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At least 19 recordsLinked to original sources
PubMed2002

16S-23S rDNA intergenic spacer region polymorphism of Lactococcus garvieae, Lactococcus raffinolactis and Lactococcus lactis as revealed by PCR and nucleotide sequence analysis.

The intergenic spacer region (ISR) between the 16S and 23S rRNA genes was tested as a tool for differentiating lactococci commonly isolated in a dairy environment. 17 reference strains, representing 11 different species belonging to the genera Lactococcus, Streptococcus, Lactobacillus, Enterococcus and Leuconostoc, and 127 wild streptococcal strains isolated during the whole fermentation process of "Fior di Latte" cheese were analyzed. After 16S-23S rDNA ISR amplification by PCR, species or genus-specific patterns were obtained for most of the reference strains tested. Moreover, results obtained after nucleotide analysis show that the 16S-23S rDNA ISR sequences vary greatly, in size and sequence, among Lactococcus garvieae, Lactococcus raffinolactis, Lactococcus lactis as well as other streptococci from dairy environments. Because of the high degree of inter-specific polymorphism observed, 16S-23S rDNA ISR can be considered a good potential target for selecting species-specific molecular assays, such as PCR primer or probes, for a rapid and extremely reliable differentiation of dairy lactococcal isolates.

Base Sequence↗
PubMed1996

Antimicrobial susceptibilities of Lactococcus lactis and Lactococcus garvieae and a proposed method to discriminate between them.

The MICs of antimicrobial agents contained in the SCEPTOR Streptococcus MIC panels (Becton Dickinson Microbiology Systems) were determined for Lactococcus lactis, L. garvieae, and unknown Lactococcus species. Several isolates had reduced susceptibilities to many of the antimicrobial agents contained in the panel. For L. garvieae, the MICs of penicillin and, possibly, cephalothin were higher than for L. lactis, and unlike L. lactis, L. garvieae was resistant to clindamycin, indicating that knowledge of the Lactococcus species causing an infection might influence the choice of antimicrobial therapy. Susceptibility to clindamycin can also be used to differentiate between L. lactis and L. garvieae.

Bacteriological Techniques↗
PubMed1990

Lactococcus piscium sp. nov. a new Lactococcus species from salmonid fish.

Chemical and molecular taxonomic studies were performed on a representative strain of some lactic acid bacteria of unknown taxonomic position isolated from salmonid fish. The results demonstrate that the fish bacterium represents a new species of the genus Lactococcus for which the name Lactococcus piscium sp. nov. is proposed. The type strain of Lactococcus piscium is NCFB 2778.

Animals↗
PubMed1991

Differentiation of Lactococcus lactis and Lactococcus garvieae from humans by comparison of whole-cell protein patterns.

We tested 12 reference and 24 clinical strains of lactococci for physiologic characteristics using a conventional test system, the Gen-Probe Enterococcus 2 chemiluminescence assay (Gen-Probe Inc., San Diego, Calif.), the Rapid Strep identification system (Analytab Products, Plainview, N.Y.), and whole-cell protein analysis. The Gen-Probe Enterococcus 2 chemiluminescence assay for Enterococcus identification was negative with all strains. Neither the conventional test nor the Rapid Strep identification system could differentiate between the two Lactococcus spp. most commonly isolated from humans. A simple procedure, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was developed for comparing the whole-cell protein patterns of Lactococcus spp. L. lactis and L. garvieae were differentiated by unique protein patterns.

Bacterial Proteins↗
PubMed1993

The use of bacterial luciferase genes as reporter genes in Lactococcus: regulation of the Lactococcus lactis subsp. lactis lactose genes.

