| characterization of the lactococcus lactis lactose operon promoter: contribution of flanking sequences and lacr repressor to promoter activity. | we determined the location, activity, and regulation of the promoter of the lactococcus lactis 8-kb lactose operon (lacabcdfegx), which encodes the enzymes of the lactose phosphotransferase system and the tagatose 6-phosphate pathway. the lac promoter sequence corresponds closely to the consensus promoter described for gram-positive bacteria and is located in a back-to-back configuration with the promoter of the divergently transcribed lacr gene, which encodes the lacr repressor. the transcripti ... | 1992 | 1372602 |
| characterization of enterococcal isolates by restriction enzyme analysis of genomic dna. | a restriction enzyme analysis (rea) of chromosomal dna for the intra-species characterization of enterococci is reported. the dna was extracted by a rapid method and digested with the restriction enzyme sal i to provide a characteristic 'fingerprint' consisting of 10-20 bands in the 1.6-5.0 kb range. one hundred and eighty enterococcal isolates were examined; 5 were type strains, 15 from an out-patient clinic and 160 from a geographically isolated british antarctic survey base. the epidemiologic ... | 1992 | 1379935 |
| structure of the exopolysaccharide produced by lactococcus lactis subspecies cremoris h414 grown in a defined medium or skimmed milk. | the structure of the exopolysaccharide of lactococcus lactis subsp. cremoris h414, isolated from a defined medium or skimmed milk, was established by linkage analysis on the native polysaccharide, and by characterisation of oligosaccharide fragments, obtained by smith degradation and partial acid hydrolysis, using methylation analysis, fabms, eims, and 1h-nmr spectroscopy. the polysaccharide has the branched-pentasaccharide repeating unit: [formula: see text] | 1992 | 1394319 |
| 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 |
| sequence encoding ribosomal protein l33 of lactococcus lactis. | a cloned fragment from lactococcus lactis chromosome encoding the l33 ribosomal protein was sequenced. two incomplete open reading frames (orfs) were also found: the upstream orf shows similarity to the tetracycline-resistance protein (tet) of bacillus stearothermophilus, and the downstream orf shows homology to a protein of bacillus subtilis participating in sporulation (spove), and to proteins of escherichia coli involved in cell division (ftsw) and the maintenance of cell shape (roda). | 1992 | 1398083 |
| nucleotide and deduced amino acid sequences of the lacr, lacabcd, and lacfe genes encoding the repressor, tagatose 6-phosphate gene cluster, and sugar-specific phosphotransferase system components of the lactose operon of streptococcus mutans. | the complete nucleotide sequences of lacrabcdf and partial nucleotide sequence of lace from the lactose operon of streptococcus mutans are presented. comparison of the streptococcal lac determinants with those of staphylococcus aureus and lactococcus lactis indicate exceptional protein and nucleotide identity. the deduced polypeptides also demonstrate significant, but lower, sequence similarity with the corresponding lactose proteins of lactobacillus casei. additionally, lacr has sequence homolo ... | 1992 | 1400164 |
| 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 |
| determination of the sequence of spae and identification of a promoter in the subtilin (spa) operon in bacillus subtilis. | an 851-residue open reading frame (orf) called spae has been discovered in the subtilin (spa) operon. interruption of this orf with a chloramphenicol acetyltransferase gene destroys the ability of bacillus subtilis lh45 delta c (a derivative of b. subtilis 168) to produce subtilin, which is an antimicrobial peptide belonging to the class of ribosomally synthesized peptide antibiotics called lantibiotics. spae shows strong homology to nisb, which is in the nisin (nis) operon in lactococcus lactis ... | 1992 | 1400221 |
| 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 |
| description and evaluation of the semiautomated 4-hour rapid id 32 strep method for identification of streptococci and members of related genera. | the rapid id 32 strep system (biomérieux, la balme les grottes, france) is a new system which allows the identification in 4 h of most streptococci and members of related genera encountered in medical and veterinary bacteriology. four hundred thirty-three isolates first identified by conventional methods and belonging to the genera streptococcus, lactococcus, enterococcus, aerococcus, gemella, leuconostoc, erysipelothrix, gardnerella, and listeria were tested. overall, rapid id 32 strep correctl ... | 1992 | 1400965 |
| protein export elements from lactococcus lactis. | broad-host-range plasmids carrying alpha-amylase or beta-lactamase reporter genes lacking a signal sequence were used to select export elements from lactococcus lactis chromosomal dna that could function as signal sequences. fragments containing such elements were identified by their ability to direct the export of the reporter proteins in escherichia coli. several of the selected export elements were also active in bacillus subtilis and l. lactis, although the efficiencies depended strongly on ... | 1992 | 1406586 |
