Chemotactic Responses of Marine Vibrio sp. Strain S14 (CCUG 15956) to Low-Molecular-Weight Substances under Starvation and Recovery Conditions

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The chemotactic responses by starved cells of marine Vibrio sp. strain S14 differed from those elicited by cells that were not nutrient limited. The rate of chemotaxis at different concentrations of several attractants varied for starved and growing cells. Vibrio sp. strain S14 showed positive chemotaxis to leucine, valine, arginine, and glucose at the onset of energy and nutrient deprivation. A continued, though decreased, positive response was demonstrated fro leucine, arginine, and glucose at 10 h of starvation. Cells starved for 3 h displayed a stronger response to glucose than those starved for shorter or longer times. However, cells starved for 5 and 10 h responded more strongly to a lower concentration of glucose than did cells starved for 0 and 3 h. Starvation for 24 h elicited no measurable chemotaxis to leucine, arginine, or glucose. The motility decreased by over 95% in the cell population after 24 h of starvation, which resulted in a low sensitivity in the chemotaxis assay. A switch in the response to valine was observed by 3 h of starvation. The addition of nutrients of 22-h-starved cells elicited a temporary positive chemotactic response to leucine by 2 and 4 h of nutrient recovery, while cells at 1 and 6 h of recovery showed no response. At 2 h of recovery, the greatest response was recorded to 10−4 M leucine, whereas at 4 h it was to 10−2 M leucine. Ten to fifty percent of the 22-h-starved cell population regained their motility after 4 h of nutrient-aided recovery. It is possible that two types of chemosensory systems exist in marine bacteria. Starved and growing cells responded to different concentrations of the attractant, and growing cells displayed a saturated chemotactic system with leucine as the attractant, unlike the response during starvation.

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