Lactose metabolism is an important industrial trait in dairy lactococci. In Lactococcus lactis, lactose is taken up via the phosphoenolpyruvate-dependent phosphotransferase system (PEP-PTS) and is subsequently metabolized via the glycolytic and tagatose 6-phosphate pathways. Genes for the lactose-specific PEP-PTS proteins, phospho-beta-galactosidase and tagatose 6-phosphate pathway enzymes are encoded by a single 8 kb operon, lacABCDFEGX, and there is a divergently transcribed lacR repressor gene. Transcriptional fusions of both the lac operon promoter and the lacR promoter to the luxAB genes of Vibrio fischeri were used to investigate the regulation of expression of both promoters. In vivo bioluminescence assays demonstrated that lacR negatively regulates the lac operon and also autoregulates itself. Induction of transcription occurred for both promoters during growth on lactose: sevenfold for lacR and fivefold for the lac operon. The lacR promoter was demonstrated to be a particularly strong promoter, being approximately four times more efficient than the lac operon promoter. Both promoters provide good potential for the inducible expression of foreign proteins in Lactococcus.

Base Sequence↗
PubMed1991

Thermosensitive plasmid replication, temperature-sensitive host growth, and chromosomal plasmid integration conferred by Lactococcus lactis subsp. cremoris lactose plasmids in Lactococcus lactis subsp. lactis.

Evidence is presented that lactose-fermenting ability (Lac+) in Lactococcus lactis subsp. cremoris AM1, SK11, and ML1 is associated with plasmid DNA, even though these strains are difficult to cure of Lac plasmids. When the Lac plasmids from these strains were introduced into L. lactis subsp. lactis LM0230, they appeared to replicate in a thermosensitive manner; inheritance of the plasmid was less efficient at 32 to 40 degrees C than at 22 degrees C. The stability of the L. lactis subsp. cremoris Lac plasmids in lactococci appeared to be a combination of both host and plasmid functions. Stabilized variants were isolated by growing the cultures at 32 to 40 degrees C; these variants contained the Lac plasmids integrated into the L. lactis subsp. lactis LM0230 chromosome. In addition, the presence of the L. lactis subsp. cremoris Lac plasmids in L. lactis subsp. lactis resulted in a temperature-sensitive growth response; growth of L. lactis subsp. lactis transformants was significantly inhibited at 38 to 40 degrees C, thereby resembling some L. lactis subsp. cremoris strains with respect to temperature sensitivity of growth.

DNA Replication↗
PubMed1995

Physical and genetic map of the Lactococcus lactis subsp. cremoris MG1363 chromosome: comparison with that of Lactococcus lactis subsp. lactis IL 1403 reveals a large genome inversion.

A physical and genetic map of the chromosome of the Lactococcus lactis subsp. cremoris reference strain MG1363 was established. The physical map was constructed for NotI, ApaI, and SmaI enzymes by using a strategy that combines creation of new rare restriction sites by the random-integration vector pRL1 and ordering of restriction fragments by indirect end-labeling experiments. The MG1363 chromosome appeared to be circular and 2,560 kb long. Seventy-seven chromosomal markers were located on the physical map by hybridization experiments. Integration via homologous recombination of pRC1-derived plasmids allowed a more precise location of some lactococcal genes and determination of their orientation on the chromosome. The MG1363 chromosome contains six rRNA operons; five are clustered within 15% of the chromosome and transcribed in the same direction. Comparison of the L. lactis subsp. cremoris MG1363 physical map with those of the two L. lactis subsp. lactis strains IL1403 and DL11 revealed a high degree of restriction polymorphism. At the genetic organization level, despite an overall conservation of gene organization, strain MG1363 presents a large inversion of half of the genome in the region containing the rRNA operons.

Bacteriophages↗
PubMed1991

Bacteriophage receptors of Lactococcus lactis subsp. 'diacetylactis' F7/2 and Lactococcus lactis subsp. cremoris Wg2-1.

Bacteriophage P008 revealed irreversible and uniform adsorption to cell walls of L. lactis subsp. 'diacetylactis' F7/2, whereas phage P127 adsorbed reversibly to a limited number of receptor sites on cell walls of L. lactis subsp. cremoris Wg2-1. Neither extraction of lipids, cell wall- and membrane-teichoic acids nor enzymatic degradation of proteins altered the binding efficiencies of both cell wall fractions. However, phage binding was inhibited, when cell walls were subjected to lysozyme, metaperiodate, or acid treatments. This reflects that a carbohydrate component embedded in the peptidoglycan matrix is part of the phage receptors of strains F7/2 and Wg2-1.