| biosynthesis and distribution of n-carboxyalkyl amino acids (opines) in bacteria. | | 1992 | 1410788 |
| 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 |
| characterization of transcription initiation and termination signals of the proteinase genes of lactococcus lactis wg2 and enhancement of proteolysis in l. lactis. | the transcription initiation signals of the prtp and prtm genes specifying the proteolytic activity of lactococcus lactis subsp. cremoris wg2 were mapped by primer extension. the strength of these promoters was analyzed with promoter-screening vector pgkv410, and they appeared to be weaker than previously isolated promoters of strain wg2. in addition, a putative transcription terminator downstream of the prtp gene was characterized by using the terminator-screening vector pgkv259. the putative t ... | 1992 | 1444428 |
| identification and characterization of two bacteriocin-producing strains of lactococcus lactis isolated from vegetables. | isolated from mixed salad and fermented carrots, 123 strains of lactic acid bacteria were screened for bacteriocin production. two strains, d53 and 23, identified as lactococcus lactis by dna-dna hybridizations, produced heat stable bacteriocins which were resistant to trypsin and pepsin, but were inactivated by alpha-chymotrypsin and proteinase k. the bacteriocins were active from ph 2 to 9 and inhibited species of listeria, lactobacillus, lactococcus, pediococcus, leuconostoc, carnobacterium, ... | 1992 | 1445757 |
| characterization of the lactococcus lactis pepn gene encoding an aminopeptidase homologous to mammalian aminopeptidase n. | the nucleotide sequence of the pepn gene from lactococcus lactis encoding a zinc-metallo aminopeptidase has been determined. the open reading frame of 2,538 base pairs encodes a protein with a calculated m(r) of 95,368, which agrees with the apparent m(r) of 95,000 of the gene product which was identified by polyclonal antibodies raised against the purified aminopeptidase. the amino acid sequence of the aminopeptidase of l. lactis was found to be similar to the corresponding enzymes of human, ra ... | 1992 | 1352755 |
| isolation and characterization of is1165, an insertion sequence of leuconostoc mesenteroides subsp. cremoris and other lactic acid bacteria. | we have cloned and characterized an insertion sequence from leuconostoc mesenteroides subsp. cremoris strain db1165. this element, designated is1165, is 1553 bp, has imperfect inverted repeat ends, contains an open reading frame of 1236 bp, and is not related to any previously described insertion sequence. the copy number of is1165 varies from 4 to 13 in l. mesenteroides subsp. cremoris strains allowing genetic fingerprinting of strains based on location and number of bands on hybridization. is1 ... | 1992 | 1325060 |
| lithium chloride-sodium propionate agar for the enumeration of bifidobacteria in fermented dairy products. | lithium chloride-sodium propionate agar has been developed for the enumeration of bifidobacteria in fermented dairy products. the medium contains lithium chloride and sodium propionate to inhibit the growth of other lactic acid bacteria. pure cultures of bifidobacteria, lactobacilli, and streptococci were tested for growth in this medium. with one exception, all bifidobacteria were able to grow in this medium and in a nonselective agar with a difference not exceeding .4 log units. however, none ... | 1992 | 1317893 |
| 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 |
| [streptococcus lactis bacteriophage in the oral cavity]. | | 1975 | 829897 |
| clinical significance of lancefield groups l-t streptococci isolated from blood and cerebrospinal fluid. | the aim of a study of all groups l-t streptococci isolated at the massachusetts general hospital during a 10-year period (1964-1974) was to ascertain the clinical significance of the less frequently occurring serological groups of streptococci. no organisms of groups p,r,s, or t were found during this time. the case records of 109 clinical isolates of alpha-reacting streptococci of lancefield groups l,m,n, and o from blood and cerebrospinal fluid cultures were reviewed. there were six cases of e ... | 1976 | 816972 |
| [identification of bacteriophages that lyse industrial strains of the producer of the antibiotic nisin]. | | 1975 | 810074 |
| [results from the central laboratory for streptococci research in kiel from 1965 to 1977 - a survey (author's transl)]. | at the central laboratory for streptococci research at the institute for hygiene of the federal dairy research centre in kiel a data bank has been established which comprises as well bibliographical data (until now more than 8000 titles out of the international literature concerning streptococci) as laboratory data of all strains which have been identified since 1965. for this present publication as a survey the total material covering 34,935 strains was analyzed and interpreted. besides a short ... | 1979 | 543350 |
