GENE-TRANSFER BY TRANSDUCTION IN THE MARINE-ENVIRONMENT

To determine the potential for bacteriophage-mediated gene transfer in the marine environment, we established transduction systems by using marine phage host isolates. Plasmid pQSR50, which contains transposon Tn5 and encodes kanamycin and streptomycin resistance, was used in pla smid transduction assays. Both marine bacterial isolates and concentra ted natural bacterial communities were used as recipients in transduct ion studies. Transductants were detected by a gene probe complementary to the neomycin phosphotransferase (nptII) gene in Tn5. The transduct ion frequencies ranged from 1.33 x 10(-7) to 5.13 x 10(-9) transductan ts/PFU in studies performed with the bacterial isolates. With the mixe d bacterial communities, putative transductants were detected in two o f the six experiments performed. These putative transductants were con firmed and separated from indigenous antibiotic-resistant bacteria by colony hybridization probed with the nptII probe and by PCR amplificat ion performed with two sets of primers specific for pQSR50. The freque ncies of plasmid transduction in the mixed bacterial communities range d from 1.58 x 10(-8) to 3.7 x 10(-9) transductants/PFU. Estimates of t he transduction rate obtained by using a numerical model suggested tha t up to 1.3 x 10(14) transduction events per year could occur in the T ampa Bay Estuary. The results of this study suggest that transduction could be an important mechanism for horizontal gene transfer in the ma rine environment.