Adsorption↗
PubMed2002

Autolytic phenotype of Lactococcus lactis strains isolated from traditional Tunisian dairy products.

AIMS: To evaluate the autolytic properties of Lactococcus lactis strains isolated from artisan Tunisian dairy products, their peptidoglycan hydrolase content and their activity spectrum. METHODS AND RESULTS: The autolytic phenotype of Lactococcus strains was evaluated under starvation conditions in potassium phosphate buffer. The results obtained highlighted a high degree of diversity among the strains analysed, allowing the identification of high and low autolytic Lactococcus lactis strains. Peptidoglycan hydrolase content was evaluated by renaturing SDS-PAGE using cells of Micrococcus lysodeikticus as a target for the enzymatic activity. A major activity band migrating at about 45 kDa was observed. The lytic activity, evaluated in the presence of different chemicals, was retained in 8% NaCl, 15 mmol l(-1) CaCl2, and in a pH range between 5 and 9.5. The substrate specificity of peptidoglycan hydrolase from Lactococcus strains was evaluated in renaturing SDS-PAGE incorporating cells of different bacterial species. The major autolysin of Lactococcus lactis was active against cells of Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus and Listeria monocytogenes. CONCLUSIONS: Autolytic activity is widely distributed in Lactococcus lactis and the rate of autolysis is strain-dependent. The major peptidoglycan hydrolase showed a wide spectrum of activity against several lactic acid bacteria and bacterial species involved in food-related infection. SIGNIFICANCE AND IMPACT OF THE STUDY: The autolytic phenotype of Lactococcus lactis strains isolated from Tunisian artisan dairy products has been determined, and the data obtained should allow the selection of strains of technological interest in the cheese-ripening process.

Bacteriolysis↗
PubMed1998

Mechanism of the citrate transporters in carbohydrate and citrate cometabolism in Lactococcus and Leuconostoc species.

Citrate metabolism in the lactic acid bacterium Leuconostoc mesenteroides generates an electrochemical proton gradient across the membrane by a secondary mechanism (C. Marty-Teysset, C. Posthuma, J. S. Lolkema, P. Schmitt, C. Divies, and W. N. Konings, J. Bacteriol. 178:2178-2185, 1996). Reports on the energetics of citrate metabolism in the related organism Lactococcus lactis are contradictory, and this study was performed to clarify this issue. Cloning of the membrane potential-generating citrate transporter (CitP) of Leuconostoc mesenteroides revealed an amino acid sequence that is almost identical to the known sequence of the CitP of Lactococcus lactis. The cloned gene was expressed in a Lactococcus lactis Cit- strain, and the gene product was functionally characterized in membrane vesicles. Uptake of citrate was counteracted by the membrane potential, and the transporter efficiently catalyzed heterologous citrate-lactate exchange. These properties are essential for generation of a membrane potential under physiological conditions and show that the Leuconostoc CitP retains its properties when it is embedded in the cytoplasmic membrane of Lactococcus lactis. Furthermore, using the same criteria and experimental approach, we demonstrated that the endogenous CitP of Lactococcus lactis has the same properties, showing that the few differences in the amino acid sequences of the CitPs of members of the two genera do not result in different catalytic mechanisms. The results strongly suggest that the energetics of citrate degradation in Lactococcus lactis and Leuconostoc mesenteroides are the same; i.e., citrate metabolism in Lactococcus lactis is a proton motive force-generating process.

Amino Acid Sequence↗
PubMed1998

[Biological response modifier activity of Lactococcus lactis 332].

The biological response modifier (BRM) activity of a preparation of heat killed cells of Lactococcus lactis 332 which can produce large amount of lactate in culture, was investigated in C3H/He and ICR mice. Intraperitoneal injection of Lactococcus lactis 332 caused an accumulation of neutrophils and macrophages in the peritoneal cavity of the mice, similarly to BRMs used clinically. As a parameter of the activation of macrophages, the effect of the Lactococcus lactis 332 preparation on the production of tumor necrosis factor (TNF) was examined. The Lactococcus lactis 332 preparation was revealed to have both priming and triggering activities for the production of TNF. The TNF level in the sera reached about 1000 IU/ml in mice 2 h after the triggering injection. This preparation also stimulated peritoneal macrophages to produce TNF in vitro. Intratumoral injection of the Lactococcus lactis 332 preparation regressed MM46 tumor cells in C3H/He mice. These results suggest that the Lactococcus lactis 332 preparation is a biological response modifier (BRM) with various activities on phagocytes similarly to a streptococcal antitumor agent, OK432, used clinically.

