Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
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| the sequence of spacers between the consensus sequences modulates the strength of prokaryotic promoters. | we constructed a library of synthetic promoters for lactococcus lactis in which the known consensus sequences were kept constant while the sequences of the separating spacers were randomized. the library consists of 38 promoters which differ in strength from 0.3 up to more than 2,000 relative units, the latter among the strongest promoters known for this organism. the ranking of the promoter activities was somewhat different when assayed in escherichia coli, but the promoters are efficient for m ... | 1998 | 9435063 |
| functional display of a heterologous protein on the surface of lactococcus lactis by means of the cell wall anchor of staphylococcus aureus protein a. | in this study, we showed that the cell wall anchor of protein a from staphylococcus aureus is functional in the food-grade organism lactococcus lactis. a fusion protein composed of the lactococcal usp45 secretion signal peptide, streptavidin monomer, and the s. aureus protein a anchor became covalently attached to the peptidoglycan when expressed in l. lactis. the streptavidin moiety of the fusion protein was functionally exposed at the cellular surface. l. lactis cells expressing the anchored f ... | 1998 | 9435087 |
| identification of the lactococcal exonuclease/recombinase and its modulation by the putative chi sequence. | studies of recbcd-chi interactions in escherichia coli have served as a model to understand recombination events in bacteria. however, the existence of similar interactions has not been demonstrated in bacteria unrelated to e. coli. we developed an in vivo model to examine components of dsdna break repair in various microorganisms. here, we identify the major exonuclease in lactococcus lactis, a gram-positive organism evolutionarily distant from e. coli, and provide evidence for exonuclease-chi ... | 1998 | 9435243 |
| [a study on anti-caries activity of genetic recombinant vaccine of streptococcus lactis. ii. immunization in vein with recombinant s. lactis in pregnant rabbits]. | the effects of immunization in vein with recombinant s. lactis hl107 carring the s. mutans surface protein pac gene in pregnant rabbits were studied. the results indicated that specific anti-pac igg in serum and milk were obviously induced 1 week after immunization and retained at high level for several weeks. it suggests that the recombinant s. lactis hl107 possessing immunogenicity of s. mutans surface protein pac is able to stimulate specific systemic immune response against pac. | 1998 | 12214406 |
| [part of biological activity of peptidoglycan from streptococcus lactis sb900]. | peptidoglycan of streptococcus lactis sb900(labpg) was isolated. it's chemical composition was analyzed and part of biological activity was examined. the pg contained 9.84% protein, 0.871 mumol/m nag, 1.14 mumol/mg nam. the amino acids of relatively high concentrations were ala, glu, asp and their concentrations were 1.046, 0.775, 0.304 mumol/mg respectively. using mice as subject, the animal experiment confirmed that labpg was non-toxic and safe. effect of i.p. labpg 0.5 mg/mouse on the phagocy ... | 1998 | 12549402 |
| cell membrane integrity and lysis in lactococcus lactis: the detection of a population of permeable cells in post-logarithmic phase cultures. | a method was developed that enabled an analysis of the proportion of permeable cells in a culture of lactococcus lactis. this used the fluorescence of propidium iodide (pi) when in contact with dna and the impermeability of the intact cell membrane to this compound. a permeability index was suggested that expresses the pi-induced fluorescence of a cell suspension as a percentage of the value obtained from wholly permeabilized cells after treatment with cetyltrimethylammonium bromide. this method ... | 1998 | 15244062 |
| a type ic restriction-modification system in lactococcus lactis. | three genes coding for the endonuclease, methylase, and specificity subunits of a type i restriction-modification (r-m) system in the lactococcus lactis plasmid pil2614 have been characterized. plasmid location, sequence homologies, and inactivation studies indicated that this r-m system is most probably of type ic. | 1998 | 9440532 |
| a bacterial antibiotic-resistance gene that complements the human multidrug-resistance p-glycoprotein gene. | bacteria have developed many fascinating antibiotic-resistance mechanisms. a protein in lactococcus lactis, lmra, mediates antibiotic resistance by extruding amphiphilic compounds from the inner leaflet of the cytoplasmic membrane. unlike other known bacterial multidrug-resistance proteins, lmra is an atp-binding cassette (abc) transporter. the human multidrug-resistance p-glycoprotein, encoded by the mdr1 gene, is also an abc transporter, overexpression of which is one of the principal causes o ... | 1998 | 9440694 |
| crystallization and preliminary x-ray diffraction studies of 6-phosphogluconate dehydrogenase from lactococcus lactis. | 6-phosphogluconate dehydrogenase is one of the seven enzymes involved in the pentose phosphate pathway. crystals of a mammalian and a protozoan enzyme have been obtained previously and structures determined. it is reported here that a bacterial 6-phosphogluconate dehydrogenase, from lactococcus lactis, has been purified and used in crystallization trials. large prisms suitable for a detailed structural analysis have been obtained and characterized as orthorhombic, space group f222, with a = 70.4 ... | 1998 | 10089526 |
| transcriptional activation of the glycolytic las operon and catabolite repression of the gal operon in lactococcus lactis are mediated by the catabolite control protein ccpa. | the lactococcus lactis ccpa gene, encoding the global regulatory protein ccpa, was identified and characterized. northern blot and primer extension analyses showed that the l. lactis ccpa gene is constitutively transcribed from a promoter that does not contain a cre sequence. inactivation of the ccpa gene resulted in a twofold reduction in the growth rate compared with the wild type on glucose, sucrose and fructose, while growth on galactose was almost completely abolished. the observed growth d ... | 1998 | 10094627 |
| bactericidal action of 308 nm excimer-laser radiation: an in vitro investigation. | the aim of the present study was to investigate the influence of 308 nm excimer-laser radiation on bacterial growth. six different bacterial strains (staphylococcus aureus, escherichia coli, streptococcus faecalis, lactococcis lactis, salmonella typhimurium, and deinococcus radiodurans) were exposed in vitro to various doses and energy densities of laser radiation. to exclude bacterial killing by supraphysiological heating, the temperature change in the samples during irradiation was measured. e ... | 1998 | 10023253 |
| persistence of escherichia coli o157:h7 in dairy fermentation systems. | we examined (i) the persistence of escherichia coli o157:h7 as a postpasteurization contaminant in fermented dairy products; (ii) the ability of e. coli o157:h7 strains with and without the general stress regulatory protein, rpos, to compete with commercial starter cultures in fermentation systems; and (iii) the survival of e. coli o157:h7 in the yogurt production process. in commercial products inoculated with 10(3) cfu/ml, e. coli o157:h7 was recovered for up to 12 days in yogurt (ph 4.0), 28 ... | 1998 | 9874336 |
