Monitoring the conjugal transfer of plasmid RP4 in activated sludge and in situ identification of the transconjugants

A GFPmut3b-tagged derivative of broad host-range plasmid RP4 was used to monitor the conjugative transfer of the plasmid from a Pseudomonas putida donor strain to indigenous bacteria in activated sludge. Transfer frequencies were determined to be in the range of 4 x 10(-6) to 1 x 10(-5) transconjugants per recipient. In situ hybridisation with fluorescently labeled, rRNA-targeted oligonucleotides was used to phylogenetically affiliate the bacteria that had received the plasmid.