Isolation of thermophilic obligately autotrophic hydrogen-oxidizing bacteria, similar to Hydrogenobacter thermophilus, from Icelandic hot springs

Abstract

Thermophilic obligately autotrophic hydrogen-oxidizing bacteria were isolated from several alkaline hot springs in Iceland. The bacteria were Gram negative rods, 0.4–0.5 μm in diameter and 3–4 μm long but 6–7 μm long cells without septa were often seen. Long and short laments are formed. Spores, flagella or lipid granules were not observed. Strains H1 and H12 grew optimally at 70° C and pH 6.5 under mixture of air plus 0.6 atm H2 and 0.1 atm CO2. The cells contained cytochromes and carotenoid-like pigments. They would not grow on agar or silicia gel plates. The cells would not grow heterotrophically on organic substrates and were inhibited by most of these same organic compounds and agar in low concentrations. They were very sensitive to common antibiotics. The role of these bacteria in the hot spring ecosystem is discussed.