| inactivation of citrate lyase from rhodopseudomonas gelatinosa by a specific deacetylase and inhibition of this inactivation by l-(+1-glutamate. | a previously unrecognized enzyme, citrate lyase deacetylase, has been purified about 140-fold from cell extracts of rhodopseudomonas gelatinosa. it catalyzed the conversion of enzymatically active acetyl-s-citrate lyase into the inactive hs-form and acetate. the enzyme exhibited an optimal rate of inactivation at ph 8.1. because of the instability of acetyl-s-citrate lyase at acidic and alkaline ph values, all assays were carried out at ph 7.2, where the spontaneous hydrolysis of the acetyl-s-ci ... | 1975 | 356 |
| on the structure of the prosthetic group of citrate (pro-3s)-lyase. | the prosthetic group of citrate (pro-3s)-lyase from klebsiella aerogenes as well as streptococcus diacetilactis was obtained eigher by beta elimination or pronase digestion of the enzyme and purified by deae-cellulose chromatography. the compound was shown to contain 3 mol of po4, 2 mol of ribose, and 1 mol of sulfhydryl/mol of adenine. 5'-amp and dephospho-coa are components of the prosthetic group. the evidence obtained so far support our proposed structure of 3' (or 2') leads to 1''-(5''-phos ... | 1977 | 197081 |
| purification and properties of citrate lyase from streptococcus diacetilactis. | citrate lyase from streptococcus diacetilactis has been purified to yield a protein that was homogeneous as judged by sedimentation velocity and sedimentation equilibrium experiments. the enzyme's sedimentation coefficient is 16.8 s and its molecular weight is around 585,000. it contains three nonidentical subunits of about 53,000, 34,000, and 10,000 daltons. the enzyme in its active form contains an acetyl group which turns over during the citrate cleavage reaction. removal of the acetyl group ... | 1975 | 238987 |
| lipid composition of cells and its variation during degradation of a culture of streptococcus diacetilactis. | the process of dying of a culture of str. diacetilactis under conditions of prolonged culturing is accompanied by substantial changes in the composition of the cell lipids. in the lipids of young cells the basic components are mono- and diglucosyldiglycerides, as well as phospholipids--two glucophospholipids, cardiolipin, and phosphatidylglycerin; triglycerides and sterols are present in negligible amounts. as the str. diacetilactis culture develops and undergoes degradation, an increase is obse ... | 1979 | 549660 |
| end products and fermentation balances for lactic streptococci grown aerobically on low concentrations of glucose. | maximum acetate produced aerobically by streptococcus diacetilactis and streptococcus cremoris was 14% of 1 to 7 mumol of glucose/ml in a partially defined medium that contained lipoic acid. y (glucose) values were 35.3 (s. diacetilactis) and 31.4 (s. cremoris) with low concentrations (1 to 7 mumol/ml) of glucose in the medium and 21 (s. diacetilactis) with higher concentrations (6 to 15 mumol/ml). y (adenosine 5'-triphosphate) values for the bacteria, determined by taking into account the end p ... | 1977 | 836024 |
| purification and properties of citrate lyase ligase from streptococcus diacetilactis. | citrate lyase ligase (acetate: sh--[acyl-carrier protein] enzyme ligase (amp) from streptococcus diacetilactis was purified 920-fold with a yield of 6.3%. the molecular weight of the enzyme was estimated to be 41000; the ligase consisted of one polypeptide chain. the acetylation of 1 mol of deacetyl-citrate lyase to enzymatically active citrate lyase required 6 mol atp. the formation of amp and pyrophosphate in the acetylation reaction was demonstrated. citrate lyase ligase was specific for the ... | 1977 | 923578 |
| [age changes in cells in streptococcus diacetilactis cultures]. | the activity of metabolism changed in the cultures of streptococcus diacetilactis, strain bogdan, with aging. the number of viable cells decreased as well as the ability to evolve oxygen, to produce c-4 compounds, and to react to ph changes by liberating acids upon alkalifying or neutral products upon acidifying. after the culture had been grown during 72 hours, 2,3-butyleneglycol was found in the cultural broth, and the number of viable cells was low. as was revealed by electron microscopy, the ... | 1976 | 979685 |
| citrate lyase from streptococcus diacetilactis. association with its acetylating enzyme. | citrate lyase (ec 4.1.3.6) was purified 38-fold from cell-free extracts of streptococcus diacetilactis. the enzyme was homogeneous in analytical ultracentrifugation and polyacrylamide gel electrophoresis. the final enzyme preparation contained acetate: hs-citrate lyase ligase--an acetylating enzyme which converts inactive hs-citrate lyase into enzymatically active acetyl-s-citrate lyase. this enzyme activity was purified 25-fold over the crude extract and seemed to be associated with citrate lya ... | 1975 | 1115558 |
| citrate utilization in milk by leuconostoc cremoris and streptococcus diacetilactis. | citrate utilization and diacetyl, acetoin and acetaldehyde production by 2 strains each of leuconostoc cremoris and streptococcus diacetilactis in milk were studied. with the leuconostoc bacteria no growth and little citrate utilization occurred unless a stimulant (yeast extract) was present, when complete utilization of citrate without concomitant production of diacetyl or acetoin was obtained. the additon of mn2+ stimulated growth resulted in diacetyl and acetoin production. destruction of dia ... | 1975 | 1173068 |
| regulation of nisin biosynthesis by continuous cultures and by resting cells of lactococcus lactis subsp. lactis. | nisin production by lactococcus lactis subsp. lactis has been investigated using lactose as carbon source. whether or not continuous cultures were lactose-limited, maximum nisin titre was observed at an intermediate mu value with a sharp peak of activity between 0.2 and 0.3/h. the maximum specific growth rate obtained in the medium used was 0.6/h and the maximum titre of nisin at mu = 0.25/h (160 au/ml) was about nine-fold higher as compared with activity obtained at a dilution rate of 0.05/h or ... | 1992 | 1299840 |
| new tools for the physical and genetic mapping of lactococcus strains. | tools for the genetic and physical analysis of the lactococcus lactis subsp. lactis genome were developed. plasmid prc1 does not replicate in gram+ bacteria; it contains unique apai, noti and smai restriction sites and an erythromycin-resistance (err) encoding gene, ermam, functional in l. lactis subsp. lactis. when a chromosomal l. lactis subsp. lactis dna fragment was cloned into this vector, the resulting plasmid became integrated, after transformation, into the bacterial chromosome by homolo ... | 1992 | 1312498 |
| development of a lactococcal integration vector by using is981 and a temperature-sensitive lactococcal replication region. | a vector (pkmp10) capable of campbell-like integration into the lactococcus lactis subsp. lactis lm0230 chromosome via homologous recombination with chromosomal is981 sequences was constructed from the replication region of lactococcal plasmid psk11l, an internal fragment of is981, and the erythromycin resistance gene and escherichia coli replication origin of pva891. the psk11l replication region is temperature sensitive for maintenance in l. lactis subsp. lactis lm0230, resulting in loss of un ... | 1992 | 1319131 |
| is946-mediated integration of heterologous dna into the genome of lactococcus lactis subsp. lactis. | the lactococcal insertion sequence is946 was used to construct suicide vectors for insertion of heterologous dna into chromosomal and plasmid sequences of lactococcus lactis subsp. lactis. electroporation of l. lactis strains, including the recombination-deficient strain mms362, with the suicide vector ptrk145 yielded 10(1) to 10(3) transformants per micrograms of dna. ptrk145 insertions occurred primarily in the chromosome, with one insertion detected in a resident plasmid. vector-specific prob ... | 1992 | 1319132 |