| molecular diversity and relationship within lactococcus lactis, as revealed by randomly amplified polymorphic dna (rapd). | lactococcus lactis strains are widely used in industrial dairy fermentations. conventional phenotypic tests have been used for years to classify members of this species into two subspecies, lactis and cremoris, and play a key role in the choice of strains to be used in particular cheese fermentations. dna hybridisation techniques have also been used for strain classification, giving rise to two genome homology groups. however, results showed discrepancies between the two methods of classificatio ... | 1998 | 9924821 |
| characterization of lactococci isolated from minimally processed fresh fruit and vegetables. | lactic acid bacteria isolated from minimally processed fresh fruit and vegetable products were identified as lactococcus lactis subsp. lactis on the basis of phenotypic tests, presence of lactococcal is elements, and partial sequence analysis of the 16s rrna gene. isolated bacteria were differentiated using pulsed-field gel electrophoresis of smai digests of genomic dna. sprouted seeds were the best source of strains, and lactococci appear to be the dominant microflora on these products during t ... | 1998 | 9924939 |
| oat bran beta-gluco- and xylo-oligosaccharides as fermentative substrates for lactic acid bacteria. | the influence of oat bran oligosaccharides on carbohydrate utilization and fermentation end-products was studied with reference to three different lactic acid bacteria (lab: lactobacillus rhamnosus, lactobacillus plantarum and lactococcus lactis). the main results were that all three lab utilized oat beta-gluco-oligosaccharides, while only l. plantarum utilized xylo-oligosaccharides. the main products of lab metabolism were lactic acid, acetic acid, formic acid and ethanol. the results indicated ... | 1998 | 9924948 |
| lactic acid bacteria growth promoters from spirulina platensis. | spirulina has been used for many years as human food because of its high protein content and nutritional value. some strains also produce bioactive substances that may inhibit or promote microbial growth. lactococcus lactis, streptococcus thermophilus, lactobacillus casei, lactobacillus acidophilus, and lactobacillus bulgaricus were grown in rich media, mrs and rm, as well as in minimal saline medium with and without addition of extracellular products obtained from a late log phase culture of sp ... | 1998 | 9927000 |
| purification, identification, and effective production of a peptide antibiotic produced by lactococcus lactis io-1 (jcm 7638). | 1998 | 9928120 | |
| [comparative study of the homology of dna in thermophilic and mesophilic lactococcal strains of various origin]. | a comparative study of dna homology among 12 strains of thermophilic streptococci currently used as ferments in the dairy industry in different regions of the cis and 16 strains of mesophilic lactococci obtained from different sources was performed by the method of optical reassociation in solution. these strains were found to form three groups with dna homology generally not exceeding 30-35% between each other. these data indicate that strains commonly classified as streptococcus thermophilus m ... | 1998 | 10234652 |
| evolution of streptococcus thermophilus bacteriophage genomes by modular exchanges followed by point mutations and small deletions and insertions. | comparative sequence analysis of 40% of the genomes from two prototype streptococcus thermophilus bacteriophages (lytic group i phage phi sfi19 and the cos site containing temperate phage phi sfi21) suggested two processes in the evolution of their genomes. in a first evolutionarily distant phase the basic genome structure was apparently constituted by modular exchanges. over the 17-kb-long dna segment analyzed in the present report, we observed clusters of genes with similarity to genes from le ... | 1998 | 9499809 |
| production of pediocin pa-1 by lactococcus lactis using the lactococcin a secretory apparatus. | the class ii bacteriocins pediocin pa-1, from pediococcus acidilactici, and lactococcin a, from lactococcus lactis subsp. lactis bv. diacetylactis wm4 have a number of features in common. they are produced as precursor peptides containing similar amino-terminal leader sequences with a conserved processing site (gly-gly at positions -1 and -2). translocation of both bacteriocins occurs via a dedicated secretory system. because of the strong antilisterial activity of pediocin pa-1, its production ... | 1998 | 9501421 |
| the citrate transport system of lactococcus lactis subsp. lactis biovar diacetylactis is induced by acid stress. | citrate transport in lactococcus lactis subsp. lactis biovar diacetylactis is catalyzed by citrate permease p (citp), which is encoded by the plasmidic citp gene. we have shown previously that citp is included in the citqrp operon, which is mainly transcribed from the p1 promoter in l. lactis subsp. lactis biovar diacetylactis. furthermore, transcription of citqrp and citrate transport are not induced by the presence of citrate in the growth medium. in this work, we analyzed the influence of the ... | 1998 | 9501425 |
| common elements regulating gene expression in temperate and lytic bacteriophages of lactococcus species. | a phage-inducible middle promoter (p15a10) from the lytic, lactococcal bacteriophage phi 31, a member of the p335 species, is located in an 888-base pair fragment near the right cohesive end. sequence analysis revealed extensive homology (> 95%) to the right cohesive ends of two temperate phages of the p335 species, phi r1t and phi lc3. sequencing upstream and downstream of p15a10 showed that the high degree of homology between phi 31 and phi r1t continued beyond the phage promoter. with the exc ... | 1998 | 9501453 |
| nucleotide sequence and analysis of the new chromosomal abortive infection gene abin of lactococcus lactis subsp. cremoris s114. | a 7.275-kb dna fragment which encodes resistance by abortive infection (abi+) to bacteriophage was cloned from lactococcus lactis subsp. cremoris s114. the genetic determinant for abortive infection was subcloned from this fragment. this gene was found to confer a reduction in efficiency of plating and plaque size for prolate-headed bacteriophage phi 53 (group i homology) and for small isometric-headed bacteriophage phi 59 (group iii homology). this new gene, termed abin, is predicted to encode ... | 1998 | 9503629 |
| sequence analysis of muta and mutm genes involved in the biosynthesis of the lantibiotic mutacin ii in streptococcus mutans. | streptococcus mutans, along with many other gram-positive bacteria produce small antibacterial peptides called bacteriocins. bacteriocins elaborated by s. mutans, termed mutacins, may provide a selective force necessary for initial or sustained colonization in dental plaque by this major dental pathogen. previously, we purified and characterized mutacin ii, the first lantibiotic found in s. mutans. specific oligonucleotides designed according to the n-terminal amino acid sequence permitted ampli ... | 1998 | 9461412 |
| lacticin 3147, a broad-spectrum bacteriocin which selectively dissipates the membrane potential. | lacticin 3147 is a broad-spectrum bacteriocin produced by lactococcus lactis subsp. lactis dpc3147 (m. p. ryan, m. c. rea, c. hill, and r. p. ross, appl. environ. microbiol. 62:612-619, 1996). partial purification of the bacteriocin by hydrophobic interaction chromatography and reverse-phase fast protein liquid chromatography revealed that two components are required for full activity. lacticin 3147 is bactericidal against l. lactis, listeria monocytogenes, and bacillus subtilis; at low concentr ... | 1998 | 9464377 |
