The microorganism was isolated from sewage and characterized as Thiobacillus novellus SRM. The optimal pH and temperature for cell growth were pH 7.0 and 30 degrees C, respectively. The content of G and C of the DNA was 67.2%. The unsaturated fat consisted of octadenoicacid plus cyclopropane of C-19(C18:1 + 19cyc) and the saturated fat of 3-hydroxydodecanoic acid (3-OH C-10:0). Thiobacillus novellus SRM oxidized S2O3-2 to S4O6-2 and S4O6-2 to SO4-2. Thiobacillus novellus SRM removed 200 ppm H2S in 1.8 h, the 50 ppm of methyl mercaptan (MM) in 2.6 h, 30 ppm of dimethyl sulphide (DMS) in 7.0 h, and 30 ppm of dimethyl disuphide (DMDS) in 6.0 h. The optimal pH for the removal of DMS was pH 7.0 and the optimal temperature was 30 degrees C. 10 g immobilized Thiobacillus novellus SRM removed 98% of 30 ppm DMDS and 50% of 40 ppm DMDS. When the DMDS concentration increased to 40 ppm, the removal efficiency decreased to less than 50%. The removal efficiency by immobilized Thiobacillus novellus SRM was H2S > MM > DMDS > DMS. 100% of H2S and MM, and 87% of DMDS were removed in 15 days. The removal efficiency of DMS was less than that of DMDS.