| analysis of a region from the bacteriophage resistance plasmid pci528 involved in its conjugative mobilization between lactococcus strains. | a 10-kb hindiii fragment of pci528 cloned into the nonconjugative shuttle vector pci3340 could be transferred by conjugative mobilization from lactococcus lactis subsp. lactis mg1363, whereas other hindiii fragments of pci528 or the vector alone were nonmobilizable. subcloning of this 10-kb region identified a 4.4-kb bglii-ecori fragment which contained all the dna essential for transfer. sequence analysis of a 2-kb region within this 4.4 kb-segment revealed a region rich in inverted repeats and ... | 1993 | 8376345 |
| two genes present on a transposon-like structure in lactococcus lactis are involved in a clp-family proteolytic activity. | the lactose-protease plasmid pucl22 of lactococcus lactis subsp. lactis strain cnrz270 contained two inverted copies of is 1076 flanking a region of 3.7 kb. this internal region was sequenced and found to contain two large open reading frames, orf1 and orfp in opposite orientations. orf1 consists of 2289 bp; the deduced 763-amino-acid sequence is similar to the atpases of the clpa family. it contains two well-conserved consensus atp-binding sites. it was named clpl. orfp consists of 930 bp encod ... | 1993 | 8387149 |
| copy number and location of insertion sequences iss1 and is981 in lactococci and several other lactic acid bacteria. | genomic dna from 49 lactococcal strains was screened by southern hybridization for the presence and relative copy number of lactococcal insertion sequence iss1: iss1 was found in 47 of 49 strains giving 1 to 20 hybridizing bands per strain. southern hybridizations of undigested plasmid dna from 17 lactococcal strains probed with iss1 and is981 showed that iss1 was present on plasmids in all 17 strains, whereas is981 was present on plasmids in 14 of the 17 strains. both insertion sequences were p ... | 1993 | 8389385 |
| insertion of lipids and proteins into bacterial membranes by fusion with liposomes. | | 1993 | 8395638 |
| energy transduction in lactic acid bacteria. | in the discovery of some general principles of energy transduction, lactic acid bacteria have played an important role. in this review, the energy transducing processes of lactic acid bacteria are discussed with the emphasis on the major developments of the past 5 years. this work not only includes the biochemistry of the enzymes and the bioenergetics of the processes, but also the genetics of the genes encoding the energy transducing proteins. the progress in the area of carbohydrate transport ... | 1993 | 8398212 |
| organization and regulation of genes for amino acid biosynthesis in lactic acid bacteria. | the recent description of large clusters of biosynthetic genes in the chromosome of lactococcus lactis and, to a lesser extent, of lactobacillus, has brought some information on gene organization and control of gene expression in these organisms. the genes involved in a given amino acid biosynthetic pathway are clustered at a single chromosomal location and form an operon. additional genes which are not required for the biosynthesis are present within some operons. genetic signals are, in genera ... | 1993 | 8398216 |
| cloning, sequence and expression of the gene encoding the malolactic enzyme from lactococcus lactis. | many lactic acid bacteria can carry out malolactic fermentation. this secondary fermentation is mediated by the nad- and mn(2+)-dependent malolactic enzyme, which catalyses the decarboxylation of l-malate to l-lactate. the gene we call mles, coding for malolactic enzyme, was isolated from lactococcus lactis. the mles gene consists of one open reading frame capable of coding for a protein with a calculated molecular mass of 59 kda. the amino acid sequence of the predicted mles gene product is hom ... | 1993 | 8405453 |
| rapid isolation of genes from bacterial lambda libraries by direct polymerase chain reaction screening. | a method for the direct screening of bacterial lambda libraries by polymerase chain reaction technology has been developed. this technique permits the identification and isolation of specific dna sequences without the need for any filter hybridisation or radioactive probing. this strategy has been used to isolate a gene encoding lactate dehydrogenase from a lactococcus lactis lambda library. | 1993 | 8405949 |
| cloning, nucleotide sequence and expression in streptomyces lividans and escherichia coli of pabb from lactococcus lactis subsp. lactis ncdo 496. | a gene (pabb) encoding the aminase activity of p-aminobenzoate (paba) synthase in lactococcus lactis subsp. lactis was cloned in pij41 and expressed in streptomyces lividans strains defective in paba biosynthesis. expression of the gene was associated with a 1.2 kb deletion between the aph promoter and the cloning site in pij41. subcloning in pbr322 and expression in escherichia coli ab3295 of the cloned l. lactis dna fragment localized the pabb-complementing gene in a 1.9 kb segment. the nucleo ... | 1993 | 8409921 |
| functional analysis of the lactococcus lactis usp45 secretion signal in the secretion of a homologous proteinase and a heterologous alpha-amylase. | the ups45 gene encodes the major extracellular protein from lactococcus lactis. the deduced sequence of the 27 residue leader peptide revealed the tripartite characteristics of a signal peptide. this leader peptide directed the efficient secretion of the homologous proteinase (prtp) in l. lactis, indicating that the putative signal peptide of prtp can be replaced by the 27 residue usp45 leader peptide. in addition, the 27 residue leader peptide could be used to secrete the bacillus stearothermop ... | 1993 | 8413193 |
| 15n- and 13c-labeled media from anabaena sp. for universal isotopic labeling of bacteriocins: nmr resonance assignments of leucocin a from leuconostoc gelidum and nisin a from lactococcus lactis. | a procedure for universal 13c and/or 15n labeling of microbial peptides which are produced by fermentation in complex media and its application to two food-preserving bacteriocins from lactic acid bacteria are described. isotopic enrichment of nisin a (from lactococcus lactis) and of leucocin a (from leuconostoc gelidum) is readily achieved using a soluble peptone derived from enzymatic hydrolysis (pepsin and chymopapain) of anabaena sp. atcc 27899 cells grown on sodium [13c]bicarbonate and/or s ... | 1993 | 8418850 |
