Isolation of an obligately chemolithoautotrophic, halophilic and aerobic hydrogen-oxidizing bacterium from marine environment

An obligately chemolithoautotrophic and aerobic hydrogen-oxidizing bacterium was isolated from seawater of the Shonan Coast, Kanagawa Pref., Japan. The isolate was a Gram-negative, comma-shaped rod cell measuring 0.2 to 0.5 by 1 to 2 μm. The cells occurred singly and were motile by a polar flagellum. The deoxyribonucleic acid base composition of the isolate was 44.1 mol% guanine plus cytosine. The optimal temperature for autotrophic growth on H₂‑O₂‑CO₂ was around 37°C, and no growth was observed at 5° C or 45° C. The optimal pH for growth was around 6.5. NaCl was required for growth with an optimum of 0.5 M. Elemental sulfur, thiosulfate or tetrathionate was utilized, as well as molecular hydrogen, as the sole energy source. No heterotrophic growth was observed on organic media tested. To our knowledge, this is the first report of the isolation of a marine, aerobic hydrogen-oxidizing bacterium, and of an obligately chemolithoautotrophic, mesophilic and aerobic hydrogen-oxidizing bacterium.