| 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 |
| phosphorylcholine-containing antigens in bacteria from the mouth and respiratory tract. | phosphorylcholine (pc)-containing antigens were sought in 269 bacterial isolates from the mouth and respiratory tract by an enzyme immunoassay method. only 41 (15%) isolates were pc-positive and of these 29 (70%) were strains of haemophilus influenzae. other species that produced positive results included two of five isolates of gemella haemolysans, two of five isolates of micrococcus spp., and a single strain each of bacillus sp., corynebacterium jeikeium, lactococcus sp. and h. parainfluenzae. ... | 1996 | 8544209 |
| 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 |
| interactions of human mannose-binding protein with lipoteichoic acids. | we explored the interaction of human recombinant mannose-binding protein and lipoteichoic acids (ltas) by enzyme-linked immunosorbent assay. the best ligand was micrococcus luteus lipomannan, followed by enterococcus spp. lta containing mono-, di-, and oligoglucosyl substituents. ltas lacking terminal sugars (those of streptococcus pyogenes and staphylococcus aureus) or containing galactosyl substituents (those of listeria spp. and lactococcus spp.) were poor ligands. these results are consisten ... | 1996 | 8557371 |
| 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 |
| characterization of the replicon from the lactococcal theta-replicating plasmid pjw563. | the replication region of the lactococcal plasmid pjw563 was localized to a 2.3-kb ecori fragment. this dna fragment was sequenced ans a 1155-bp open reading frame, repb563, encoding a putative protein repb563 of 385 amino acids was found. an at-rich noncoding region, repa563, was found upstream of repb563. this segment included several direct and inverted repeats. a downstream 591-bp open reading frame, orf x, which was not necessary for replication, was putatively translationally coupled to re ... | 1995 | 8559799 |
| 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 |
| immunological and electrophoretic study of the proteolytic enzymes from various lactococcus and lactobacillus strains. | cell extracts of various lactobacilli and two lactococcus strains were investigated for their immunoresponse with monoclonal and polyclonal antibodies raised against various proteolytic enzymes from lc. lactis. except for lactobacillus casei sbt 2233, none of the lactobacilli proteins showed immunoresponse with the monoclonal antibodies. with polyclonal antibodies raised against aminopeptidases n and c and endopeptidase of lc. lactis an immunoresponse was observed. however, the molecular masses ... | 1995 | 8568031 |
| enterococcus seriolicida is a junior synonym of lactococcus garvieae, a causative agent of septicemia and meningoencephalitis in fish. | the reference strains of enterococcus seriolicida (atcc 49156t) (t = type strain) and of lactococcus garvieae (atcc 43921t) and 30 field strains of gram-positive cocci isolated from diseased rainbow trout in italy were found to be phenotypically (api 20 strept and api 50 ch) and genetically (dna-dna hybridization) similar. the high dna-dna homologies (70-100%) and the low delta tme (less than 1.1 degrees c) among these strains showed that enterococcus seriolicida and lactococcus garvieae are syn ... | 1996 | 8574132 |
| 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 |
| a convenient and reproducible method to genetically transform bacteria of the genus bifidobacterium. | a protocol was developed for the introduction of foreign plasmid dna into various bifidobacterium strains. the method, which is applicable to all bifidobacterium species tested so far, is based on electroporation of bacteria made competent by preincubation in electroporation buffer for several hours at 4 degrees c. transformation of bifidobacterium could be achieved with a plasmid vector originating from bifidobacterium and with plasmid vectors from corynebacterium, but not with vectors carrying ... | 1996 | 8581157 |
| a gene replacement strategy for engineering nisin. | a lactococcal expression system was developed which allows the exclusive production of novel nisins encoded by mutated pre-nisin (nisa) genes. this system is based on a combination of a specifically constructed host strain and vectors which facilitate the genetic manipulation of the nisa gene. the wild-type chromosomal gene is effectively replaced with a variant nisa gene, by the technique of gene replacement. the recovery of full nisin immunity was employed as a means of directly selecting stra ... | 1996 | 8581169 |
| genetics of streptococci, enterococci and lactococci. proceedings of the 4th international conference. santa fe, new mexico, usa, may 15-18, 1994. | | 1995 | 8586158 |
| 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 |
