ISOLATION AND SOME PROPERTIES OF A MODERATELY THERMOPHILIC IRON-OXIDIZING BACTERIUM

A novel moderately thermophilic iron-oxidizing bacterium was isolated from a coal dump in Iizuka City, Japan, and designated strain TI-1. St rain TI-1 was a Gram negative, non-spore-forming, and rod-shaped bacte rium, which had a optimum temperature and pH for growth at 48-degrees- C and 2.2, respectively. The mean G+C content of the DNA was 56.2 mol% . Strain TI-1 required yeast extract for growth and did not have the a bility to fix carbon dioxide as a carbon source, indicating that the s train is not chemolithoautotroph. When grown on Fe2+ (1.7%)-yeast extr act medium, Fe2+ was oxidized concomitantly with cell growth. The opti mum pH and temperature for Fe2+ oxidation by washed intact cells of TI -1 were 2.8 and 50-degrees-C, respectively. The properties of strain T I-1 shown above, such as the G+C mol content of the DNA, the requireme nt of yeast extract for growth, and the inability to fix carbon dioxid e, suggest that strain TI-1 belongs to a new type of mederately thermo philic, acidophilic iron-oxidizing bacterium.