ISOLATION AND CHARACTERIZATION OF A METHYL-CHLORIDE UTILIZING, STRICTLY ANAEROBIC BACTERIUM

From sludge obtained from the sewage digester plant in Stuttgart-Mohringen a strictly anaerobic bacterium was enriched and isolated with methyl chloride as the energy source. The isolate, which was tentatively called strain MC, was nonmotile, gram-positive, and occurred as elongated cocci arranged in chains. Cells of strain MC formed about 3 mol of acetate per 4 mol of CH3Cl consumed, indicating that the organism was a homoacetogenic bacterium fermenting methyl chloride plus CO2 according to: 4 CH3Cl + 2 CO2 + 2 H2O --> 3 CH3COO- + 7 H+ + 4 Cl-. The organism grew with 2-3% methyl chloride in the gas phase at a doubling time of near 30 h. Dichloromethane was not utilized. The bacterium also grew on carbon monoxide, H2 plus CO2, and methoxylated aromatic compounds. Optimal growth with methyl chloride was observed at 25-degrees-C and pH 7.3-7.7. The G + C-content of the DNA was 47.5 +/- 1.5%. The methyl chloride conversion appeared to be inducible, since H2 plus CO2-grown cells lacked this ability. From the morphological and physiological characteristics, the isolate could not be affiliated to a known species.