Production of hydrogen sulfide from tetrathionate by the iron-oxidizing bacterium Thiobacillus ferrooxidans NASF-1

Kim Yong Ng, Kazuo Kamimura, Tsuyoshi Sugio

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

When incubated under anaerobic conditions, five strains of Thiobacillus ferrooxidans tested produced hydrogen sulfide (H2S) from elemental sulfur at pH 1.5. However, among the strains, T. ferrooxidans NASF-1 and AP19-3 were able to use both elemental sulfur and tetrathionate as electron acceptors for H2S production at pH 1.5. The mechanism of H2S production from tetrathionate was studied with intact cells of strain NASF-1. Strain NASF-1 was unable to use dithionate, trithionate, or pentathionate as an electron acceptor. After 12 h of incubation under anaerobic conditions at 30°C, 1.3 μmol of tetrathionate in the reaction mixture was decomposed, and 0.78 μmol of H2S and 0.6 μmol of trithionate were produced. Thiosulfate and sulfite were not detected in the reaction mixture. From these results, we propose that H2S is produced at pH 1.5 from tetrathionate by T. ferrooxidans NASF-1, via the following two-step reaction, in which AH2 represents an unknown electron donor in NASF-1 cells. Namely, tetrathionate is decomposed by tetrathionate-decomposing enzyme to give trithionate and elemental sulfur (S4O62-→S3O62- + S°, Eq. 1), and the elemental sulfur thus produced is reduced by sulfur reductase using electrons from AH2 to give H2S (S°+ AH2→H2S + A, Eq. 2). The optimum pH and temperature for H2S production from tetrathionate under argon gas were 1.5 and 30°C, respectively. Under argon gas, the H2S production from tetrathionate stopped after 1 d of incubation, producing a total of 2.5 μmol of H2S/5 mg protein. In contrast, under H2 conditions, H2S production continued for 6 d, producing a total of 10.0 μmol of H2S/5 mg protein. These results suggest that electrons from H2 were used to reduce elemental sulfur produced as an intermediate to give H2S. Potassium cyanide at 0.5 mM slightly inhibited H2S production from tetrathionate, but increased that from elemental sulfur 3-fold. 2,4-Dinitrophenol at 0.05 mM, carbonylcyanide-m-chlorophenyl- hydrazone at 0.01 mM, mercury chloride at 0.05 mM, and sodium selenate at 1.0 mM almost completely inhibited H2S production from tetrathionate, but not from elemental sulfur.

Original languageEnglish
Pages (from-to)193-198
Number of pages6
JournalJournal of Bioscience and Bioengineering
Volume90
Issue number2
DOIs
Publication statusPublished - Jan 1 2000

Keywords

  • Hydrogen sulfide
  • Sulfur reductase
  • Tetrathionate decomposition
  • Thiobacillus ferrooxidans

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

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