Intracellular deposition of sulfur by Sphaerotilus natans.

During the course of studies of the bacterial and algal flora of creek waters we were puzzled by the absence of any representatives of the genus Thiothrix from samples in which there was a regular and abundant growth of Beggiatoa species. Associated with Beggiatoa in many of these samples was the colorless sheathed organism Sphaerotilus natans. In view of the very gross similarity of Sphaerotilus morphologically to the recorded descriptions of Thiothrix, it was decided to test the ability of the organism to oxidize hydrogen sulfide in a manner similar to that recorded for the species of the genera Beggiatoa, Thiothrix and other filamentous sulfur bacteria.