Maintenance of Different Mannitol Uptake Systems during Starvation in Oxidative and Fermentative Marine Bacteria

The mannitol uptake systems in marine Vibrio and Pseudomonas isolates from the kelp beds off the South African west coast were examined. The fermentative Vibrio isolate possessed a constitutive rapid mannitol uptake system and also a soluble mannitol-1-phosphate dehydrogenase, indicative of a mannitol phosphotransferase system. An inducible, relatively less active mannitol uptake system was detected in the oxidative Pseudomonas isolate, and this strain possessed a mannitol dehydrogenase. The maintenance of these systems during starvation survival was studied. The Vibrio isolate maintained its initial uptake system for approximately 5 weeks of starvation, after which time the uptake system was replaced by one with a higher affinity for mannitol. The mannitol transport system of the Pseudomonas isolate was depressed early in starvation (30 h) but could be readily induced by exogenous mannitol after 6 weeks of starvation. The relative proportions of mannitol which was incorporated and respired were determined in starved Vibrio and Pseudomonas strains.