| properties of nisin z and distribution of its gene, nisz, in lactococcus lactis. | two natural variants of the lantibiotic nisin that are produced by lactococcus lactis are known. they have a similar structure but differ in a single amino acid residue at position 27; histidine in nisin a and asparagine in nisin z (j.w.m. mulders, i.j. boerrigter, h.s. rollema, r.j. siezen, and w.m. de vos, eur. j. biochem, 201:581-584, 1991). the nisin variants were purified to apparent homogeneity, and their biological activities were compared. identical mics of nisin a and nisin z were found ... | 1993 | 8439149 |
| cloning and sequencing of pepc, a cysteine aminopeptidase gene from lactococcus lactis subsp. cremoris am2. | a gene coding for an aminopeptidase (pepc) from lactococcus lactis subsp. cremoris am2 was cloned by complementation of an escherichia coli mutant lacking aminopeptidase activity. the nucleotide sequence was determined. a portion of the predicted amino acid sequence of pepc (436 amino acids) showed strong homology to the active site of cysteine proteases. no signal sequence was found, indicating an intracellular location of the enzyme. | 1993 | 8439160 |
| stability analysis of the lactococcus lactis drc1 lactose plasmid using pulsed-field gel electrophoresis. | pulsed-field agarose gel electrophoresis of smai digests of genomic dna was used to examine lactose plasmid copy number and stability in lactococcus lactis. in l. lactis strain drc1, the plasmid was found to exist as a single-copy plasmid. transconjugants of strain hid113 carrying this plasmid were unstable. variants were isolated with improved phenotypic stability resulting from improved maintenance of the lactose plasmid or from integration of part of the plasmid into the lactococcal chromosom ... | 1993 | 8441771 |
| in vitro pore-forming activity of the lantibiotic nisin. role of protonmotive force and lipid composition. | nisin is a lantibiotic produced by some strains of lactococcus lactis subsp. lactis. the target for nisin action is the cytoplasmic membrane of gram-positive bacteria. nisin dissipates the membrane potential (delta psi) and induces efflux of low-molecular-mass compounds. evidence has been presented that a delta psi is needed for nisin action. the in vitro action of nisin was studied on liposomes loaded with the fluorophore carboxyfluorescein. nisin-induced efflux of carboxyfluorescein was observ ... | 1993 | 8444179 |
| cloning, nucleotide sequence, and regulatory analysis of the lactococcus lactis dnaj gene. | the dnaj gene of lactococcus lactis was isolated from a genomic library of l. lactis nizo r5 and cloned into puc19. nucleotide sequencing revealed an open reading frame of 1,137 bp in length, encoding a protein of 379 amino acids. the deduced amino acid sequence showed homology to the dnaj proteins of escherichia coli, mycobacterium tuberculosis, bacillus subtilis, and clostridium acetobutylicum. the level of the dnaj monocistronic mrna increased approximately threefold after heat shock. the tra ... | 1993 | 8449872 |
| characterization of genetic elements required for site-specific integration of the temperate lactococcal bacteriophage phi lc3 and construction of integration-negative phi lc3 mutants. | the genetic elements required for the integration of the temperate lactococcal bacteriophage phi lc3 into the chromosome of its bacterial host, lactococcus lactis subsp. cremoris, were identified and characterized. the phi lc3 phage attachment site, attp, was mapped and sequenced. dna sequence analysis of attp and of the bacterial attachment site, attb, as well as the two phage-host junctions, attr and attl, in the chromosome of a phi lc3 lysogen, identified a 9-bp common core region, 5'-ttcttca ... | 1993 | 8449882 |
| gene organization, primary structure and rna processing analysis of a ribosomal rna operon in lactococcus lactis. | southern blot analysis of genomic dna of the mesophilic lactic bacterium lactococcus lactis subsp. lactis strain il1403, illuminated six rrna gene clusters. each cluster contains one copy each of three rrna genes, displaying the typical eubacterial organization of physically linked 16 s, 23 s and 5 s rrna genes. five of the six rrna clusters were cloned into plasmid pbr322. one recombinant plasmid, pslcm6, containing a 6500 base-pair genomic dna fragment, was characterized by physical mapping an ... | 1993 | 8450551 |
| di-tripeptides and oligopeptides are taken up via distinct transport mechanisms in lactococcus lactis. | lactococcus lactis ml3 possesses two different peptide transport systems of which the substrate size restriction and specificity have been determined. the first system is the earlier-described proton motive force-dependent di-tripeptide carrier (e. j. smid, a. j. m. driessen, and w. n. konings, j. bacteriol. 171:292-298, 1989). the second system is a metabolic energy-dependent oligopeptide transport system which transports peptides of four to at least six amino acid residues. the involvement of ... | 1993 | 8458848 |
| cloning and sequencing of the gene for a lactococcal endopeptidase, an enzyme with sequence similarity to mammalian enkephalinase. | the gene specifying an endopeptidase of lactococcus lactis, named pepo, was cloned from a genomic library of l. lactis subsp. cremoris p8-2-47 in lambda embl3 and was subsequently sequenced. pepo is probably the last gene of an operon encoding the binding-protein-dependent oligopeptide transport system of l. lactis. the inferred amino acid sequence of pepo showed that the lactococcal endopeptidase has a marked similarity to the mammalian neutral endopeptidase ec 3.4.24.11 (enkephalinase), wherea ... | 1993 | 8458851 |
| lysines 72, 80 and 213 and aspartic acid 210 of the lactococcus lactis lacr repressor are involved in the response to the inducer tagatose-6-phosphate leading to induction of lac operon expression. | site-directed mutagenesis of the lactococcus lactis lacr gene was performed to identify residues in the lacr repressor that are involved in the induction of lacabcdfegx operon expression by tagatose-6-phosphate. a putative inducer binding domain located near the c-terminus was previously postulated based on homology studies with the escherichia coli deor family of repressors, which all have a phosphorylated sugar as inducer. residues within this domain and lysine residues that are charge conserv ... | 1993 | 8475045 |