| molecular characterization of a phage-inducible middle promoter and its transcriptional activator from the lactococcal bacteriophage phi31. | an inducible middle promoter from the lactococcal bacteriophage phi31 was isolated previously by shotgun cloning an 888-bp fragment (p15a10) upstream of the beta-galactosidase (beta-gal) gene (lacz.st) from streptococcus thermophilus (d. j. o'sullivan, s. a. walker, s. g. west, and t. r. klaenhammer, bio/technology 14:82-87, 1996). the promoter showed low levels of constitutive beta-gal activity which could be induced two- to threefold over baseline levels after phage infection. during this stud ... | 1998 | 9473048 |
| a chloride-inducible acid resistance mechanism in lactococcus lactis and its regulation. | previously, a promoter was identified in lactococcus lactis that is specifically induced by chloride. here, we describe the nucleotide sequence and functional analysis of two genes transcribed from this promoter, gadc and gadb. gadc is homologous to putative glutamate-gamma-aminobutyrate antiporters of escherichia coli and shigella flexneri and contains 12 putative membrane-spanning domains. gadb shows similarity to glutamate decarboxylases. a l. lactis gadb mutant and a strain that is unable to ... | 1998 | 9484886 |
| kinetics and specificity of peptide uptake by the oligopeptide transport system of lactococcus lactis. | to obtain amino acids for growth, lactococcus lactis uses a proteolytic system to degrade exogenous proteins such as caseins. the extracellular cell wall-attached proteinase prtp and the oligopeptide transport system opp mediate the first two steps in the utilization of caseins. beta-casein is degraded by prtp to fragments of 5-30 amino acid residues, and only a limited number of peptides are selected from this pool for uptake via opp. to study the specificity of opp and the kinetics of peptide ... | 1998 | 9843435 |
| production of cholera toxin b subunit in lactobacillus. | the intracellular expression of the b subunit of cholera toxin (ctb) was first achieved in lactobacillus paracasei lbtgs1.4 with an expression cassette including the p25 promoter of streptococcus thermophilus combined with the translation initiation region from the strongly expressed l. pentosus d-lactate dehydrogenase gene (ldhd). secretion of ctb was next attempted in l. paracasei lbtgs1.4 and l. plantarum ncimb8826 with four different signal sequences from exported proteins of lactic acid bac ... | 1998 | 9851032 |
| maltose metabolism of lactobacillus sanfranciscensis: cloning and heterologous expression of the key enzymes, maltose phosphorylase and phosphoglucomutase. | the maltose degradation operon containing genes encoding maltose phosphorylase mapa and phosphoglucomutase pgma from lactobacillus sanfranciscensis dsm20451t were cloned and expressed in escherichia coli. these genes represent the first genetic data available for this species beyond taxonomic classification. mapa encodes a 754-amino acid polypeptide representing maltose phosphorylase, mapa, with a calculated molecular mass of 85.7 kda. comparative sequence analysis showed that mapa is of a new t ... | 1998 | 9851037 |
| characterization of lactococci isolated from milk produced in the camembert region of normandy. | thirty-eight lactococcus strains, isolated from raw milk produced in two dairy areas in normandy, were identified at the phenotypic level. only lactococcus lactis strains with the lactis phenotype were found in the milk samples. most strains fermented lactose (97%) and showed proteinase activity (76%). isolates were characterized by rapd technique and rrna gene restriction analysis. more l. lactis strains with the lactis genotype were found in the first area, while l. lactis strains with the cre ... | 1998 | 9871320 |
| synergistic antimicrobial effect of nisin whey permeate and lactic acid on microbes isolated from fish. | the antimicrobial activity of a combination of lactic acid and whey permeate fermented by a nisin-producing lactococcus lactis strain was tested by the agar diffusion method using bacteria isolated from fish as test organisms. lactic acid inhibited all bacterial strains studied, but nisin whey permeate inhibited gram-positive bacteria only. the combination was more effective than lactic acid alone against pseudomonas fluorescens and staphylococcus hominis isolated from fish, and pseudomonas aeru ... | 1998 | 9871352 |
| sequence and analysis of the 60 kb conjugative, bacteriocin-producing plasmid pmrc01 from lactococcus lactis dpc3147. | the complete sequence of pmrc01, a large conjugative plasmid from lactococcus lactis ssp. lactis dpc3147, has been determined. using a shotgun sequencing approach, the 60,232 bp plasmid sequence was obtained by the assembly of 1056 underlying sequences (sevenfold average redundancy). sixty-four open reading frames (orfs) were identified. analysis of the gene organization of pmrc01 suggests that the plasmid can be divided into three functional domains, with each approximately 20 kb region separat ... | 1998 | 9767571 |
| conservation of the major cold shock protein in lactic acid bacteria. | primers designed from consensus regions of the major cold shock gene of different bacterial species were used in pcr amplification of lactic acid bacteria (lab). an appropriately-sized pcr product was obtained from lactococcus lactis subsp. lactis ll43-1 and mg1363; lactococcus lactis subsp. cremoris lc10-1, lc11-1, and lc12-1; streptococcus thermophilus st1-1; enterococcus faecalis ef1-1; lactobacillus acidophilus la1-1; lactobacillus helveticus lh1-1; pediococcus pentosaceus pp1-1; and bifidob ... | 1998 | 9767713 |
| the site-specific recombination system of the lactobacillus species bacteriophage a2 integrates in gram-positive and gram-negative bacteria. | the region of the bacteriophage a2 genome involved in site-specific recombination with the dna of lactobacillus spp. has been identified. two orfs, transcribed from the same strand, have been found immediately upstream of the phage attachment site (attp). the orf adjacent to attp predicts a 385-amino-acid protein that presents significant similarity with site-specific recombinases of the integrase family. the other orf encodes a basic polypeptide of 76 amino acid residues. the junctions of the p ... | 1998 | 9770432 |
| crystal structures of a unique thermal-stable thymidylate synthase from bacillus subtilis. | unlike all other organisms studied to date, bacillus subtilis expresses two different thymidylate synthases: bsts-a and bsts-b. bsts-a displays enhanced enzymatic and structural thermal stability uncharacteristic of most tss. despite the high level of ts conservation across most species, bsts-a shares low sequence identity (<40%) with the majority of tss from other organisms. this ts and the tss from lactococcus lactis and phage phi3t-to which it is most similar-have been of interest for some ti ... | 1998 | 9778348 |
| analysis of the bacteriolytic enzymes of the autolytic lactococcus lactis subsp. cremoris strain am2 by renaturing polyacrylamide gel electrophoresis: identification of a prophage-encoded enzyme | lactococcus lactis subsp. cremoris am2 was previously shown to lyse early and extensively during cheese ripening (m.-p. chapot-chartier, c. deniel, m. rousseau, l. vassal, and j.-c. gripon, int. dairy j. 4:251-269, 1994). we analyzed the bacteriolytic activities of autolytic strain am2 by using renaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis performed with two different substrates in the gel, micrococcus lysodeikticus and l. lactis autoclaved cells. several lytic activities ... | 1998 | 9797258 |