| transfer of tn916 between lactococcus lactis subsp. lactis strains is nontranspositional: evidence for a chromosomal fertility function in strain mg1363. | lactococcus lactis subsp. lactis mg1363 can act as a conjugative donor of chromosomal markers. this requires a chromosomally located fertility function that we designate the lactococcal fertility factor (laff). using inter- and intrastrain crosses, we identified other l. lactis strains (lmo230 and mms373) that appear to lack laff. the selectable marker in our crosses was tcr, carried by tn916, a transposon present on the chromosome. the transfer of tcr was not due to tn916-encoded conjugative fu ... | 1992 | 1325966 |
| physical and genetic map of the chromosome of lactococcus lactis subsp. lactis il1403. | a combined physical and genetic map of the chromosome of lactococcus lactis subsp. lactis il1403 was determined. we constructed a restriction map for the noti, apai, and smai enzymes. the order of the restriction fragments was determined by using the randomly integrative plasmid prl1 and by performing indirect end-labeling experiments. the strain il1403 chromosome was found to be circular and 2,420 kb in size. a total of 24 chromosomal markers were mapped on the chromosome by performing hybridiz ... | 1992 | 1328163 |
| nonidentity between plasmid and chromosomal copies of iss1-like sequences in lactococcus lactis subsp. lactis cnrz270 and their possible role in chromosomal integration of plasmid genes. | the nucleotide sequence of an insertion sequence (is) observed during mating experiments using the lactose-protease plasmid, pucl22, of lactococcus (lc.) lactis subsp. lactis cnrz270, was found to be similar to that of iss1 from lc. lactis subsp. lactis ml3. the is was named iss1rs. the chromosome of this strain contains several copies of iss1-like is as assessed by hybridization. one of these copies was cloned and named iss1ch. its sequence differs from that of the plasmid-borne copy, and appea ... | 1992 | 1339371 |
| high efficiency electroporation of lactococcus lactis subsp. lactis lm0230 with plasmid pgb301. | electroporation-mediated transformation of lactococcus lactis with plasmid pgb301, a 9.8 kilobase pair vector (behnke et al. 1981), has been reported by mcintyre & harlander (1989a). improved transformation efficiencies of 10(2)-10(3)/micrograms dna were achieved by altering the conditions under which the bacteria were grown prior to electroporation (mcintyre & harlander 1989b). this present investigation sought to improve still further transformation efficiencies in order to provide a reliable ... | 1990 | 1367468 |
| lysozyme expression in lactococcus lactis. | three lysozyme-encoding genes, one of eukaryotic and two of prokaryotic origin, were expressed in lactococcus lactis subsp. lactis. hen egg white lysozyme (hel) could be detected in l. lactis lysates by western blotting. no lysozyme activity was observed, however, presumably because of the absence of correctly formed disulphide bonds in the l. lactis product. the functionally related lysozymes of the e. coli bacteriophages t4 and lambda were produced as biologically active proteins in l. lactis. ... | 1992 | 1368776 |
| batch cultures of recombinant lactococcus lactis subsp. lactis in a stirred fermentor. i. effect of plasmid content on bacterial growth and on genetic stability in pure cultures. | the effect of plasmid introduction into lactococcus lactis subsp. lactis il2661 on the growth of this strain and on plasmid stability was studied in pure batch cultures. the plasmids used (coding for erythromycin or chloramphenicol resistance) were the following: pil205 (42 kb), pil252 (4.6 kb, 6-9 copies), pil253 (4.8 kb, 45-85 copies) and pe194 (inserted in the chromosome). growth and acidification of l. lactis subsp. lactis il2661 were similar to those of the derived recombinant lactococci. t ... | 1992 | 1368909 |
| batch cultures of recombinant lactococcus lactis subsp. lactis in a stirred fermentor. ii. plasmid transfer in mixed cultures. | the transfer of plasmids was studied in a stirred fermentor in the course of mixed batch cultures combining recombinant strains of lactococcus lactis subsp. lactis (donor strains) with l. lactis subsp. lactis cnrz 268m3 (recipient strain). donor strains contained one or two of the following plasmids (coding for erythromycin or chloramphenicol resistance): pil205 (self-transmissible), pil252, pil253 (non-transmissible but mobilizable by pil205, respectively small and large copy number) and pe194 ... | 1992 | 1368910 |
| plasmid involvement in the formation of a spontaneous bacteriophage insensitive mutant of lactococcus lactis. | lactococcus lactis subsp. lactis biovar. diacetylactis dpc721 is a spontaneous bacteriophage insensitive mutant of strain dpc220, isolated after challenge with an industrial bacteriophage, phi d1. plasmid analysis demonstrated that the bacteriophage insensitivity was associated with the absence of two native dpc220 plasmids (pah82 and pah33), and the presence of a novel plasmid (pah90) in dpc721. the plasmids were transferred by conjugative mobilization to a plasmid free background where it was ... | 1992 | 1398028 |
| tryptophan biosynthesis genes in lactococcus lactis subsp. lactis. | the lactococcus lactis chromosomal region containing the seven structural genes required for tryptophan biosynthesis was characterized by cloning and sequencing. all of the trp genes were identified by the homology of their products with known trp proteins from other organisms. the identification was confirmed for five genes by their ability to complement trp mutations in escherichia coli. the seven structural genes are present in the order trpegdcfba and span a 7,968-bp segment. each gene is pr ... | 1992 | 1400208 |
| histidine biosynthesis genes in lactococcus lactis subsp. lactis. | the genes of lactococcus lactis subsp. lactis involved in histidine biosynthesis were cloned and characterized by complementation of escherichia coli and bacillus subtilis mutants and dna sequencing. complementation of e. coli hisa, hisb, hisc, hisd, hisf, hisg, and hisie genes and the b. subtilis hish gene (the e. coli hisc equivalent) allowed localization of the corresponding lactococcal genes. nucleotide sequence analysis of the 11.5-kb lactococcal region revealed 14 open reading frames (orfs ... | 1992 | 1400209 |
| branched-chain amino acid biosynthesis genes in lactococcus lactis subsp. lactis. | the genes for biosynthesis of the branched-chain amino acids leucine, isoleucine, and valine in lactococcus lactis subsp. lactis ncdo2118 were characterized by cloning, complementation in escherichia coli and bacillus subtilis, and nucleotide sequence analysis. nine structural genes are clustered on a 12-kb dna fragment in the order leuabcd ilvdbnca. upstream of these genes, the nucleotide sequence suggests the existence of regulation by transcriptional attenuation. between the leud and ilvd gen ... | 1992 | 1400210 |
| cloning, nucleotide sequence, expression, and chromosomal location of ldh, the gene encoding l-(+)-lactate dehydrogenase, from lactococcus lactis. | a gene (designated ldh) that encodes fructose-1,6-bisphosphate-activated l-(+)-lactate dehydrogenase was cloned from lactococcus lactis subsp. lactis. plasmids containing ldh conferred fructose-1,6-bisphosphate-activated l-(+)-lactate dehydrogenase activity on escherichia coli cells. this activity was conferred only when a promoter had been introduced into the plasmid to express the cloned ldh. the nucleotide sequence of ldh predicted a chain length of 324 amino acids and a subunit molecular wei ... | 1992 | 1400245 |
