Lactococcus lactis: A non-pathogenic species of LACTOCOCCUS found in DAIRY PRODUCTS and responsible for the souring of MILK and the production of LACTIC ACID.Lactococcus: A genus of gram-positive, coccoid bacteria mainly isolated from milk and milk products. These bacteria are also found in plants and nonsterile frozen and dry foods. Previously thought to be a member of the genus STREPTOCOCCUS (group N), it is now recognized as a separate genus.Nisin: A 34-amino acid polypeptide antibiotic produced by Streptococcus lactis. It has been used as a food preservative in canned fruits and vegetables, and cheese.Cheese: A nutritious food consisting primarily of the curd or the semisolid substance formed when milk coagulates.Bacterial Proteins: Proteins found in any species of bacterium.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Bacteriophages: Viruses whose hosts are bacterial cells.Bacteriocins: Substances elaborated by specific strains of bacteria that are lethal against other strains of the same or related species. They are protein or lipopolysaccharide-protein complexes used in taxonomy studies of bacteria.Genes, Bacterial: The functional hereditary units of BACTERIA.Siphoviridae: A family of BACTERIOPHAGES and ARCHAEAL VIRUSES which are characterized by long, non-contractile tails.Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Leuconostoc: A genus of gram-positive, facultatively anaerobic bacteria whose growth is dependent on the presence of a fermentable carbohydrate. It is nonpathogenic to plants and animals, including humans.Lactobacillus: A genus of gram-positive, microaerophilic, rod-shaped bacteria occurring widely in nature. Its species are also part of the many normal flora of the mouth, intestinal tract, and vagina of many mammals, including humans. Pathogenicity from this genus is rare.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Fermentation: Anaerobic degradation of GLUCOSE or other organic nutrients to gain energy in the form of ATP. End products vary depending on organisms, substrates, and enzymatic pathways. Common fermentation products include ETHANOL and LACTIC ACID.Plasmids: Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Kluyveromyces: An ascomycetous yeast of the fungal family Saccharomycetaceae, order SACCHAROMYCETALES.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Milk: The white liquid secreted by the mammary glands. It contains proteins, sugar, lipids, vitamins, and minerals.Operon: In bacteria, a group of metabolically related genes, with a common promoter, whose transcription into a single polycistronic MESSENGER RNA is under the control of an OPERATOR REGION.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Lactose: A disaccharide of GLUCOSE and GALACTOSE in human and cow milk. It is used in pharmacy for tablets, in medicine as a nutrient, and in industry.Cultured Milk Products: Milk modified with controlled FERMENTATION. This should not be confused with KAFFIR LIME or with KAFFIR CORN.Acetoin: A product of fermentation. It is a component of the butanediol cycle in microorganisms. In mammals it is oxidized to carbon dioxide.Conjugation, Genetic: A parasexual process in BACTERIA; ALGAE; FUNGI; and ciliate EUKARYOTA for achieving exchange of chromosome material during fusion of two cells. In bacteria, this is a uni-directional transfer of genetic material; in protozoa it is a bi-directional exchange. In algae and fungi, it is a form of sexual reproduction, with the union of male and female gametes.Diacetyl: Carrier of aroma of butter, vinegar, coffee, and other foods.Open Reading Frames: A sequence of successive nucleotide triplets that are read as CODONS specifying AMINO ACIDS and begin with an INITIATOR CODON and end with a stop codon (CODON, TERMINATOR).Streptococcus thermophilus: A species of thermophilic, gram-positive bacteria found in MILK and milk products.Food Microbiology: The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept.Food Industry: The industry concerned with processing, preparing, preserving, distributing, and serving of foods and beverages.Streptococcus Phages: Viruses whose host is Streptococcus.Genetic Engineering: Directed modification of the gene complement of a living organism by such techniques as altering the DNA, substituting genetic material by means of a virus, transplanting whole nuclei, transplanting cell hybrids, etc.Culture Media: Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.Pediococcus: A genus of gram-positive, facultatively