Sequence Analysis of Leuconostoc œnos DNA: Organization of pLo13, a Cryptic Plasmid

Abstract

A Leuconostoc œnos plasmid, pLo13, was studied to analyze its genetic organization and to define its functions. The nucleotide sequence (3948 bp) revealed three major open reading frames. Features commonly found in plasmids that replicate via a rolling-circle mechanism were identified within pLo13; first a sequence coding for a protein with an amino acid sequence homologous to the plasmid recombination enzymes (Pre), but for which a specific target site similar to those previously described was not found; second, a sequence probably encoding a replication protein (Rep). The putative pLo13 Rep protein amino acid sequence is divergent from the pC194-pUB110 family Rep proteins. However, the consensus sequence of the Rep protein active site was found, as well as the Rep protein consensus target site. No sequence similar to the previously described minus-origins (SSOs) are present in pLo13; nevertheless, a 200-bp sequence rich in imperfect palindromes may be involved in the minus-strand replication. These overall differences are in agreement with the previously reported important phylogenetic distance existing between Ln. œnos and other lactic acid bacteria.