STUDIES ON THE METABOLISM OF A SULFUR-OXIDIZING BACTERIUM: I. OXIDATION OF SULFUR

1. Thiobacillus thiooxidans, isolated in our laboratory, was foundto oxidize sulfur, but not thiosulfate. Tetrathionate is alsooxidized slightly. Its ability to oxidize sulfur is inactivatedeven by such a mild treatment as keeping the cells in a frozenstate.
2. Inhibitory action of alcohols on the sulfur oxidationincreasesas the length of carbon chain of alcohols increases.Carboxylicacids do not inhibit the sulfur oxidation at pH abovetheirpK, while they strongly inhibit the reaction at pH belowthepK.
3. The sulfur oxidation is inhibited by cyanide, azide,diethyldithiocarbamateand carbon monoxide, and the inhibitionby carbon monoxide isnot reversed by light. These results suggestthe presence ofmetal enzymes in the sulfur oxidation system.The terminal enzymeof this reaction appears to be differentfrom the usual cytochromeoxidase.

(Received May 13, 1960; )