Animals↗
PubMed2026

Development of a Multiplex Polymerase Chain Reaction Assay for Differentiating Three Lactococcus Species Associated With Piscine Lactococcosis.

Piscine lactococcosis is an important bacterial disease of farmed fish. The causative agents, Lactococcus garvieae, Lactococcus petauri and Lactococcus formosensis, are closely related, which complicates species-level identification. We developed a conventional multiplex PCR assay targeting species-specific genes identified by comparative genomic analysis. Average nucleotide identity reassignment of 441 publicly available genome assemblies identified 111 L. garvieae, 255 L. petauri and 75 L. formosensis genomes. Species-specific primers and a tuf-based Lactococcus common control were evaluated using in silico polymerase chain reaction (PCR) against target genomes and 10,460 off-target assemblies representing 474 taxa in 12 genera. Experimental specificity was assessed using six target strains and 19 non-target fish pathogens. Distinct amplicons of 195, 333 and 500 bp were produced for L. garvieae, L. petauri and L. formosensis, respectively, together with a 132-bp control amplicon. No cross-amplification was observed. All target species were detected in mixed-DNA samples and spiked kidney and spleen homogenates from two fish species. Analytical detection limits were estimated based on microscopic cell counts of bacterial suspensions before DNA extraction and ranged from 0.956 to 8.55 cell equivalents per reaction. This assay represents a rapid, low-cost method for differentiating lactococcosis-causing Lactococcus species using standard PCR and agarose gel electrophoresis.

Lactococcus garvieae↗
PubMed1992

Novel paired starter culture system for sauerkraut, consisting of a nisin-resistant Leuconostoc mesenteroides strain and a nisin-producing Lactococcus lactis strain.

Nisin-resistant Leuconostoc mesenteroides NCK293 and nisin-producing Lactococcus lactis subsp. lactis NCK401 were evaluated separately and in combination for growth and nisin production in a model sauerkraut fermentation. Strains were genetically marked and selectively enumerated by using antibiotic-containing media. The growth and survival of L. mesenteroides were similar in the presence and absence of Lactococcus lactis subsp. lactis. The growth of Lactococcus lactis subsp. lactis was not inhibited, although the maximum cell density was reduced and the population decline was more pronounced in the presence of L. mesenteroides. Nisin was detected within 24 h, and levels were relatively constant over the 12-day test period. The maximum cell populations and nisin level achieved could be altered by changing the initial cell ratios of L. mesenteroides and lactococcus lactis subsp. lactis. Isogenic nisin-producing and nisin-negative Lactococcus lactis subsp. lactis derivatives were used in combination with nisin-resistant L. mesenteroides to demonstrate that nisin levels produced in mixed culture were sufficient to retard the onset of the growth of nisin-sensitive, homofermentative Lactobacillus plantarum ATCC 14917.

Colony Count, Microbial↗
PubMed2026

Phenotypic and phylogenomic characterization of Lactococcus garvieae isolates from rainbow trout (Oncorhynchus mykiss) in Türkiye.

