Isolation and identification of an iron-oxidizing bacterium which can grow on tetrathionate medium and the properties of a tetrathionate-decomposing enzyme isolated from the bacterium

• Published in: Journal of fermentation and bioengineering 1996-01, Vol.82 (3), p.233-238
• Main Authors: Sugio, Tsuyoshi, Kanao, Tadayoshi, Furukawa, Hirotaka, Nagasawa, Toru, Blake, Robert C.
• Format: Article
• Language: English
• Subjects: BACTERIA; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; chemolithotrophic bacterium; FER; Fundamental and applied biological sciences. Psychology; HIERRO; IDENTIFICACION; IDENTIFICATION; IRON; Isolation and description; Mission oriented research; OXIDACION; OXIDATION; OXYDATION; sulfur metabolism; tetrathionate-decomposing enzyme; Thiobacillus ferrooxidans
• ISSN: 0922-338X
• DOI: 10.1016/0922-338X(96)88813-1

Among 150 pure strains of iron-oxidizing bacteria obtained from natural environments, two strains, Funis 2-1 and OK1-50, had the ability to use potassium tetrathionate (K2S4O6) as a sole energy source for growth. Funis 2-1 was a gram-negative, rod-shaped, acidophilic iron- and sulfur-oxidizing chemolithotrophic bacterium and had the same cytochrome composition and mean G + C content of DNA as Thiobacillus ferrooxidans, indicating that the strain is T. ferrooxidans. A tetrathionate-decomposing enzyme that catalyzes the disproportionate metabolism of 4 mol of tetrathionate into 7 mol of thiosulfate and 2 mol of sulfate was located on the plasma membrane of K2S4O6-grown, but not Fe2+-grown Funis 2-1 cells. Washed intact cells and cell extracts prepared from Funis 2-1 cells grown on K2S4O6 medium supplemented with more than 11 mM FeSO4 did not show K2S4O6-decomposing enzyme activity. K2S4O6-decomposing enzyme was purified to homogeneity from K2S4O6-grown Funis 2-1 cells. The apparent molecular weight of this enzyme was estimated to be 50,000 by gel filtration, 50,000 by SDS-PAGE, and 49,600 using a time-of-flight mass spectrometer, indicating that the enzyme is monomeric. The enzyme was most active at pH 3.5 and 50°C and the activity was enhanced approximately 18 fold by a concentration of 200 mM of sulfate ion. The Michaelis constant of this enzyme for K2S4O6 was 0.73 mM.