Physical geography shapes the distribution characteristics of extracellular polymeric substances in periphytic biofilms

Abstract

Background: Extracellular polymeric substances (EPS) are the glue that holds periphytic biofilms together. However, little is known about the chemical composition of the EPS and whether and if so how these components vary over different geographic regions. Therefore, we collected a large series of periphytic biofilms from paddy fields in different geographic regions to study the content, geographical distribution, and potential ecological function of EPS in periphytic biofilms, as well as the function of microbial components on EPS in periphytic biofilm.Results: EPS accounted for 1.3-2.9% of the total biomass of periphytic biofilms, while the protein content in periphytic biofilm was 1.8 to 20 times higher than that of the polysaccharides. The geographical distribution of EPS in periphytic biofilms follows the typical latitudinal diversity gradient theory: EPS contents decreased with increasing latitudes, but the ratio of protein to polysaccharide in periphytic biofilms showed the opposite trend. Physical geography characteristics, including temperature and light, are the principal forces driving the geographical distribution of EPS in periphytic biofilms, affecting their microbial composition. Prokaryotes in periphytic biofilm negatively affect the EPS content in periphytic biofilm, suggesting that prokaryotes may function as EPS consumers, while eukaryotes may be EPS producers, because they positively affect the EPS content in periphytic biofilm. Functionally, EPS components contribute to N and P accumulation in periphytic biofilms, as well as enhance the total organic carbon content in periphytic biofilm.Conclusion: These analyses provide invaluable information on the biogeochemistry of EPS in periphytic biofilms and their potential role in modulating nutrient cycles in paddy fields.