| molecular biology of lactococcal bacteriophage c2. | the 22163 bp genome of the lytic prolate-headed lactococcal phage c2 was fully sequenced. mapping of restriction sites and rna transcripts demonstrated the presence of early and late genes. early and late promoters were identified. the early region contained 21 orfs, with predicted protein products of 4.4-32.9 kda, all reading right to left. significant similarity was found between a putative protein encoded by an early region orf and the erf (essential recombination function) gene product of sa ... | 1995 | 8586233 |
| 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 |
| genetics of non-lantibiotic bacteriocins. | | 1995 | 8586245 |
| 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 |
| a food-grade process for isolation and partial purification of bacteriocins of lactic acid bacteria that uses diatomite calcium silicate. | bacteriocins, including nisin, pediocin po2, brevicin 286, and piscicolin 126, were extracted from fermentation media by adsorption onto micro-cel (a food-grade diatomite calcium silicate anticaking agent) and subsequent desorption. the optimal conditions for desorption of piscicolin 126 were determined and applied to other bacteriocins, and the relative purities of the desorbed preparations were compared. piscicolin was not successfully desorbed from micro-cel at ph 1.0 to 12.0, with organic so ... | 1996 | 8633875 |
| 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 |
| biosynthesis of lantibiotic nisin. posttranslational modification of its prepeptide occurs at a multimeric membrane-associated lanthionine synthetase complex. | the lantibiotic nisin of lactococcus lactis is matured from a ribosomally synthesized prepeptide by postranslational modification. genetic and biochemical evidence suggests that genes nisb and nisc of the nisin gene cluster encode proteins necessary for prenisin modification. inactivation of both genes resulted in complete loss of nisin production. the preparation of membrane vesicles revealed that nisb and nisc are attached to the cellular membrane, and co-immunoprecipitation experiments showed ... | 1996 | 8647829 |
| functional analysis of promoters in the nisin gene cluster of lactococcus lactis. | the promoters in the nisin gene cluster nisabtciprkfeg of lactococcus lactis were characterized by primer extension and transcriptional fusions to the escherichia coli promoterless beta-glucuronidase gene (gusa). three promoters preceding the nisa, nisr, and nisf genes, which all give rise to gusa expression in the nisin-producing strain l. lactis nz9700, were identified. the transcriptional autoregulation of nisa by signal transduction involving the sensor histidine kinase nisk and the response ... | 1996 | 8655538 |
| splicing of a group ii intron involved in the conjugative transfer of prs01 in lactococci. | analysis of a region involved in the conjugative transfer of the lactococcal conjugative element prs01 has revealed a bacteria] group ii intron. splicing of this lactococcal intron (designated ll.ltrb) in vivo resulted in the ligation of two exon messages (ltrbe1 and ltrbe2) which encoded a putative conjugative relaxase essential for the transfer of prs01. like many group ii introns, the ll.ltrb intron possessed an open reading frame (ltra) with homology to reverse transcriptases. remarkably, se ... | 1996 | 8655550 |
| regulation of sugar uptake via the phosphoenolpyruvate-dependent phosphotransferase systems in bacillus subtilis and lactococcus lactis is mediated by atp-dependent phosphorylation of seryl residue 46 in hpr. | by using both metabolizable and nonmetabolizable sugar substrates of the phosphoenolpyruvate-dependent phosphotransferase system (pts), we show that pts sugar uptake into intact cells and membrane vesicles of lactococcus lactis and bacillus subtilis is strongly inhibited by high concentrations of any of several metabolizable pts sugars. inhibition requires phosphorylation of seryl residue 46 in the phosphocarrier protein of the pts, hpr, by the metabolite-activated, atp-dependent protein kinase. ... | 1996 | 8655554 |
| purification of tributyrin esterase from lactococcus lactis subsp. cremoris e8. | a tributyrin esterase was purified from lactococcus lactis subsp. cremoris e8 using fplc chromatography. this was the major esterase activity observed in strain e8 and was associated with a single protein with a subunit molecular mass of 29 kda and a holoenzyme of molecular mass 109 kda. the enzyme was active against tributyrin and p-nitrophenyl butyrate. the n-terminal sequence of the enzyme was determined. the enzyme had a ph optimum in the neutral range, was stable on freezing at -20 degrees ... | 1996 | 8655738 |