| molecular characterization of a second abortive phage resistance gene present in lactococcus lactis subsp. lactis me2. | the fifth phage resistance factor from the prototype phage-insensitive strain lactococcus lactis subsp. lactis me2 has been characterized and sequenced. the genetic determinant for prf (phage resistance five) was subcloned from the conjugative plasmid ptn20, which also encodes a restriction and modification system. typical of other abortive resistance mechanisms, prf reduces the efficiency of plaquing to 10(-2) to 10(-3) and decreases the plaque size and burst size of the small isometric-headed ... | 1992 | 1429469 |
| is thermotolerance correlated to heat-shock protein synthesis in lactococcus lactis subsp. lactis? | exposure of lactococcus lactis subsp. lactis cells to a heat shock at 40 degrees c for 30 min induces thermotolerance, the increased ability of bacterial cells to survive exposure to lethal temperature (52 degrees c for 25 min). this transient state of thermal resistance is accompanied, as in escherichia coli, by the synthesis of a new set of specific proteins termed heat-shock proteins (hsps). pre-treatment of the bacterial cells by antibiotics (streptomycin, spiramycin, kanamycin and erythromy ... | 1992 | 1445769 |
| studies on antimutagenic effect of milk cultured with lactic acid bacteria on the trp-p2-induced mutagenicity to ta98 strain of salmonella typhimurium. | the inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5h-pyrido[4,3-b]indole (trp-p2), a tryptophan pyrolysate for salmonella typhimurium ta98. each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of trp-p2. the milk cultured with lactobacillus acidophilus la106 (la2) showed the highest inhibition of 82.1% among the strains used. milk sa ... | 1992 | 1452836 |
| genetic analysis of scra and scrb from streptococcus sobrinus 6715. | a dna fragment containing scra and scrb, which encode enzyme ii of the phosphoenolpyruvate-dependent sucrose phosphotransferase system and sucrose-6-phosphate hydrolase, respectively, was isolated from a lambda gt10 genomic dna library of streptococcus sobrinus 6715. both genes were located on a 4.2-kb dna fragment which was maintained stably in escherchia coli on low-copy-number vector pgb2. the recombinant e. coli clone expressed sucrose-hydrolytic activity on macconkey agar base supplemented ... | 1992 | 1500184 |
| use of degenerate primers for polymerase chain reaction cloning and sequencing of the lactococcus lactis subsp. lactis reca gene. | two particularly well-conserved stretches in the reca protein sequences were chosen as templates to synthesize degenerate oligonucleotides, which were used in polymerase chain reaction to amplify an internal reca dna fragment of lactococcus lactis subsp. lactis ml3. using this fragment, we recovered and sequenced the entire lactococcal reca gene. the end of an open reading frame present upstream of the reca gene shows strong homology with formamidopyrimidine-dna-glycosylase, a protein involved i ... | 1992 | 1514816 |
| molecular characterization of the integration of the lactose plasmid from lactococcus lactis subsp. cremoris sk11 into the chromosome of l. lactis subsp. lactis. | when lactococcus lactis subsp. lactis lm0230 is transformed by the lactose plasmid (psk11l) from lactococcus lactis subsp. cremoris sk11, variants with psk11l in the integrated state can be derived (j. m. feirtag, j. p. petzel, e. pasalodos, k. a. baldwin, and l. l. mckay, appl. environ. microbiol. 57:539-548, 1991). in the present study, a 1.65-kb xbai-xhoi fragment of psk11l was subcloned for use as a probe in southern hybridization analyses of the mechanism of integration, which was shown to ... | 1992 | 1539968 |
| jenseniin g, a heat-stable bacteriocin produced by propionibacterium jensenii p126. | the genus propionibacterium includes cutaneous species typically found on human skin and the dairy or classical species (propionibacterium freudenreichii, p. jensenii, p. thoenii, and p. acidipropionici) used industrially for the production of swiss cheese and propionic acid. grinstead (1989, m.s. thesis, iowa state university, ames) has previously observed that some dairy propionibacteria inhibit other species in the classical grouping. we further investigated the inhibitor(s) produced by p. je ... | 1992 | 1539976 |
| nucleotide sequence and functional properties of a sodium-dependent citrate transport system from klebsiella pneumoniae. | the gene of the sodium-dependent citrate transport system from klebsiella pneumoniae (cits) is located on plasmid pes3 (schwarz, e., and oesterhelt, d. (1985) embo j. 4, 1599-1603) and encodes a 446-amino acid protein. transport of citrate via this citrate transport protein (cits) is dependent on the presence of sodium ions and is inhibited by magnesium ions. the delta ph (ph gradient across the membrane) is the major driving force for uptake. it is postulated that, in analogy with the proton-de ... | 1992 | 1577734 |
| cloning and partial sequencing of the proteinase gene complex from lactococcus lactis subsp. lactis uc317. | the proteinase genes from lactococcus lactis subsp. lactis uc317 were identified on a plasmid, pci310, which is a deletion derivative of a cointegrate between pci301, the 75 kb lac prt plasmid from uc317 and the 38.5 kb cryptic plasmid from that strain. the prt genes were cloned using a replacement cloning strategy whereby fragments from pci310 were exchanged with the equivalent fragments in pnz521, which contains the cloned proteinase genes from l. lactis subsp. lactis sk112. this generated two ... | 1992 | 1588305 |
| substrate specificity of the cell envelope-located proteinase of lactococcus lactis subsp. lactis ncdo 763. | 1. the specificity of the cell envelope-located proteinase of lactococcus lactis subsp. lactis ncdo 763 towards caseins has been submitted to a statistical study. positive and negative relations have been evidenced between several amino acids and positions p6 to p'2 of the cleaved bonds. 2. fragment 1-23 of alpha s1 and oxidized b chain of insulin are well cleaved by the proteinase while cmp (fragment 106-169 of kappa-casein) is a poor substrate. 3. comparison with other cell envelope-located pr ... | 1992 | 1592148 |
| influence of the carbon source on nisin production in lactococcus lactis subsp. lactis batch fermentations. | nisin production by lactococcus lactis subsp. lactis nizo 22186 was studied in batch fermentation using a complex medium. nisin production showed primary metabolite kinetics: nisin biosynthesis took place during the active growth phase and completely stopped when cells entered the stationary phase. a stringent correlation could be observed between the expression of the prenisin gene (nisa) and the synthesis of the post-translationally enzymically modified and processed mature nisin peptide. more ... | 1992 | 1593266 |
| characterization of two nisin-producing lactococcus lactis subsp. lactis strains isolated from a commercial sauerkraut fermentation. | two lactococcus lactis subsp. lactis strains, nck400 and ljh80, isolated from a commercial sauerkraut fermentation were shown to produce nisin. ljh80 was morphologically unstable and gave rise to two stable, nisin-producing (nip+) derivatives, nck318-2 and nck318-3. nck400 and derivatives of ljh80 exhibited identical morphological and metabolic characteristics, but could be distinguished on the basis of plasmid profiles and genomic hybridization patterns to a dna probe specific for the iso-iss1 ... | 1992 | 1622214 |
| novel paired starter culture system for sauerkraut, consisting of a nisin-resistant leuconostoc mesenteroides strain and a nisin-producing lactococcus lactis strain. | nisin-resistant leuconostoc mesenteroides nck293 and nisin-producing lactococcus lactis subsp. lactis nck401 were evaluated separately and in combination for growth and nisin production in a model sauerkraut fermentation. strains were genetically marked and selectively enumerated by using antibiotic-containing media. the growth and survival of l. mesenteroides were similar in the presence and absence of lactococcus lactis subsp. lactis. the growth of lactococcus lactis subsp. lactis was not inhi ... | 1992 | 1622215 |
