RETROTRANSFER OF INCP1-LIKE PLASMIDS FROM AQUATIC BACTERIA

The first observation of plasmid retrotransfer by plasmids isolated fr om environmental sources is reported. A high incidence of retrotransfe rring ability amongst plasmids isolated from epilithic bacteria was fo und; some of these plasmids retrotransferred an IncQ plasmid at very h igh frequencies. Despite the broad host-range of the majority of the p lasmids, only five out of 12 could be assigned to an incompatibility g roup by DNA hybridization. All five were designated IncP1; this reveal ed a limitation of probes derived from clinical sources for use with e nvironmental isolates. Incompatibility testing by plate mating suggest ed that four additional plasmids displayed varying, albeit lower, degr ees of incompatibility to the IncP1 plasmid RP1.