Carboxydocellca sporoproducens sp nov., a novel anaerobic CO-utilizing/H2-producing thermophilic bacterium from a Kamchatka hot spring

A novel anaerobic, thermophilic, CO-utilizing bacterium, strain Kar(T), was isolated from a hot spring of Karymskoe Lake, Kamchatka Peninsula. The cells of the novel isolate were Gram-positive, spore-forming, short rods. The bacterium grew chemolithoautotrophically on CO, producing equimolar quantities of H-2 and CO2 (according to the equation CO + H2O -> CO2 + H-2), and in the absence of CO, under N-2 in the gas phase, chemoorganolneterotrophically with yeast extract, sucrose or pyruvate. Growth was observed in the temperature range 50-70 degrees C, with an optimum at 60 degrees C, and in the pH range 6.2-8.0, with an optimum at pH 6.8. The micro-organism did not grow on solid media; it was able to grow only in semi-solid medium containing 0.5% agar. The generation time under optimal conditions for chemolithoautotrophic growth was 1 h. The G+C content of the DNA was 46.5 +/- 1 mol%. Growth was completely inhibited by penicillin, novobiocin, streptomycin, kanamycin and neomycin. Analysis of the 16S rRNA gene sequence showed that the isolate should be assigned to the genus Carboxydocella. On the basis of the results of DNA-DNA hybridization and morphological and physiological analyses, strain KarT represents a novel species of the genus Carboxydocella, for which the name Carboxydocella sporoproducens sp. nov, is proposed. The type strain is Kar(T) (= DSM 16521(T) = VKM B-2358(T)).