ACETOGENIC COCCOID SPORE-FORMING BACTERIA ISOLATED FROM THE RUMEN

Thirteen strains of a new acetogenic bacterium were isolated from the rumen contents of lambs, Ilamas and bisons. This paper is the first re port of Gram-positive coccoid spore-forming bacteria occurring in chai ns and able to use H-2 + CO2 as energy source and produce acetate from this gas mixture. One of them, chosen as the reference strain for its efficiency in utilizing H-2/CO2 likely via the acetyl-CoA pathway, wa s characterized in detail. The G+C ratio of the DNA of the organism wa s 46.5 mol%. The temperature and pH optimum were 37 degrees-40 degrees C and 6.3-6.8, respectively. Numerous organic substrates including so me o-methylate aromatic compounds were used heterotrophically. The ful l 16S rRNA gene sequence was determined. The phylogeny, physiology, mo rphology and numerous features described here are sufficiently differe nt from those of any bacteria described today to justify the definitio n of a new species. The name ''New acetogenic bacterium'' is temporari ly proposed, awaiting a future taxonomic: revision of the genus Clostr idium.