| cloning vectors for lactococci based on a plasmid encoding resistance to cadmium. | an 8.8-kb plasmid (pnd302) was identified in lactococcus lacti spp lactis m71 which encodes cadmium resistance (cdr). most of the commercial lactococcal strains tested were sensitive to cadmium. therefore, cdr should provide a useful selectable marker for constructing cloning vectors in lactococci. pnd302 was mapped with a number of restriction enzymes and found to contain a unique ecori site suitable for cloning. two e. coli/l lactis shuttle cloning vectors, pnd304 and pnd624, were constructed ... | 1996 | 8661686 |
| identification, classification, and clinical relevance of catalase-negative, gram-positive cocci, excluding the streptococci and enterococci. | several new genera and species of gram-positive, catalase-negative cocci that can cause infections in humans have been described. although these bacteria were isolated in the clinical laboratory, they were considered nonpathogenic culture contaminants and were not thought to be the cause of any diseases. isolation of pure cultures of these bacteria from normally sterile sites has led to the conclusion that these bacteria can be an infrequent cause of infection. this review describes the new bact ... | 1995 | 8665466 |
| analysis of the catalytic domain of the lysin of the lactococcal bacteriophage tuc2009 by chimeric gene assembling. | an active chimeric cell wall lytic enzyme (tsl) has been constructed by fusing the region coding for the n-terminal half of the lactococcal phage tuc2009 lysin and the region coding for the c-terminal domain of the major pneumococcal autolysin. the chimeric enzyme exhibited a glycosidase activity capable of hydrolysing choline-containing pneumococcal cell walls. this experimental approach demonstrated that the tuc2009 lysin possesses a modular structure and further supports the hypothesis that m ... | 1996 | 8666197 |
| the lactic acid stress response of lactococcus lactis subsp. lactis | the lactic acid tolerance response (latr) of the lactic acid bacterium lactococcus lactis subsp. lactis has been studied. a dramatic increase in survival to a severe acid stress (ph 3.9) was obtained by preexposing the cells for 30 min to a mildly acid shock at ph 5.5. whole-cell protein extract analysis revealed that during the acid tolerance response 33 polypeptides are induced over the level of naive cells. among these are the major heat shock proteins dnak and groel. in conjunction with a pr ... | 1996 | 8672097 |
| antimicrobial activity of lactic acid bacteria isolated from goat's milk and artisanal cheeses: characteristics of a bacteriocin produced by lactobacillus curvatus ifpl 105. | a total of 203 lactic acid bacteria isolated from raw goat's milk and artisanal cheese were tested for antibacterial activity. only two strains of lactococcus lactis, one strain of enterococcus faecalis and one strain of lactobacillus curvatus were shown to produce a bacteriocin-like substance. lactobacillus curvatus ifpl105 produced a heat-stable bacteriocin, which was hydrolysed by alpha-chymotrypsin, proteinase k and pancreatin and exhibited a broad spectrum of inhibitory activity. the bacter ... | 1996 | 8675482 |
| beta-casomorphins: analysis in cheese and susceptibility to proteolytic enzymes from lactococcus lactis ssp. cremoris. | commercial cheese products were surveyed for beta-casomorphin peptides. two extraction methods were compared: 1) water and 2) chloroform and methanol. peptide profiles were determined using reverse-phase hplc and multiple wavelength detection. beta-casomorphin standards were used for comparison with cheese peptide profiles. results indicated that peptides were present in cheeses with hplc elution times that were similar to those for beta-casomorphins. however, comparison of absorbancies of the p ... | 1996 | 8675779 |
| transfer of conjugative plasmid pam beta 1 from lactococcus lactis to mouse intestinal bacteria. | conjugal transfer of plasmid pam beta 1 from lactococcus lactis to intestinal bacteria of balb/c mice was studied. plasmid transfer was observed to enterococcus faecalis in vitro by a filter mating method with transfer frequencies of 2.3 x 10-3 and with lower frequencies to other species. in vivo, using gastric intubation with the pam beta 1-bearing lactococcus lactis as donor and ent. faecalis as recipient, a few transconjugants were detected from faecal ent. faecalis. however, when these mice ... | 1996 | 8679141 |
| bacteriophage resistance in lactococcus. | lactic acid bacteria are industrial microorganisms used in many food fermentations. lactococcus species are susceptible to bacteriophage infections that may result in slowed or failed fermentations. a substantial amount of research has focused on characterizing natural mechanisms by which bacterial cells defend themselves against phage. numerous natural phage defense mechanisms have been identified and studied, and recent efforts have improved phage resistance by using molecular techniques. the ... | 1995 | 8680935 |
