Genotypic distribution of an indigenous model microorganism along an estuarine gradient.

Using the genus Desulfobulbus as an indigenous model, microbial distribution along an estuarine gradient was investigated. Denaturing gradient gel electrophoresis analysis indicated a sequential change in Desulfobulbus genotypes along the estuary with marine, brackish and freshwater genotypes detected. This differential distribution was significantly correlated with porewater concentrations of chloride, sulphate and nitrate. Temporal analysis indicated that there was a shift in the whole Desulfobulbus community towards to marine end of the estuary by the end of the winter compared with the late summer. This distribution pattern is similar to those seen with other estuarine organisms and, given the correlation with chloride and sulphate, is indicative of classic niche separation within this genus driven by gross environmental factors such as salinity. These results will help in developing a truly ecological description of microbial biodiversity.