Thermacetogenium phaeum gen. nov., sp nov., a strictly anaerobic, thermophilic, syntrophic acetate-oxidizing bacterium

novel anaerobic, thermophilic, syntrophic acetate-oxidizing bacterium, stra in PBT, was isolated from a thermophilic (55 degrees C) anaerobic methanoge nic reactor which had been treating kraft-pulp waste water. The bacterium o xidized acetate in co-culture with a thermophilic hydrogenotrophic methanog en. Strain PBT, a Cram-positive, spore-forming, rod-shaped bacterium grew o ptimally at 58 degrees C and pH 6.8. The bacterium grew acetogenically on s everal alcohols, methoxylated aromatics, pyruvate, glycine, cysteine, forma te and hydrogen/CO2. Strain PBT also oxidized acetate with reduction of sul fate or thiosulfate as the electron acceptor. The bacterium contained MK-7 as the major quinone. The G+C content of the DNA was 53.5 mol%. Comparative 16S rDNA analysis indicated that strain PBT belongs to the Bacillus-Clostr idium subphylum. However, it was distant from any known genera or microorga nism. The closest known relative was Thermoterrabacterium ferrireducens wit h 87.4% similarity. The name Thermacetogenium phaeum gen. nov., sp. nov. is proposed. The type strain is strain PBT (= DSM 12270(T)).