| cloning and transcriptional analysis of two threonine biosynthetic genes from lactococcus lactis mg1614. | two genes, hom and thrb, involved in threonine biosynthesis in lactococcus lactis mg1614, were cloned and sequenced. these genes, which encode homoserine dehydrogenase and homoserine kinase, were initially identified by the homology of their gene products with known homoserine dehydrogenases and homoserine kinases from other organisms. the identification was supported by construction of a mutant containing a deletion in hom and thrb that was unable to grow in a defined medium lacking threonine. ... | 1996 | 8682767 |
| tomato prf is a member of the leucine-rich repeat class of plant disease resistance genes and lies embedded within the pto kinase gene cluster. | in tomato, resistance to pseudomonas syringae pv. tomato (pst) strains expressing the avirulence gene avrpto requires the presence of at least two host genes, designated pto and prf. here we report that prf encodes a protein with leucine-zipper, nucleotide-binding, and leucine-rich repeat motifs, as are found in a number of resistance gene products from other plants. prf mutant alleles (4) were found to carry alterations within the prf coding sequence. a genomic fragment containing prf complemen ... | 1996 | 8689679 |
| positive selection, cloning vectors for gram-positive bacteria based on a restriction endonuclease cassette. | lactococcus lactis contains numerous restriction and modification (r/m) systems of different specificities. a novel iis type r/m system encoded by the llai operon has previously been characterized from the l. lactis conjugative plasmid ptr2030. the llai operon is composed of six genes: first, a small regulatory gene llaic precedes the methylase gene llaim. the following three genes, llai.1, llai.2, llai.3, are all essential for restriction endonuclease activity and are designed as the restrictio ... | 1996 | 8693025 |
| regulation of the nisin operons in lactococcus lactis n8. | the antibiotic peptide nisin produced by lactococcus lactis is used as a food preservative due to its activity against spores and vegetative cells of gram-positive bacteria. the post-translational maturation of this secreted peptide includes dehydration of serine and threonine residues, lanthionine formation and a proteolytic processing of 23 amino acids from the n-terminus. mutations in the nisz, nisb and nisp genes of the biosynthetic niszbtciprk nisin operon were made by gene replacement or i ... | 1996 | 8698664 |
| nucleotide sequence and analysis of pwc1, a pc194-type rolling circle replicon in lactococcus lactis. | a 2.8-kb cryptic plasmid showing no homology to either pfx3 (rolling circle, pe194-type) or pci305 (theta-type) lactococcal replicons was identified in lactococcus lactis subsp. cremoris 2204. the plasmid, pwc1, was compatible with both pci3340 (a pci305 derivative) and pfx3 in l. lactis subsp. cremoris 2204. sequence analysis of pwc1 showed one major orf encoding a protein with a deduced size of 316 amino acids (aa). database comparisons showed that the protein was distinct from the pfx- and pc ... | 1996 | 8700966 |
| purification and characterization of a malic enzyme from the ruminal bacterium streptococcus bovis atcc 15352 and cloning and sequencing of its gene. | malic enzyme (ec 1.1.1.39), which catalyzes l-malate oxidative decarboxylation and pyruvate reductive carboxylation, was purified to homogeneity from streptococcus bovis atcc 15352, and properties of this enzyme were determined. the 2.9-kb fragment containing the malic enzyme gene was cloned, and the sequence was determined and analyzed. the enzymatic properties of the s. bovis malic enzyme were almost identical to those of other malic enzymes previously reported. however, we found that the s. b ... | 1996 | 8702261 |
| structure-activity relationships in the peptide antibiotic nisin: role of dehydroalanine 5. | a mutant of the peptide antibiotic nisin in which the dehydroalanine residue at position 5 has been replaced by an alanine has been produced and structurally characterized. it is shown to have activity very similar to that of wild-type nisin in inhibiting growth of lactococcus lactis and micrococcus luteus but is very much less active than nisin as an inhibitor of the outgrowth of spores of bacillus subtilis. these observations, which parallel those of w. liu and j. n. hansen (appl. environ. mic ... | 1996 | 8702290 |
