Constrictibacter antarcticus gen. nov., sp nov., a cryptoendolithic micro-organism from Antarctic white rock

A Gram-negative, non-spore-forming, ovoid to rod-shaped aerobic or microaerobic bacterium, strain 262-8(T), was isolated from a cavity within white rock collected in Antarctica. Strain 262-8(T) grew at 5-30 degrees C (optimum 25 degrees C), at pH 6-8 (optimum approximately pH 7) and with 0.1-2.0% (w/v) NaCl (optimum 0.5% NaCl). The addition of tryptone or yeast extract was essential for growth. Strain 262-8(T) was able to utilize organic compounds such as ribose, pyruvate and succinate in the presence of a low concentration of tryptone. Ubiquinone 10 was the major respiratory quinone. The major fatty acids were C(18:1), C(16:0) and C(18:0). The G+C content of the genomic DNA was 69.8 mol%. Comparative analyses of 16S rRNA gene sequences and physiological characteristics indicated that strain 262-8(T) was a phylogenetically novel bacterium that should be classified in a new genus of the family Rhodospirillaceae, for which the name Constrictibacter antarcticus gen. nov., sp. nov. is proposed. The type strain of the type species is 262-8(T) (= JCM 16422(T) = ATCC BAA-1906(T)).