Project description:Pangenome arrays contain DNA oligomers targeting several sequenced reference genomes from the same species. In microbiology these can be employed to investigate the often high genetic variability within a species by comparative genome hybridization (CGH). The biological interpretation of pangenome CGH data depends on the ability to compare strains at a functional level, particularly by comparing the presence or absence of orthologous genes. Due to the high genetic variability, available genotype-calling algorithms can not be applied to pangenome CGH data. Therefore, we have developed the algorithm PanCGH that incorporates orthology information about genes to predict the presence or absence of orthologous genes in a query organism using CGH arrays that target the genomes of sequenced representatives of a group of microorganisms. PanCGH was tested and applied in the analysis of genetic diversity among 39 Lactococcus lactis strains from three different subspecies (lactis, cremoris, hordniae) and isolated from two different niches (dairy and plant). Clustering of these strains using the presence/absence data of gene orthologs revealed a clear separation between different subspecies and reflected the niche of the strains. Keywords: CGH, CGH analysis, orthology, Lactococcus lactis
Project description:P335 group phages represent the most divergent phage group infecting dairy Lactococcus lactis strains and have significant implications for the dairy processing industry. Here, we report the complete genome sequences of eight lactococcal prophages chemically induced from industrial lactococcal strains that propagate lytically on one of two laboratory strains.
Project description:Three Lactococcus lactis strains with the ability to secrete various amino acids (leucine, isoleucine, methionine, valine, glutamic acid, and histidine) were sequenced in order to identify the mechanisms involved in the secretion. Amino acids contribute to flavor formation; therefore, bacterial strains with this ability are relevant for the food industry.
Project description:We have previously reported the construction of a food-grade cloning vector for Lactococcus using the ochre suppressor, supB, as the selective marker. This vector, pFG1, causes only a slight growth inhibition in the laboratory strain MG1363 but is unstable in the industrial strains tested. As supB suppresses both amber and ochre stop codons, which are present in 82% of all known lactococcal genes, this undesirable finding may result from the accumulation of elongated mistranslated polypeptides. Here, we report the development of a new food-grade cloning vector, pFG200, which is suitable for overexpressing a variety of genes in industrial strains of Lactococcus lactis. The vector uses an amber suppressor, supD, as selectable marker and consists entirely of Lactococcus DNA, with the exception of a small polylinker region. Using suppressible pyrimidine auxotrophs, selection and maintenance are efficient in any pyrimidine-free medium including milk. Importantly, the presence of this vector in a variety of industrial strains has no significant effect on the growth rate or the rate of acidification in milk, making this an ideal system for food-grade modification of industrially relevant L. lactis strains. The usefulness of this system is demonstrated by overexpressing the pepN gene in a number of industrial backgrounds.
Project description:Bacteria are normally haploid, maintaining one copy of their genome in one circular chromosome. We have examined the cell cycle of laboratory strains of Lactococcus lactis, and, to our surprise, we found that some of these strains were born with two complete nonreplicating chromosomes. We determined the cellular content of DNA by flow cytometry and by radioactive labeling of the DNA. These strains thus fulfill the criterion of being diploid. Several dairy strains were also found to be diploid while a nondairy strain and several other dairy strains were haploid in slow-growing culture. The diploid and haploid strains differed in their sensitivity toward UV light, in their cell size, and in their D period, the period between termination of DNA replication and cell division.
Project description:In this study, we describe the genetic organizations of six and five apparent prophage-like elements present in the genomes of the Lactococcus lactis subsp. cremoris strains MG1363 and SK11, respectively. Phylogenetic investigation as well bioinformatic analyses indicates that all 11 prophages belong to subdivisions of the lactococcal P335 group of temperate bacteriophages.
Project description:Inflammatory bowel diseases (IBD) are gastrointestinal disorders characterized by a breakdown in intestinal homeostasis by inflammatory immune responses to luminal antigens. Novel strategies for ameliorating IBD have been proposed in many studies using animal models. Our group has demonstrated that administration of Lactococcus lactis NCDO 2118 can improve clinical parameters of colitis induced by oral administration of dextran sulphate sodium (DSS). However, it is not clear whether other strains of L. lactis can yield the same effect. The objective of present study was to analyze the effects of three different L. lactis strains (NCDO2118, IL1403 and MG1363) in the development of DSS-induced colitis in C57BL/6 mice. Acute colitis was induced in C57/BL6 mice by the administration of 2% DSS during 7 consecutive days. Body weight loss and shortening of colon length were observed in DSS-treated mice, and none of L. lactis strains had an impact in these clinical signs of colitis. On the other hand, all strains improved the global macroscopical disease index and prevented goblet cells depletion as well as the increase of intestinal permeability. TNF-α production was reduced in gut mucosa of L. lactis DSS-treated mice indicating a modulation of a critical pro-inflammatory response by all strains tested. However, only L. lactis NCDO2118 and MG1363 induced a higher frequency of CD11c+CD11b-CD103+ tolerogenic dendritic cells in lymphoid organs of mice at steady state. We conclude that all tested strains of L. lactis improved the clinical scores and parameters of colitis, which confirm their anti-inflammatory properties in this model of colitis.
Project description:The intra sub-species diversity of six strains of Lactococcus lactis subsp. lactis was investigated at the genomic level and in terms of phenotypic and transcriptomic profiles in UF-cheese model. Six strains were isolated from various sources, but all are exhibiting a dairy phenotype. Our results showed that, the six strains exhibited small phenotypic differences since similar behaviour in terms of growth was obtained during cheese ripening while only different acidification capability was detected. Even if all strains displayed high genomic similarities, sharing a high core genome of almost two thousands genes, the expression of this core genome directly in the cheese matrix revealed major strain-specific differences. This strains with the same dairy origin.
Project description:Lactic acid bacteria (LAB) isolated from medicinal herb Murraya koenigii, commonly known as curry leaf, which promotes the growth and maintenance of gut microbiota, were studied for their probiotic potential. The key objective of this research was to isolate and evaluate probiotic characteristics, test adherence capabilities, and confirm their safety. Lactococcus lactis (MKL8), isolated from Murraya koenigii, was subjected to in vitro analysis to assess its resistance to the gastric environment, ability to adhere Caco-2 cells, anti-microbial activity, hydrophobicity, auto-aggregation, and safety profiling through MTT assay and hemolytic. MKL8 exhibited growth at 0.5% phenol concentrations (> 80%) and was able to survive in conditions with high bile concentrations (> 79%) and a relatively low pH (72%-91%). It shows high tolerance to high osmotic conditions (> 73%) and simulated gastric juice (> 72%). Additionally, MKL8 demonstrated strong hydrophobicity (85%), auto-aggregation (87.3%-91.7%), and adherence to Caco-2 cells. Moreover, it had an inhibitory effect against pathogens too. By performing the hemolytic and MTT assays, the non-toxicity of MKL8 isolate was examined, and it exhibited no harmful characteristics. Considering MKL8's resistance to gastrointestinal tract conditions, high surface hydrophobicity, non-toxicity, and ability to inhibit the tested pathogens, it can be concluded that MKL8 demonstrated promising probiotic properties and has potential for use in the food industry.