| conjugal transfer in lactococcus lactis of a 68-kilobase-pair chromosomal fragment containing the structural gene for the peptide bacteriocin nisin. | nisin-producing transconjugants were generated by mating nisin-producing strains of lactococcus lactis subsp. lactis with derivatives of l. lactis subsp. lactis lm0230. the sucrose-utilizing ability and reduced bacteriophage sensitivity were also transferred with the nisin-producing character. pulsed-field gel electrophoretic analysis of genomic dna from donor, recipient, and nisin-producing transconjugants indicated that 68 kbp of dna was transferred from the chromosome of the donor into the ch ... | 1992 | 1622237 |
| molecular analyses of the lactococcin a gene cluster from lactococcus lactis subsp. lactis biovar diacetylactis wm4. | the genes responsible for bacteriocin production and immunity in lactococcus lactis subsp. lactis biovar diacetylactis wm4 were localized and characterized by dna restriction fragment deletion, subcloning, and nucleotide sequence analysis. the nucleotide sequence of a 5.6-kb avaii restriction fragment revealed a cluster with five complete open reading frames (orfs) in the same orientation. dna and protein homology analyses, combined with deletion and tn5 insertion mutagenesis, implicated four of ... | 1992 | 1622271 |
| isolation, characterization, and physiological role of the pyruvate dehydrogenase complex and alpha-acetolactate synthase of lactococcus lactis subsp. lactis bv. diacetylactis. | the pyruvate dehydrogenase complex of lactococcus lactis subsp. lactis bv. diacetylactis has a specific activity of 6.6 u/mg and a km of 1 mm for pyruvate. the specific activities of e2 and e3 in the complex are 30 and 0.36 u/mg, respectively. the complex is very sensitive to nadh inhibition and consists of four subunits: e1 alpha (44 kda), e1 beta (35 kda), e2 (73 kda), and e3 (60 kda). the l. lactis alpha-acetolactate synthase has a specific activity of 103 u/mg and a km of 50 mm for pyruvate. ... | 1992 | 1624471 |
| identification, dna sequence, and distribution of is981, a new, high-copy-number insertion sequence in lactococci. | an insertion in the lactococcal plasmid pgbk17, which inactivated the gene(s) encoding resistance to the prolate-headed phage c2, was cloned, sequenced, and identified as a new lactococcal insertion sequence (is). is981 was 1,222 bp in size and contained two open reading frames, one large enough to encode a transposase. is981 ended in imperfect inverted repeats of 26 of 40 bp and generated a 5-bp direct repeat of target dna at the site of insertion. is981 was present on the chromosome of lactoco ... | 1991 | 1645511 |
| transposon-encoded sucrose metabolism in lactococcus lactis. purification of sucrose-6-phosphate hydrolase and genetic linkage to n5-(l-1-carboxyethyl)-l-ornithine synthase in strain k1. | sucrose-6-phosphate hydrolase from lactococcus lactis subsp. lactis k1-23 (formerly streptococcus lactis k1-23) has been purified 600-fold to electrophoretic homogeneity. purification of the enzyme was achieved by deae-sephacel, phosphocellulose p-11, and gel exclusion (ultrogel aca 54) chromatography. the purified enzyme (specific activity 31 units/mg) catalyzed the hydrolysis of both 6-o-phosphoryl-alpha-d-glucopyranosyl-1,2-beta-d-fructofuranoside (sucrose 6-phosphate) and sucrose (km = 0.1 a ... | 1991 | 1650362 |
| construction of an is946-based composite transposon in lactococcus lactis subsp. lactis. | an artificial composite transposon was constructed based on the lactococcal insertion sequence is946. a 3.0-kb element composed of the pc194 cat gene (cmr) flanked by inversely repeated copies of is946 was assembled on pbluescript ks+. when subcloned into the shuttle vector psa3 (emr), two putative transposons were created on the recombinant plasmid ptrk128: the 3.0-kb cmr element (tn-cma) and an inverse 11.5-kb emr element (tn-ema). ptrk128 was electroporated into the recombination-deficient st ... | 1991 | 1657893 |
| purification and properties of fructokinase i from lactococcus lactis. localization of scrk on the sucrose-nisin transposon tn5306. | two electrophoretically distinct proteins with fructokinase (atp:fructose-6-phosphotransferase) activity were detected in lactococcus lactis subsp. lactis k1. whereas fructokinase i was induced specifically by growth of the organism on sucrose, fructokinase ii was derepressed during growth on ribose, galactose, maltose, and lactulose. fructokinase i was purified about 1000-fold to electrophoretic homogeneity (specific activity 112 units/mg). the amino acid composition, n-terminal sequence, nucle ... | 1991 | 1658003 |
| comparison of methods for discrimination between strains of listeria monocytogenes from epidemiological surveys. | total cellular dna from 28 strains of listeria monocytogenes isolated from food implicated in food-borne illness and from patients with listeriosis was digested with the restriction endonucleases hindiii, haeiii, and ecori. following agarose gel electrophoresis, the fragments were subjected to southern blot hybridization with a digoxigenin-labeled cdna probe transcribed from escherichia coli 16s and 23s rrna. the patterns of bands from genomic (dna fingerprints) and rdna fingerprints (ribotypes) ... | 1991 | 1662932 |
| chromosomal integration of plasmid dna by homologous recombination in enterococcus faecalis and lactococcus lactis subsp. lactis hosts harboring tn919. | integration of pci192, a pbr322-derived vector plasmid containing homology to the chromosomally located conjugative transposon tn919 was observed in two strains that harbor tn919, namely, enterococcus faecalis gf590 and lactococcus lactis subsp. lactis ch919. hybridization analysis indicated that single-copy integration of the plasmid had occurred at low frequency. the tn919::plasmid structure was conjugated from an e. faecalis donor to a l. lactis recipient, although at lower frequencies than w ... | 1991 | 1662938 |
| phage abortive infection mechanism from lactococcus lactis subsp. lactis, expression of which is mediated by an iso-iss1 element. | a 5-kb dna fragment conferring a phage abortive infection phenotype (abi+) has been cloned from lactococcus lactis subsp. lactis il416. the abi+ determinant was subcloned on a 2-kb fragment which carried an iso-iss1 element and an open reading frame of 753 bp designated orfx. deletion within orfx entailed the loss of the abi+ phenotype, establishing that orfx is the structural abi-416 gene. the expression of abi-416 was shown to be mediated by the iso-iss1 element, which contains a sequence fitt ... | 1991 | 1664711 |
| cloning and dna sequence analysis of an x-prolyl dipeptidyl aminopeptidase gene from lactococcus lactis subsp. lactis ncdo 763. | lactococcus lactis subsp. lactis ncdo 763 (also designated ml3) possesses an x-prolyl dipeptidyl aminopeptidase (x-pdap; ec 3.4.14.5). x-pdap mutants were selected by an enzymatic plate assay on the basis of their inability to hydrolyze an l-phenylalanyl-l-proline-beta-naphthylamide substrate. a dna bank from l. lactis subsp. lactis ncdo 763 was constructed in one of these x-pdap mutants, and one clone in which the original x-pdap phenotype was restored was detected by the enzymatic plate assay. ... | 1991 | 1674656 |
