Isolation and Growth Characteristics of Deep-Sea Barophilic Bacteria from the Japan Trench

Abstract

Deep-sea bacteria were isolated from seawater samples collected from the Japan Trench by repeatedly culturing in liquid and solid media. A modified High-Pressure-Temperature Gradient Instrument (PTG apparatus) was constructed to observe growth responses of the isolated deep-sea bacteria under the combination of various pressure and temperature levels. Growth characteristics of two deep-sea bacterial strains isolated from different depths were studied with this PTG system. An obligate barophilic bacterium, strain JT761, showed growth in the temperature range between 0 and 14°C and pressure between 30 and 70 MPa, and showed optimum growth, 0.054 h-1, at 60 MPa and 1.8°C. A facultative barophilic bacterium, strain JT403, showed growth in the temperature range between 0 and 14°C and pressure between 0.1 and 60 MPa, and showed optimum growth, 0.047 h-1, at 20 MPa and 5.1°C.