MOLECULAR CHARACTERIZATION OF THE REPLICON OF THE PEDIOCOCCUS-PENTOSACEUS-43200 PEDIOCIN-A PLASMID-PMD136

The pediocin A-encoding plasmid of Pediococcus pentosaceus 43200, pMD1 36, was characterized by restriction enzyme analysis. Analysis of its replicon was facilitated by the construction of a probe Vector consist ing of the Escherichia coli plasmid pSP72 and the cat gene from Staphy lococcus aureus plasmid pC194. The replication region of pMD136 was lo calized on a 1.6-kb EcoRI/Bg/II fragment. Sequencing analysis revealed a non-coding region, repA, spanning the first 440 bp, followed by an open reading frame, repB, encoding a putative protein of 390 amino aci ds. The non-coding region contained two sets of 6-bp and two sets of 2 2-bp direct repeats and two sets of inverted repeats upstream of the o pen reading frame. Strong homology of the isolated replicon was found to theta-type replicons of Lactococcus lactis plasmids. Segregational stability assay suggested at least two regions as potentially involved in the stabilization of pMD136. The plasmid's strong homology to othe r theta-type replicons and its relatively high stability suggest that pMD136 belongs to the widespread family of theta-replication plasmids.