Characterization of pMC11, a plasmid with dual origins of replication isolated from Lactobacillus casei MCJ and construction of shuttle vectors with each replicon

Appl Microbiol Biotechnol. 2014 Jul;98(13):5977-89. doi: 10.1007/s00253-014-5649-z. Epub 2014 Mar 22.

Abstract

Many lactic acid bacteria carry different plasmids, particularly those that replicate via a theta mechanism. Here we describe Lactobacillus casei MCJ(CCTCC AB20130356), a new isolate that contains pMC11, carrying two distinct theta-type replicons. Each replicon contained an iteron in the origin of replication (oriV1 or oriV2) and a gene coding for the replicase (RepA_1 or RepB_1), both of which are essential for plasmid replication. Escherichia coli/Lactobacillus shuttle vectors were constructed with each replicon, yielding pEL5.7 and pEL5.6 that are based on oriV2 and oriV1 replicons, respectively. These plasmids showed distinct properties: pEL5.7 was capable of replicating in L. casei MCJΔ1 and Lactobacillus delbrueckii subsp. lactic LBCH-1 but failed to do so in two other tested lactobacilli strains whereas pEL5.6 replicated in three different strains, including L. casei MCJΔ1, L. casei NJ, Lactobacillus paracasei LPC-37 and L. delbrueckii subsp. lactic LBCH-1. Plasmid stability was studied: pEL5.6 and pEL5.7 were very stably maintained in L. casei, as the loss rate was lower than 1 % per generation. pEL5.7 was also stable in L. delbrueckii subsp. lactic LBCH-1 with the loss rate estimated to be 3 %. These vectors were employed to express a green fluorescent protein (GFP) using the promoter of S-layer protein SlpA from Lactobacillus acidophilus. And a growth-phase regulated expression of GFP was observed in different strains. In conclusion, these shuttle vectors provide efficient genetic tools for DNA cloning and heterologous gene expression in lactobacilli.

MeSH terms

  • DNA Replication
  • DNA, Bacterial
  • DNA-Directed DNA Polymerase / genetics
  • Escherichia coli / genetics
  • Gene Expression Profiling
  • Genetic Vectors*
  • Genomic Instability
  • Lacticaseibacillus casei / genetics*
  • Molecular Sequence Data
  • Plasmids / isolation & purification*
  • Replication Origin*
  • Sequence Analysis, DNA

Substances

  • DNA, Bacterial
  • DNA replicase
  • DNA-Directed DNA Polymerase

Associated data

  • GENBANK/KF986324
  • RefSeq/NC_025132