Caminicella sporogenes gen. nov., sp. nov., a novel thermophilic spore-forming bacterium isolated from an East-Pacific Rise hydrothermal vent

Abstract

A novel thermophilic, anaerobic, strictly chemoorganoheterotrophic bacterium, designated as AM1114T, was isolated from a deep-sea hydrothermal vent sample from the East-Pacific Rise (EPR 13 degrees N). The cells were long (3-10 microm) rods, motile with peritrichous flagella, and exhibited a gram-negative cell wall ultrastructure. In the late stationary phase of growth, cells formed an ovoid, refractile, terminal endospore. They grew at 45-65 degrees C inclusive (optimum 55-60 degrees C; doubling time approx. 45 min), at pH 4.5-8.0 inclusive (optimum pH 7.5-8.0) and at sea salt concentrations of 20-60 g l(-1) inclusive (optimum 25-30 g l(-1)). Strain AM1114T was an obligately heterotrophic bacterium able to ferment a mixture of 20 amino acids, complex proteinaceous substrates (such as yeast extract, brain-heart infusion or peptone), and carbohydrates such as glucose, galactose or maltose. The main fermentation products on glucose/yeast extract/peptone/sulfur medium were hydrogen, carbon dioxide, butyrate, ethanol, acetate, formate and L-alanine. The G+C content of the genomic DNA (determined by thermal denaturation) was 24.2+/-1 mol%. Phylogenetic analyses of the 16S rRNA gene located the strain within cluster XI of the lineage encompassing the genus Clostridium and related genera (sensu Collins et al., 1994), in the bacterial domain. On the basis of 16S rDNA sequence comparisons and physiological and biochemical characteristics, it is proposed that the isolate should be described as a novel genus, namely Caminicella gen. nov., of which Caminicella sporogenes sp. nov. is the type species. The type strain is AM1114T (= DSM 14501T = CIP 107141T).