| identification of a novel operon in lactococcus lactis encoding three enzymes for lactic acid synthesis: phosphofructokinase, pyruvate kinase, and lactate dehydrogenase. | the discovery of a novel multicistronic operon that encodes phosphofructokinase, pyruvate kinase, and lactate dehydrogenase in the lactic acid bacterium lactococcus lactis is reported. the three genes in the operon, designated pfk, pyk, and ldh, contain 340, 502, and 325 codons, respectively. the intergenic distances are 87 bp between pfk and pyk and 117 bp between pyk and ldh. plasmids containing pfk and pyk conferred phosphofructokinase and pyruvate kinase activity, respectively, on their host ... | 1993 | 8478320 |
| characterization of the lactococcus lactis nisin a operon genes nisp, encoding a subtilisin-like serine protease involved in precursor processing, and nisr, encoding a regulatory protein involved in nisin biosynthesis. | biosynthesis of the lantibiotic peptide nisin by lactococcus lactis nizo r5 relies on the presence of the conjugative transposon tn5276 in the chromosome. a 12-kb dna fragment of tn5276 including the nisa gene and about 10 kb of downstream dna was cloned in l. lactis, resulting in the production of an extracellular nisin precursor peptide. this peptide reacted with antibodies against either nisin a or the synthetic leader peptide, suggesting that it consisted of a fully modified nisin with the n ... | 1993 | 8478324 |
| scrfi restriction-modification system of lactococcus lactis subsp. cremoris uc503: cloning and characterization of two scrfi methylase genes. | two genes from the total genomic dna of dairy starter culture lactococcus lactis subsp. cremoris uc503, encoding scrfi modification enzymes, have been cloned and expressed in escherichia coli. no homology between the two methylase genes was detected, and inverse polymerase chain reaction of flanking chromosomal dna indicated that both were linked on the lactococcus genome. neither clone encoded the cognate endonuclease. the dna sequence of one of the methylase genes (encoded by pci931m) was dete ... | 1993 | 8481004 |
| cloning and sequencing of the lactococcus lactis subsp. lactis groesl operon. | the operon (groesl) coding for the lactococcus lactis subsp. lactis heat-shock proteins groel and groes, has been isolated and its complete nucleotide (nt) sequence determined. a set of degenerate pcr primers, deduced from amino acids which are conserved in a number of prokaryotic groels, were synthesized and used to amplify a 957-bp fragment. this pcr fragment was used as a probe to isolate a 5.0-kb ecori chromosomally derived fragment. a region of this 5.0-kb ecori fragment was sequenced and r ... | 1993 | 8486277 |
| monitoring tripeptidase activity using capillary electrophoresis. comparison with the ninhydrin assay. | capillary electrophoresis (ce) was used to assay the activity of a tripeptidase from a crude extract of lactococcus lactis subsp. lactis ncdo 712 against the substrate, gly-gly-phe and a comparison with a standard ninhydrin assay was made. standard curves of the substrates and products showed a significantly variable colorimetric reaction to ninhydrin making accurate quantification of the tripeptidase problematic. the ce assay further demonstrated that the presence of contaminating enzymes in cr ... | 1993 | 8491837 |
| influence of intracellular ph on light emission from a luxa/b derivative of lactococcus lactis subsp. diacetylactis. | high levels of constitutive aldehyde-dependent light emission were obtained from nongrowing cells of lactococcus lactis subsp. diacetylactis f712 transformed with iuxa/b when they were suspended in buffered solutions. inductions of light emission was time-dependent and was not due to growth, synthesis of luciferase or stimulation of metabolism by fermentable carbohydrate. the major factor controlling light emission in such cells appears to be the intracellular ph value. experiments with ionophor ... | 1993 | 8493883 |
| application of in vivo bioluminescence to the study of ionophoretic action. | ionophores (carbonyl cyanide m-chlorophenylhydrazone; valinomycin; and the hop-derived compounds colupulone, trans-isohumulone and trans-humulinic acid) reduced the rate of dodecanal-dependent light emission from iuxa/b-transformed cells of lactococcus lactis subsp. diacetylactis f712 when the cells were suspended in a buffered medium (ph 6.4) containing glucose. this allowed an assay for ionophores to be devised and permitted measurement of the effects of such compounds on the test organism by ... | 1993 | 8493884 |
| high-efficiency gene inactivation and replacement system for gram-positive bacteria. | a system for high-efficiency single- and double-crossover homologous integration in gram-positive bacteria has been developed, with lactococcus lactis as a model system. the system is based on a thermosensitive broad-host-range rolling-circle plasmid, pg+host5, which contains a pbr322 replicon for propagation in escherichia coli at 37 degrees c. a nested set of l. lactis chromosomal fragments cloned onto pg+host5 were used to show that the single-crossover integration frequency was logarithmical ... | 1993 | 8501066 |
| a simple, low energy requiring method of coagulating leaf proteins for food use. | a simple method for coagulating proteins in aqueous leaf extract, through microbial fermentation, has been reported. the leaf protein concentrate (lpc) obtained through this fermentation has been compared with those obtained through conventional heat coagulation methods to show that the former improves the yield and nutritional quality of lpc. | 1993 | 8506239 |
| cloning and expression of the manganese superoxide dismutase gene of escherichia coli in lactococcus lactis and lactobacillus gasseri. | the escherichia coli soda gene encoding the antioxidant enzyme mn-containing superoxide dismutase (mnsod), was cloned in the expression vector pmg36e. this vector has a multiple cloning site downstream of a promoter and shine-dalgarno sequences derived from lactococcus. the protein-coding region of soda from e. coli was amplified by the polymerase chain reaction, using a thermocycler and taq dna polymerase before cloning into pmg36e. when introduced into e. coli, the recombinant plasmid expresse ... | 1993 | 8510661 |