| monoclonal antibodies raised against native major capsid proteins of lactococcal c2-like bacteriophages. | phage q38, a representative member of the c2 species, was purified by cscl gradient and used to immunize balb/c mice. monoclonal antibodies (mabs) were raised and then characterized by enzyme-linked immunosorbent assay. two mabs of isotype immunoglobulin g2a, designated 2a5 and 6g7, reacted only with phages belonging to the c2 species and not with phages of the 936 and p335 species, with a lactococcus lactis cell extract, or with phage dna. immunoelectron microscopy showed that both mabs recogni ... | 1998 | 9797273 |
| cloning and expression of the lactococcus lactis purdek genes, required for growth in milk. | an operon containing the genes purd and pure and part of the purk gene was cloned from the facultative anaerobic gram-positive bacterium lactococcus lactis by complementation of the purd mutation in escherichia coli so609. the genes encode enzymes in the de novo pathway of purine nucleotides. the expression of the genes was regulated approximately 35-fold at the transcription level by the availability of purines in the growth medium. deletion analysis of the nucleotide region upstream of purd in ... | 1998 | 9797284 |
| humic acid reduction by propionibacterium freudenreichii and other fermenting bacteria | iron-reducing bacteria have been reported to reduce humic acids and low-molecular-weight quinones with electrons from acetate or hydrogen oxidation. due to the rapid chemical reaction of amorphous ferric iron with the reduced reaction products, humic acids and low-molecular-weight redox mediators may play an important role in biological iron reduction. since many anaerobic bacteria that are not able to reduce amorphous ferric iron directly are known to transfer electrons to other external accept ... | 1998 | 9797315 |
| genetic characterization of pepp, which encodes an aminopeptidase p whose deficiency does not affect lactococcus lactis growth in milk, unlike deficiency of the x-prolyl dipeptidyl aminopeptidase. | we sequenced the pepp gene of lactococcus lactis, which encodes an aminopeptidase p (pepp), and demonstrated that the x-prolyl dipeptidyl aminopeptidase pepx plays a more important role than pepp in nitrogen nutrition. pepp shares homology with methionine aminopeptidases and could play a role in the maturation of nascent proteins. | 1998 | 9797327 |
| design of a phage-insensitive lactococcal dairy starter via sequential transfer of naturally occurring conjugative plasmids | the plasmid-free lactococcus lactis subsp. cremoris mg1614 is highly phage sensitive and lacks lactose fermenting ability (lac) and primary casein degrading ability (prt). food grade gene transfer systems were used to sequentially superimpose different phage defense systems on this background, resulting in a gradual increase in resistance to bacteriophage in the derivatives. plp712, encoding lac and prt, was then transferred to one of these hosts, into which plasmids encoding adsorption inhibiti ... | 1998 | 9797334 |
| use of a broad-host-range bacteriocin-producing lactococcus lactis transconjugant as an alternative starter for salami manufacture. | lactococcus lactis dpc4268 is widely used for cheddar cheese manufacture in ireland where it is recognised for its reliable fast acid producing ability in dairy environments. a transconjugant of this strain, l. lactis dpc4275, was generated which produces the broad spectrum, two-component bacteriocin lacticin 3147, which is inhibitory to a variety of undesirable gram-positive bacteria including clostridium, bacillus, enterococcus, listeria, staphylococcus and streptococcus. both dpc4268 and dpc4 ... | 1998 | 9801199 |
| clustered organization and transcriptional analysis of a family of five csp genes of lactococcus lactis mg1363. | a family of genes encoding cold-shock proteins, named cspa, cspb, cspc, cspd and cspe, was cloned and sequenced from lactococcus lactis mg1363. the genes cspa and cspb and the genes cspc and cspd are located in tandem repeats, an organization of csp genes that has never been encountered before. the five genes encode small (7.1-7.6 kda) proteins with high mutual sequence identities (up to 85%) and high identities (about 45-65%) with the major cold-shock proteins from escherichia coli (cspa) and b ... | 1998 | 9802030 |
| procedure for quantifiable assessment of nutritional parameters influencing nisin production by lactococcus lactis subsp. lactis. | a modified rapid plate assay procedure was developed, that allowed quantifiable measurement of nisin production by lactococcus lactis growing directly on agar media. using this direct plate assay, several nutritional parameters were assessed for their influence on nisin production (as distinct from their influence on growth) by l. lactis subsp. lactis atcc 11454 growing on standard m17 based media over 3 and 6 h incubation periods. glucose was found to be the optimal carbon source tested, with g ... | 1998 | 9803535 |
| proton-driven dipeptide uptake in primary cultured rabbit conjunctival epithelial cells. | to characterize proton-driven carrier-mediated dipeptide uptake in primary cultured conjunctival epithelial cells of the pigmented rabbit using beta-alanyl-l-histidine (l-carnosine) as a model dipeptide substrate. | 1998 | 9804145 |
| molecular characterization of the lactococcus lactis llakr2i restriction-modification system and effect of an is982 element positioned between the restriction and modification genes. | the nucleotide sequence of the plasmid-encoded llakr2i restriction-modification (r-m) system of lactococcus lactis subsp. lactis biovar diacetylactis kr2 was determined. this r-m system comprises divergently transcribed endonuclease (llakr2ir) and methyltransferase (llakr2im) genes; located in the intergenic region is a copy of the insertion element is982, whose putative transposase gene is codirectionally transcribed with llakr2im. the deduced sequence of the llakr2i endonuclease shared homolog ... | 1998 | 9811640 |
| a saccharomyces cerevisiae mutant lacking a k+/h+ exchanger. | the kha1 gene corresponding to the open reading frame yjl094c (2.62 kb) encoding a putative k+/h+ antiporter (873 amino acids) in saccharomyces cerevisiae was disrupted by homologous recombination. the core protein is similar to the putative na+/h+ antiporters from enterococcus hirae (napa gene) and lactococcus lactis (llupp gene) and the putative k+/h+ exchanger from escherichia coli (kefc gene). disruption of the kha1 gene resulted in an increased k+ accumulation and net influx without a signi ... | 1998 | 9811642 |
| autolysis of lactococcus lactis is influenced by proteolysis. | the autolysin acma of lactococcus lactis was shown to be degraded by the extracellular lactococcal proteinase prtp. autolysis, as evidenced by reduction in optical density of a stationary-phase culture and concomitant release of intracellular proteins, was greatly reduced when l. lactis mg1363 cells expressed the cell wall-anchored lactococcal proteinase prtp of the pi-type caseinolytic specificity (pi). on the other hand, lactococcal strains that did not produce the proteinase showed a high lev ... | 1998 | 9811653 |
| use of 13c nuclear magnetic resonance and gas chromatography to examine methionine catabolism by lactococci. | formation of methanethiol from methionine is widely believed to play a significant role in development of cheddar cheese flavor. however, the catabolism of methionine by cheese-related microorganisms has not been well characterized. two independent methionine catabolic pathways are believed to be present in lactococci, one initiated by a lyase and the other initiated by an aminotransferase. to differentiate between these two pathways and to determine the possible distribution between the pathway ... | 1998 | 9835547 |
