Analysis of pYC2, a cryptic plasmid in Lactobacillus sakei BM5 isolated from kimchi

Characterization of a Cryptic Rolling-Circle Replication Plasmid pMK8 from Enterococcus durans 1-8

A novel cryptic plasmid from Enterococcus durans 1-8, designated as pMK8, was sequenced and analyzed in this study. It consists of 3337 bp with a G + C content of 33.11%. Sequence analysis of pMK8 revealed three putative open reading frames (ORFs). Based on homology, two of them were identified as genes encoding replication initiation (RepC) and mobilization (Mob) protein, respectively. Sequence analysis revealed a pT181 family double-strand origin (dso) and a putative single-strand origin (sso) located upstream of the repC gene. Sequence homology analysis indicated that the sso belongs to the ssoW family. Southern hybridization confirmed the presence of single-strand DNA (ssDNA) intermediates, suggesting that pMK8 replicates via the RCR mechanism. Furthermore, the relative copy number of pMK8 was estimated by real-time PCR to be 175 ± 14 copies in each cell.

Characterization of a Rolling-Circle Replication Plasmid pM411 from Lactobacillus plantarum 1-3

A cryptic plasmid pM411 isolated from Lactobacillus plantarum 1-3 consisted of a 2303-bp circular molecule with a G + C content 32.96 %. Sequence analysis of pM411 revealed four putative open reading frames (ORFs). ORF1 shared 99 and 94 % similarities, respectively, with the Rep proteins of plasmids pLC2 and pYC2, which belong to the rolling-circle replication pMV158 family. A typical pMV158 family double-strand origin (dso) and a putative single-strand origin (sso) located upstream of the rep gene. Southern hybridization confirmed the presence of single-strand DNA (ssDNA) intermediates, suggesting that pM411 belongs to the RCR pMV158 family. Sequence homology analysis indicated that the sso belongs to the ssoW family. Furthermore, the relative copy number of pM411 was about 88 copies in each cell by real-time PCR.

Plasmids from Food Lactic Acid Bacteria: Diversity, Similarity, and New Developments

Plasmids are widely distributed in different sources of lactic acid bacteria (LAB) as self-replicating extrachromosomal genetic materials, and have received considerable attention due to their close relationship with many important functions as well as some industrially relevant characteristics of the LAB species. They are interesting with regard to the development of food-grade cloning vectors. This review summarizes new developments in the area of lactic acid bacteria plasmids and aims to provide up to date information that can be used in related future research.

Characterization of pR18, a novel rolling-circle replication plasmid from Lactobacillus plantarum

Lactobacillus plantarum PA18, a strain originally isolated from the leaves of Pandanus amaryllifolius, contains a pR18 plasmid. The pR18 plasmid is a 3211bp circular molecule with a G+C content of 35.8%. Nucleotide sequence analysis revealed two putative open reading frames, ORF1 and ORF2, in which ORF2 was predicted (317 amino acids) to be a replication protein and shared 99% similarity with the Rep proteins of pLR1, pLD1, pC30il, and pLP2000, which belong to the RCR pC194/pUB110 family. Sequence analysis also indicated that ORF1 was predicted to encode linA, an enzyme that enzymatically inactivates lincomycin. The result of Southern hybridization and mung bean nuclease treatment confirmed that pR18 replicated via the RCR mechanism. Phylogenetic tree analysis of pR18 plasmid proteins suggested that horizontal transfer of antibiotic resistance determinants without genes encoding mobilization has not only occurred between Bacillus and Lactobacillus but also between unrelated bacteria. Understanding this type of transfer could possibly play a key role in facilitating the study of the origin and evolution of lactobacillus plasmids. Quantitative PCR showed that the relative copy number of pR18 was approximately 39 copies per chromosome equivalent.

Construction and evaluation of shuttle vector, pGYC4α, based on pYC2 from Lactobacillus sakei

The shuttle vector pGYC4α (6,157 bp) was constructed based on the sigma-replicon plasmid pYC2 from Lactobacillus sakei BM5 isolated from kimchi. The vector contained inserts of the ColE1 replicon, α-amylase gene from Bacillus licheniformis containing its own signal peptide, and lactococcal promoter P32. Transformation and expression of a selection marker gene (α-amylase) with pGYC4α were demonstrated in Escherichia coli and several lactic acid bacteria (LAB). The highest α-amylase activity in LAB transformants was obtained in M17/0.25% glucose media with 0.5% CaCO(3). The segregational stability of the shuttle vector in LAB was 100% for more than 100 generations in the absence of antibiotic pressure. The developed vector might be useful as a genetic tool for food industries.