| a system to generate chromosomal mutations in lactococcus lactis which allows fast analysis of targeted genes. | a system for generating chromosomal insertions in lactococci is described. it is based on the conditional replication of lactococcal pwv01-derived ori+ repa- vector pori19, containing lacz alpha and the multiple cloning site of puc19. chromosomal alui fragments of lactococcus lactis were cloned in pori19 in repa+ helper strain escherichia coli ec101. the frequency of campbell-type recombinants, following introduction of this plasmid bank into l. lactis (repa-), was increased by combining the sys ... | 1995 | 8522504 |
| characterization of transposon tn5469 from the cyanobacterium fremyella diplosiphon. | a transposon, designated tn5469, was isolated from mutant strain fdr1 of the filamentous cyanobacterium fremyella diplosiphon following its insertion into the rcac gene. tn5469 is a 4,904-bp noncomposite transposon with 25-bp near-perfect terminal inverted repeats and has three tandemly arranged, slightly overlapping potential open reading frames (orfs) encoding proteins of 104.6 kda (909 residues), 42.5 kda (375 residues), and 31.9 kda (272 residues). insertion of tn5469 into the rcac gene in s ... | 1995 | 8522506 |
| nucleotide sequence and characterization of peb4a encoding an antigenic protein in campylobacter jejuni. | the 29-kda protein peb4, a major antigen of campylobacter jejuni, is present in all c. jejuni strains tested and elicits an antibody response in infected patients. by screening a lambda gt11 library of chromosomal dna fragments of c. jejuni strain 81-176 in escherichia coli y1090 cells with antibody raised against purified peb4, a recombinant phage with a 2-kb insert expressing an immunoreactive protein of 29 kda was isolated. dna sequence analysis revealed that the insert contains two complete ... | 1995 | 8525063 |
| involvement of enzyme-substrate charge interactions in the caseinolytic specificity of lactococcal cell envelope-associated proteinases. | three series of oligopeptides were synthesized to investigate the proposal that a major factor in determining the differences in specificity of the lactococcal cell surface-associated proteinases against caseins is the interactions between charged amino acids in the substrate and in the enzyme. the sequences of the oligopeptides were based on two regions of kappa-casein (residues 98 to 111 and 153 to 169) which show markedly different susceptibilities to pi- and piii-type lactococcal proteinases ... | 1995 | 8526506 |
| metabolic engineering of lactococcus lactis: influence of the overproduction of alpha-acetolactate synthase in strains deficient in lactate dehydrogenase as a function of culture conditions. | the als gene for alpha-acetolactate synthase of lactococcus lactis mg1363 was cloned on a multicopy plasmid under the control of the inducible l. lactis laca promoter. more than a hundredfold overproduction of alpha-acetolactate synthase was obtained in l. lactis under inducing conditions as compared with that of the host strain, which contained a single chromosomal copy of the als gene. the effect of alpha-acetolactate synthase overproduction on the formation of end products in various l. lacti ... | 1995 | 8526510 |
| sequence analysis of the lactococcus lactis temperate bacteriophage bk5-t and demonstration that the phage dna has cohesive ends. | the lactococcus lactis temperate bacteriophage bk5-t is a type phage in the lactococcal phage classification (a. w. jarvis, g. f. fitzgerald, m. mata, a. mercenier, h. neve, i. b. powell, c. ronda, m. saxelin, and m. teuber, intervirology 32:2-9, 1991). the nucleotide sequence of 18,935 bp of the genome of bk5-t was determined and analyzed for the presence of open reading frames and other structural features. thirty-two open reading frames longer than 60 codons were identified, and these appeare ... | 1995 | 8526523 |
| identification of prophage genes expressed in lysogens of the lactococcus lactis bacteriophage bk5-t. | bacteriophage bk5-t is a small isometric-headed temperate phage that infects lactococcus lactis subsp. cremoris. northern (rna) analysis of mrna produced by lysogenic strains containing bk5-t prophage revealed four major bk5-t transcripts that are 0.8, 1.3, 1.8, and 1.8 kb in size and enabled a transcription map of the prophage genome to be prepared. the position and size of each transcript corresponded closely to the position and size of open reading frames predicted from the nucleotide sequenc ... | 1995 | 8526524 |
| spontaneous deletion mutants of the lactococcus lactis temperate bacteriophage bk5-t and localization of the bk5-t attp site. | spontaneous deletion mutants of the temperate lactococcal bacteriophage bk5-t were obtained when the phage was grown vegetatively on the indicator strain lactococcus lactis subsp. cremoris h2. one deletion mutant was unable to form stable lysogens, and analysis of this mutant led to the identification of the bk5-t attp site and the integrase gene (int). the core sequences of the bk5-t attp and host attb regions are conserved in a number of lactococcal phages and l. lactis strains. | 1995 | 8526525 |
| lactococcal bacteriocins: mode of action and immunity. | bacteriocins are antimicrobial peptides produced by bacteria. some of those synthesized by lactococcus lactis have been characterized in great detail recently. the lactococcal bacteriocins are hydrophobic cationic peptides, which form pores in the cytoplasmic membrane of sensitive cells. | 1995 | 8528613 |
| cloning and dna sequence analysis of two abortive infection phage resistance determinants from the lactococcal plasmid pnp40. | the lactococcal plasmid pnp40, from lactococcus lactis subsp. lactis biovar diacetylactis drc3, confers complete resistance to the prolate-headed phage phi c2 and the small isometric-headed phage phi 712 in l. lactis subsp. lactis mg1614. a 6.0-kb ncoi fragment of pnp40 cloned in the lactococcal escherichia coli shuttle vector pam401 was found to confer partial resistance to phi 712. subcloning and deletion analysis of the recombinant plasmid ppg01 defined a 2.5-kb scaihpai fragment as conferrin ... | 1995 | 8534099 |
| sequencing and analysis of the prolate-headed lactococcal bacteriophage c2 genome and identification of the structural genes. | the 22,163-bp genome of the lactococcal prolate-headed phage c2 was sequenced. thirty-nine open reading frames (orfs), early and late promoters, and a putative transcription terminator were identified. twenty-two orfs were in the early gene region, and 17 were in the late gene region. putative genes for a dna polymerase, a recombination protein, a sigma factor protein, a transcription regulatory protein, holin proteins, and a terminase were identified. transcription of the early and late genes p ... | 1995 | 8534101 |
