EXOGENOUS ISOLATION OF HG-R PLASMIDS FROM COASTAL MEDITERRANEAN WATERS AND THEIR EFFECT ON GROWTH AND SURVIVAL OF ESCHERICHIA-COLI IN SEA-WATER

Four self-conjugative plasmids conferring mercury resistance were exog enously isolated from coastal Mediterranean sea water. All the plasmid s isolated (93.2, 73.1, 65.2 and 221 kb) showed narrow-spectrum mercur y resistance, and no UV resistance; three of them conferred cadmium re sistance (Cd-r 1.5 mM) and two of them encoded streptomycin resistance (50 mu g/ml). Their influence on the survival of the recipient strain Escherichia coli JGL1 in different seawater media was studied and com pared with that of two plasmids previously isolated by the same proced ure from an epilithic community of the Bristol Channel, Great Britain. A significant negative influence was observed for the largest (221 kb ) of the plasmids isolated and one of the epilithic plasmids (239 kb). The effect of the plasmids on E. coli JGL1 was dependent on the seawa ter media.