Nucleotide sequence analysis of pRS1, a cryptic plasmid from Oenococcus oeni

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.

The use of the replication region of plasmid pRS7 from Oenococcus oeni as a putative tool to generate cloning vectors for lactic acid bacteria

A chimeric plasmid, pRS7Rep (6.1 kb), was constructed using the replication region of pRS7, a large plasmid from Oenococcus oeni, and pEM64, a plasmid derived from pIJ2925 and containing a gene for resistance to chloramphenicol. pRS7Rep is a shuttle vector that replicates in Escherichia coli using its pIJ2925 component and in lactic acid bacteria (LAB) using the replication region of pRS7. High levels of transformants per µg of DNA were obtained by electroporation of pRS7Rep into Pediococcus acidilactici (1.5 × 10(7)), Lactobacillus plantarum (5.7 × 10(5)), Lactobacillus casei (2.3 × 10(5)), Leuconostoc citreum (2.7 × 10(5)), and Enterococcus faecalis (2.4 × 10(5)). A preliminary optimisation of the technical conditions of electrotransformation showed that P. acidilactici and L. plantarum are better transformed at a later exponential phase of growth, whereas L. casei requires the early exponential phase for better electrotransformation efficiency. pRS7Rep contains single restriction sites useful for cloning purposes, BamHI, XbaI, SalI, HincII, SphI and PstI, and was maintained at an acceptable rate (>50%) over 100 generations without selective pressure in L. plantarum, but was less stable in L. casei and P. acidilactici. The ability of pRS7Rep to accept and express other genes was assessed. To the best of our knowledge, this is the first time that the replication region of a plasmid from O. oeni has been used to generate a cloning vector.

Identification of pOENI-1 and related plasmids in Oenococcus oeni strains performing the malolactic fermentation in wine

Plasmids in lactic acid bacteria occasionally confer adaptive advantages improving the growth and behaviour of their host cells. They are often associated to starter cultures used in the food industry and could be a signature of their superiority. Oenococcus oeni is the main lactic acid bacteria species encountered in wine. It performs the malolactic fermentation that occurs in most wines after alcoholic fermentation and contributes to their quality and stability. Industrial O. oeni starters may be used to better control malolactic fermentation. Starters are selected empirically by virtue of their fermentation kinetics and capacity to survive in wine. This study was initiated with the aim to determine whether O. oeni contains plasmids of technological interest. Screening of 11 starters and 33 laboratory strains revealed two closely related plasmids, named pOENI-1 (18.3-kb) and pOENI-1v2 (21.9-kb). Sequence analyses indicate that they use the theta mode of replication, carry genes of maintenance and replication and two genes possibly involved in wine adaptation encoding a predicted sulphite exporter (tauE) and a NADH:flavin oxidoreductase of the old yellow enzyme family (oye). Interestingly, pOENI-1 and pOENI-1v2 were detected only in four strains, but this included three industrial starters. PCR screenings also revealed that tauE is present in six of the 11 starters, being probably inserted in the chromosome of some strains. Microvinification assays performed using strains with and without plasmids did not disclose significant differences of survival in wine or fermentation kinetics. However, analyses of 95 wines at different phases of winemaking showed that strains carrying the plasmids or the genes tauE and oye were predominant during spontaneous malolactic fermentation. Taken together, the results revealed a family of related plasmids associated with industrial starters and indigenous strains performing spontaneous malolactic fermentation that possibly contribute to the technological performance of strains in wine.

Cloning Vectors Based on Cryptic Plasmids Isolated from Lactic Acid Bacteria:Their Characteristics and Potential Applications in Biotechnology

Lactic acid bacteria (LAB) are Gram positive bacteria, widely distributed in nature, and industrially important as they are used in a variety of industrial food fermentations. The use of genetic engineering techniques is an effective means of enhancing the industrial applicability of LAB. However, when using genetic engineering technology, safety becomes an essential factor for the application of improved LAB to the food industry. Cloning and expression systems should be derived preferably from LAB cryptic plasmids that generally encode genes for which functions can be proposed, but no phenotypes can be observed. However, some plasmid-encoded functions have been discovered in cryptic plasmids originating from Lactobacillus, Streptococcus thermophilus, and Pediococcus spp. and can be used as selective marker systems in vector construction. This article presents information concerning LAB cryptic plasmids, and their structures, functions, and applications. A total of 134 cryptic plasmids collated are discussed.

Transformation of Lactobacillus plantarum by electroporation with in vitro modified plasmid DNA

An improved method for the electrotransformation of Lactobacillus plantarum CECT 220 (ATCC 8014) with plasmid DNA isolated from Escherichia coli is described. The two main modifications with respect to existing methods are: (i) isolation of plasmid DNA from E. coli JM110 grown in minimal medium and (ii) in vitro modification of the DNA by cell-free extracts of the host L. plantarum. Optimal electrotransformation was obtained with exponentially growing cells of L. plantarum concentrated to 6x10(9) cfu ml-1, with electric pulses of 13 kV cm-1 in cuvettes with 1 mm inter-electrode distance. We consider that this method constitutes a useful tool for routine manipulation of L. plantarum, and can probably be extended to other lactic acid bacteria.

Nucleotide sequence analysis of pRS2 and pRS3, two small cryptic plasmids from Oenococcus oeni

Nucleotide sequence analysis of two cryptic plasmids, pRS2 (2544 bp) and pRS3 (3948 bp), from Oenococcus oeni revealed the presence in both of three major open reading frames with significant similarity to other small cryptic plasmids from O. oeni. The results suggest that those plasmids could be separated into two subfamilies, one represented by pLo13 and pRS3, the other represented by pOg32, pRS1, and pRS2.