Studies on the metabolism of a sulfur-oxidizing bacterium IV. Growth and oxidation of sulfur compounds in Thiobacillus thiooxidans

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By immersing a few small cellophane bags containing BaCO_3 powder in STARKEY'S medium, the duration of lag phase in the growth of Thiobacillus thiooxidans is minimized and the yield of cells is increased ten times that of the previous method. The activities of oxidation for sulfur and sulfite change with growth. Sulfite is oxidized at a comparable rate to that of sulfur oxidation at pH values between 6.0 and 6.5. In the presence of cysteine or glutathione, thiosulfate can be oxidized at a pH above 5.0. At pH values below 4.5, apparent oxidation of thiosulfate and tetrathionate to sulfate is observed. This result is accounted for by the facts that thiosulfate is decomposed to sulfur and sulfite under the acidic condition at pH values below 4.5, and that tetrathionate is reduced to thiosulfate enzymatically. In the oxidation of tetrathionate, oxygen uptake begins after a lag phase, the duration of which depends on the concentrations of cells and of tetrathionate. Cysteine is oxidized to cystine. The oxidation is strongly inhibited by metal-chelating agents. The cysteine oxidizing activity is, however, quite stable and is not lost by treating cells with organic solvents, sonic oscillation, by heating or lyophilization.
日本植物生理学会の論文