| comparison of membrane proteins from lactic streptococci by gel electrophoresis. | | 1979 | 539224 |
| peptide utilization by group n streptococci. | the rate of glycylleucine uptake by group n streptococci varied widely. one strain of streptococcus cremoris did not transport the dipeptide or utilize tripeptides. in peptide-utilizing strains, amino acid, dipeptide and tripeptide transport were distinct, although dipeptides inhibited tripeptide utilization. specificity determinants for peptide transport and utilization were similar to those reported in gram-negative bacteria. peptide utilization in s. lactis was not completely dependent on the ... | 1978 | 416171 |
| incidence and properties of temperate bacteriophages induced from lactic streptococci. | sixty-three strains of lactic streptococci isolated from commercial lactic streptococcal starter cultures were examined for lysogeny by treatment with ultraviolet light or mitomycin c. after treatment with the inducing agent, all strains, whether or not they lysed, were examined for evidence of phage release by electron microscopy. thirty-eight strains yielded intact phages or phage particles of varying morphology. all the temperate phages had isometric heads and noncontractile tails; some had c ... | 1977 | 402110 |
| the nature of the stimulation of the growth of streptococcus lactis by yeast extract. | yeast extract was fractionated on sephadex g-25 into 7 fractions. the fraction most stimulatory to the growth of streptococcus lactis c10 contained over 70% of the amino n present in yeast extract and consisted of a wide variety of free amino acids and a small amount of peptide material. examination of possible replacement factors for this fraction revealed that the amino -acid material present was largely responsible for the stimulation of str. lactis c10. purine and pyrimidine bases and inorga ... | 1975 | 235576 |
| occurence of lactose-negative mutants in chemostat cultures of lactic streptococci. | batch and chemostat cultures of streptococcus cremoris hp and streptococcus lactis 829 were examined for lactose-hegative (lac-)mutants on indicator agar. in batch cultures, s. cremoris hp gave less than 1% of the total count as lac- colonies while s. lactis 829 consistently contained about 15% of the total as lac- colonies. in chemostat cultures of s. cremoris hp in 2% skim milk containing casamino acids and yeast extract (0.1% each), the percentage of lac- colonies increased markedly when the ... | 1975 | 234782 |
| lactose metabolism in streptococcus lactis: phosphorylation of galactose and glucose moieties in vivo. | starved cells of streptococcus lactis ml3 grown previously on lactose, galactose, or maltose were devoid of adenosine 5'-triphosphate contained only three glycolytic intermediates: 3-phosphoglycerate, 2-phosphoglycerate, and phosphoenolpyruvate (pep). the three metabolites (total concentration, ca 40 mm) served as the intracellular pep potential for sugar transport via pep-dependent phosphotransferase systems. when accumulation of [14c]lactose by iodoacetate-inhibited starved cells was abolished ... | 1979 | 118155 |
| studies on the relationship between glycerophosphoglycolipids and lipoteichoic acids. iv. trigalactosylglycerophospho-acylkojibiosyldiacylglycerol and related compounds from streptococcus lactis kiel 42172. | streptococcus lactis kiel 42172 contains at least six unusually polar glycerophosphoglycolipids. the predominant one was composed of d-galactose, d-glucose, glycerol, acyl groups and phosphorus in a molar ratio of approx. 3 : 2 : 2 : 3 : 1. by analysis of the breakdown products of hf hydrolysis and smith-degradation the structure was established to be [galp (alpha 1 leads to 6)galp(alpha 1 leads to 3)-sn-glycero(2 comes from 1 alpha galp)-1-phospho] leads to 6glcp(alpha 1 leads to 2), acyl leads ... | 1979 | 117837 |
| [immunoluminescent method for detecting enterococci in dairy products]. | | 1978 | 100374 |
| 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 |
| engineering dehydrated amino acid residues in the antimicrobial peptide nisin. | the small antimicrobial peptide nisin, produced by lactococcus lactis, contains the uncommon amino acid residues dehydroalanine and dehydrobutyrine and five thio ether bridges. since these structures are posttranslationally formed from ser, thr, and cys residues, it is feasible to study their role in nisin function and biosynthesis by protein engineering. here we report the development of an expression system for mutated nisin z (nisz) genes, using nisin a producing l. lactis as a host. replacem ... | 1992 | 1447185 |