| isolation and characterization of lactococcus lactis subsp. lactis promoters. | dna fragments with promoter activity were isolated from the chromosome of lactococcus lactis subsp. lactis. for the isolation, a promoter probe vector based on the cat gene was constructed, which allowed direct selection with chloramphenicol in bacillus subtilis and l. lactis. four of the putative promoters (p1, p2, p10, and p21) were analyzed further by sequencing, mapping of the 5' end of the mrna, northern (rna blot) hybridization, and chloramphenicol acetyltransferase activity measurements. ... | 1991 | 1707605 |
| physical map of the chromosome of lactococcus lactis subsp. lactis dl11 and localization of six putative rrna operons. | a physical map of the chromosome of lactococcus lactis subsp. lactis dl11 was constructed by using the contour-clamped homogeneous electric field mode of pulsed-field gel electrophoresis in one- and two-dimensional separations to analyze restriction digests of high-molecular-weight genomic dna. the map, which shows all the observed noti and smai sites (six and 21, respectively) and 8 of approximately 30 sali sites, is circular and yields a total size of 2.58 megabase pairs for the l. lactis subs ... | 1991 | 1708377 |
| cloning and partial characterization of genes for ribosomal ribonucleic acid in lactococcus lactis subsp. lactis. | a cosmid gene library of the genome of lactococcus lactis subsp. lactis 712 was probed for the presence of 16s rrna genes, using 32p 5' end-labelled 16s rrna fragments. cosmid dna from positive clones responsible for hybridisation was subcloned into a high copy number vector and a restriction map was constructed. the location of the 16s, 23s and 5s rrna genes was determined on this map. transcriptional promoter activity was identified upstream of the 5' end of the 16s rrna gene. by probing l. la ... | 1991 | 1710195 |
| plasmid-encoded determinants for bacteriocin production and immunity in a lactococcus lactis strain and purification of the inhibitory peptide. | lactococcin, a bacteriocin produced by lactococcus lactis subsp. lactis adria 85lo30, was purified as a 2.3-2.4 kda peptide. six non-bacteriocin-producing (bac-) and non-immune (imm-) strains were isolated after curing experiments. these strains had in common the loss or modification of two plasmids: pos4 (32 kb) and pos5 (70 kb). by comparing pos5 and several modified plasmids, a dna region from pos5 of about 10 kb, which was necessary for wild-type bacteriocin production and immunity, was iden ... | 1991 | 1770357 |
| nucleotide sequence of a lactococcus lactis gene cluster encoding adenylate kinase, initiation factor 1 and ribosomal proteins. | we have previously isolated a putative promoter from the lactococcus lactis subsp. lactis chromosome. we now report the sequence of the promoter fragment and its extension in the 5'-direction. the region contains several open-reading frames which correspond to ribosomal protein l15, secy, adenylate kinase, initiation factor 1 and ribosomal proteins b and s13. the order of the genes, rplo (l15), secy, adk, infa, rpmj (b) and rpsm (s13), is similar to that in the spc and alpha operon region of bac ... | 1991 | 1783905 |
| nisin treatment for inactivation of salmonella species and other gram-negative bacteria. | nisin, produced by lactococcus lactis subsp. lactis, has a broad spectrum of activity against gram-positive bacteria and is generally recognized as safe in the united states for use in selected pasteurized cheese spreads to control the outgrowth and toxin production of clostridium botulinum. this study evaluated the inhibitory activity of nisin in combination with a chelating agent, disodium edta, against several salmonella species and other selected gram-negative bacteria. after a 1-h exposure ... | 1991 | 1785933 |
| a transposon-like element on the lactose plasmid of lactococcus lactis subsp. lactis z270. | an inverted repeat previously called ir was identified on the lactose plasmid of lactococcus lactis subsp. lactis z270 by self-annealing; it was now named is1076. the two sequences were 3.3 kb apart. both copies were cloned in e. coli, sequenced and found to be identical, except for an additional 44 bp direct repeat at the 5' end of the right-hand copy; they were thus respectively 1296 bp (is1076r) and 1252 bp (is1076l) long. both elements end in near-perfect 39 bp inverted repeats, similar to t ... | 1991 | 1848522 |
| molecular organization of the minimal replicon of novel, narrow-host-range, lactococcal plasmid pci305. | plasmid pci305 is an 8.7-kb, narrow-host-range, cryptic plasmid originating from lactococcus lactis subsp. lactis uc317. the nucleotide sequence of the pci305 replication region was determined. a single open reading frame of 1158 bp was identified in the trans-active domain repb. the size of the predicted repb protein (46 kda) is in close agreement with the size of the repb product visualized in vivo in escherichia coli when repb was placed under control of the inducible phi t7 rna polymerase pr ... | 1991 | 1852014 |
| isolation and characterization of chromosomal promoters of streptococcus salivarius subsp. thermophilus. | a promoter probe vector, ptg244, was constructed with the aim of isolating transcription initiation signals from streptococcus thermophilus (streptococcus salivarius subsp. thermophilus). ptg244 is based on the escherichia coli-streptococcus shuttle vector ptg222, into which the promoterless chloramphenicol acetyltransferase gene of bacillus pumilus (cat-86) was cloned. random sau3a fragments from the s. thermophilus a054 chromosomal dna were cloned upstream of the cat-86 gene by using e. coli a ... | 1991 | 1854195 |
| secretion of tem beta-lactamase with signal sequences isolated from the chromosome of lactococcus lactis subsp. lactis. | with tem beta-lactamase as a reporter gene, a set of expression-secretion-promoting fragments were isolated from the chromosome of lactococcus lactis subsp. lactis. the fact that only translocated beta-lactamase renders cells resistant to ampicillin allowed direct ampicillin selection with an escherichia coli vector (pkth33). the clones showing the greatest ampicillin resistance were subcloned onto a replicon capable of replication in lactic acid bacteria (pvs2), and the nucleotide sequences of ... | 1991 | 1901704 |
| improved vector for promoter screening in lactococci. | fragments of lactococcus lactis subsp. lactis np45 chromosomal dna provided promoter activity in escherichia coli when cloned into the promoter probe vector pgkv210. only 13% of these recombinant plasmids promoted detectable cat-86 activity when transferred to l. lactis, i.e., expressed chloramphenicol resistance. in these promoter-containing versions of pgkv210, the cat-86 gene specifies chloramphenicol-inducible chloramphenicol acetyltransferase expression. this could be a limiting factor for ... | 1991 | 1901705 |
| thermosensitive plasmid replication, temperature-sensitive host growth, and chromosomal plasmid integration conferred by lactococcus lactis subsp. cremoris lactose plasmids in lactococcus lactis subsp. lactis. | evidence is presented that lactose-fermenting ability (lac+) in lactococcus lactis subsp. cremoris am1, sk11, and ml1 is associated with plasmid dna, even though these strains are difficult to cure of lac plasmids. when the lac plasmids from these strains were introduced into l. lactis subsp. lactis lm0230, they appeared to replicate in a thermosensitive manner; inheritance of the plasmid was less efficient at 32 to 40 degrees c than at 22 degrees c. the stability of the l. lactis subsp. cremori ... | 1991 | 1901709 |
| molecular cloning, characterization, and nucleotide sequence of the tagatose 6-phosphate pathway gene cluster of the lactose operon of lactococcus lactis. | the tagatose 6-phosphate pathway gene cluster (lacabcd) encoding galactose-6-phosphate isomerase, tagatose-6-phosphate kinase, and tagatose-1,6-diphosphate aldolase of lactococcus lactis subsp. lactis mg1820 has been characterized by cloning, nucleotide sequence analysis, and enzyme assays. transcription studies showed that the four tagatose 6-phosphate pathway genes are the first genes of the lactose-inducible lactose-phosphotransferase operon consisting of the lacabcdfegx genes. using a t7 exp ... | 1991 | 1901863 |
