A slightly halophilic, extremely halotolerant, alkaliphilic, and facultatively anaerobic rod bacterium was isolated from a decomposing marine alga collected in Okinawa, Japan. The isolate, designated O15-7
T, was Gram-positive, endospore-forming, catalase-positive, menaquinone-7-possessing bacterium that is motile by peritrichous flagella. The isolate was an inhabitant of marine environments; the optimum NaCl concentration for growth was 0.75–3.0% (w/v) with a range of 0–22.0%, and the optimum pH was 7.0–8.5 with a range of 5.5–9.5. Catalase was produced in aerobic cultivation but not in anaerobic cultivation. Carbohydrate, sugar alcohol or a related carbon compound was required for growth. In aerobic cultivation, the isolate produced pyruvate, acetate and CO
2 from glucose, and in anaerobic cultivation, it produced lactate, formate, acetate and ethanol with a molar ratio of approximately 2 : 1 : 1 for the last three products. No gas was produced anaerobically. Lactate yield per consumed glucose was markedly affected by the pH of the fermentation medium: 51% at pH 6.5 and 8% at pH 9.0. The cell-wall peptidoglycan contained
meso-diaminopimelic acid. Phylogenetically, the isolate occupied an independent lineage within the group composed of the halophilic/halotolerant/alkaliphilic and/or alkalitolerant species in
Bacillus rRNA group 1 with the highest 16S rRNA gene sequence similarity of 95.2% to the genus
Gracilibacillus. For this isolate,
Paraliobacillus ryukyuensis gen. nov., sp. nov. was proposed. The type strain, O15-7
T (G+C=35.6 mol%), has been deposited in the DSMZ, IAM, NBRC, and NRIC (DSM 15140
T=IAM 15001
T=NBRC 10001
T=NRIC 0520
T).
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