| cloning and sequence analysis of the gene encoding l-lactate dehydrogenase from lactococcus lactis: evolutionary relationships between 21 different ldh enzymes. | lactate dehydrogenase (ldh; ec1.1.1.27) is a key enzyme in the fermentation of milk by lactic acid bacteria used in the dairy industry. an 800-bp dna fragment containing part of the gene (ldh) encoding ldh was amplified from lactococcus lactis in a polymerase chain reaction using primers designed from the partial amino acid sequence of a lactococcal ldh. this fragment was radioactively labelled and used to probe a phage lambda library of lc. lactis genomic dna. fragments containing ldh were subc ... | 1992 | 1452029 |
| 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 |
| growth and activities of lactococcus lactis in milk enriched with low mineral retentate powders. | the growth and activities of three strains of lactococcus lactis ssp. cremoris (wg2, e8, and hp) and their proteinase-negative variants were studied in skim milk enriched with three types of retentate powder. the performance of these strains in enriched milks was compared with that determined in reconstituted skim milk. proteinase-positive strains of l. lactis ssp. cremoris exhibited higher maximum specific growth rates than protease-negative variants. moreover, maximum specific growth rates of ... | 1992 | 1452841 |
| molecular rearrangement of lactose plasmid dna associated with high-frequency transfer and cell aggregation in lactococcus lactis 712. | high-frequency conjugation of the lactose plasmid plp712 is associated with a constitutive cell aggregation phenotype and is facilitated by cointegration with a sex factor. analysis of 23 independently derived enlarged lactose plasmids revealed that the sex factor dna present in cointegrates varied in size. this suggested that more than simple cointegration with a sex factor plasmid was involved. further analysis led to the discovery of a chromosomally located sex factor that could excise and be ... | 1992 | 1453959 |
| accelerated natural lactic fermentation of cereal-based formulas at reduced water activity. | energy required to dehydrate fermented cereal-based food formulas plays a significant part in the production cost. therefore the effect of reduced moisture content on the fermentation was investigated. generally, lactic fermentation at reduced moisture content resulted in increased final ph. significant acidification still occurred at 0.33 kg water/kg dry matter corresponding to either aw = 0.925 in a sorghum-maize-soya (sms) mixture, or aw = 0.950 in a sorghum-maize-milk powder (smm) mixture. a ... | 1992 | 1457290 |
| identification of the active site serine of the x-prolyl dipeptidyl aminopeptidase from lactococcus lactis. | the active site serine of the x-prolyl dipeptidyl aminopeptidase from lactococcus lactis (pepx) was identified. the enzyme was labeled by [3h]dfp, treated by cnbr and the resulting peptides were separated by reverse-phase-hplc. the main radiolabeled peptide was sequenced. ser-348, in the following sequence, gly-lys-ser-tyr-leu-gly, was identified as the active site serine. a sequence comparison between the active site of pepx and other serine proteases was made, showing only limited sequence hom ... | 1992 | 1459244 |
| enhancement of the chemical and antimicrobial properties of subtilin by site-directed mutagenesis. | subtilin and nisin are gene-encoded antibiotic peptides that are ribosomally synthesized by bacillus subtilis and lactococcus lactis, respectively. gene-encoded antibiotics are unique in that their structures can be manipulated by mutagenesis of their structural genes. although subtilin and nisin share considerable structural homology, subtilin has a greater tendency than nisin to undergo spontaneous inactivation. this inactivation is a accompanied by chemical modification of the dehydroalanine ... | 1992 | 1460009 |
| b-cell mitogenic activity of slime products produced from slime-forming, encapsulated lactococcus lactis ssp. cremoris. | the mitogenic activities of whole cell lyophylized preparations, cell-wall components, and slime products obtained from lactococcus lactis ssp. cremoris kvs20 were examined on murine spleen cells. whole cell lyophylized preparations and slime products significantly (p < .05) stimulated mitogenic responses of the cells. the highest activity was induced by slime products in which the optimal concentration was 116 microg/ml. the significant (p < .05) increase of mitogenic activity induced by slime ... | 1992 | 1460126 |
| reconstitution of the leucine transport system of lactococcus lactis into liposomes composed of membrane-spanning lipids from sulfolobus acidocaldarius. | the effect of bipolar tetraether lipids, extracted from the thermophilic archaebacterium sulfolobus acidocaldarius, on the branched-chain amino acid transport system of the mesophilic bacterium lactococcus lactis was investigated. liposomes were prepared from mixtures of monolayer lipids and the bilayer lipid phosphatidylcholine (pc), analyzed on their miscibility, and fused with membrane vesicles from l. lactis. freeze-fracture electron microscopy demonstrates that the bipolar lipids in the hyb ... | 1992 | 1463735 |
