Microbial communities and exopolysaccharides from Polynesian mats

Microbial mats present in two shallow atolls of French Polynesia were chara cterized by high amounts of exopolysaccharides associated with cyanobacteri a as the predominating species. Cyanobacteria were found in the first centi meters of the gelatinous mats, whereas deeper layers showing the occurrence of the sulfate reducers Desulfovibrio and Desulfobacter species as determi ned by the presence of specific biomarkers. Exopolysaccharides were extract ed from these mats and partially characterized. All fractions contained bot h neutral sugars and uronic acids with a predominance of the former. The la rge diversity in monosaccharides can be interpreted as the result of exopol ymer biosynthesis by either different or unidentified cyanobacterial specie s.