Leuconostoc

About: Leuconostoc is a research topic. Over the lifetime, 1859 publications have been published within this topic receiving 65937 citations.

Identification of the Bacterial Microflora in Dairy Products by Temporal Temperature Gradient Gel Electrophoresis

Abstract: Numerous microorganisms, including bacteria, yeasts, and molds, are present in cheeses, forming a complex ecosystem. Among these organisms, bacteria are responsible for most of the physicochemical and aromatic transformations that are intrinsic to the cheesemaking process. Identification of the bacteria that constitute the cheese ecosystem is essential for understanding their individual contributions to cheese production. We used temporal temperature gradient gel electrophoresis (TTGE) to identify different bacterial species present in several dairy products, including members of the genera Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Streptococcus, and Staphylococcus. The TTGE technique is based on electrophoretic separation of 16S ribosomal DNA (rDNA) fragments by using a temperature gradient. It was optimized to reveal differences in the 16S rDNA V3 regions of bacteria with low-G+C-content genomes. Using multiple control strains, we first set up a species database in which each species (or group of species) was characterized by a specific TTGE fingerprint. TTGE was then applied to controlled dairy ecosystems with defined compositions, including liquid (starter), semisolid (home-made fermented milk), and solid (miniature cheese models) matrices. Finally, the potential of TTGE to describe the bacterial microflora of unknown ecosystems was tested with various commercial dairy products. Subspecies, species, or groups of species of lactic acid bacteria were distinguished in dairy samples. In conclusion, TTGE was shown to distinguish bacterial species in vitro, as well as in both liquid and solid dairy products.

Controlled gene expression systems for lactic acid bacteria: transferable nisin-inducible expression cassettes for Lactococcus, Leuconostoc, and Lactobacillus spp.

Abstract: A transferable dual-plasmid inducible gene expression system for use in lactic acid bacteria that is based on the autoregulatory properties of the antimicrobial peptide nisin produced by Lactococcus lactis was developed. Introduction of the two plasmids allowed nisin-inducible gene expression in Lactococcus lactis MG1363, Leuconostoc lactis NZ6091, and Lactobacillus helveticus CNRZ32. Typically, the beta-glucuronidase activity (used as a reporter in this study) remained below the detection limits under noninducing conditions and could be raised to high levels, by addition of subinhibitory amounts of nisin to the growth medium, while exhibiting a linear dose-response relationship. These results demonstrate that the nisin-inducible system can be functionally implemented in lactic acid bacteria other than Lactococcus lactis.

Application of electroporation for transfer of plasmid DNA to Lactobacillus, Lactococcus, Leuconostoc, Listeria, Pediococcus, Bacillus, Staphylococcus, Enterococcus and Propionibacterium

Abstract: Plasmid DNA was introduced by electroporation into Bacillus, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Listeria, Pediococcus, Propionibacterium and Staphylococcus as an alternative to competent-cell or protoplast transformation. Plasmid-containing transformants were recovered in these recipients at frequencies ranging from 10(1) to 10(5) transformants micrograms-1 of pGK12. Several parameters of the protocol, including DNA concentration, voltage, plating regimen and electroporation buffers were evaluated to determine conditions that improved transformation frequencies for Lactobacillus acidophilus. Using optimized conditions, the following plasmids were introduced into L. acidophilus: pAMB1, pC194, pGB354, pGKV1, pSA3, pTRK13, pTV1 and pVA797. The ability to transfer plasmid DNA via eletroporation will greatly facilitate the application of recombinant DNA methodology and transposon technology to Gram-positive bacteria for cloning and analysis of significant genes.

Proposal To Reclassify Leuconostoc oenos as Oenococcus oeni (corrig.) gen. nov., comb. nov.

Abstract: Wine strains belonging to the genus Leuconostoc were classified as Leuconostoc oenos by Garvie in 1967, and this name was confirmed on the Approved Lists of Bacterial Names in 1980. L. oenos is distinguished from other Leuconostoc spp. by its growth in acidic media, by its requirement for a growth factor in tomato juice, and by a number of carbohydrate fermentation characteristics. In addition, the results of a total soluble cell protein analysis, an electrophoretic analysis of NAD-dependent d-(—)-lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and alcohol dehydrogenase, and an analysis of cross-reactivity with anti-glucose-6-phosphate dehydrogenase and anti-NAD-dependent d-(—)-lactate dehydrogenase performed with other Leuconostoc spp. clearly indicated that L. oenos should be distinguished from the other Leuconostoc species. Phylogenetic studies, in particular 16S and 23S rRNA sequencing studies, have revealed that L. oenos represents a distinct subline that is separate from other Leuconostoc spp. and lactic acid bacteria. In view of the phenotypic and phylogenetic distinctiveness of L. oenos, we propose that this species should be assigned to a new genus as Oenococcus oeni [corrig.] gen. nov., comb. nov. The type strain of O. oeni is NCDO 1674 (= ATCC 23179).