A method for the estimation of bacterial biomass and community structure in mangrove-associated sediments

Many recent reports have proposed that certain monocarboxylic fatty acids found in sediments originate in the in situ bacterial population. In this study we have divided the acids derived from bacteria into nine subgroups, each characteristic of a distinct compositional group of bacteria. It is proposed that the abundance of selected marker acids from each bacterial subgroup (chemotype) can be used to estimate the biomass of that chemotype. Conversion factors from acid abundance to bacterial biomass have been estimated using literature data. Since this procedure results in nine biomass parameters, bacterial communities can be compared in terms of both total biomass and chemotype distribution, that is, biomass and community structure. The ability of this procedure to resolve community structure variations is illustrated with the interpretation of the fatty acid profiles of a spatially distributed set of mangrove-associated sediments.