anaerobic bacteria whose growth is dependent on the presence of a fermentable carbohydrate. No endospores are produced. Its organisms are found in fermenting plant products and are nonpathogenic to plants and animals, including humans.Chromosomes, Bacterial: Structures within the nucleus of bacterial cells consisting of or containing DNA, which carry genetic information essential to the cell.Dairy Products: Raw and processed or manufactured milk and milk-derived products. These are usually from cows (bovine) but are also from goats, sheep, reindeer, and water buffalo.Phosphofructokinases: Allosteric enzymes that regulate glycolysis and gluconeogenesis. These enzymes catalyze phosphorylation of fructose-6-phosphate to either fructose-1,6-bisphosphate (PHOSPHOFRUCTOKINASE-1 reaction), or to fructose-2,6-bisphosphate (PHOSPHOFRUCTOKINASE-2 reaction).Restriction Mapping: Use of restriction endonucleases to analyze and generate a physical map of genomes, genes, or other segments of DNA.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Industrial Microbiology: The study, utilization, and manipulation of those microorganisms capable of economically producing desirable substances or changes in substances, and the control of undesirable microorganisms.Cholates: Salts and esters of CHOLIC ACID.Bacteriolysis: Rupture of bacterial cells due to mechanical force, chemical action, or the lytic growth of BACTERIOPHAGES.Aminopeptidases: A subclass of EXOPEPTIDASES that act on the free N terminus end of a polypeptide liberating a single amino acid residue. EC 3.4.11.Lactobacillus plantarum: A species of rod-shaped, LACTIC ACID bacteria used in PROBIOTICS and SILAGE production.Caseins: A mixture of related phosphoproteins occurring in milk and cheese. The group is characterized as one of the most nutritive milk proteins, containing all of the common amino acids and rich in the essential ones.DNA Transposable Elements: Discrete segments of DNA which can excise and reintegrate to another site in the genome. Most are inactive, i.e., have not been found to exist outside the integrated state. DNA transposable elements include bacterial IS (insertion sequence) elements, Tn elements, the maize controlling elements Ac and Ds, Drosophila P, gypsy, and pogo elements, the human Tigger elements and the Tc and mariner elements which are found throughout the animal kingdom.Transformation, Bacterial: The heritable modification of the properties of a competent bacterium by naked DNA from another source. The uptake of naked DNA is a naturally occuring phenomenon in some bacteria. It is often used as a GENE TRANSFER TECHNIQUE.Lactic Acid: A normal intermediate in the fermentation (oxidation, metabolism) of sugar. The concentrated form is used internally to prevent gastrointestinal fermentation. (From Stedman, 26th ed)Cell Wall: The outermost layer of a cell in most PLANTS; BACTERIA; FUNGI; and ALGAE. The cell wall is usually a rigid structure that lies external to the CELL MEMBRANE, and provides a protective barrier against physical or chemical agents.Food Technology: The application of knowledge to the food industry.Streptococcus: A genus of gram-positive, coccoid bacteria whose organisms occur in pairs or chains. No endospores are produced. Many species exist as commensals or parasites on man or animals with some being highly pathogenic. A few species are saprophytes and occur in the natural environment.Phosphoglucomutase: An enzyme that catalyzes the conversion of alpha D-glucose 1-phosphate to alpha D-glucose 6-phosphate. EC A rod-shaped, gram-positive, non-acid-fast, non-spore-forming, non-motile bacterium that is a genus of the family Bifidobacteriaceae, order Bifidobacteriales, class ACTINOBACTERIA. It inhabits the intestines and feces of humans as well as the human vagina.Micrococcal Nuclease: An enzyme that catalyzes the endonucleolytic cleavage to 3'-phosphomononucleotide and 3'-phospholigonucleotide end-products. It can cause hydrolysis of double- or single-stranded DNA or RNA. (From Enzyme Nomenclature, 1992) EC Dehydrogenase: A tetrameric enzyme that, along with the coenzyme NAD+, catalyzes the interconversion of LACTATE and PYRUVATE. In vertebrates, genes for three different subunits (LDH-A, LDH-B and LDH-C) exist.Lactobacillaceae: A family of gram-positive bacteria found regularly in the mouth and intestinal tract of man and other animals, in food and dairy products, and in fermenting vegetable juices. A few species are highly pathogenic.

