ISOLATION AND GROWTH-CHARACTERISTICS OF DEEP-SEA BAROPHILIC BACTERIA FROM THE JAPAN TRENCH

Deep-sea bacteria were isolated from seawater samples collected from t he Japan Trench by repeatedly culturing in liquid and solid media. A m odified High-Pressure-Temperature Gradient Instrument (PTG apparatus) was constructed to observe growth responses of the isolated deep-sea b acteria under the combination of various pressure and temperature leve ls. Growth characteristics of two deep-sea bacterial strains isolated from different depths were studied with this PTG system. An obligate b arophilic bacterium, strain JT761, showed growth in the temperature ra nge between 0 and 14 degrees C and pressure between 30 and 70 MPa, and showed optimum growth, 0.054 h(-1), at 60 MPa and 1.8 degrees C. A fa cultative barophilic bacterium, strain JT403, showed growth in the tem perature range between 0 and 14 degrees C and pressure between 0.1 and 60 MPa, and showed optimum growth, 0.047 h(-1), at 20 MPa and 5.1 deg rees C.