Mechanism of growth inhibition by tungsten in Acidithiobacillus ferrooxidans

• Published in: Bioscience, biotechnology, and biochemistry Vol. 65; no. 3; pp. 555 - 562
• Main Authors: Sugio, T. (Okayama Univ. (Japan)), Kuwano, H, Negishi, A, Maeda, T, Takeuchi, F, Kamimura, K
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Society for Bioscience, Biotechnology, and Agrochemistry 01-03-2001; Japan Society for Bioscience Biotechnology and Agrochemistry; Oxford University Press
• Subjects: Acidithiobacillus ferrooxidans; BACTERIA; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Culture Media; CYTOCHROME C OXIDASE; cytochrome-c oxidoreductase; Electron Transport Complex IV - metabolism; Ferrous Compounds - metabolism; Fundamental and applied biological sciences. Psychology; Gammaproteobacteria - drug effects; Gammaproteobacteria - growth & development; Gammaproteobacteria - metabolism; GROWTH INHIBITORS; Hydrogen-Ion Concentration; inhibition site; IRON; Metals; Mission oriented research; OXIDATION; Oxidation-Reduction; Physiology and metabolism; sodium molybdenum; sodium tungstate(VI); TUNGSTEN; Tungsten - metabolism; Tungsten Compounds - metabolism; Tungsten Compounds - pharmacology; Microorganism growth; Enzymatic activity; Enzyme; Tungsten; Cytochrome-c oxidase; Bacteria; Iron; Oxidation; Oxidoreductases; Inhibition; Mechanism
• ISSN: 0916-8451; 1347-6947
• DOI: 10.1271/bbb.65.555

Cell growth of three hundred iron-oxidizing bacteria isolated from natural environments was inhibited strongly by 0.05 mM, and completely by 0.2 mM of sodium tungstate (Na
2
WO
4
), respectively. Since no great difference in the level of tungsten inhibition was observed among the 300 strains tested, the mechanism of inhibition by Na
2
WO
4
was studied with Acidithiobacillus ferrooxidans strain AP19-3. When resting cells of AP19-3 were incubated in 0.1 M β-alanine-SO
2-
4
buffer (pH 3.0) with 0.1 mM Na
2
WO
4
for 1 h, the amount of tungsten bound to the cells was 12 μg/mg protein. The optimum pH for tungsten binding to the resting cells was 2∼3. Approximately 2 times more tungsten bound to the cells at pH 3.0 than at pH 6.0 The tungsten binding was specifically inhibited by sodium molybdenum. However, copper, nickel, cadmium, zinc, manganese, cobalt, and vanadate did not disturb tungsten binding to the resting cells. The iron-oxidizing activity of AP19-3 was inhibited 24, 62, and 77% by 1, 5, and 10 mM of Na
2
WO
4
, respectively. Among the components of iron oxidation enzyme system, iron: cytochrome c oxidoreductase activity was not inhibited by 10 mM of Na
2
WO
4
. In contrast, the activity of cytochrome c oxidase purified highly from the strain was inhibited 50 and 72%, respectively, by 0.05 and 0.1 mM of Na
2
WO
4
. The amounts of tungsten bound to plasma membrane, cytosol fraction, and a purified cytochrome c oxidase were 8, 0.5, and 191 μg/mg protein, respectively. From the results, the growth inhibition by Na
2
WO
4
observed in A. ferrooxidans is explained as follows: tungsten binds to cytochrome c oxidase in plasma membranes and inhibits cytochrome c oxidase activity, and as a results, the generation of energy needed for cell growth from the oxidation of Fe
2+
is stopped.