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

Tsuyoshi Sugio, Tadayoshi Kanao, Hirotaka Furukawa, Toru Nagasawa, Robert C. Blake

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

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 tool of tetrathionate into 7 mol of thiosulfate and 2 tool 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.

Original languageEnglish
Pages (from-to)233-238
Number of pages6
JournalJournal of Fermentation and Bioengineering
Volume82
Issue number3
DOIs
Publication statusPublished - Jan 1 1996

Keywords

  • Thiobacillus ferrooxidans
  • chemolithotrophic bacterium
  • sulfur metabolism
  • tetrathionate-decomposing enzyme

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology

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