| genes responsible for nisin synthesis, regulation and immunity form a regulon of two operons and are induced by nisin in lactoccocus lactis n8. | nisin is a small post-translationally modified lanthionine-containing peptide (lantibiotic) produced by certain lactococcus lactis strains which has a high antimicrobial activity against several pathogenic gram-positive bacteria. northern blots and rt/pcr analysis of the nisin-producing strain n8 revealed that the niszbtciprkfeg gene cluster, responsible for nisin biosynthesis, immunity and regulation, consists of two operons, niszbtciprk and nisfeg. the promoter of the nisfeb operon was mapped. ... | 1996 | 8704967 |
| interaction of the lantibiotic nisin with membranes revealed by fluorescence quenching of an introduced tryptophan. | nisin is a lantibiotic produced by strains of lactococcus lactis subsp. lactis. the target for nisin action is the cytoplasmic membrane of gram-positive bacteria. to aid understanding of its mode of action, the interaction of nisin with vesicles of differing phospholipid composition were investigated by fluorescence techniques, using a variant of nisin in which the isoleucine at position 30 was replaced by a tryptophan residue. activity of the site-directed variant containing tryptophan was esta ... | 1996 | 8706701 |
| structure-activity relationships in the peptide antibiotic nisin: antibacterial activity of fragments of nisin. | the post-translationally modified peptide antibiotic nisin has been cleaved by a number of proteases and the fragments produced purified, characterised chemically, and assayed for activity in inhibiting the growth of lactococcus lactis mg1614 and micrococcus luteus ncdo8166. these results provide information on the importance of different parts of the nisin molecule for its growth-inhibition activity. removal of the c-terminal five residues leads to approximately a 10-fold decrease in potency, w ... | 1996 | 8706842 |
| antimicrobial susceptibilities of lactococcus lactis and lactococcus garvieae and a proposed method to discriminate between them. | the mics of antimicrobial agents contained in the sceptor streptococcus mic panels (becton dickinson microbiology systems) were determined for lactococcus lactis, l. garvieae, and unknown lactococcus species. several isolates had reduced susceptibilities to many of the antimicrobial agents contained in the panel. for l. garvieae, the mics of penicillin and, possibly, cephalothin were higher than for l. lactis, and unlike l. lactis, l. garvieae was resistant to clindamycin, indicating that knowle ... | 1996 | 8727924 |
| inducible gene expression mediated by a repressor-operator system isolated from lactococcus lactis bacteriophage r1t. | a regulatory region of the temperate lactococcus lactis bacteriophage r1t chromosome has been cloned and characterized. it encompasses the two divergently oriented genes rro, encoding the phage repressor, and tec. both genes, of which the transcription start sites have been mapped, are preceded by consensus -35 and -10 promoter sequences. the region contains three 21 bp direct repeats with internal dyad symmetry which probably act as operators. two of these repeats partially overlap the two prom ... | 1996 | 8730874 |
| sequence analysis and molecular characterization of the temperate lactococcal bacteriophage r1t. | the temperate lactococcal bacteriophage r1t was isolated from its lysogenic host and its genome was subjected to nucleotide sequence analysis. the linear r1t genome is composed of 33,350 bp and was shown to possess 3' staggered cohesive ends. fifty open reading frames (orfs) were identified which are, probably, organized in a life-cycle-specific manner. nucleotide sequence comparisons, n-terminal amino acid sequencing and functional analyses enabled the assignment of possible functions to a numb ... | 1996 | 8730875 |
| nisp is related to nisin precursor processing and possibly to immunity in lactococcus lactis. | in this study, a plasmid was integrated into nisp, creating the first defined mutation in a nisin biosynthetic gene. the mutant strain secreted fully modified nisin with the n-terminal leader still attached. the presence of the leader was confirmed by n-terminal sequencing of the purified precursor. the dehydration and lanthionine formation of the precursor were already completed as active nisin could be formed by cleaving the leader from the inactive precursor by a trypsin treatment or by incub ... | 1995 | 8731921 |
| purification and characterization of dihydroorotate dehydrogenase a from lactococcus lactis, crystallization and preliminary x-ray diffraction studies of the enzyme. | lactococcus lactis is the only organism known to contain two dihydroorotate dehydrogenases, i.e., the a- and b-forms. in this paper, we report the overproduction, purification, and crystallization of dihydroorotate dehydrogenase a. in solution, the enzyme is bright yellow. it is a dimer of subunits (34 kda) that contain one molecule of flavin mononucleotide each. the enzyme shows optimal function in the ph range 7.5-9.0. it is specific for l-dihydroorotate as substrate and can use dichlorophenol ... | 1996 | 8732756 |