Isolation and some properties of Thiobacillus ferrooxidans strains with differing levels of mercury resistance from natural environments

Fumiaki Takeuchi, Kenji Iwahori, Kazuo Kamimura, Tsuyoshi Sugio

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

Fifty iron-oxidizing bacteria isolated from natural environments were screened for resistance to mercuric ions (Hg2+). Thiobacillus ferrooxidans Funis 2-1, the strain found to show the greatest resistance to Hg2+ among the fifty isolates, gave a cell yield of 7.0 x 107 cells/ml after 8 d cultivation in an Fe2+-medium (pH 2.5) containing 0.7 μM Hg2+. Funis 2-1 volatilized 80% of the total mercury added to the medium over 8 d of cultivation. T. ferrooxidans AP19-3, more sensitive to Hg2+ than Funis 2-1, could not grow in an Fe2+-medium (pH 2.5) containing 0.7 μM Hg2+ even over a 28 d cultivation period. When resting cells of strains Funis 2-1 and AP19-3 were incubated for 3 h in a salt solution containing 0.7 μM Hg2+ (pH 3.0), 14.3% and 7.9% of the total mercury added to the reaction mixtures respectively, were volatilized. The activity of the mercuric reductase from Funis 2-1 was only 2.8 times higher than that of the enzyme from AP19-3. Since the markedly higher mercury resistance of Funis 2-1 compared with that of AP19-3 cannot be explained only by the level of the mercuric reductase activity, the levels of mercury resistance of iron oxidase and cytochrome c oxidase were studied. The 1 μM mercuric ions inhibited the 35% of iron- oxidizing activity from AP19-3. In contrast, the same concentration of Hg2+ did not inhibit the activity of iron oxidase from Funis 2-1. In the case of the cytochrome c oxidases purified from both strains, the 0.2 μM Hg2+ inhibited approximately 40% of cytochrome c oxidizing activity from AP19-3, on the contrary, the activity of the enzyme from Funis 2-1 was activated 1.8- and 1.2-fold, respectively, in the presence of 0.08 and 0.2 μM Hg2+. Since cytochrome c oxidase is one of the most important components of the iron- oxidizing system, these results indicate that both the existence of cytochrome c oxidase resistant to Hg2+ as well as that of mercuric reductase in the cells is responsible for the more rapid growth of Funis 2-1 than that of in an Fe2+-medium containing 0.7 μM Hg2+.

Original languageEnglish
Pages (from-to)387-392
Number of pages6
JournalJournal of Bioscience and Bioengineering
Volume88
Issue number4
DOIs
Publication statusPublished - 1999

Keywords

  • Iron-oxidizing bacterium
  • Mercuric reductase
  • Mercury resistance
  • Thiobacillus ferrooxidans

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

Fingerprint

Dive into the research topics of 'Isolation and some properties of Thiobacillus ferrooxidans strains with differing levels of mercury resistance from natural environments'. Together they form a unique fingerprint.

Cite this