| molecular characterization of the nisin resistance region of lactococcus lactis subsp. lactis biovar diacetylactis drc3. | the nisin resistance determinant of lactococcus lactis subsp. lactis biovar diacetylactis drc3 was localized onto a 1.3-kb ecori-ndei fragment by subcloning and interrupting the ndei site by cloning random ndei fragments into it; the nisin resistance determinant was then sequenced. the nucleotide sequence revealed a large open reading frame containing 318 codons. putative transcription and translation signal sequences were located directly upstream from the initiation codon. immediately downstre ... | 1991 | 1903915 |
| genetic analysis of a lactococcal plasmid replicon. | the sequence and genetic organization was determined of the 2508 bp lactococcal portion of pfx2, which was derived from a cryptic lactococcus lactis subsp. lactis plasmid and used as the basis for construction of a series of lactococcal vectors. a lactococcal plasmid plus origin and two replication protein-coding regions (repa and repb) were located. repa has a helix-turn-helix motif, a geometry typical of dna-binding proteins. repb shows a high degree of homology to the plasmid replication init ... | 1991 | 1904536 |
| expression of a beta-galactosidase gene from clostridium acetobutylicum in lactococcus lactis subsp. lactis. | a beta-galactosidase gene from clostridium acetobutylicum ncib 2951 was expressed after cloning into psa3 and electroporation into derivatives of lactococcus lactis subsp. lactis strains h1 and 7962. when the clostridial gene was introduced into a plasmid-free derivative of the starter-type lact. lactis subsp. lactis strain h1, the resulting construct had high beta-galactosidase activity but utilized lactose only slightly faster than the recipient. beta-galactosidase activity in the construct de ... | 1991 | 1910034 |
| a membrane protein is required for bacteriophage c2 infection of lactococcus lactis subsp. lactis c2. | phage-resistant mutants, isolated from cultures of lactococcus lactis subsp. lactis c2 infected with phage c2, did not form plaques but bound phage normally. the mutants were sensitive to another phage, sk1, although the number of plaques was reduced approximately 56% and the plaques were four times smaller. binding to phage sk1 was reduced about 10%. another group of phage-resistant mutants, isolated from cultures infected with phage sk1, bound normally to both phages c2 and sk1 but did not for ... | 1991 | 1917843 |
| cloning and characterization of the determinant for abortive infection of bacteriophage from lactococcal plasmid pci829. | the genetic determinant for abortive infection of bacteriophage (abi) from the lactococcal plasmid pci829 was cloned on a 6.2 kb stui fragment in escherichia coli using the shuttle vector psa3. in lactococcus lactis subsp. lactis mg1363sm the resulting recombinant plasmid pci816 conferred complete insensitivity to the small isometric-headed phage 712 and a reduced plaque size in the case of the prolate-headed phage c2. the determinant was further localized by subcloning and nuclease bal31 deleti ... | 1991 | 1919509 |
| single-stranded dna plasmid, vector construction and cloning of bacillus stearothermophilus alpha-amylase in lactobacillus. | vector plasmids were constructed by ligating chloramphenicol and erythromycin resistance genes to taqi-digested dna of a cryptic plasmid from lactobacillus plantarum. the minimal region of lactobacillus plasmid dna that was required for dna replication was defined and a single-stranded dna intermediate replication system was observed. homologies with other origins of replication of plasmids from gram-positive bacteria, replicating via rolling circle mechanism, were found. it was shown that the c ... | 1991 | 1961976 |
| conjugal mobilization of streptococcal plasmid pmv158 between strains of lactococcus lactis subsp. lactis. | pmv158, a non-self-transmissible plasmid encoding tetracycline resistance, was conjugally transferred from enterococcus faecalis jh203 to lactococcus lactis subsp. lactis il1403. this transfer appeared to be dependent on the cotransfer of the conjugative plasmids pam beta 1 or pip501. intraspecies conjugal transfer of pmv158 also occurred in strain il1403. in contrast to the transfer from e. faecalis, transfer in il1403 did not require the presence of a conjugative plasmid in the donor strain bu ... | 1990 | 2104609 |
| high-frequency, site-specific recombination between lactococcal and pam beta 1 plasmid dnas. | in vivo recombination events involving the 75-kilobase lactose proteinase plasmid pci301 of lactococcus lactis subsp. lactis uc317 and the conjugative enterococcal plasmid pam beta 1 were analyzed. a fragment, identified as containing the pci301 recombination site, mediated greatly elevated levels of mobilization and recombination with pam beta 1 when cloned in a nonmobilizable l. lactis-escherichia coli shuttle vector. this latter recombination event was site and orientation specific on both pl ... | 1990 | 2111809 |
| cloning of the citrate permease gene of lactococcus lactis subsp. lactis biovar diacetylactis and expression in escherichia coli. | the citrate plasmid (cit+ plasmid) from lactococcus lactis subsp. lactis biovar diacetylactis was cloned into the ecori site of plasmid puc18. this recombinant plasmid enabled escherichia coli k-12 to transport and utilize citrate as a source of energy, indicating expression of the citrate permease from l. lactis biovar diacetylactis. the citrate permease was under the control of the lac promoter of puc18. genetic expression of the cit+ plasmid in maxicells revealed that the plasmid encoded two ... | 1990 | 2117878 |
| cloning and characterization of the thymidylate synthase gene from lactococcus lactis subsp. lactis. | the thymidylate synthase (thya) gene has been isolated from lactococcus lactis subsp. lactis. the cloned gene was strongly expressed in escherichia coli both in vivo and in vitro (maxicells and cell-free transcription and translation systems) and complemented e. coli thya mutants. dna-dna hybridizations demonstrated that the thya gene is encoded by the chromosome of l. lactis subsp. lactis. by sequential deletion of dna outside the complementing region, the thya gene was localized to a 1.1-kilob ... | 1990 | 2117882 |
| thymidylate synthase gene from lactococcus lactis as a genetic marker: an alternative to antibiotic resistance genes. | the potential of the thymidylate synthase thya gene cloned from lactococcus lactis subsp. lactis as a possible alternative selectable marker gene to antibiotic resistance markers has been examined. the thya mutation is a recessive lethal one; thya mutants cannot survive in environments containing low amounts of thymidine or thymine (such as luria-bertani medium) unless complemented by the thya gene. the cloned thya gene was strongly expressed in l. lactis subsp. lactis, escherichia coli, rhizobi ... | 1990 | 2117883 |
| relationship between utilization of proline and proline-containing peptides and growth of lactococcus lactis. | proline, which is the most abundant residue in beta-casein, stimulates growth of lactococcus lactis in a proline-requiring strain (lactococcus lactis subsp. cremoris wg2) and in a proline-prototrophic strain (lactococcus lactis subsp. lactis ml3). both strains lack a proline-specific uptake system, and free proline can enter the cell only by passive diffusion across the cytoplasmic membrane. on the other hand, lactococci can actively take up proline-containing peptides via the lactococcal di- an ... | 1990 | 2118509 |