| a non-essential glutamyl aminopeptidase is required for optimal growth of lactococcus lactis mg1363 in milk. | degenerate pcr primers were designed from the n-terminal amino acid sequence of a glutamyl aminopeptidase (pepa) from lactococcus lactis. these primers were used to screen a lambda library for clones containing the gene (pepa) encoding pepa. the dna sequence of a 2.1 kb fragment containing pepa was determined. the sequence revealed the presence of one complete and two incomplete open reading frames (orfs). the complete orf encodes a putative protein of 353 amino acids with a predicted n-terminal ... | 1995 | 8535515 |
| the three-dimensional structure of 6-phospho-beta-galactosidase from lactococcus lactis. | the enzyme 6-phospho-beta-galactosidase hydrolyzes phospholactose, the product of a phosphor-enolpyruvate-dependent phosphotransferase system. it belongs to glycosidase family 1 and no structure has yet been published for a member of this family. | 1995 | 8535789 |
| lactococcin g is a potassium ion-conducting, two-component bacteriocin. | lactococcin g is a novel lactococcal bacteriocin whose activity depends on the complementary action of two peptides, termed alpha and beta. peptide synthesis of the alpha and beta peptides yielded biologically active lactococcin g, which was used in mode-of-action studies on sensitive cells of lactococcus lactis. approximately equivalent amounts of both peptides were required for optimal bactericidal effect. no effect was observed with either the alpha or beta peptide in the absence of the compl ... | 1996 | 8550488 |
| efficient insertional mutagenesis in lactococci and other gram-positive bacteria. | in lactococci, the study of chromosomal genes and their regulation is limited by the lack of an efficient transposon mutagenesis system. we associated the insertion sequence iss1 with the thermosensitive replicon pg+ host to generate a mutagenic tool that can be used even in poorly transformable strains. iss1 transposition is random in different lactococcal strains as well as in enterococcus faecalis and streptococcus thermophilus. high-frequency random insertion (of about 1%) obtained with this ... | 1996 | 8550537 |
| structural and functional analysis of the single-strand origin of replication from the lactococcal plasmid pwv01. | the single-strand origin (sso) of the rolling-circle (rc), broad-host-range lactococcal plasmid pwvo1 was functionally characterized. the activity of this sso in the conversion of single-stranded dna to double-stranded dna was tested both in vivo and in vitro. in addition, the effect of this sso on plasmid maintenance was determined. the functional pwvo1 sso comprises a 250 bp region, containing two inverted repeats (irs). the activity of each ir was tested, separately and in combination, in a p ... | 1995 | 8552032 |
| use of capillary zone electrophoresis in an investigation of peptide uptake by dairy starter bacteria. | a capillary zone electrophoresis (cze) method to separate the peptide series val-glyn, where n is 1 to 4, has been evaluated and compared to separation by reversed-phase high-performance liquid chromatography (rp-hplc). the method was able to quantitate peptides present a very low concentrations (down to 0.05 mm) with high reproducibility and accuracy and was capable of separating peptides differing in size by only a single glycine residue. it could also separate the peptides val-gly and leu-gly ... | 1995 | 8556163 |
| maturation pathway of nisin and other lantibiotics: post-translationally modified antimicrobial peptides exported by gram-positive bacteria. | lantibiotics form a family of highly modified peptides which are secreted by several gram-positive bacteria. they exhibit antimicrobial activity, mainly against other gram-positive bacteria, by forming pores in the cellular membrane. these antimicrobial peptides are ribosomally synthesized and contain leader peptides which do not show the characteristics of signal sequences. several amino acid residues of the precursor lantibiotic are enzymatically modified, whereafter secretion and processing o ... | 1995 | 8559062 |
| comparison of proteolytic activities in various lactobacilli. | a total of 169 lactobacillus strains from 12 species (lb. acidophilus, lb. brevis, lb. buchneri, lb. casei, lb. delbrueckii subsp. bulgaricus, lb. delbrueckii subsp. delbrueckii, lb. delbrueckii subsp. lactis, lb. fermentum, lb. helveticus, lb. paracasei subsp. paracasei, lb. plantarum and lb. rhamnosus), isolated from raw milk and various milk products, and 9 lactococcus lactis strains were evaluated for peptidase activities with five chromogenic substrates and a tryptic digest of casein. withi ... | 1995 | 8568030 |
| an x-prolyl dipeptidyl aminopeptidase (pepx) gene from lactobacillus helveticus. | the x-prolyl dipeptidyl aminopeptidase gene (pepx) of an industrially used lactobacillus helveticus strain has been detected by nucleic acid hybridization, cloned, characterized and sequenced. one orf of 2379 bp with coding capacity for a 90.6 kda protein (pepx) was found. the orf was preceded by a typical prokaryotic promoter region. an inverted repeat structure with delta g of -84.1 kj mol-1 was found downstream of the coding region. the deduced amino acid sequence of the 90.6 kda protein show ... | 1995 | 8574400 |
| a study of the substrate specificity of aminopeptidase n from lactococcus lactis subsp. cremoris wg2. | a systematic study was made of the ability of aminopeptidase n from lactococcus lactis subsp. cremoris wg2 to hydrolyse different peptide substrates. the enzyme showed a marked preference for substrates containing arginine as the n-terminal residue but, to a lesser extent, was also capable of cleaving other residues such as lysine and leucine. there was a tendency for the activity to increase with the hydrophobicity index of the c-terminal residue of dipeptide substrates. it was also observed th ... | 1995 | 8579823 |
