding the organic matter properties and algae-bacterial behavior in the phycosphere environment.