Abstract
The oxidation pathway of sulfite to sulfate in Thiobacillus thiooxidans JCM 7814 was investigated. Most of the activities of sulfite oxidation were in the membrane fractions of the cells. The addition of AMP (adenosine 5'-monophosphate) did not affect the activity. Two other reference strains of T. thiooxidans also gave the same results. Sulfite oxidation by T. denitrificans with an APS (adenosine 5'-phosphosulfate) pathway was evidently stimulated by the addition of AMP, while none of the effects occured upon the addition to T. novellus, which has an AMP-independent pathway. Although T. denitrificans produced APS from sulfite and AMP, T. thiooxidans JCM 7814 neither consumed AMP nor produced APS. T. thiooxidans JCM 7814 had sulfite dehydrogenase activity. These results showed that T. thiooxidans JCM 7814 has only the AMP-independent pathway. The presence of cytochromes a, b, and c was also shown from the difference spectrum of the membrane fraction prepared from T. thiooxidans JCM 7814 cells.