| characteristics of tn5307 exchange and intergeneric transfer of genes associated with nisin production. | transfer of the lactococcus lactis 11454 nisin-sucrose conjugative transposon, tn5307, was investigated to develop a methodology for conjugation of this element to other lactic acid bacteria. tn5307 exchange was sensitive to temperature and ph but was not affected by protease or amylase treatments to donor cells. moreover, conjugation studies demonstrated that the direct-plate method could be employed to rapidly identify lm2301 transconjugants able to transfer tn5307 at least ten times more effi ... | 1995 | 8579827 |
| genomic organization of lactococci. | the genus lactococcus contains four species of which l. lactis is the most thoroughly studied. its genome is a+t-rich and consists of a circular chromosome of 2.0 to 2.7 mbp, a wide range of plasmids, and frequently one or more prophages. insertion sequence elements are commonly present in both the chromosome and the plasmids, while one conjugative transposon of 68 kbp has been described. genetic maps of the chromosomes of a number of different l. lactis strains have been determined and found to ... | 1995 | 8586212 |
| molecular analysis of the lactococcus lactis sex factor. | | 1995 | 8586213 |
| metabolic operons in lactococci. | the genes for the biosynthesis of histidine, tryptophan and branched-chain amino acids (ilv for isoleucine, leucine and valine) are clustered in large operons. in addition to genes encoding the pathway enzymes, the his and the ilv operons contain 4 and 3 other genes, respectively. the functions of two of these, orf3 and aldb are regulatory. the second gene of the his operon, orf3, encodes a protein homologous to the histidyl-trna synthetases. it is involved in transcription attenuation upstream ... | 1995 | 8586214 |
| environmentally regulated promoters in lactococci. | | 1995 | 8586215 |
| stress response in lactococcus lactis. | | 1995 | 8586216 |
| reca gene involvement in oxidative and thermal stress in lactococcus lactis. | the reca gene is best known for its effects on homologous recombination and dna repair via sos induction. there is gathering evidence that reca also affects expression of genes associated with different types of stress. we studied reca properties in lactococcus lactis by generating a reca-disrupted mutant of mg1363 and comparing it with the wild type strain. reca appears to have an important role in cell survival upon oxygen or thermal stress, in addition to its conserved role in dna repair. oxy ... | 1995 | 8586217 |
| polysaccharide expression in lactococci. | lactococcus lactis produces polysaccharide under defined environmental conditions. three approaches are being used to identify regulators of polysaccharide synthesis in the organism. i) two new lactococcal vectors, each of which contains a promoterless reporter gene, have been developed. they are being used to select for chromosomal insertions that affect expression of polysaccharide ii) genetic complementation with lactococcal genomic libraries identified two classes of lactococcal genomic acti ... | 1995 | 8586218 |
| lon and clp-like atp-dependent proteases of lactococcus lactis. | | 1995 | 8586220 |
| genetic modification and the proteolytic system of lactococci. | | 1995 | 8586222 |
| genetics of peptide degradation in lactococcus: gene cloning, construction and analysis of peptidase negative mutants. | | 1995 | 8586223 |
| plasmid-mediated oligopeptide transport system in lactococci. | | 1995 | 8586224 |
| integration strategies and vectors. | | 1995 | 8586226 |
| nonsense suppression in lactococcus lactis: construction of a "food-grade" cloning vector. | | 1995 | 8586227 |
| specificity of insertion of tn1545 transposon family in lactococcus lactis subsp. lactis. | a collection of lactococcus lactis subsp. lactis strains carrying a derivative of tn1545 inserted in the chromosome was generated. some 34 insertions were cloned in escherichia coli and the flanking dna sequences determined. insertions are distributed non randomly and several hot spots were observed. the hot spots do not have sequence features which would distinguish them from other insertion sites, suggesting that they may have special structural properties. insertions in open reading frames oc ... | 1995 | 8586228 |
| characterization of the conjugation system associated with the lactococcus lactis ssp. lactis plasmid prs01. | | 1995 | 8586229 |
| high expression of a foreign reporter gene in streptococcus thermophilus. | | 1995 | 8586230 |
| a protein, belonging to a family of rna-binding transcriptional anti-terminators, controls beta-glucoside assimilation in lactococcus lactis. | | 1995 | 8586232 |
| characterization of a cloned gene (pip) from lactococcus lactis required for phage infection. | | 1995 | 8586234 |
| specific chromosomal sequences can contribute to the appearance of a new lytic bacteriophage in lactococcus. | | 1995 | 8586235 |
| bacteriophage resistance in lactococcus: molecular characterization of the scrfi restriction/modification system from lactococcus lactis subsp. cremoris uc503. | | 1995 | 8586236 |
| c.llai is a bifunctional regulatory protein of the llai restriction modification operon from lactococcus lactis. | | 1995 | 8586237 |
| physical and genetic maps of the chromosome of the lactococcus lactis subsp. lactis strain il1403 and lactococcus lactis subsp. cremoris strain mg1363. | | 1995 | 8586238 |
| lactococcal expression systems for protein engineering of nisin. | | 1995 | 8586239 |
| genetics of the nisin operon and the sucrose-nisin conjugative transposon tn5276. | | 1995 | 8586240 |
| analysis of lactococcin secretion and immunity in lactococcus lactis. | | 1995 | 8586246 |
| comparative effectiveness of nisin and bacteriocin j46 at different ph values. | a comparative study of the inhibitory activity of nisin, the well-known lantibiotic produced by certain strains of lactococcus lactis subsp. lactis, and of the bacteriocin produced by l. lactis subsp. cremoris j46, a strain previously isolated from fermented milk, was conducted. for both bacteriocins, the activity against l. lactis subsp. cremoris decreased with increasing ph. in addition, the bacteriocin preparations were more stable at 4 degrees than at 20 degrees c. the influence of the stora ... | 1996 | 8588891 |
| purification, crystallization, and preliminary x-ray analysis of pepx, an x-prolyl dipeptidyl aminopeptidase from lactococcus lactis. | the x-prolyl dipeptidyl aminopeptidase pepx, a serine peptidase isolated originally from lactococcus lactis subsp lactis ncdo 763, was cloned and overproduced in escherichia coli. the enzyme was isolated in its active form in two purification steps. crystals of pepx were grown by the hanging drop vapor diffusion method using polyethyleneglycol 4000 as precipitant at ph 5.0. the crystals are orthorhombic with cell dimensions a = 92.8 a, b = 102.6 a, and c = 101.6 a, space group p2(1)2(1)2, and pr ... | 1995 | 8592708 |
