A methylotrophic, mesophilic, gram-negative sulfate-reducing bacterium, named strain UFZ B 378, was isolated from the sediment of a wastewater pond of a derelict sugar factory. The rod shaped to slightly curved cells are motile and 1.5 to 3.5 pm long and 0.5 pm wide. Formation of spores was not observed. The G+C content of the DNA was 58.7 mol%. Sulfate is used as electron acceptor, methanol can be used as sole source of carbon. Other electron donors included pyruvate, lactate, acetate, ethanol, butanol, propanol, choline, betaine, succinate, fumarate and benzoate without the addition of H,. Growth occurred from pH 4 to 9.0, the optimum pH was found to be around 7.0. The temperature range for growth was between 3 "C and 40 "C, with an optimum at 30 "C. Vitamins or other supplines were not required. The strain was found to be tolerant to ferric and ferrous sulfate (5 m and 100 m respectively) on their own and in combination in the culture medium. The pH in batch cultures with methanol increased from 6.3 to 8.0 over a period of 48 days due to the reduction of sulfate and formation of hydrogen sulfide. Production of methane was not found.