Lactococcosis is an important bacterial disease of farmed fish and causes substantial economic losses in rainbow trout (Oncorhynchus mykiss) aquaculture. In this study, Lactococcus garvieae isolates recovered from rainbow trout farms in Türkiye were characterized using phenotypic, molecular, and phylogenomic methods. Among 32 presumptive Lactococcus isolates recovered from 127 dead rainbow trout, four were confirmed as L. garvieae and exhibited identical biochemical characteristics, Pulsed Field Gel Electrophoresis (PFGE) profiles, and broad growth tolerance across different pH, salinity, and temperature conditions. All isolates were presumptively classified as resistant to ciprofloxacin and florfenicol, while remaining susceptible to tetracycline and penicillin. Based on the AMR profiles, strain LG2, which exhibited the most susceptible antimicrobial profile among the isolates, was selected for whole-genome sequencing (WGS). WGS of the representative isolate LG2 generated a single 2,214,687-bp chromosomal contig with 38.5% GC content and 99.0% BUSCO completeness. In silico PCR assigned LG2 to serotype I, and the genome contained an intact capsule-associated cps/kps locus. The chromosomal lsa(D) determinant and an mdt(A)-like efflux-associated gene were detected, whereas no plasmid replicons or acquired quinolone or florfenicol resistance genes were identified, indicating discordance between the phenotypic and genomic AMR results. Taxonomic verification of 236 publicly available Lactococcus assemblies yielded 41 verified public L. garvieae genomes, which, together with LG2, formed a 42-genome within-species dataset. LG2 was most closely related to the Turkish isolate OS-37, sharing 99.96% ANI and differing by three core SNPs; both belonged to ST109, whereas the other Turkish isolates belonged to ST139. cgMLST identified a conserved genomic backbone, while pan-genome analysis identified 5,655 gene clusters and an open pan-genome characterized by a large cloud-gene fraction. These findings demonstrate the importance of species verification in Lactococcus population genomics and reveal substantial accessory-genome diversity within L. garvieae. The genomic features of LG2 provide a basis for future pathogenicity and immunogenicity studies, although experimental validation is required. Overall, these findings highlight the importance of local genomic surveillance for understanding L. garvieae population structure and provide a genomic framework for future region-specific vaccine research.

Animals↗
PubMed1994

Genetic analysis of the minimal replicon of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate plasmid.

Using a combination of mutagenesis with the transposon gamma delta and polymerase chain reaction subcloning, the essential elements of the replication region of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate plasmid have been identified. An open reading frame, coding for a protein with homology to Rep proteins from other Lactococcus plasmids, is essential. This protein is trans-acting and could not be replaced by the Rep protein from another Lactococcus plasmid. A second open reading frame immediately downstream from the first could be removed or inactivated with no apparent effect on plasmid replication. A region containing two 10 bp direct repeats and three tandem repeats of a 22 bp sequence, immediately upstream of the essential open reading frame, is also essential and probably includes the origin of replication. A 181-bp DNA fragment containing this region was sufficient to allow replication in Lactococcus if the trans-acting protein was provided on another replicon. Single-stranded replication intermediates could not be detected, suggesting that the citrate plasmid uses theta replication rather than rolling-circle replication.

Amino Acid Sequence↗
PubMed1991

Development and application of oligonucleotide probes for identification of Lactococcus lactis subsp. cremoris.

Lactococcus lactis subsp. cremoris is of considerable interest to the dairy industry, which relies upon the few available strains for the manufacture of cheddar cheese free of fermented and fruity flavors. The subspecies cremoris differs from related subspecies by the lack of a few phenotypic traits. Our purpose was to identify unique rRNA sequences that could be used to discriminate L. lactis subsp. cremoris from related subspecies. The 16S rRNAs from 13 Lactococcus strains were partially sequenced by using reverse transcriptase to identify domains unique to L. lactis subsp. cremoris. All five strains of the subspecies cremoris had a unique base sequence in a hypervariable region located 70 to 100 bases from the 5' terminus. In this region, all L. lactis subsp. lactis biovar diacetylactis strains examined had a sequence identical to that of L. lactis subsp. lactis 7962, which was different from other strains of the subspecies lactis by only one nucleotide at position 90 (Escherichia coli 16S rRNA structural model) (J. Brosius, J. L. Palmer, J. P. Kennedy, and H. F. Noller, Proc. Natl. Acad. Sci. USA 75:4801-4805, 1978). Oligonucleotide probes specific for the genus Lactococcus (212RLa) and for the subspecies cremoris (68RCa) were synthesized and evaluated by hybridization to known rRNAs as well as fixed whole cells. Efficient and specific hybridization to the genus-specific probe was observed for the 13 Lactococcus strains tested. No hybridization was seen with the control species. All five strains of the subspecies cremoris hybridized to the subspecies-specific probe.

Base Sequence↗