THE MEASUREMENT OF MICROBIAL CARBOHYDRATE EXOPOLYMERS FROM INTERTIDALSEDIMENTS

Measurements of microbial extracellular polymeric substances (EPS) of natural field populations are required to understand the processes of biogenic stabilization and the microbial ecology of intertidal sedimen ts. EPS in sediments can be measured by the phenol-sulfuric acid assay to measure carbohydrate concentration in sediment samples. We conduct ed comparative studies of storage and extraction methods for carbohydr ate fractions on intertidal estuarine sediments. Measurements of both total and colloidal (material remaining in suspension after aqueous ex traction and centrifugation) carbohydrate concentrations were highly d ependent on storage conditions, sample size, extraction media, and tim e. Precipitation (in 70% ethanol) of EPS from saline (25 parts per tho usand) extractions of colloidal carbohydrate (colloidal S) from four d ifferent sediment microbial assemblages showed that 20% of colloidal c arbohydrate present in extracts consisted of EPS. Concentrations of co lloidal S were highly correlated with diatom biomass as determined by chlorophyll a concentrations. Extractions that used 100 mM Na(2)EDTA a s the extracting medium (colloidal EDTA) increased the concentrations of colloidal carbohydrate obtained and, in sediments dominated by bact eria and cyanobacteria, increased the percentage of EPS in the materia l to 38%. Uronic acids comprised 20% of the total amount of carbohydra te measured in both total sediment and colloidal-S extracts but increa sed to 65% in colloidal-EDTA extracts, suggesting that colloidal-EDTA extractions remove bacterial capsular EPS and EPS more closely associa ted with sediment particles.