| isolation of purine auxotrophic mutants of lactococcus lactis and characterization of the gene hpt encoding hypoxanthine guanine phosphoribosyltransferase. | five purine auxotrophic mutants of lactococcus lactis were isolated. l. lactis was capable of converting adenine, guanine and hypoxanthine to amp, gmp and imp, respectively, indicating the existence of adenine phosphoribosyltransferase (aprt) and hypoxanthine guanine phosphoribosyltransferase (hgprt) activities. a 1.3 kb dna fragment from l. lactis was cloned by complementation of the hpt mutation in escherichia coli. introduction of this fragment into l. lactis resulted in an increase in hgprt ... | 1992 | 1465108 |
| ribosomes, ribosomal subunits and ribosomal proteins of lactococcus lactis il1403. | | 1992 | 1477144 |
| a lactococcal expression system for engineered nisins. | the nisin-producing lactococcus lactis strain fi5876 has been modified and developed for use as an expression system for engineered nisin variants. insertional inactivation of the resident nisa gene had a polar effect on downstream genes, including those involved in nisin immunity. however, subsequent chromosomal rearrangements in this region involving a newly discovered insertion element (is905) generated a strain that was deficient in the nisa gene product but expressed those nisin determinant ... | 1992 | 1482189 |
| biosynthesis of the lantibiotic nisin: genomic organization and membrane localization of the nisb protein. | nisin produced by lactococcus lactis 6f3 is used as a food preservative and is the most important member of a group of peptide-antibiotics containing lanthionine bridges (lantibiotics) (n. schnell, k.-d. entian, u. schneider, f. götz, h. zähner, r. kellner, and g. jung, nature [london] 333:276-278, 1988). nisin is ribosomally synthesized, and its structural gene, nisa, encodes a prepeptide that is posttranslationally modified, revealing the active lantibiotic (c. kaletta and k.-d. entian, j. bac ... | 1992 | 1482192 |
| 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 |
| bacteriophage resistance in lactococcus lactis ssp. lactis using antisense ribonucleic acid. | antisense rna against a conserved bacteriophage gene when expressed in a lactococcus lactis ssp. lactis strain renders it resistant to bacteriophage infection. two open reading frames have been identified in a l. lactis ssp. lactis bacteriophage that are conserved in a majority of isolates. they code for an 18-kda (designated gp18c) protein and a 24-kda (gp24c) protein, respectively, which are arranged along with previously identified open reading frames in a tandem motif similar to other bacter ... | 1992 | 1500572 |
| a novel lactococcal bacteriocin whose activity depends on the complementary action of two peptides. | a lactococcal bacteriocin, termed lactococcin g, was purified to homogeneity by a simple four-step purification procedure that includes ammonium sulfate precipitation, binding to a cation exchanger and octyl-sepharose cl-4b, and reverse-phase chromatography. the final yield was about 20%, and nearly a 7,000-fold increase in the specific activity was obtained. the bacteriocin activity was associated with three peptides, termed alpha 1, alpha 2, and beta, which were separated by reverse-phase chro ... | 1992 | 1512201 |
| cloning, sequencing and expression of the gene encoding the cell-envelope-associated proteinase from lactobacillus paracasei subsp. paracasei ncdo 151. | the gene encoding the cell-envelope-associated proteinase of lactobacillus paracasei subsp. paracasei ncdo 151 (formerly lactobacillus casei ncdo 151) was cloned and sequenced. the gene was located on the chromosome and encoded a polypeptide of 1902 amino acids. the proteinase is n-terminally cleaved upon maturation. it shows extensive homology to the lactococcus lactis subsp. cremoris wg2 proteinase. similar to the situation in lactococcus, a maturation gene was found upstream of the proteinase ... | 1992 | 1512565 |
| characterization of lactococcus lactis phage antigens. | phage phi 197 is representative of a widespread lactococcal phage group characterized by a particular morphology (prolate head with a noncontractile tail). in order to develop an immunoenzymatic phage detection test, fusion proteins containing beta-galactosidase fused to epitopes of phage phi 197 structural proteins were constructed by cloning random dna fragments from the phage genome upstream of a lacz gene on a plasmid vector. recombinant plasmids containing certain fragments encoded the synt ... | 1992 | 1514794 |
| 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 |
| [isolation of nisin from native solution and its purification on cationites]. | it was found possible to use organic sorbents and in particular carboxylic cationites for isolation of nisin from the fermentation broth filtrate and its purification. nisin is known as a polypeptide antibiotic applied as a preservative. the sorbents were shown to have high exchange capacities by the isolated substance and mechanical strength and resistance. they also proved to be highly stable. | 1992 | 1514869 |
| 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 |