| an ecological study of lactococci isolated from raw milk in the camembert cheese registered designation of origin area. | the genetic diversity of lactococci isolated from raw milk in the camembert cheese registered designation of origin area was studied. two seasonal samples (winter and summer) of raw milk were obtained from six farms in two areas (bessin and bocage falaisien) of normandy. all of the strains analyzed had a lactococcus lactis subsp. lactis phenotype, whereas the randomly amplified polymorphic dna (rapd) technique genotypically identified the strains as members of l. lactis subsp. lactis or l. lacti ... | 1998 | 9835555 |
| cloning, expression, and chromosomal stabilization of the propionibacterium shermanii proline iminopeptidase gene (pip) for food-grade application in lactococcus lactis. | proline iminopeptidase produced by propionibacterium shermanii plays an essential role in the flavor development of swiss-type cheeses. the enzyme (pip) was purified and characterized, and the gene (pip) was cloned and expressed in escherichia coli and lactococcus lactis, the latter species being an extensively studied, primary cheese starter culture that is less fastidious in its growth condition requirements than p. shermanii. the levels of expression of the pip gene could be enhanced with a f ... | 1998 | 9835556 |
| abiq, an abortive infection mechanism from lactococcus lactis. | lactococcus lactis w-37 is highly resistant to phage infection. the cryptic plasmids from this strain were coelectroporated, along with the shuttle vector psa3, into the plasmid-free host l. lactis lm0230. in addition to psa3, erythromycin- and phage-resistant isolates carried psrq900, an 11-kb plasmid from l. lactis w-37. this plasmid made the host bacteria highly resistant (efficiency of plaquing <10(-8)) to c2- and 936-like phages. psrq900 did not confer any resistance to phages of the p335 s ... | 1998 | 9835558 |
| use of a genetically enhanced, pediocin-producing starter culture, lactococcus lactis subsp. lactis mm217, to control listeria monocytogenes in cheddar cheese | cheddar cheese was prepared with lactococcus lactis subsp. lactis mm217, a starter culture which contains pmc117 coding for pediocin pa-1. about 75 liters of pasteurized milk (containing ca. 3.6% fat) was inoculated with strain mm217 (ca. 10(6) cfu per ml) and a mixture of three listeria monocytogenes strains (ca. 10(3) cfu per ml). the viability of the pathogen and the activity of pediocin in the cheese were monitored at appropriate intervals throughout the manufacturing process and during ripe ... | 1998 | 9835572 |
| lactococcus lactis phage operon coding for an endonuclease homologous to ruvc. | the function of the lactococcus lactis bacteriophage bil66 middle time-expressed operon (m-operon), involved in sensitivity to the abortive infection mechanism abid1, was examined. expression of the m-operon is detrimental to escherichia coli cells, induces the sos response and is lethal to reca and recbc e. coli mutants, which are both deficient in recombinational repair of chromosomal double-stranded breaks (dsbs). the use of an inducible expression system allowed us to demonstrate that the m- ... | 1998 | 9643549 |
| cloning and characterization of the lactococcal plasmid-encoded type ii restriction/modification system, lladii. | the lladii restriction/modification (r/m) system was found on the naturally occurring 8.9-kb plasmid phw393 in lactococcus lactis subsp. cremoris w39. a 2.4-kb psti-ecori fragment inserted into the escherichia coli-l. lactis shuttle vector pci3340 conferred to l. lactis lm2301 and l. lactis smq86 resistance against representatives of the three most common lactococcal phage species: 936, p335, and c2. the lladii endonuclease was partially purified and found to recognize and cleave the sequence 5' ... | 1998 | 9647810 |
| glutamate biosynthesis in lactococcus lactis subsp. lactis ncdo 2118 | unlike other lactic acid bacteria, lactococcus lactis subsp. lactis ncdo 2118 was able to grow in a medium lacking glutamate and the amino acids of the glutamate family. growth in such a medium proceeded after a lag phase of about 2 days and with a reduced growth rate (0.11 h-1) compared to that in the reference medium containing glutamate (0.16 h-1). the enzymatic studies showed that a phosphoenolpyruvate carboxylase activity was present, while the malic enzyme and the enzymes of the glyoxylic ... | 1998 | 9647819 |
| use of luciferase genes as biosensors to study bacterial physiology in the digestive tract. | a method based on the use of the bacterial luciferase genes was developed in order to investigate lactococcus lactis gene expression in the mouse digestive tract. germfree mice were monoassociated with different strains containing transcriptional fusions of promoters with the luciferase genes. our results demonstrate that this method is readily applicable to the study of promoter strength and physiology of bacteria in the digestive tract. | 1998 | 9647856 |
| the crystal structure of lactococcus lactis dihydroorotate dehydrogenase a complexed with the enzyme reaction product throws light on its enzymatic function. | dihydroorotate dehydrogenases (dhods) catalyze the oxidation of (s)-dihydroorotate to orotate, the fourth step and only redox reaction in the de novo biosynthesis of pyrimidine nucleotides. a description is given of the crystal structure of lactococcus lactis dihydroorotate dehydrogenase a (dhoda) complexed with the product of the enzyme reaction orotate. the structure of the complex to 2.0 a resolution has been compared with the structure of the native enzyme. the active site of dhoda is known ... | 1998 | 9655329 |
| characterization of a novel insertion sequence, is1194, in streptococcus thermophilus. | a novel insertion sequence, is1194, has been identified in the lactic acid bacterium streptococcus thermophilus cnrz368. this 1200-bp element has 16-bp imperfect terminal inverted repeats. the single large open reading frame of this element encodes a 332-amino-acid protein that displays similarities with transposases encoded by bacterial insertion sequences belonging to the is5 group of the is4 family. a single copy of is1194 was detected by hybridization in only 2 of the 19 s. thermophilus stra ... | 1998 | 9657932 |
| inducible gene expression systems in lactococcus lactis. | lactococcus lactis is industrially important microorganism used in many dairy fermentations. numerous genes and gene expression signals from this organism have now been identified and characterized. recently, several naturally occurring, inducible gene-expression systems have also been described in l. lactis. the main features of these systems can be exploited to design genetically engineered expression cassettes for controlled production of various proteins and enzymes. novel gene-expression sy ... | 1998 | 9658390 |
| a leucine repeat motif in abia is required for resistance of lactococcus lactis to phages representing three species. | the abia gene encodes an abortive bacteriophage infection mechanism that can protect lactococcus species from infection by a variety of bacteriophages including three unrelated phage species. five heptad leucine repeats suggestive of a leucine zipper motif were identified between residues 232 and 266 in the predicted amino acid sequence of the abia protein. the biological role of residues in the repeats was investigated by incorporating amino acid substitutions via site-directed mutagenesis. eac ... | 1998 | 9661658 |
