Thiosulphate oxidation and cytochromes in Thiobacillus X. 1. Fractionation of bacterial extracts and properties of cytochromes

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Abstract
Three soluble cytochromes, Thiobacillus X cytochromes 550 (1), 553.5 and 557 (1), and an enzyme system oxidizing thiosulphate, have been separated from extracts of the aerobic sulphur bacterium Thiobacillus X. A fifth fraction (acidic fraction) contained two additional cytochrome components with a bands at 550 and 557 mu respectively in the reduced state. All the cytochromes appear to be of the c type, are labile to heat and acid and do not combine with carbon monoxide. They are auto-oxidizable to varying degrees. Cytochromes 550 (1) and 557 (1) are basic, and are adsorbed on to Amberlite IRC-50 at pH 7. Their E''o values at pH 7 are + 0.20 and + 0.15v respectively. Cytochrome 553.5 is acidic but is adsorbed on to Amberlite at pH 5. Its E''o value is +0.21v. The cytochromes of the acidic fraction are not adsorbed on IRC-50. Otherwise their properties are very similar to those of cytochromes 550 (1) and 557 (1) respectively. Addition of thiosulphate to whole cells causes a rapid reduction of cytochrome components with a peaks at 549-558 m[mu] and 562 m[mu].