Vibrio alginolyticus, Vibrio logei, Vibrio natriegens, and Vibrio neries were grown in nutrient-limited continuous cultures at generation times (TD) of 5–135 h on complex media with cell yields of 0.8–12 × 106 bacteria/mL. Average cell volume, as determined by image analysis of video fluorescence microscopy, decreased for V. logei and V. neries, did not change for V. alginolyticus, and increased for V. natriegens with increasing TD. The increase in cell volume observed for V. natriegens was due to the development of filamentous cells. Batch cultures were grown on media with 10 times the nutrient concentration of continuous cultures. Tritiated thymidine incorporation was measured using phenol–chloroform extractions; leucine incorporation was measured in trichloroacetic acid precipitates. At concentrations of exogenous thymidine high enough to inhibit de novo synthesis of thymidine, the number of bacteria produced per mole of thymidine incorporated did not vary with changing generation time, or between batch and continuous cultures examined in this study. However, the number of bacteria produced per mole of leucine incorporated decreased per unit production with increasing TD for all four vibrios. A significant difference in the bacterial production conversion factor (bacteria produced per mole of label incorporated) for thymidine was found for V. neries relative to the three other Vibrio species, but no significant differences were found between growth conditions within species. Corrections for biovolume differences between species and growth rates reduced variability in conversion factors, and also yielded a significantly different conversion factor for V. neries. Conversion factors for leucine incorporation spanned three orders of magnitude, from 1015 to 1018 bacteria/mol of leucine incorporated.Key words: leucine, thymidine, bacterial production, chemostats.
Empirical Leucine-to-Carbon Conversion Factors for Estimating Heterotrophic Bacterial Production: Seasonality and Predictability in a Temperate Coastal Ecosystem