| the -16 region of bacillus subtilis and other gram-positive bacterial promoters. | the bacillus subtilis alpha-amylase promoter amy p contains an essential tgtg motif (-16 region) upstream of the -10 region. mutations of this region significantly reduced in vitro promoter strength. a -15 g-->c transversion eliminated transcription from amy p by both b.subtilis and escherichia coli rna polymerase (rnap). a second alpha-amylase promoter ( amy p2) also required the -16 region for function. to determine conserved sequences in promoters containing -16 region elements, sequences of ... | 1998 | 9671823 |
| acid stress, anaerobiosis and gadcb: lessons from lactococcus lactis and escherichia coli. | 1998 | 9675796 | |
| involvement of antisense rna in replication control of the lactococcal plasmid pnd324. | pnd324 belongs to a family of closely related theta-type plasmids from lactococcus lactis. an antisense rna, termed countertranscript (ctrna), was identified which is complementary to the leader sequence of the mrna that encodes repb, a protein essential for plasmid replication. when the synthesis of ctrna was abolished by site-directed mutagenesis within its promoter region, the mutant replicon showed a 1.8-fold increase in copy number. similar ctrna promoter sequences are readily identifiable ... | 1998 | 9682491 |
| cofactor engineering: a novel approach to metabolic engineering in lactococcus lactis by controlled expression of nadh oxidase. | nadh oxidase-overproducing lactococcus lactis strains were constructed by cloning the streptococcus mutans nox-2 gene, which encodes the h2o-forming nadh oxidase, on the plasmid vector pnz8020 under the control of the l. lactis nisa promoter. this engineered system allowed a nisin-controlled 150-fold overproduction of nadh oxidase at ph 7.0, resulting in decreased nadh/nad ratios under aerobic conditions. deliberate variations on nadh oxidase activity provoked a shift from homolactic to mixed-ac ... | 1998 | 9683475 |
| induced levels of heat shock proteins in a dnak mutant of lactococcus lactis. | the bacterial heat shock response is characterized by the elevated expression of a number of chaperone complexes and proteases, including the dnak-grpe-dnaj and the groels chaperone complexes. in order to investigate the importance of the dnak chaperone complex for growth and heat shock response regulation in lactococcus lactis, we have constructed two dnak mutants with c-terminal deletions in dnak. the minor deletion of 65 amino acids in the dnakdelta2 mutant resulted in a slight temperature-se ... | 1998 | 9683484 |
| activation control of pur gene expression in lactococcus lactis: proposal for a consensus activator binding sequence based on deletion analysis and site-directed mutagenesis of purc and purd promoter regions. | a comparison of the purc and purd upstream regions from lactococcus lactis revealed the presence of a conserved accgaacaat decanucleotide sequence located precisely between -79 and -70 nucleotides upstream from the transcriptional start sites. both promoters have well-defined -10 regions but lack sequences resembling -35 regions for sigma70 promoters. fusion studies indicated the importance of the conserved sequence in purine-mediated regulation. adjacent to the conserved sequence in purc is a s ... | 1998 | 9683487 |
| a transcriptional activator, homologous to the bacillus subtilis purr repressor, is required for expression of purine biosynthetic genes in lactococcus lactis. | a purr::pgh9:iss1 mutant of lactococcus lactis was obtained following transposon mutagenesis of strain mg1363 and selection for purine auxotrophs. after determination of the nucleotide sequence and deduction of the purr reading frame, the purr product was found to be highly similar to the purr-encoded repressor from bacillus subtilis. the wild-type purr gene complemented the purine auxotrophy of a purr::iss1 mutant, and it was shown that the purr::iss1 mutation lowered the level of transcription ... | 1998 | 9683488 |
| complete sequence of the new lactococcal abortive phage resistance gene abio. | 1998 | 9684156 | |
| production of gamma-aminobutyric acid by cheese starters during cheese ripening. | nine mixed-strain starters were examined for their abilities to produce gamma-aminobutyric acid. six commercial starters were found to produce gamma-aminobutyric acid in a skim milk culture. the bacterium that produced gamma-aminobutyric acid was isolated from the mixed-strain starters, identified as citrate-utilizing lactococcus lactis ssp. lactis (formerly l. lactis ssp. lactis biovar diacetylactis) and designated as strain 01-7. a cell extract showed glutamate decarboxylase activity, for whic ... | 1998 | 9684157 |
| use of the lactococcal nisa promoter to regulate gene expression in gram-positive bacteria: comparison of induction level and promoter strength. | we characterized the regulated activity of the lactococcal nisa promoter in strains of the gram-positive species streptococcus pyogenes, streptococcus agalactiae, streptococcus pneumoniae, enterococcus faecalis, and bacillus subtilis. nisa promoter activity was dependent on the proteins nisr and nisk, which constitute a two-component signal transduction system that responds to the extracellular inducer nisin. the nisin sensitivity and inducer concentration required for maximal induction varied a ... | 1998 | 9687428 |
| estimation of the state of the bacterial cell wall by fluorescent in situ hybridization. | fluorescent in situ hybridization (fish) is now a widely used method for identification of bacteria at the single-cell level. with gram-positive bacteria, the thick peptidoglycan layer of a cell wall presents a barrier for entry of horseradish peroxidase (hrp)-labeled probes. therefore, such probes do not give any signal in fish unless cells are first treated with enzymes which hydrolyze the peptidoglycan. we explored this feature of fish to detect cells which have undergone permeabilization due ... | 1998 | 9687473 |
| the abc family of multidrug transporters in microorganisms. | multidrug transporters are membrane proteins that are able to expel a broad range of toxic molecules from the cell. in humans, the overexpression of the multidrug resistance p-glycoprotein (pgp) and the multidrug resistance-associated protein mrp1 (mrp) is a principal cause of resistance of cancers to chemotherapy. these multidrug transporters belong to the atp-binding cassette (abc) family of transport proteins that utilize the energy of atp hydrolysis for activity. in microorganisms, multidrug ... | 1998 | 9693718 |
| effect of cold shock on protein synthesis and on cryotolerance of cells frozen for long periods in lactococcus lactis. | aspects of the cold-shock response in lactococcus lactis subsp. lactis ll41-1 were investigated. first, it was determined whether new proteins were synthesized in response to cold shock. cell-free extracts were prepared from a cold-shocked (exposed to 10 degreesc for 5 h) culture (cfe-cs) and from a non-cold-shocked (held at 30 degreesc continuously) culture (cfe-non), and were subjected to sodium dodecyl sulphate-polyacrylamide gel electrophoresis. a protein of approximately 6.3 kda was present ... | 1998 | 9698433 |
| trnatrp as a key element of antitermination in the lactococcus lactis trp operon. | the expression of the trp operon of lactococcus lactis is regulated in response to tryptophan availability by a mechanism of transcription antitermination. we present evidence in support of a previously described model involving trnatrp as a key element in the sensing of tryptophan levels and the realization of the regulatory response to tryptophan limitation. in agreement with this model, two sites of presumed direct interaction between the trp leader transcript and trnatrp are found to be of c ... | 1998 | 9701803 |
