A new family of conditional replicating plasmids and their cognate Escherichia coli host strains.

We constructed a family of conditionally replicating plasmids, the pTX1 family, which are based on the IncPalpha oriV origin of replication that is dependent on the trfA-encoded protein. We constructed several Escherichia coli derivatives expressing trfA from different chromosomal loci, which can be transduced by phage P1 to any E. coli strain. The pTX1 plasmids also carry the oriTRP4 origin of transfer, and can be conjugated to E. coli, Vibrio cholerae and likely to a broad range of bacteria from the commonly used donor strains SM10 and S17-1, which sustain replication of the plasmids through the trfA gene carried by their integrated RP4. If TrfA is not provided in trans, these plasmids behave as suicide vectors. As such they can be used as a platform for a variety of applications such as those developed on the popular conditionally replicating plasmids carrying the oriVR6Kgamma origin of replication that is controlled by the Pi protein. Their ability to be used as efficient suicide vectors for gene disruption in V. cholerae has been demonstrated.