Novel characteristic for distinguishing Lactococcus lactis subsp. lactis from subsp. cremoris. (1/1459)

Lactococcus lactis strains were examined for their ability to produce gamma-aminobutyric acid (GABA). Results showed that strains of L. lactis subsp. lactis were able to produce this acid, whereas L. lactis subsp. cremoris were not. GABA production thus represents another effective characteristic for distinguishing L. lactis subsp. lactis from L. lactis subsp. cremoris.  (+info)

Mechanism of citrate metabolism in Lactococcus lactis: resistance against lactate toxicity at low pH. (2/1459)

Measurement of the flux through the citrate fermentation pathway in resting cells of Lactococcus lactis CRL264 grown in a pH-controlled fermentor at different pH values showed that the pathway was constitutively expressed, but its activity was significantly enhanced at low pH. The flux through the citrate-degrading pathway correlated with the magnitude of the membrane potential and pH gradient that were generated when citrate was added to the cells. The citrate degradation rate and proton motive force were significantly higher when glucose was metabolized at the same time, a phenomenon that could be mimicked by the addition of lactate, the end product of glucose metabolism. The results clearly demonstrate that citrate metabolism in L. lactis is a secondary proton motive force-generating pathway. Although the proton motive force generated by citrate in cells grown at low pH was of the same magnitude as that generated by glucose fermentation, citrate metabolism did not affect the growth rate of L. lactis in rich media. However, inhibition of growth by lactate was relieved when citrate also was present in the growth medium. Citrate did not relieve the inhibition by other weak acids, suggesting a specific role of the citrate transporter CitP in the relief of inhibition. The mechanism of citrate metabolism presented here provides an explanation for the resistance to lactate toxicity. It is suggested that the citrate metabolic pathway is induced under the acidic conditions of the late exponential growth phase to make the cells (more) resistant to the inhibitory effects of the fermentation product, lactate, that accumulates under these conditions.  (+info)

A general method for selection of alpha-acetolactate decarboxylase-deficient Lactococcus lactis mutants to improve diacetyl formation. (3/1459)

The enzyme acetolactate decarboxylase (Ald) plays a key role in the regulation of the alpha-acetolactate pool in both pyruvate catabolism and the biosynthesis of the branched-chain amino acids, isoleucine, leucine, and valine (ILV). This dual role of Ald, due to allosteric activation by leucine, was used as a strategy for the isolation of Ald-deficient mutants of Lactococcus lactis subsp. lactis biovar diacetylactis. Such mutants can be selected as leucine-resistant mutants in ILV- or IV-prototrophic strains. Most dairy lactococcus strains are auxotrophic for the three amino acids. Therefore, the plasmid pMC004 containing the ilv genes (encoding the enzymes involved in the biosynthesis of IV) of L. lactis NCDO2118 was constructed. Introduction of pMC004 into ILV-auxotrophic dairy strains resulted in an isoleucine-prototrophic phenotype. By plating the strains on a chemically defined medium supplemented with leucine but not valine and isoleucine, spontaneous leucine-resistant mutants were obtained. These mutants were screened by Western blotting with Ald-specific antibodies for the presence of Ald. Selected mutants lacking Ald were subsequently cured of pMC004. Except for a defect in the expression of Ald, the resulting strain, MC010, was identical to the wild-type strain, as shown by Southern blotting and DNA fingerprinting. The mutation resulting in the lack of Ald in MC010 occurred spontaneously, and the strain does not contain foreign DNA; thus, it can be regarded as food grade. Nevertheless, its application in dairy products depends on the regulation of genetically modified organisms. These results establish a strategy to select spontaneous Ald-deficient mutants from transformable L. lactis strains.  (+info)

Characterization of the divergent sacBK and sacAR operons, involved in sucrose utilization by Lactococcus lactis. (4/1459)

The divergently transcribed sacBK and sacAR operons, which are involved in the utilization of sucrose by Lactococcus lactis NZ9800, were examined by transcriptional and gene inactivation studies. Northern analyses of RNA isolated from cells grown at the expense of different carbon sources revealed three sucrose-inducible transcripts: one of 3.2 kb containing sacB and sacK, a second of 3.4 kb containing sacA and sacR, and a third of 1.8 kb containing only sacR. The inactivation of the sacR gene by replacement recombination resulted in the constitutive transcription of the sacBK and sacAR operons in the presence of different carbon sources, indicating that SacR acts as a repressor of transcription.  (+info)

Membrane topology of the lactococcal bacteriocin ATP-binding cassette transporter protein LcnC. Involvement of LcnC in lactococcin a maturation. (5/1459)

Many non-lantibiotic bacteriocins of lactic acid bacteria are produced as precursors with N-terminal leader peptides different from those present in preproteins exported by the general sec-dependent (type II) secretion pathway. These bacteriocins utilize a dedicated (type I) secretion system for externalization. The secretion apparatus for the lactococcins A, B, and M/N (LcnA, B, and M/N) from Lactococcus lactis is composed of the two membrane proteins LcnC and LcnD. LcnC belongs to the ATP-binding cassette transporters, whereas LcnD is a protein with similarities to other accessory proteins of type I secretion systems. This paper shows that the N-terminal part of LcnC is involved in the processing of the precursor of LcnA. By making translational fusions of LcnC to the reporter proteins beta-galactosidase (LacZ) and alkaline phosphatase (PhoA*), it was shown that both the N- and C-terminal parts of LcnC are located in the cytoplasm. As the N terminus of LcnC is required for LcnA maturation and is localized in the cytoplasm, we conclude that the processing of the bacteriocin LcnA to its mature form takes place at the cytosolic side of the cytoplasmic membrane.  (+info)

