This study will address the question: What are the physiological characteristics of those microorganisms that are responsible for the mineralization processes in the deep sea? And more specifically: Are the temperature and pressure adaptations of deep-sea bacteria invariable with nutrition? Strains from a stock of known barophilic (pressure tolerant) organisms, as well as freshly-obtained deep sea isolates, will be used. Growth experiments will be carried out: 1. as continuous culture experiments at atmospheric pressure, and at in situ substrate concentrations and a temperature range of 2-20 oC; and 2. as batch cultures at in situ pressures, and temperatures again of 2- 20 oC and nutrient substrates at the experimentally lowest possible concentrations attainable. Under experimental conditions, changes in population density (cell counts and biomass) and/or radioactive substrate turnover will be used as a sensitive indicator of growth rate response to changes of the various controllable environmental factors: temperature, pressure and substrate concentration. This study potentially will provide new insights into factors regulating microbial growth and the rates of microbial transformations of matter in deep sea environments.
