NUCLEOTIDE-SEQUENCE AND STRUCTURAL ORGANIZATION OF THE SMALL, BROAD-HOST-RANGE PLASMID PCI411 FROM LEUCONOSTOC-LACTIS-533

The nudeotide sequence of the Leuconostoc lactis 533 cryptic plasmid p C1411 (2926 bp) was determined. Analysis revealed the presence of thre e open reading frames (ORFs). ORF 1 was capable of encoding a 24.9 kDa peptide which shared homology with the replication initiation protein (RepB) from a number of Gram-positive rolling circle plasmids. ORF 2 could encode a peptide of 6.6 kDa which was homologous to the RepC pro tein of the lactococcal plasmid pWV01. A function could not be assigne d to ORF 3, which was capable of encoding a 12.1 kDa peptide. Transcri ption-translation analysis indicated the presence of three peptides of the predicted molecular masses. A putative double strand origin of re plication (DSO) was identified which showed strong similarity with the DSO of a number of Gram-positive plasmids including pE194 from Staphy lococcus. Structural analysis identified a number of direct and indire ct repeats in addition to putative recombination-specific sites (RS, a nd RS,) in the non-coding region of pC1411. The observed characteristi cs suggest that this plasmid replicates using the rolling circle mecha nism. pC1411, which could be introduced into Leuconostoc, Lactococcus, Streptococcus, Lactobacillus and Bacillus is the first plasmid from t he genus Leuconostoc to be characterized in such detail.