Acetogenic coccoid spore-forming bacteria isolated from the rumen

SUMMARY Thirteen strains of a new acetogenic bacterium were isolated from the tureen contents of lambs, llamas and bisons. This paper is the first report of Gram-positive coccoid spore-forming bacteria occurring in chains and able to use H. + CO2as energy source and produce acetate from this gas mixture. One of them. chosen as the reference strain for its efF¢iency in utilizing HzlCO 2 likely via the acetyI-CoA pathway, was characterized in detail. The G+C ratio ef the DNA of the organism was 46.5 mol%. The temperature and pH optimum were 370-400C and 6.3-6.8, respectively. Numerous organic substrates including some ~methylate aromatic compounds were used heterotrophically. The full 16S rRNA gene sequence was determined. The phylogeny, physiology, morphology and numerous features described here are sufficiently different from those of any bacteria described today to justify the definition of a new species. The name "New acetogenic bacterium" is temporarily proposed, awaiting a future taxonomic revision of the genus Clostridium.