MORPHOLOGICAL, PHYSIOLOGICAL, AND CHEMOTAXONOMICAL CHARACTERISTICS OF IRON- AND SULFUR-OXIDIZING BACTERIA ISOLATED FROM ACID MINE DRAINAGE WATERS

Abstract

Two strains, Fe1 and Fe2, of iron-oxidizing bacteria from acid drainage water at the Matsuo mine showed dissimilar characteristics of red-brown colonies on FeSO₄-9K silica gel plates. The Fe1 colonies were large and irregular. The Fe2 colonies were minute and circular. These bacteria, identified as Thiobacillus ferrooxidans on the basis of their physiological and chemotaxonomical properties (fatty acid composition, ubiquinone type, and DNA base composition), were different strains. Fe2 differed from Fe1 in its extremely low oxidizing activity of sulfur and thiosulfate. Two strains, S2 and S3, of sulfur-oxidizing bacteria were separately isolated on Na₂S₂O₃-9K silica gel plates and agar plates, respectively. However, S2 and S3 formed pale brown and pale yellow colonies on the silica gel and agar plates, respectively. Since these two strains were identical in their properties, they were judged to be quite similar or the same strain. From their morphological, physiological, and chemotaxonomical properties, they were identified as Thiobacillus thiooxidans. The oxidation characteristics of both sulfur and thiosulfate by the strains of iron- and sulfur-oxidizing bacteria were also investigated.