Hydrolysis of alphas1- and beta-casein-derived peptides with a broad specificity aminopeptidase and proline specific aminopeptidases from Lactococcus lactis subsp. cremoris AM2. (6/1459)

Aminopeptidase hydrolysis of alpha(s)1 - and beta-casein-derived synthetic peptides containing non-consecutive and consecutive proline residues was characterised. Aminopeptidase P (Pep P) (EC or post-proline dipeptidyl aminopeptidase (PPDA) (EC along with lysine-paranitroanilide hydrolase (KpNA-H) (EC activities are required in the degradation of peptides containing non-consecutive proline residues. However, both Pep P and PPDA along with KpNA-H are required for hydrolysis of peptides containing consecutive proline residues. The results demonstrate the mechanism by which combinations of purified general and proline specific aminopeptidases from Lactococcus lactis subsp. cremoris AM2 hydrolyse peptides containing proline residues.  (+info)

Regulation of expression of the Lactococcus lactis histidine operon. (7/1459)

In Lactococcus lactis, the his operon contains all the genes necessary for histidine biosynthesis. It is transcribed from a unique promoter, localized 300 bp upstream of the first gene. The region corresponding to the untranslated 5' end of the transcript, named the his leader region, displays the typical features of the T box transcriptional attenuation mechanism which is involved in the regulation of many amino acid biosynthetic operons and tRNA synthetase genes in gram-positive bacteria. Here we describe the regulation of transcription of the his operon by the level of histidine in the growth medium. In the absence of histidine, two transcripts are present. One covers the entire operon, while the other stops at a terminator situated about 250 bp downstream of the transcription start point. DNA sequences implicated in regulation of the his operon were identified by transcriptional fusion with luciferase genes and site-directed mutagenesis. In addition to the previously defined sequences necessary for effective T-box-mediated regulation, new essential regions were identified. Eighteen percent of the positions of the his leader region were found to differ in seven distantly related strains of L. lactis. Analysis of the variable positions supports the folding model of the central part of the his leader region. Lastly, in addition to the T-box-mediated regulation, the operon is regulated at the level of initiation of transcription, which is repressed in the presence of histidine. An operator site, necessary for full repression, overlaps the terminator involved in the T box attenuation mechanism. The functionality of the operator is altered on plasmids with low and high copy numbers, suggesting that supercoiling may play a role in the expression of the his operon. The extents of regulation at the levels of initiation and attenuation of transcription are 6- to 8-fold and 14-fold, respectively. Together, the two levels of control allow a 120-fold range of regulation of the L. lactis operon by histidine.  (+info)

Disruption and analysis of the clpB, clpC, and clpE genes in Lactococcus lactis: ClpE, a new Clp family in gram-positive bacteria. (8/1459)

In the genome of the gram-positive bacterium Lactococcus lactis MG1363, we have identified three genes (clpC, clpE, and clpB) which encode Clp proteins containing two conserved ATP binding domains. The proteins encoded by two of the genes belong to the previously described ClpB and ClpC families. The clpE gene, however, encodes a member of a new Clp protein family that is characterized by a short N-terminal domain including a putative zinc binding domain (-CX2CX22CX2C-). Expression of the 83-kDa ClpE protein as well as of the two proteins encoded by clpB was strongly induced by heat shock and, while clpC mRNA synthesis was moderately induced by heat, we were unable to identify the ClpC protein. When we analyzed mutants with disruptions in clpB, clpC, or clpE, we found that although the genes are part of the L. lactis heat shock stimulon, the mutants responded like wild-type cells to heat and salt treatments. However, when exposed to puromycin, a tRNA analogue that results in the synthesis of truncated, randomly folded proteins, clpE mutant cells formed smaller colonies than wild-type cells and clpB and clpC mutant cells. Thus, our data suggest that ClpE, along with ClpP, which recently was shown to participate in the degradation of randomly folded proteins in L. lactis, could be necessary for degrading proteins generated by certain types of stress.  (+info)

