Cetia pacifica gen. nov., sp nov., a chemolithoautotrophic, thermophilic, nitrate-ammonifying bacterium from a deep-sea hydrothermal vent

A thermophilic, anaerobic, chemolithoautotrophic bacterium, strain TB-6(T), was isolated from a deep-sea hydrothermal vent located on the East Pacific Rise at 9 degrees N. The cells were Gram-staining-negative and rod-shaped with one or more polar flagella. Cell size was approximately 1-1.5 mu m in length and 0.5 mu m in width. Strain TB-6(T) grew between 45 and 70 degrees C (optimum 55-60 degrees C), 0 and 35 g NaCl l(-1) (optimum 20-30 gl(-1)) and pH 4.5 and 7.5 (optimum pH 5.5-6.0). Generation time under optimal conditions was 2 h. Growth of strain TB-6(T) occurred with H-2 as the energy source, CO2 as the carbon source and nitrate or sulfur as electron acceptors, with formation of ammonium or hydrogen sulfide, respectively. Acetate, (+)-n-glucose, Casamino acids, sucrose and yeast extract were not used as carbon and energy sources. Inhibition of growth occurred in the presence of lactate, peptone and tryptone under a H-2/CO2 (80 :20; 200 kPa) gas phase. Thiosulfate, sulfite, arsenate, selenate and oxygen were not used as electron acceptors. The G +C content of the genomic DNA was 36.8 molo/o. Phylogenetic analysis of the 16S rRNA gene of strain TB-6(T) showed that this organism branched separately from the three most closely related genera, Caminibacter, Nautilia and Lebetimonas, within the family Nautiliaceae. Strain TB-6(T) contained several unique fatty acids in comparison with other members of the family Nautiliaceae. Based on experimental evidence, it is proposed that the organism represents a novel species and genus within the family Nautiliaceae, Cetia pacifica, gen. nov., sp. nov. The type strain is TB-6(T) (=DSM 27783T=JCM 19563(T)).