Starved cultures of a marine Pseudomonas sp. showed a 99.9% decrease in viable cell count during the first 25 days of starvation, yet the culture maintained 105 viable cells per ml for over 1 year. The physiological responses of populations of a marine Pseudomonas sp. to nutrient starvation were observed for periods of up to 40 days. At various intervals during starvation, the numbers of total, viable, and respiring cells were determined within the cultures. The ATP content, endogenous respiration rate, uptake rates, and percent respiration for exogenous glucose and glutamate were determined throughout the starvation period to characterize the physiological changes in the cells. It was observed that, after initial adjustment periods, all parameters tested reached stabilized states after 18 to 25 days of starvation. The results indicate that the actively respiring subpopulation, rather than the viable or total cell numbers, is the most appropriate denominator for interpretation of observed activities on an individual cell basis.
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