ISOLATION AND SOME PROPERTIES OF AN IRON-OXIDIZING BACTERIUM THIOBACILLUS FEROOXIDANS RESISTANT TO BISULFITE ION

An iron-oxidizing bacterium Thiobacillus ferrooxidans resistant to bis ulfite ion (strain OK1-50) was isolated from stream water from Okayama City, Japan and characterized. When grown statically on FeSO4 . 7H(2) O (3%)-salts medium without sodium sulfite, OK1-50 and T. ferrooxidans strain AP19-3 had the same level of cell growth (200 x 10(6) cells/ml ). However, when cultured in FeSO4 . 7H(2)O (3%)-salts medium with 5 m M sodium sulfite, OK1-50 and AP19-3 gave maximal cell yield of 105 x 1 0(6) and 35 x 10(6) cells/ml, respectively, suggesting that OK1-50 was much more resistant to bisulfite ion than AP19-3 is. The inhibition s ite of bisulfite ion on iron oxidase system is cytochrome c oxidase, w hich is one of the essential constituents of the iron oxidase system. Iron-oxidizing activity of AP19-3 was completely inhibited by 0.2 mM b isulfite ion. In contrast, the activity of OK1-50 was not inhibited by 2 mM sodium sulfite. Cytochrome c oxidase activity of AP19-3 was comp letely inhibited by 2 mM bisulfite ion. However, 5 mM bisulfite ion di d not inhibit the activity of OK1-50. A similar level of sulfite:ferri c ion oxidoreductase activity was observed in both strains. Hydrogen s ulfide:ferric ion oxidoreductase activity of OK1-50 was one half of th e activity of AP19-3. NADH-dependent sulfite reductase activity of OK1 -50 was three times higher than that of AP19-3. These results indicate that having an iron oxidase system resistant to bisulfite ion makes s train OK1-50 much more resistant to bisulfite ion than AP19-3 is.