PLASMID TRANSFER BETWEEN MARINE VIBRIO STRAINS DUPING PREDATION BY THE HETEROTROPHIC MICROFLAGELLATE CAFETERIA-ROENBERGENSIS

The effect of grazing by the heterotrophic microflagellate Cafeteria r oenbergensis on plasmid transfer between marine Vibrio S14 strains was studied by using artificial seawater. Several factors of potential im portance for regulation of the plasmid transfer, such as nutrient rele ase, production of a flagellate-derived substance(s) that may affect p lasmid transfer, and the presence of surfaces, were investigated. Only living flagellates gave rise to, at instances, plasmid transfer enhan ced more than 2 orders of magnitude. We propose that the activity of g razing flagellates allows for the significant increase in plasmid tran sfer observed under predation conditions. This may be due to a localiz ed increase in bacterial numbers through filter feeding, thus providin g high cell densities with increased possibility for cell-to-cell-cont act and hence plasmid transfer.