CHARACTERIZATION OF BAROPHILIC DEEP-SEA MICROORGANISMS

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To characterize barophilic deep-sea microorganisms, studies were conducted from two ways, namely, one during a cruise on board the research vessel, Hakuho-maru or Tansei-maru, Ocean Research Institute, University of Tokyo, and another one in the laboratory with isolated strains of bacteria from deep-sea. During the cruise by Hakuho-maru, several strains of barophilic deep-sea bacteria were isolated from the Japan Trench under pressure. The growth characteristics of these strains were investigated using High-Pressure-Temperature-Gradient Instrument (PTG apparatus). One strain JT403, isolated from 4000m, showed optimum growth, 0.047 h^<-1>, at 20MPa and 5.1C.Another obligate barophilic bacterial strain JT 761, showed optimum growth, 0.054h-1, at 600MPa and 1.8 C.Grouping of 60 marine Vibrio strains isolated from surface water to deep-sea in the Pacific Ocean using PCR/RFLP analysis of 16S rRNA genes were conducted. The clusters were depended on the isolated n niche of the strains and showed significant differences in the genotype composition between the strains from the deep-sea and the coastal area of Japan. One large phylogenetic line was psychrophilic or psychrotrophic deep-sea vibrios very close to Vibrio marinus. Another line was V.splendidus-like group distributed in the coastal area of Japan.