| an application in cheddar cheese manufacture for a strain of lactococcus lactis producing a novel broad-spectrum bacteriocin, lacticin 3147. | lactococcus lactis dpc3147, a strain isolated from an irish kefir grain, produces a bacteriocin with a broad spectrum of inhibition. the bacteriocin produced is heat stable, particularly at a low ph, and inhibits nisin-producing (nip+) lactococci. on the basis of the observation that the nisin structural gene (nisa) does not hybridize to dpc3147 genomic dna, the bacteriocin produced was considered novel and designated lacticin 3147. the genetic determinants which encode lacticin 3147 are contain ... | 1996 | 8593062 |
| the reca gene of lactococcus lactis: characterization and involvement in oxidative and thermal stress. | the role of reca in lactococcus lactis, a microaerophilic fermenting organism, was examined by constructing a reca-disrupted strain. this single alteration had a surprisingly pleiotropic effect. in addition to its roles in homologous recombination and dna repair, reca is also involved in responses to oxygen and heat stresses. we found that oxygen stress induced by aeration causes reductions in growth and stationary-phase survival of the reca strain. toxicity is a consequence of hydroxyl radical ... | 1995 | 8594331 |
| transposons tn916 and tn925 can transfer from enterococcus faecalis to leuconostoc oenos. | the streptococcal transposons tn916 and tn925 were transferred to several strains of leuconostoc (ln.) oenos using the filter mating method. the insertion of both transposons into the chromosome occurred at different sites. transconjugants of ln. oenos carrying tn916 could serve as donors in mating experiments with lactococcus lactis lm2301. further analysis of l. lactis lm2301 transconjugants showed that the insertion of the transposon tn916 into the chromosome was site-specific. these studies ... | 1996 | 8595855 |
| role of scalar protons in metabolic energy generation in lactic acid bacteria. | lactic acid bacteria are able to generate a protonmotive force across the cytoplasmic membrane by various metabolic conversions without involvement of substrate level phosphorylation or proton pump activity. weak acids like malate and citrate are taken up in an electrogenic process in which net negative charge is translocated into the cell thereby generating a membrane potential. the uptake is either an exchange process with a metabolic end-product (precursor/ product exchange) or a uniporter me ... | 1995 | 8595982 |
| the occurrence of two intracellular oligoendopeptidases in lactococcus lactis and their significance for peptide conversion in cheese. | two intracellular oligopeptide-preferring endopeptidases have been detected in lactococcus lactis. a neutral thermolysin-like oligoendopeptidase (nop) has been purified to homogeneity and an alkaline oligoendopeptidase has been partially purified. the specificity of the oligoendopeptidases towards important intermediary cheese peptides, produced by chymosin action on the caseins, clearly differs from that of the cell-envelope proteinase (cep). nop is active under conditions prevailing in cheese ... | 1995 | 8597539 |
| highly bioluminescent streptococcus thermophilus strain for the detection of diary-relevant antibiotics in milk. | inefficient translational initiation is often the cause of poor foreign gene expression in gram-positive organisms. the expression of bacterial luciferase (lux) genes in streptococcus thermophilus (bioluminescence) was improved by addressing this problem in two ways; by ribosome-binding site (rbs) replacement, and by enhancing lux rbs access by polymerase chain reaction modification either alone or combined with translational coupling to a truncated upstream open- reading frame (orf') having its ... | 1995 | 8597542 |
| lactococcin a overexpression in a lactococcus lactis subsp. lactis transformant containing a tn5 insertion in the lcnd gene. | lactococcin a production in lactococci has recently been linked to a signal-sequence-independent secretory system consisting of a four-gene cluster. lactococcus lactis subsp. lactis llm23l-a1 has been obtained after tn5 mutagenesis of pllm23, a plasmid containing the gene cluster responsible for lactococcin a production. in contrast to other tn5-generated mutants, strain llm23l-al exhibited a 12-fold increase in lactococcin a production. overproduction of lactococcin a was not linked to an incre ... | 1995 | 8597543 |
| transcriptional activation of the citrate permease p gene of lactococcus lactis biovar diacetylactis by an insertion sequence-like element present in plasmid pcit264. | the lactococcal plasmid pcit264 contains a cluster of three genes (citq, citr and citp) involved in the transport of citrate in lactococcus lactis biovar diacetylactis. the cit cluster contains a copy of a newly discovered insertion sequence (is)-like element located between its promoter p1 and the first gene of the cluster. in this report, we show that this is-like element can act as a mobile switch for the downstream genes, creating two new transcriptional promoters named p2 and p2'. the p2 pr ... | 1996 | 8602160 |
| a genomic region of lactococcal temperate bacteriophage tp901-1 encoding major virion proteins. | two major structural proteins, mhp (major head protein) and mtp (major tail protein), from the lactococcal temperate phage tp901-1 were sequenced at their amino acid termini, and derived degenerate oligonucleotides were used to locate the corresponding genes in the phage genome. this genomic region was sequenced. the sequence characterized includes a total of 11 open reading frames (orfs) showing an operon structure. upstream of each orf, except orf b2 and orf x, potential ribosome-binding sites ... | 1996 | 8610457 |
| sequence of a lactococcus lactis dna fragment homologous to the recf gene of bacillus subtilis. | the recf gene of lactococcus lactis atcc 7962 is located 3 kb downstream from the lacz gene and is transcribed in the opposite orientation. the recf gene is immediately preceded by a 121-codon orf, and both recf and orf121 may be transcribed from the same promoter. the deduced recf amino-acid sequence shows high homology to that of the bacillus subtilis and streptococcus pyogenes recf proteins. | 1996 | 8621080 |
