Influences of temperature, salinity and starvation on the motility and chemotactic response of Vibrio anguillarum

The role of growth factors for the motility and chemotaxis of the fish pathogen Vibrio anguillarum was determined. Cells of V anguillarum were chemotactic to serine in the temperature range 5-25 degreesC and in 0.8-2-7% NaCl. The chemotactic response was significantly higher at 25 degreesC than at 5 or 15 degreesC. Growth in medium with 1(.)5% NaCl gave a higher response than growth with 3% NaCl; when the salinity of the chemotaxis buffer was raised, the chemotactic response was reduced. The role of starvation was also studied; V. anguillarum showed a high chernotactic response after starvation for 2 and 8 days. Motility and chemotaxis are important virulence factors for this bacterium. Not only was the ability to perform chernotactic motility maintained after starvation, but also it was shown that starvation does not interfere with the ability of the organism to cause infection in rainbow trout after a bath challenge. The swimming speed was reduced at lower temperatures. Within the range of salinity and starvation studied, the motile cells swam with the same velocity, indicating that V. anguillarum under all the examined conditions has a functional flagellum and rotates it with constant speed. Phenamil, a specific inhibitor of Na+-driven flagella, reduced the motility of both starved and non-starved cells of V anguillarum indicating that, in both cases, a Na+ motive force drives the flagellum.