BAROPHILIC BACTERIA IN SOME DEEP SEA SEDIMENTS

Abstract

Bacterial populations ranging from 103 to 106 per g wet mud were demonstrated in several samples taken from water depths of 7000 to 10,000 m on the Galathea Deep-sea Expedition. Many of the bacteria taken from such depths grew in nutrient medium only when compressed to pressures of 700 to 1000 atm. Deep-sea bacteria which grew at 1 atm. but not at the high pressures characteristic of the environment where found may be dormant aliens from shallower depths or they may be passive mutants. Cultures of obligate barophilic sulfate-reducing bacteria were transplanted several times and maintained in the laboratory for more than 5 years at a pressure of 700 atm. Such barophilic bacteria, like psychrophilic forms, grow very slowly at high pressures and low temperatures. Many barophilic bacteria were found associated with deep-sea fauna. Bacteria may contribute substantially to the nutrition of animals on the deep-sea floor.