Comparative and evolutionary analysis of plasmid pREN isolated from Lactobacillus rennini, a novel member of the theta-replicating pUCL287 family

Here, we describe plasmid pREN of Lactobacillus rennini ACA-DC 1534, isolated from traditional Kopanisti cheese. pREN is a circular molecule of 4371 bp. Orf calling revealed a novel repA-orf2 operon with the deduced product of orf2 showing no similarity to other known proteins. Downstream of this operon, a gene cluster encoding different mobilization proteins, namely mobC, mobA1, mobA2 and mobB, was detected. Based on the sequence of the origin of replication (ori) and the similarity pattern of RepA, pREN was placed in the pUCL287 family of theta-replicating plasmids. Multiple sequence alignment demonstrated for the first time the degree of conservation in the pUCL287 oris. Our analysis supported that the identified conserved repeats could drive similar secondary structures in the oris of all plasmids. Furthermore, comparative mapping of pREN with its related plasmids (i.e. pLB925A03 and pLJ42) showed that they retain a unique combination in the architecture of their replication and mobilization elements within the pUCL287 family. Phylogenetic analysis also established that these plasmids have undergone a modular evolutionary process in order to acquire their mob genes. Research on plasmids from uncommon lactic acid bacteria will expand our appreciation for their divergence and will aid their rational selection for biotechnological applications.