| proteinase overproduction in lactococcus lactis strains: regulation and effect on growth and acidification in milk. | multicopy plasmids that contained the complete of 3'-deleted forms of the proteinase (prtp) gene of lactococcus lactis subsp. cremoris sk11 under the control of different promoters were constructed and introduced into prt- lactococcal strains. the production and location of the sk11 proteinase was determined in different hosts grown in industrial and laboratory media. in spite of the 10-fold-higher copy number of the prt genes, no overproduction of proteinase was observed in strain sk1128, a prt ... | 1992 | 1539995 |
| antagonism between listeria monocytogenes and lactococci during fermentation of products from ultrafiltered skim milk. | tyndallized samples of unfiltered skim milk and retentate (concentrated fivefold or twofold by volume) and permeate from uf skim milk were inoculated with 5.5 x 10(3) to 1.5 x 10(5) cfu/ml of listeria monocytogenes strains california or v7 together with 4 x 10(7) to 2.3 x 10(8) cfu/ml of mesophilic lactic acid bacteria. numbers of l. monocytogenes (mcbride listeria agar) and lactic acid bacteria (all purpose tween agar) were determined after 0, 6, 12, 24, 30, and 36 h of incubation at 30 degrees ... | 1992 | 1541740 |
| acidic phospholipids are required during solubilization of amino acid transport systems of lactococcus lactis. | the branched-chain amino acid transport system of lactococcus lactis was solubilized with n-octyl beta-d-gluco-pyranoside and reconstituted into proteoliposomes. transport activity was recovered only when solubilization was performed in the presence of acidic phospholipids. omission of acidic phospholipids during solubilization resulted in an inactive transport protein and the activity could not be restored in the reconstitution step. similar results have been obtained for the arginine/ornithine ... | 1992 | 1547262 |
| staphylococcal phosphoenolpyruvate-dependent phosphotransferase system: molecular cloning and nucleotide sequence of the staphylococcus carnosus ptsi gene and expression and complementation studies of the gene product. | a digoxigenin-labeled dna probe that was complementary to the gene ptsh and the beginning of the gene ptsi was used to clone a 3.2-kb hincii-bamhi restriction fragment containing the complete ptsi gene of staphylococcus carnosus. the restriction fragment was cloned in the antisense orientation to the lac promoter in the low-copy-number vector psu18. the nucleotide sequences of the ptsi gene, which encodes enzyme i (ec 2.7.3.9), and the corresponding flanking regions were determined. the primary ... | 1992 | 1551842 |
| zinc, a novel structural element found in the family of bacterial adenylate kinases. | the adk gene from bacillus stearothermophilus was cloned and overexpressed in escherichia coli under the control of the lac promoter. the primary structure of b. stearothermophilus adenylate kinase exhibited 76% identity with the enzyme from bacillus subtilis, 60% identity with the enzyme from lactococcus lactis, and 42% identity with the enzyme from e. coli. the most striking property of the adenylate kinase from b. stearothermophilus is the presence of a structural zinc atom bound to four cyst ... | 1992 | 1554691 |
| gene expression in lactococcus lactis. | lactic acid bacteria are of major economic importance, as they occupy a key position in the manufacture of fermented foods. a considerable body of research is currently being devoted to the development of lactic acid bacterial strains with improved characteristics, that may be used to make fermentations pass of more efficiently, or to make new applications possible. therefore, and because the lactococci are designated 'gras' organisms ('generally recognized as safe') which may be used for safe p ... | 1992 | 1558766 |
| sequence of a gene (lap) encoding a 95.3-kda aminopeptidase from lactococcus lactis ssp. cremoris wg2. | a gene (lap) coding for a lactococcus lactis ssp. cremoris wg2 aminopeptidase was cloned from genomic libraries of size-fractionated lactococcal dna. the 5' end of the lap gene was isolated by using a polymerase chain reaction hybridization probe of 77 nucleotides (nt) synthesized from two degenerate primers derived from the n-terminal amino acid (aa) sequence of the lactococcal lysine-aminopeptidase (lap). the remaining part(s) of the gene were recovered by a search for overlapping sequences in ... | 1992 | 1563625 |
| the efflux of a fluorescent probe is catalyzed by an atp-driven extrusion system in lactococcus lactis. | many bacteria, both gram positive and gram negative, extrude in an energy-dependent manner the fluorescent ph indicator 2',7'-bis-(2-carboxyethyl)-5[and -6]-carboxyfluorescein (bcecf) (d. molenaar, t. abee, and w. n. konings, biochim. biophys. acta 1115:75-83, 1991). this efflux was studied in detail in lactococcus lactis, and several indications that a transport system is involved were found. this transport system is most likely driven by atp or a related compound. the evidence is that bcecf ex ... | 1992 | 1577684 |
