Use of combined microautoradiography and fluorescence in situ hybridization to determine carbon metabolism in mixed natural communities of unculturedbacteria from the genus Achromatium

Combined microautoradiography and fluorescence in situ hybridization (FISH) was used to investigate carbon metabolism in uncultured bacteria from the genus Achromatium. All of the Achromatium species identified in a freshwate r sediment from Rydal Water, Cumbria, United Kingdom, which were distinguis hable only by FISH, assimilated both [C-14]bicarbonate and [C-14]acetate, T his extends previous findings that Achromatium spp, present at another loca tion could only utilize organic carbon sources. Achromatium spp,, therefore , probably exhibit a range of physiologies, i.e., facultative chemolithoaut otrophy, mixotrophy, and chemoorganoheterotrophy, similar to other large su lfur bacteria (e.g., Beggiatoa spp.).