| molecular cloning and expression of a proteinase gene from lactococcus lactis subsp. cremoris h2 and construction of a new lactococcal vector pfx1. | the 6.5 kb hindiii dna fragment of the lactococcus lactis subsp. cremoris h2 plasmid pdi21 was cloned into escherichia coli pop13 with lambda nm1149, and also directly into lactococcus lactis subsp. lactis 4125 using a newly-constructed broad host-range vector pfx1. proteinase was expressed in both transformed organisms. the proteinase resembles a pi type since it preferentially degraded beta-casein. the restriction map of the 6.5 kb proteinase gene fragment has minor differences from those of p ... | 1990 | 2118753 |
| nucleotide sequence and expression in escherichia coli of the lactococcus lactis citrate permease gene. | the plasmid-encoded citrate determinant of the lactococcus lactis subsp. lactis var. diacetylactis ncdo176 was cloned and functionally expressed in a cit- escherichia coli k-12 strain. from deletion derivative analysis, a 3.4-kilobase region was identified which encodes the ability to transport citrate. analysis of proteins encoded by the cloned fragment in a t7 expression system revealed a 32,000-dalton protein band, which correlated with the ability of cells to transport citrate. energy-depend ... | 1990 | 2120190 |
| molecular cloning, transcriptional analysis, and nucleotide sequence of lacr, a gene encoding the repressor of the lactose phosphotransferase system of lactococcus lactis. | the repressor gene (lacr) of the lactose phosphotransferase system of lactococcus lactis subsp. lactis strain mg1820 has been cloned and characterized. transcription of lacr, into a 1.2-kilobase monocistronic messenger, is repressed approximately 5-fold during growth on lactose. nucleotide sequence analysis of the lacr gene showed the presence of an open reading frame of 861 base pairs. the deduced amino acid sequence of lacr is homologous to three escherichia coli regulatory proteins (deor, fuc ... | 1990 | 2120234 |
| cloning of usp45, a gene encoding a secreted protein from lactococcus lactis subsp. lactis mg1363. | we have cloned usp45, a gene encoding an extracellular secretory protein of lactococcus lactis subsp. lactis strain mg1363. unidentified secreted 45-kda protein (usp45) is secreted by every mesophilic l. lactis strain we tested so far and it is chromosomally encoded. the nucleotide sequence of the usp45 gene revealed an open reading frame of 1383 bp encoding a protein of 461 amino acids (aa), composed of a 27-aa signal peptide and a mature protein initiated at asp28. the gene contains a consensu ... | 1990 | 2123812 |
| heterologous gene expression in lactococcus lactis subsp. lactis: synthesis, secretion, and processing of the bacillus subtilis neutral protease. | the bacillus subtilis npre gene lacking its own promoter sequence was inserted in the lactococcal expression vector pmg36e. upon introduction of the recombinant plasmid into lactococcus lactis subsp. lactis strain mg1363, neutral protease activity could be visualized by the appearance of large clearing zones around colonies grown on milk agar plates. by measuring the activities of the neutral protease and the intracellular enzyme lactate dehydrogenase in culture supernatants and cell fractions, ... | 1990 | 2125811 |
| integration and excision of plasmid dna in lactococcus lactis subsp. lactis. | the capacity of the 75-kb lactose-proteinase plasmid pci301 from lactococcus lactis subsp. lactis uc317 to recombine with the lactococcal chromosome was examined. low-frequency integration of pci301 sequences was detected following protoplast transformation of strain mg136sm with total plasmid dna from strain uc317. excision of integrated sequences was subsequently observed at a low level. excised sequences were rescued through recombination with and mobilization by the conjugative enterococcal ... | 1990 | 2128962 |
| cloning of a chromosomal fragment from lactococcus lactis subsp. lactis partially complementing escherichia coli reca functions. | a reca-like gene was isolated from a gene library of lactococcus lactis subsp. lactis by intergeneric complementation of an e. coli reca mutant. a plasmid was obtained which fully complemented the reca response to dna damaging agents and uv inducibility of prophage, but not p1 plating efficiency in an e. coli reca mutant. the cloned dna fragment also partially complemented the rec mutation in lc. lactis mms36. hybridization studies showed that there was no detectable sequence homology between th ... | 1990 | 2150659 |
| simultaneous loss of n5-(carboxyethyl)ornithine synthase, nisin production, and sucrose-fermenting ability by lactococcus lactis k1. | a spontaneous derivative of lactococcus lactis subsp. lactis k1 (formerly streptococcus lactis k1) lacking n5-(carboxyethyl)ornithine synthase (ec 1.5.1.24) was isolated. this mutant had also lost the abilities to ferment sucrose and to produce the antibiotic nisin. hybridization studies indicate that these linked traits are encoded on the chromosome of l. lactis k1 and that they may be located on a conjugative transposon. | 1990 | 2163399 |
| nucleotide sequence of is904 from lactococcus lactis subsp. lactis strain nizo r5. | | 1990 | 2165590 |
| characterization of a plasmid involved with cointegrate formation and lactose metabolism in lactococcus lactis subsp. lactis ozs1. | a 55 kilobase (kb) plasmid (pozs550) in the non-clumping lactococcus lactis subsp. lactis strain ozs1 carrying genes for lactose metabolism was characterised. a mobilizable cointegrate plasmid which is formed between pozs550 and pozs448 carries the necessary information for conjugation and transfer. cointegrate formation was found to involve an insertional element located on pozs550. the insertion sequence was found to be identical to iss1 located on psk08 in the clumping l. lactis subsp. lactis ... | 1990 | 2177590 |
| isolation of a replication region of a large lactococcal plasmid and use in cloning of a nisin resistance determinant. | the replication region of a 28-kilobase-pair (kbp) cryptic plasmid from lactococcus lactis subsp. lactis biovar diacetylactis ssd207 was cloned in l. lactis subsp. lactis mg1614 by using the chloramphenicol resistance gene from the streptococcal plasmid pgb301 as a selectable marker. the resulting 8.1-kbp plasmid, designated pvs34, was characterized further with respect to host range, potential cloning sites, and location of replication gene(s). in addition to lactococci, pvs34 transformed lacto ... | 1990 | 2389931 |
| genetic transformation of intact lactococcus lactis subsp. lactis by high-voltage electroporation. | to apply recombinant dna techniques for genetic manipulation of the industrially important lactococci, an efficient and reliable high-frequency transformation system must be available. high-voltage electric pulses have been demonstrated to enhance uptake of dna into protoplasts and intact cells of numerous gram-negative and gram-positive microorganisms. the objective of this study was to develop a system for electroporating intact cells of lactococcus lactis subsp. lactis lm0230 (previously desi ... | 1989 | 2494937 |
| construction of a lactococcal expression vector: expression of hen egg white lysozyme in lactococcus lactis subsp. lactis. | a pair of vectors for expression of heterologous genes in lactococcus lactis was constructed. in addition to an origin of replication that has a broad host range, these vectors contain a multiple cloning site flanked by gene expression signals originating from l. lactis subsp. cremoris wg2. the two vectors, about 3.7 kilobase pairs in size, differ only in the type of antibiotic resistance they confer to their hosts. pmg36 carries a kanamycin resistance marker, which was replaced by an erythromyc ... | 1989 | 2495760 |