| 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 |
| cloning, sequencing, and expression in escherichia coli of lcnb, a third bacteriocin determinant from the lactococcal bacteriocin plasmid p9b4-6. | on the bacteriocin plasmid p9b4-6 of lactococcus lactis subsp. cremoris 9b4, a third bacteriocin determinant was identified. the genes encoding bacteriocin production and immunity resided on a 1.2-kb celii-scai fragment and were located adjacent to one of two previously identified bacteriocin operons (m. j. van belkum, b. j. hayema, r. e. jeeninga, j. kok, and g. venema, appl. environ. microbiol. 57:492-498, 1991). the fragment was sequenced and analyzed by deletion and mutation analyses. the ba ... | 1992 | 1610182 |
| the plasmid-encoded lactococcal envelope-associated proteinase is encoded by a chromosomal gene in lactococcus lactis subsp. cremoris bc101. | the plasmid-free strain lactococcus lactis subsp. cremoris bc101 produced an extracellular proteinase physicochemically similar to the proteinase encoded by the plasmid-linked prtp gene of other lactococcal strains. the absence of detectable plasmids in strain bc101 indicated that the prtp proteinase gene may be chromosomally located. the chromosomal linkage of the prtp proteinase gene in bc101 was confirmed by pulsed-field electrophoresis of chromosomal dna and hybridization, using as a probe t ... | 1992 | 1610200 |
| lactococcus lactis release from calcium alginate beads. | cell release during milk fermentation by lactococcus lactis immobilized in calcium alginate beads was examined. numbers of free cells in the milk gradually increased from 1 x 10(6) to 3 x 10(7) cfu/ml upon successive reutilization of the beads. rinsing the beads between fermentations did not influence the numbers of free cells in the milk. cell release was not affected by initial cell density within the beads or by alginate concentration, although higher acidification rates were achieved with in ... | 1992 | 1622208 |
| 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 |
| rapid genomic fingerprinting of lactococcus lactis strains by arbitrarily primed polymerase chain reaction with 32p and fluorescent labels. | arbitrarily primed polymerase chain reaction, with incorporation of either radioactive or fluorescent labels, was used as a rapid and sensitive method for obtaining genomic fingerprints of strains of lactococcus lactis. closely related strains produced almost identical fingerprints. fingerprints of other strains showed only some similarities. | 1992 | 1622250 |
| 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 |
| the effect of resuscitation and the incubation-temperature on recovery of uninjured, heat injured and freeze injured enterococci. | five strains of enterococci were inoculated on the slanetz and bartley enterococcus agar (ea), and incubated at 37 degrees c and 44 degrees c following: no injury, heat-injury and freeze-injury. the experiments were repeated introducing a 2 h resuscitation step in tryptic soy agar (tsa) at 37 degrees c and subsequent overlay with ea (tsa/ea) followed by incubation at both 37 degrees c and 44 degrees c. the tsa/ea method gave a significantly better recovery (1% confidence level) than the ea metho ... | 1992 | 1622754 |
| 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 |
| an investigation of dye reduction by food-borne bacteria. | the rates of reduction of seven redox dyes by 13 bacterial strains were measured and found to vary greatly between different bacterium/dye combinations. phenazine ethosulphate and toluidine blue were the most rapidly reduced dyes by the majority of bacteria and resorufin and 2-hydroxy-1,4-naphthoquinone were reduced slowly, if at all. there was also considerable variation in the rates of reduction with any single dye/organism combination. glucose stimulated the rates of endogenous dye reduction ... | 1992 | 1644703 |
| phage dna synthesis and host dna degradation in the life cycle of lactococcus lactis bacteriophage c6a. | bacteriophage c6a is a lytic phage that infects strains of lactococcus lactis. infection of l. lactis strain c6 resulted in inhibition of culture growth within 10 min, mature intracellular phage particles appeared after 17.5 min, and cell lysis occurred after 25 min. a culture of strain c6 carrying 3h-labelled dna was infected with c6a, and the fate of the radiolabel was monitored. the results showed that degradation of host cell dna began within 6 min of infection and that the breakdown product ... | 1992 | 1645131 |
| 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 |
| lactose metabolism by staphylococcus aureus: characterization of lacabcd, the structural genes of the tagatose 6-phosphate pathway. | the nucleotide and deduced amino acid sequences of the laca and lacb genes of the staphylococcus aureus lactose operon (lacabcdfeg) are presented. the primary translation products are polypeptides of 142 (mr = 15,425) and 171 (mr = 18,953) amino acids, respectively. the lacabcd loci were shown to encode enzymes of the tagatose 6-phosphate pathway through both in vitro studies and complementation analysis in escherichia coli. a serum aldolase assay, modified to allow detection of the tagatose 6-p ... | 1991 | 1655695 |
