Environmental and Applied Microbiology (Shin-ichi MIYOSHI)

Environmental and Applied Microbiology Shin-ichi MIYOSHI, PhD


Major Areas of Research

Pathogenic and beneficial actions of environmental microorganisms: infectious diseases, food poisoning and bioremediation

  1. Quorum-sensing (QS) regulation systems in human pathogenic vibrios (Fig. 1).
  2. Pathological and biological actions of bacterial protein toxins and their domains.
  3. Bioremediation of chemical pollutants by using environmental microorganisms.


Fig.1. Infectious diseases caused by vibrios and quorum-sensing regulation systems


Current Research Interests and Recent Research Progress

  1. Many bacteria have the quorum-sensing (QS) regulation systems to recognize the cell density of the surrounding environment, and to adapt to the change of the environmental condition. Namely, when the cell density is increased, the bacteria start several coordinated actions, such as production of antibacterial agents and/or extracellular enzymes and formation of the biofilm, which may contribute to cause infectious diseases. Therefore, the effective prevention of infectious diseases is possible by the artificial control of the QS regulation system. We have investigated the QS regulation systems of human pathogenic Vibrio species, and the systems were found to be commonly mediated by a small signal molecule termed autoinducer 2 (AI-2).
  2. For suitable control and prevention of bacterial infectious diseases, molecular studies on the action mechanisms of protein toxins and/or virulence factors are important. In our laboratory, the action mechanisms and maturation processes of cytolytic toxins and proteolytic enzymes from pathogenic Vibrio species have been studied.
  3. Microorganisms are useful tools for restoration of the soil or water environments polluted with the harmful chemical compounds. We recently isolated a bacterial strain that could digest dichloromethane and constructed the bioreactor through immobilization of the bacterial cells to the resins.

Selected Recent Publications

  1. Inactivation of Vibrio vulnificus hemolysin through mutation of the N- or C-terminus of the lectin-like domain. Miyoshi, S., Abe, Y., Senoh, M., Mizuno, T., Maehara, Y. and Nakao, H. (2011) Toxicon 57, 904-908.
  2. Defensive effects of human antimicrobial peotide a-defensins against Enterococcus faecalis. Miyoshi. S., Koyama, K., Mizuno, T., Kashihara, M., Maehara, Y. and Nakao, H. (2010) J Health Sci. 56, 618-622.
  3. Assimilation of metal ions bound to porphyrins or porphyrin-peptides by Vibrio vulnificus, a human pathogen inhabiting estuarine and marine environments. Miyoshi, S., Sasaki, T., Kaku, N., Inoue, T., Uozumi, N., Maehara, Y. and Nakao, H. (2010) Biocontrol Sci. 14, 1-6.
  4. Modulation of Vibrio mimicus hemolysin through limited proteolysis by an endogenous metalloprotease. Mizuno, T., Sultan, S.Z., Kaneko, Y., Yoshimura, T., Maehara, Y., Nakao, H., Tsuchiya, T., Shinoda, S. and Miyoshi, S. (2009) FEBS J. 276, 825-834.
  5. Differential gene expression and extracellular secretion of the collagenolytic enzymes by the pathogen Vibrio parahaemolyticus. Miyoshi, S., Nitanda, Y., Fujii, K., Li, T., Maehara, Y., Ramamurthy, T., Takeda, Y. and Shinoda, S. (2008) FEMS Microbiol. Lett. 283, 176-181.
  6. The crucial amino acid residue related to inactivation of Vibrio vulnificus hemolysin. Senoh, M., Okita, Y., Shinoda, S. and Miyoshi, S. (2008) Microb. Pathog. 44, 78-83.