| transcription of the trp operon in lactococcus lactis is controlled by antitermination in the leader region. | the regulatory functions of the leader region preceding the lactococcus lactis trp operon have been studied by mutagenesis analysis. this leader presents striking similarity to 't-box' leaders found upstream of many gram-positive aminoacyl-trna synthetase genes and some amino acid biosynthesis operons, which are controlled by antitermination through interaction of the leader transcript with cognate uncharged trna. a region of the l. lactis leader transcript also contains a series of (g/u) ag rep ... | 1998 | 9720031 |
| temporal transcription of the lactococcal temperate phage tp901-1 and dna sequence of the early promoter region. | transcriptional analysis by northern blotting identified clusters of early, middle and late transcribed regions of the temperate lactococcal bacteriophage tp901-1 during one-step growth experiments. the latent period was found to be 65 min and the burst size 40 +/- 10. the eight early transcripts, all mapping in a 13 kb region adjacent to the attachment site of tp901-1, were present at maximal levels 10 min after infection. the four middle transcripts, observed at maximal levels 30 min after inf ... | 1998 | 9720042 |
| the carb gene encoding the large subunit of carbamoylphosphate synthetase from lactococcus lactis is transcribed monocistronically. | the biosynthesis of carbamoylphosphate is catalyzed by the heterodimeric enzyme carbamoylphosphate synthetase. the genes encoding the two subunits of this enzyme in procaryotes are normally transcribed as an operon, but the gene encoding the large subunit (carb) in lactococcus lactis is shown to be transcribed as an isolated unit. carbamoylphosphate is a precursor in the biosynthesis of both pyrimidine nucleotides and arginine. by mutant analysis, l. lactis is shown to possess only one carb gene ... | 1998 | 9721272 |
| minimum inhibitory concentration of smoke wood extracts against spoilage and pathogenic micro-organisms associated with foods. | antimicrobial activity of seven commercial smoke preparations (four liquid and three solid) was studied. the minimum inhibitory concentration (mic) was determined against a selection of food spoilage and pathogenic micro-organisms. the main smoke components were identified and quantified by gas chromatography/mass spectrometry. the most effective condensate was s2. all strains except salmonella enteritidis were inhibited by s2 with an mic < 0.5-1.5%. smoke extract l2 inhibited growth of vibrio v ... | 1998 | 9722997 |
| modeling of the competitive growth of listeria monocytogenes and lactococcus lactis in vegetable broth. | current mathematical models used by food microbiologists do not address the issue of competitive growth in mixed cultures of bacteria. we developed a mathematical model which consists of a system of nonlinear differential equations describing the growth of competing bacterial cell cultures. in this model, bacterial cell growth is limited by the accumulation of protonated lactic acid and decreasing ph. in our experimental system, pure and mixed cultures of lactococcus lactis and listeria monocyto ... | 1998 | 9726854 |
| conversion of methionine to thiols by lactococci, lactobacilli, and brevibacteria | methanethiol has been strongly associated with desirable cheddar cheese flavor and can be formed from the degradation of methionine (met) via a number of microbial enzymes. methionine gamma-lyase is thought to play a major role in the catabolism of met and generation of methanethiol in several species of bacteria. other enzymes that have been reported to be capable of producing methanethiol from met in lactic acid bacteria include cystathionine beta-lyase and cystathionine gamma-lyase. the objec ... | 1998 | 9726877 |
| genetic characterization and physiological role of endopeptidase o from lactobacillus helveticus cnrz32. | a previously identified insert expressing an endopeptidase from a lactobacillus helveticus cnrz32 genomic library was characterized. nucleotide sequence analysis revealed an open reading frame of 1,941 bp encoding a putative protein of 71.2 kda which contained a zinc-protease motif. protein homology searches revealed that this enzyme has 40% similarity with endopeptidase o (pepo) from lactococcus lactis p8-2-47. northern hybridization revealed that pepo is monocistronic and is expressed througho ... | 1998 | 9726890 |
| retrohoming of a bacterial group ii intron: mobility via complete reverse splicing, independent of homologous dna recombination. | the mobile group ii intron of lactococcus lactis, ll.ltrb, provides the opportunity to analyze the homing pathway in genetically tractable bacterial systems. here, we show that ll.ltrb mobility occurs by an rna-based retrohoming mechanism in both escherichia coli and l. lactis. surprisingly, retrohoming occurs efficiently in the absence of reca function, with a relaxed requirement for flanking exon homology and without coconversion of exon markers. these results lead to a model for bacterial ret ... | 1998 | 9727488 |
| a natural large chromosomal inversion in lactococcus lactis is mediated by homologous recombination between two insertion sequences. | comparative analysis of chromosomal macrorestriction polymorphism of the two closely related lactococcus lactis subsp. cremoris strains mg1363 and ncdo763 revealed the presence of a large inversion covering half of the genome. to determine what kind of genetic element could be implicated in this rearrangement, the two inversion junctions of mg1363 and ncdo763 chromosomes were cloned and characterized. nucleotide sequence analysis showed the presence of one copy of the lactococcal is905 element i ... | 1998 | 9733685 |
| transcriptional regulation and evolution of lactose genes in the galactose-lactose operon of lactococcus lactis ncdo2054. | the genetics of lactose utilization within the slow-lactose-fermenting lactococcus lactis strain ncdo2054 was studied with respect to the organization, expression, and evolution of the lac genes. initially the beta-galactosidase gene (lacz) was cloned by complementation of an escherichia coli mutant on a 7-kb hpai fragment. nucleotide sequence analysis of the complete fragment revealed part of a gal-lac operon, and the genes were characterized by inactivation and complementation analyses and in ... | 1998 | 9733693 |
| two methods for the genetic differentiation of lactococcus lactis ssp. lactis and cremoris based on differences in the 16s rrna gene sequence. | the 16s ribosomal rna gene sequences of lactococcus lactis ssp. lactis and ssp. cremoris differ by 9-10 bp (depending on strain), within the first 200 bp of the sequence. these differences were used to develop two methods of genetically differentiating lactis and cremoris strains. primers to conserved sequences in the 16s rrna gene were used in a pcr reaction to amplify fragments of the 16s rrna gene. a single base difference at position 180 of the sequence was utilised to develop a ligase chain ... | 1998 | 9741080 |
| binding properties of streptococcus gordonii sspa and sspb (antigen i/ii family) polypeptides expressed on the cell surface of lactococcus lactis mg1363. | the oral bacterium streptococcus gordonii expresses two cell wall-associated polypeptides, designated sspa (1,542 amino acid residues) and sspb (1,462 amino acid residues), that have 70% sequence identity. these polypeptides are members of the antigen i/ii family of oral streptococcal adhesins and mediate the binding of streptococci to salivary glycoproteins, collagen, and other oral microorganisms such as actinomyces naeslundii. to determine if sspa and sspb have differential binding properties ... | 1998 | 9746559 |