  • in the genome of L. lactis MG1363. (
  • A novel plant-niche-related PTS component Llmg_0963 forming a hybrid transporter Llmg_0963PtcBA and a glucose/mannose-specific PTS are shown to be involved in galactose transport in L. lactis MG1363. (
  • Lactococcus lactis is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease. (
  • lactis is added to milk, the bacterium uses enzymes to produce energy molecules (ATP), from lactose. (
  • A bill to designate Lactococcus lactis , a bacterium used in making cheese, as the state microbe has passed the Wisconsin Assembly and is now going to be voted by the state senate. (
  • Oral and Intra nasal vaccination with recombinant Lactococcus lactis can induce high level immune responses to tetanus toxin fragment C elicits. (
  • A recombinant Lactococcus lactis which produced and secreted pEGF at 1000 ng/ml in culture supernatant was generated. (
  • We have generated a recombinant Lactococcus lactis which produced and secreted fully biologically active porcine EGF. (
  • L. lactis is one of the best characterized low GC Gram positive bacteria with detailed knowledge on genetics, metabolism and biodiversity. (
  • Bacteriophages specific to L. lactis cause significant economic losses each year by preventing the bacteria from fully metabolizing the milk substrate. (
  • In Shuichi Nakamura's, Yusuke V. Marimoto, and Seishi Kudo's study, they seek to prove that some fermentation produced by L.lactis can hinder motility in pathogenic bacteria. (
  • It is produced by lactic acid bacteria Lactococcus lactis subsp. (
  • Applications are invited for the position of Junior Research Fellow on SERB sponsored project entitled "Evaluation of immunogenicity and protective efficacy of bivalent vaccine candidate against Shigella and Salmonella using food grade bacteria Lactococcus lactis " under the supervision of Dr. Priti Desai, Institute of Advanced Research, Koba Institutional Area, Koba, Gandhinagar-382 007. (
  • L. lactis makes sense for Wisconsin - the bacteria helps make cheese, and Wisconsin is known as the "Cheese State. (
  • Consistent with the results from comparative genomics (see references above) this resulted in L. lactis losing or down-regulating genes which are dispensable in milk and the up-regulation of peptide transport. (
  • We established a procedure for robust estimation of the ribosomal density in hundreds of genes from Lactococcus lactis polysome size measurements. (
  • The success of this strain's construction helped to inhibit migration and expansion of cancer cells, showing that the secretion properties of L.lactis of this particular peptide illustrates a hopeful future in Cancer therapy. (
  • Genetic marking of Lactococcus lactis shows its survival in the human gastrointestinal tract. (
  • Lactococcus lactis IO-1 (JCM7638) produces L-lactic acid predominantly when grown at high xylose concentrations, and its utilization is highly desired in the green plastics industry. (
  • The capability to produce lactic acid is one of the reasons why L. lactis is one of the most important microorganisms in the dairy industry. (
  • van der Heide, T., and Poolman, B. (2000) Osmoregulated ABC-transport system of Lactococcus lactis senses water stress via changes in the physical state of the membrane. (
  • New insights into the complex regulation of the glycolytic pathway in Lactococcus lactis. (
  • The engineering of glycerol metabolism in L. lactis was initiated from three different perspectives: overexpression of glycerol kinase from L. lactis, introduction of a heterologous glycerol assimilation pathway and construction of a library of NADH oxidase activity. (
  • Ganesan, B, Dobrowolski, P & Weimer, BC 2006, ' Identification of the leucine-to-2-methylbutyric acid catabolic pathway of Lactococcus lactis ', Applied and Environmental Microbiology , vol. 72, no. 6, pp. 4264-4273. (
  • SubC signal for extracellular localization in B. licheniformis, was also recognized by L. lactis Sec pathway, although with lower efficiency, as shown by a 3-fold lower protease activity in the medium. (
  • Comparative Genome Analysis of Lactococcus lactis Indicates Niche Adaptation and Resolves Genotype/Phenotype Disparity. (
  • lactis may be a useful tool for preventing infections by multiple bacterial species. (
  • During industrial processes, L. lactis is often exposed to multiple environmental stresses (low and high temperature, low pH, high osmotic pressure, nutrient starvation and oxidation) that can cause loss or reduction of bacterial viability, reproducibility, as well as organoleptic and/or fermentative qualities. (
  • The most cost-effective method for the preservation of L. lactis starter cultures is spray drying, but during this process cultures encounter heat and oxidative stress, typically resulting in low survival rates. (
  • During the last two decades, considerable efforts have been made to improve our knowledge of oxidative stress in L. lactis. (
  • Expression of SARS-coronavirus nucleocapsid protein in Escherichia coli and Lactococcus lactis for serodiagnosis and mucosal vaccination. (