| the ribonucleotide reductase system of lactococcus lactis. characterization of an nrdef enzyme and a new electron transport protein. | escherichia coli contains the genetic information for three separate ribonucleotide reductases. two of them (class i enzymes), coded by the nrdab and nrdef genes, respectively, contain a tyrosyl radical, whose generation requires oxygen. the nrdab enzyme is physiologically active. the function of the nrdef gene is not known. the third enzyme (class iii), coded by nrddg, operates during anaerobiosis. the dna of lactococcus lactis contains sequences homologous to the nrddg genes. surprisingly, an ... | 1996 | 8621514 |
| identical transcriptional control of the divergently transcribed prtp and prtm genes that are required for proteinase production in lactococcus lactis sk11. | we have investigated transcriptional regulation of the divergently transcribed genes required for proteinase production (prtp and prtm) of lactococcus lactis sk11. their promoters partially overlap and are arranged in a face-to-face configuration. the medium-dependent activities of both prtp and prtm promoters were analyzed by quantitative primer extension studies and beta-glucuronidase assays with l. lactis mg1363 cells harboring transcriptional gene fusions of each promoter with the promoterle ... | 1996 | 8626277 |
| identification and characterization of the eps (exopolysaccharide) gene cluster from streptococcus thermophilus sfi6. | we report the identification and characterization of the eps gene cluster of streptococcus thermophilus sfi6 required for exopolysaccharide (eps) synthesis. this report is the first genetic work concerning eps production in a food microorganism. the eps secreted by this strain consists of the following tetrasaccharide repeating unit:-->3)-beta-d-galp-(1-->3)-[alpha-d-galp-(1-->6)]-beta-d- d-galp-(1-->3)-alpha-d-galp-d-galpnac-(1-->. the genetic locus the genetic locus was identified by tn916 mut ... | 1996 | 8626297 |
| topology of lcnd, a protein implicated in the transport of bacteriocins from lactococcus lactis. | four in-frame translational fusions to both the reporter proteins beta-galactosidase and alkaline phosphatase support a topological model of lcnd, a protein implicated in the transport of several bacteriocins from lactococcus lactis, in which the n-terminal part is located intracellularly and one transmembrane helix spans the cytoplasmic membrane. | 1996 | 8626308 |
| augmented production of extracellular superoxide by blood isolates of enterococcus faecalis. | to assess the frequency of extracellular superoxide (o-2) production by enterococci, multiple species were surveyed in a whole organism assay for their ability to reduce ferricytochrome c in a superoxide dismutase-inhibitable fashion. for stool and clinical enterococcal isolates and 12 type strains, only enterococcus faecalis (87/91 isolates and atcc 19433), enterococcus faecium (5/13 isolates), enterococcus casseliflavus (atcc 25778), and enterococcus gallinarum (atcc 35038) produced extracellu ... | 1996 | 8627044 |
| nisin z, mutant nisin z and lacticin 481 interactions with anionic lipids correlate with antimicrobial activity. a monolayer study. | monomolecular layers of lipids at the air/water interface have been used as a model membrane to study membrane interactions of the lantibiotic nisin. the natural lantibiotics nisin a and nisin z proved to have a high affinity for the anionic lipids phosphatidylglycerol and bis(phosphatidyl)glycerol (cardiolipin). the interaction with zwitterionic phopholipids or neutral lipids is very low at surface pressures higher than 32 mn/m. nisin, nisin mutants and lacticin 481 show a remarkable correlatio ... | 1996 | 8631341 |
| multiple-peptidase mutants of lactococcus lactis are severely impaired in their ability to grow in milk. | to examine the contribution of peptidases to the growth of lactococcus lactis in milk, 16 single- and multiple-deletion mutants were constructed. in successive rounds of chromosomal gene replacement mutagenesis, up to all five of the following peptidase genes were inactivated (fivefold mutant): pepx, pepo, pept, pepc, and pepn. multiple mutations led to slower growth rates in milk, the general trend being that growth rates decreased when more peptidases were inactivated. the fivefold mutant grew ... | 1996 | 8631666 |
| the genes for secretion and maturation of lactococcins are located on the chromosome of lactococcus lactis il1403. | southern hybridization and pcr analysis were used to show that lactococcus lactis il1403, a plasmid-free strain that does not produce bacteriocin, contains genes on its chromosome that are highly homologous to lcnc and lcnd and encode the lactococcin secretion and maturation system. the lcnc and lcnd homologs on the chromosome of il1403 were interrupted independently by campbell-type integrations. both insertion mutants were unable to secrete active lactococcin. part of the chromosomal lcnc gene ... | 1996 | 8633867 |
| variacin, a new lanthionine-containing bacteriocin produced by micrococcus varians: comparison to lacticin 481 of lactococcus lactis. | a new lanthionine-containing bacteriocin, variacin, displaying a broad host range of inhibition against gram-positive food spoilage bacteria, has been identified from two strains of micrococcus varians isolated from meat fermentations. the new bacteriocin was purified, and its amino-terminal end and total amino acid composition were determined. the structural gene was isolated and analyzed. variacin is resistant to heat and ph conditions from 2 to 10. its primary sequence shows significant homol ... | 1996 | 8633879 |
| peptides inhibitory to endopeptidase and aminopeptidase from lactococcus lactis ssp. lactis mg1363, released from bovine beta-casein by chymosin, trypsin or chymotrypsin. | peptides inhibitory to the 70-kda endopeptidase (pepo) from the cytoplasm of lactococcus lactis ssp. lactis mg1363 were isolated from the supernatant (ph 4.6) of chymosin, tryptic and alpha-chymotryptic hydrolysates of beta-casein (beta-cn) by reversed-phase hplc and identified by sequencing and mass spectrometry. chymosin released beta-cn f193-209, kinetic constant (ki) of which for inhibition of pepo was 60 microm. this peptide also inhibited (ki = 1700 microm) the 95-kda aminopeptidase (pepn) ... | 1996 | 8638436 |