| campbell-like integration of heterologous plasmid dna into the chromosome of lactococcus lactis subsp. lactis. | integrable vectors were constructed based on the plasmid phv60, which is essentially a pbr322 replicon carrying a chloramphenicol resistance marker, by inserting 1.3-kilobase chromosomal fragments of lactococcus lactis subsp. lactis mg1363 into this plasmid. three constructs as well as phv60 were electroporated to strain mg1363. transformants were obtained with all constructs, and also with phv60 (albeit with low frequency). by using southern hybridizations, it appeared that phv60 showed homolog ... | 1989 | 2497708 |
| insertion and amplification of foreign genes in the lactococcus lactis subsp. lactis chromosome. | the plasmid pe194 is unable to replicate in lactococcus lactis subsp. lactis (formerly streptococcus lactis). when linked to resident bacteriophage sequences, pe194 was able to integrate into the l. lactis subsp. lactis chromosome either by campbell-like recombination or by double crossing over with deletion. integration occurred into the dna of the prophage and prevented its multiplication. when a selective pressure was applied to an integrant in which pe194 was flanked by two direct repeats of ... | 1989 | 2504115 |
| response of lactococcus (streptococcus) lactis to n-methyl-n'-nitro-n-nitrosoguanidine: absence of adaptive response. | pretreatment of cells of lactococcus lactis subsp. lactis with low levels of n-methyl-n'-nitro-n-nitrosoguanidine does not reduce the cytotoxic and mutagenic effects caused by high concentration of this agent. this observation indicates that there is no efficient inducible error-free repair system for alkylation damage similar to the 'adaptive response' described in detail for escherichia coli. | 1989 | 2506405 |
| conjugal transfer of genetic material by lactococcus lactis subsp. lactis 11007. | conjugal transfer of genetic material by lactococcus lactis subsp. lactis 11007 was examined. a plasmid of 88 mda (pjs88) was identified in addition to the previously reported conjugally transferred plasmids of 32 (pkb32) and 4.8 mda. proteinase activity, reduced bacteriophage sensitivity, bacteriocin resistance, and conjugal transfer ability were encoded by pjs88. the ability to metabolize lactose (lac+) was encoded by pkb32, and the 4.8-mda plasmid was cryptic. when a strain containing both pk ... | 1989 | 2506592 |
| characterization of the genetic element coding for lactose metabolism in lactococcus lactis subsp. lactis kp3. | the lactococcus lactis subsp. lactis kp3 lac genetic element was investigated. kp3 is a lactose-positive (lac+) transconjugant which contains no detectable plasmid dna. the kp3 lac genetic element was self-transmissible (tra+) and encoded a reduced bacteriophage sensitivity (rbs+) phenotype. matings of kp3 with a recombination-deficient (rec-) recipient resulted in lac+ transconjugants which were phenotypically indistinguishable from kp3 and contained a 96-mda plasmid (pjs96). phenotypic and phy ... | 1989 | 2506593 |
| cloning of chromosomal genes of lactococcus by heterologous complementation: partial characterisation of a putative lactose transport gene. | a cosmid gene library of the genome of lactococcus lactis subsp. lactis 712 has been constructed in the broad host range plasmid plafr1 in escherichia coli le392. three lactococcal genes from the bank were identified by heterologous complementation of specific mutations in strains of e. coli. a cosmid clone encoding a putative lactose transport gene was identified by complementing an e. coli lacy mutant. the complemented clone supported the uptake of 14c lactose in transport assays. the dna frag ... | 1989 | 2513247 |
| improved electroporation efficiency of intact lactococcus lactis subsp. lactis cells grown in defined media. | the impact of growth conditions on electroporation of lactococcus lactis subsp. lactis lm0230 (previously designated streptococcus lactis lm0230) was evaluated. cells grown in m17 broth supplemented with 0.5% glucose (m17-glu) and two chemically defined synthetic media, fmc and rpmi 1640, all supplemented with 0.24% dl-threonine or 0.5% glycine, were harvested, washed with double-distilled water, diluted, and porated in the presence of 1 microgram of pgb301 dna with a transfector 100 (btx, inc., ... | 1989 | 2513778 |
| structure and expression of the lactococcus lactis gene for phospho-beta-galactosidase (lacg) in escherichia coli and l. lactis. | the lactococcus lactis subsp. lactis 712 lacg gene encoding phospho-beta-galactosidase was isolated from the lactose mini-plasmid pmg820 and cloned and expressed in escherichia coli and l. lactis. the low phospho-beta-galactosidase activity in l. lactis transformed with high-copy-number plasmids containing the lacg gene contrasted with the high activity found in l. lactis containing the original, low-copy-number lactose plasmid pmg820, and indicated that the original lactose promoter was absent ... | 1989 | 2515252 |
| reaction of woodward's reagent k with d-xylose isomerases. modification of an active site carboxylate residue. | d-xylose isomerases from streptomyces violaceoruber, streptomyces sp., lactobacillus xylosus, lactobacillus brevis and bacillus coagulans were rapidly inactivated by woodward's reagent k. second-order rate constants in the absence of ligands, at ph 6.0 and 25 degrees c, were 41, 36, 22, 95 and 26 m-1.min-1 respectively. spectral analysis at 340 nm revealed that inactivation was correlated with modification of five, six, two, three and six carboxylate residues per monomer respectively. in the pre ... | 1989 | 2775179 |
| evidence for an essential histidine residue in d-xylose isomerases. | diethyl pyrocarbonate inactivated d-xylose isomerases from streptomyces violaceoruber, streptomyces sp., lactobacillus xylosus and lactobacillus brevis with second-order rate constants of 422, 417, 99 and 92 m-1.min-1 respectively (at ph 6.0 and 25 degrees c). activity was completely restored by the addition of neutral hydroxylamine, and total protection was afforded by the substrate analogue xylitol in the presence of either mg2+ or mn2+ according to the genus studied. the difference spectra of ... | 1988 | 3355509 |
| comparative peptide specificity of cell wall, membrane and intracellular peptidases of group n streptococci. | solubilized cell walls of group n streptococci contain two electrophoretically distinct peptidases, one of which hydrolysed trileucine only, while the second hydrolysed a wide range of di- and tripeptides. neither enzyme possessed leucine aminopeptidase or endopeptidase activity. four and three peptidases, respectively, were separated in intracellular extracts of streptococcus lactis subsp. lactis and strep. lactis subsp. cremoris produced by osmotic lysis of spheroplasts. in contrast with the c ... | 1985 | 3924874 |
| incorporation of radioactive acetate into diacetyl by streptococcus diacetilactis. | streptococcus diacetilactis was grown in a partially defined, lipoic acid-free medium containing radioactive acetate with and without addition of 0.1% unlabeled sodium pyruvate. labeled carbon was incorporated into diacetyl, but neither the amount of diacetyl produced nor its specific activity was influenced by addition of pyruvate. acetoin had low specific activity, indicating that it was a mixture of radioactive and nonradioactive acetoin. the specific activity of acetoin was lower when pyruva ... | 1973 | 4148640 |
| repression of staphylococcus aureus in associative culture. | the growth of staphylococcus aureus mf 31 was suppressed when grown in association with streptococcus diacetilactis and other lactic streptococci. the data indicated that the initial proportion of staphylococci present in the medium was of less importance than the depletion of vital nutrients. investigation revealed that factors present in yeast nitrogen base medium could reverse the inhibition which was due to antagonism. the major factor found was nicotinamide, and further study revealed that ... | 1965 | 4222452 |