| characterization of a mutant of lactococcus lactis with reduced membrane-bound atpase activity under acidic conditions. | a mutant of lactococcus lactis subsp. lactis c2 with reduced membrane-bound atpase activity was characterized to clarify its acid sensitivity. the cytoplasmic ph of the mutant was measured in reference to the parental strain under various ph conditions. at low ph, the mutant could not maintain its cytoplasmic ph near neutral, and lost its viability faster than the parental strain. the atpase activities of cells cultured under neutral and acidic conditions using ph-controlled jar fermentors were ... | 1998 | 9757564 |
| the colonization of a simulator of the human intestinal microbial ecosystem by a probiotic strain fed on a fermented oat bran product: effects on the gastrointestinal microbiota. | the effects of lactobacillus-gg-fermented oat bran product on the microbiota and its metabolic activity in the human gut were investigated, using a simulator of the human intestinal microbial ecosystem (shime), by analysing the bacterial population, shortchain fatty acids and gas production. in addition, the effects of fermented oat bran supernatant and supernatant samples from reactors 4, 5 and 6 (large intestine) on the growth of escherichia coli ihe 13047, enterococcus faecalis vtt e-93203, l ... | 1998 | 9763692 |
| characterization of multiple regions involved in replication and mobilization of plasmid pnz4000 coding for exopolysaccharide production in lactococcus lactis. | we characterized the regions involved in replication and mobilization of the 40-kb plasmid pnz4000, encoding exopolysaccharide (eps) production in lactococcus lactis nizo b40. the plasmid contains four highly conserved replication regions with homologous rep genes (repb1, repb2, repb3, and repb4) that belong to the lactococcal theta replicon family. subcloning of each replicon individually showed that all are functional and compatible in l. lactis. plasmid pnz4000 and genetically labeled derivat ... | 1998 | 9765557 |
| evidence for a mosaic structure of the tn5481 in lactococcus lactis n8. | the sequences of the left end of the nisin-sucrose transposon tn5481 in lactococcus lactis subsp. lactis n8, the adjacent 1.5 kb chromosomal region upstream of the junction site as well as a 5.0 kb region downstream of the niszbtciprkfeg genes within the transposon have been determined. in the upstream chromosomal region, an incomplete open reading frame encoding a protein with strong n-terminal homology to the low-affinity branched chain amino acid carriers was identified. within the transposon ... | 1998 | 10524753 |
| characterization of the nisfeg operon of the nisin z producing lactococcus lactis subsp. lactis n8 strain. | biosynthesis of the food additive nisin, a posttranslationally modified peptide antibiotic existing as two natural variants (a and z), requires eleven genes (nisa/zbtciprkfeg) involved in modification, secretion, regulation and self-immunity. the suggested self-immunity genes (nisfeg) of the nisin z producer lactococcus lactis subsp. lactis n8 were cloned and sequenced. putative binding sites of the nisr transcription factor were recognized upstream of the nisf promoter. the hydrophilic nisf pro ... | 1998 | 10524754 |
| artificial promoters for metabolic optimization. | in this article, we review some of the expression systems that are available for metabolic control analysis and metabolic engineering, and examine their advantages and disadvantages in different contexts. in a recent approach, artificial promoters for modulating gene expression in micro-organisms were constructed using synthetic degenerated oligonucleotides. from this work, a promoter library was obtained for lactococcus lactis, containing numerous individual promoters and covering a wide range ... | 1998 | 10191389 |
| acetate production from whey lactose using co-immobilized cells of homolactic and homoacetic bacteria in a fibrous-bed bioreactor. | acetate was produced from whey lactose in batch and fed-batch fermentations using co-immobilized cells of clostridium formicoaceticum and lactococcus lactis. the cells were immobilized in a spirally wound fibrous sheet packed in a 0.45-l column reactor, with liquid circulated through a 5-l stirred-tank fermentor. industrial-grade nitrogen sources, including corn steep liquor, casein hydrolysate, and yeast hydrolysate, were studied as inexpensive nutrient supplements to whey permeate and acid whe ... | 1998 | 10099456 |
| diacetyl production mechanism by a strain of lactococcus lactis spp. lactis bv. diacetylactis. study of alpha-acetolactic acid extracellular accumulation under anaerobiosis. | diacetyl production via alpha-acetolactic acid (ala) extracellular decarboxylation in lactococcus lactis spp. lactis bv. diacetylactis sd 933 cultures has been assessed under anaerobiosis both in batch and continuous fermentations at ph 5.5 and 8.0 by studying the effects of alpha-acetolactate decarboxylase (adc) addition in the culture broth. this enzyme, favoring the formation of acetoin instead of diacetyl, was added extracellularly and did not disturb diacetyl production. moreover, oxidation ... | 1998 | 18574730 |
| altered specificity of lactococcal proteinase p(i) (lactocepin i) in humectant systems reflecting the water activity and salt content of cheddar cheese. | by using various humectant systems, the specificity of hydrolysis of alpha(s1)-, beta-, and kappa-caseins by the cell envelope-associated proteinase (lactocepin; ec 3.4.21.96) with type p(1) specificity (i.e., lactocepin i) from lactococcus lactis subsp. lactis bn1 was investigated at water activities (a(w)) and salt concentrations reflecting those in cheddar type cheese. in the presence of polyethylene glycol 20000 (peg 20000)-nacl (a(w) = 0.95), hydrolysis of beta-casein resulted in production ... | 1998 | 16349501 |
| nisin z production by lactococcus lactis io-1 using xylose as a carbon source. | lactococcus lactis io-1 was able to use xylose as a carbon source for nisin z production; the yield based on sugar consumption was about 20% superior to that made with glucose under the same fermentation conditions. the optimal conditions for nisin z production were with 4% xylose at ph 6.0 and 37°c. addition of 0.1 m cacl2 increased nisin z production specifically, but not cell growth, acid production, or xylose consumption, and resulted in the maximum nisin z activity of about 1.5 times that w ... | 1998 | 27392594 |
| purification and partial identification of bacteriocin isk-1, a new lantibiotic produced by pediococcus sp. isk-1. | bacteriocin isk-1 is a proteinaceous inhibitory substance produced by pediococcus sp. isk-1 isolated from well-aged nukadoko. bacteriocin isk-1 was purified by acid treatment, ammonium sulfate precipitation, cation-exchange chromatography, and reversed-phase hplc from the culture supernatant of pediococcus sp. isk-1. purification of bacteriocin isk-1 resulted in a 30-fold increase in the specific activity and the recovery was 17%. molecular mass of bacteriocin isk-1 measured by fast atom bombard ... | 1998 | 27392396 |
| effect of alpha-acetolactate decarboxylase inactivation on alpha-acetolactate and diacetyl production by lactococcus lactis subsp. lactis biovar diacetylactis. | strains of lactococcus lactis subsp. lactis biovar diacetylactis deficient in alpha-acetolactate decarboxylase produce alpha-acetolactate. this unstable compound is a precursor of acetoin and an aromatic compound, diacetyl. following random mutagenesis of strain cnrz 483, alpha-acetolactate decarboxylase-negative mutant 483 m1 was selected. when grown in milk, its growth and acidification characteristics were similar to those of the parental strain. in anaerobic conditions, the parental strain p ... | 1999 | 16232430 |