Experiments in Deep-Sea Biology

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9415371 Jannasch The principal objective of this project is to study the major growth characteristics of those microorganisms that are actively growing and mineralizing organic carbon in the deep-sea. The project will test the hypothesis whether adaptation to in situ temperature and pressure (psychrophily and barophily) of deep-sea bacteria are invariant with nutrition. More specifically, whether oligotrophy (adaptation to growth at extremely low nutrient levels) and barophily are metabolically linked in the microbial deep-sea flora. Earlier observations during the last research period with batch culture studies at various pressures and with continuos culture studies at 1 Atm, resulted in data that clearly indicated an effect of substrate concentration on barophilic activity. The data also demonstrated the need for working with typical oligotrophic bacteria in the presence of substrate concentrations lower than those inherent to batch culture and the need to carry out growth experiments in steady state cultures under pressure. To this end a new pressurizable chemostat has been designed and constructed. This project will employ existing pressure equipment in combination with the new capability to enrich for deep-sea bacteria at low substrate levels in the pressurized chemostat. The pressurizable chemostat will be used to obtain deep-sea samples in the absence of decompression for the isolation of truly oligotrophic barophiles. The significance of this work lies in the fact that the microbial turnover of the largest portion of dissolved organic carbon in the biosphere, the oceanic portion, is unknown. Data clarifying the metabolic strategies of the adapted deep-sea bacteria will be of great value for calculation of the global carbon cycle. ***