[METHYL-H-3]THYMIDINE AND [H-3] LEUCINE INCORPORATION IN VIBRIO SPP GROWN IN NUTRIENT-LIMITED CONTINUOUS CULTURES

Vibrio alginolyticus, Vibrio logei, Vibrio natriegens, and Vibrio neri es were grown in nutrient-limited continuous cultures at generation ti mes (T-D) of 5-135 h on complex media with cell yields of 0.8-12 x 10( 6) bacteria/mL. Average cell volume, as determined by image analysis o f video fluorescence microscopy, decreased for V. logei and V. neries, did not change for V. alginolyticus, and increased for V. natriegens with increasing T-D. The increase in cell volume observed for V. natri egens was due to the development of filamentous cells. Batch cultures were grown on media with 10 times the nutrient concentration of contin uous cultures. Tritiated thymidine incorporation was measured using ph enol-chloroform extractions; leucine incorporation was measured in tri chloroacetic acid precipitates. At concentrations of exogenous thymidi ne high enough to inhibit de novo synthesis of thymidine, the number o f bacteria produced per mole of thymidine incorporated did not vary wi th changing generation time, or between batch and continuous cultures examined in this study. However, the number of bacteria produced per m ole of leucine incorporated decreased per unit production with increas ing T-D for all four vibrios. A significant difference in the bacteria l production conversion factor (bacteria produced per mole of label in corporated) for thymidine was found for V. neries relative to the thre e other Vibrio species, but no significant differences were found betw een growth conditions within species. Corrections for biovolume differ ences between species and growth rates reduced variability in conversi on factors, and also yielded a significantly different conversion fact or for V. neries. Conversion factors for leucine incorporation spanned three orders of magnitude, from 10(15) to 10(18) bacteria/mol of leuc ine incorporated.