New molecular variants of epsilon and beta IncP-1 plasmids are present in estuarine waters.

In this work the presence of broad-host-plasmids in an estuary in Portugal has been investigated. Pseudomonas putida KT2442 was used as model recipient bacteria in biparental matings with tetracycline and mercury to select for resistance phenotypes. As a result, 7 transconjugants were shown to carry broad-host-plasmids from the IncP-1 group, as seen by PCR amplification of the trfA gene. Sequence analysis confirmed the isolation of 4 plasmids from β-1 subgroup and 3 assigned to the recently described ε subgroup. To our knowledge this is the first report concerning the detection and isolation of IncP-1β and ε plasmids in estuarine waters. Moreover it is shown that, even though the retrieved plasmids are phylogenetically close to previously characterized plasmids, such as pB10 and pKJK5, respectively, they constitute new molecular variants.