Formation of Sulfide by Some Sulfur Bacteria.

Abstract

Previous studies with the strictly autotrophic sulfur bacterium, Thiobacillus thiooxidans, growing on elemental sulfur have shown that the sulfur is rapidly oxidized to sulfate without the accumulation of intermediate products.1 The strictly autotrophic sulfur bacterium Th. thioparus transforms thiosulfate to the 2 products, sulfate and elemental sulfur.2 No question has arisen concerning the initial stages of transformation of thiosulfate, but, by reason of the relatively large size of the particles of elemental sulfur compared to the tiny bacterial cells (about 0.5 × 0.8μ) it has been suggested that some initial transformation to a reduced or oxidized substance may precede passage of the sulfur material through the cell membrane, after which the reactions leading to the release of energy for growth takes place.3 However, McCallan and Wilcoxon present evidence which shows that the vapor pressure of elemental sulfur is sufficiently high to permit sulfur vapor to enter cells which are not even in contact w...