Graduate School of Environmental and Life Science | Okayama University

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Microbial Function

Applied and environmental microbiology on chemoautotrophic iron- and sulfur-oxidizing bacteria

Staff

Takashi_TAMURA
  • Prof. TAMURA Takashi , Ph. D.
  • E-mail:tktamura@(@cc.okayama-u.ac.jp)
  • Application of Microbial Enzymes for Bioenergy Development
> Directory of Researchers > Research Introduction
Tadayoshi_KANEO
  • Assoc. Prof. KANAO Tadayoshi , Ph. D.
  • E-mail:tkanao@(@okayama-u.ac.jp)
  • Analysis of the mechanism for sulfur metabilism in acidophilic bacteria
> Directory of Researchers

Research Topics

Chemolithotrophic microorganisms (bacteria and archaea) are widespread among extreme environments such as high temperature (> 55°C), low pH (< 3) and high salinity. Acidic environments may occur naturally in geothermal areas, or arise due to human activities (especially metals and coal mining). The iron- and sulfur-oxidizing bacteria play a key role as primary producers in the acidic environments. Also, they are important for biomining owing to their ability to produce ferric iron and sulfate. One of our research topic aims to clarify the dissimilatory oxidation of reduced inorganic sulfur compounds (RISCs) in these bacteria. They have unique enzymes to oxidize RISCs. These enzymes (and sometimes whole cells) are interesting not only scientific aspects but also industrial applications. Tetrathionate hydrolase (4THase) is one of the "unique" proteins involving in the RISCs oxidation in acidophilic iron- and sulfur-oxidizing bacterium Acidithiobacillus ferrooxidans. We have identified the gene encoding the enzyme for the first time and successfully obtained the recombinant 4THase as an active form. We investigate the 3D structure, reaction mechanism, the gene expression, and the regulations. Another RISCs oxidation enzymes such as thiosulfate dehydrogenase are also investigated from marine acidophiles and moderate thermophilic sulfur-oxidizing bacteria as well as A. ferrooxidans. We are interested in microbial communities in acidic environments such as acid mine drainage (AMD). Yanahara pyrite mine is located in North-East Okayama prefecture. We investigate the microbial communities in the AMD from Yanahara mine. Many acidophilic iron- or sulfur- (or both) oxidizing microorganisms were detected by DGGE and RFLP analyses. These bacteria could be used for AMD treatment to avoid environmental damage.

Publication List

  • Kanao, T., Kosaka, M., Yoshida, K., Nakayama, H., Tamada, T., Kuroki, R., Yamada, H., Takada, J., Kamimura, K.: Crystallization and X-ray diffraction analysis of tetrathionate hydrolase from Acidithiobacillus ferrooxidans. Acta Crystallogr. Sect. F, Struct. Biol. Cryst. Commun., 69, 692-694 (2013)
  • Kikumoto, M., Nogami, S., Kanao, T., Takada, J., Kamimura, K.: Tetrathionate-forming thiosulfate dehydrogenase from the acidophilic, chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans.Appl. Environ. Microbiol.,79, 113-120 (2013)
  • Johnson, D. B., Kanao, T., Hedrich, S.: Redox transformations of iron at extremely low pH: Fundamental and applied aspects,Front. Microbiol.,3, Article 96 (2012)
  • Manchur, M. A., Kikumito, M., Kanao, T., Takada, J., Kamimura, K.: Characterization of an OmpA-like outer membrane protein of the acidophilic iron-oxidizing bacterium,Acidithiobacillus ferrooxidans,Extremophiles,15, 403-410 (2011)
  • Kanao T., Matsumoto C., Shiraga K., Yoshida K., Takada J., Kamimura K.: Recombinant tetrathionate hydrolase from Acidithiobacillus ferrooxidans requires exposure to acidic condition for proper folding.FEMS Microbiol. Lett.,309, 43-47 (2010)

Introduction Video