| 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 |
| molecular cloning and sequence analysis of the x-prolyl dipeptidyl aminopeptidase gene from lactococcus lactis subsp. cremoris. | lactococcus lactis subsp. cremoris p8-2-47 contains an x-prolyl dipeptidyl aminopeptidase (x-pdap; ec 3.4.14.5). a mixed-oligonucleotide probe prepared on the basis of the n-terminal amino acid sequence of the purified protein was made and used to screen a partial chromosomal dna bank in escherichia coli. a partial xbai fragment cloned in puc18 specified x-pdap activity in e. coli clones. the fragment was also able to confer x-pdap activity on bacillus subtilis. the fact that none of these organ ... | 1991 | 1674655 |
| 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 |
| characterization and overexpression of the lactococcus lactis pepn gene and localization of its product, aminopeptidase n. | the chromosomal pepn gene encoding lysyl-aminopeptidase activity in lactococcus lactis has been identified in a lambda embl3 library in escherichia coli by using an immunological screening with antiserum against a purified aminopeptidase fraction. the pepn gene was localized and subcloned in e. coli on the basis of its expression and hybridization to a mixed-oligonucleotide probe for the previously determine n-terminal amino acid sequence of lysyl-aminopeptidase (p. s. t. tan and w. n. konings, ... | 1991 | 1685079 |
| differentiation of lactococci by rrna gene restriction analysis. | strains of the subspecies of lactococcus lactis could be differentiated by rrna gene restriction fragment length polymorphisms (rflp). 16s rrna-specific oligonucleotide as well as polynucleotide dna probes were used for the detection of restriction fragments. in addition, a site-specific probe was designed for the intergenic spacer region of 23s and 5s rrna genes. for all lactococcal strains the putative presence of six rrna operons was confirmed. a non-radioactive hybridization assay was used b ... | 1991 | 1687138 |
| 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 |
| development and application of oligonucleotide probes for identification of lactococcus lactis subsp. cremoris. | lactococcus lactis subsp. cremoris is of considerable interest to the dairy industry, which relies upon the few available strains for the manufacture of cheddar cheese free of fermented and fruity flavors. the subspecies cremoris differs from related subspecies by the lack of a few phenotypic traits. our purpose was to identify unique rrna sequences that could be used to discriminate l. lactis subsp. cremoris from related subspecies. the 16s rrnas from 13 lactococcus strains were partially seque ... | 1991 | 1713027 |
| a possible contribution of mrna secondary structure to translation initiation efficiency in lactococcus lactis. | gene expression signals derived from lactococcus lactis were linked to lacz-fused genes with different 5'-nucleotide sequences. computer predictions of mrna secondary structure were combined with lacz expression studies to direct base-substitutions that could possibly influence gene expression. mutations were made such that the dna sequence upstream of the atg start codon was not changed. moreover, care was taken that the substitutions, which were all within the first six codons, neither affecte ... | 1991 | 1715834 |
| heat shock induces thermotolerance and inhibition of lysis in a lysogenic strain of lactococcus lactis. | in this preliminary work, the heat shock response of lactic acid bacteria was investigated and characterized. log-phase lactococcus lactis cells pre-incubated at 40 degrees c before heat challenge at 52 degrees c for 30 min demonstrated increased thermotolerance as compared with cells pre-incubated at 30 degrees c. the response persisted for at least 60 min. additionally, we demonstrated that: (i) the physiological expression of the heat shock response is temperature dependent; (ii) ethanol 4.0% ... | 1991 | 1742167 |
| the bacteriocin lactococcin a specifically increases permeability of lactococcal cytoplasmic membranes in a voltage-independent, protein-mediated manner. | lactococcin a is a bacteriocin produced by lactococcus lactis. its structural gene has recently been cloned and sequenced (m. j. van belkum, b. j. hayema, r. e. jeeninga, j. kok, and g. venema, appl. environ. microbiol. 57:492-498, 1991). purified lactococcin a increased the permeability of the cytoplasmic membrane of l. lactis and dissipated the membrane potential. a significantly higher concentration of lactococcin a was needed to dissipate the membrane potential in an immune strain of l. lact ... | 1991 | 1744049 |
| microbiological analysis and starter culture growth in retentates. | pasteurized skim milk was concentrated by uf to 2-, 4-, and 5-fold. the retentates were evaluated for microbiological quality, heat treatments to inactivate microorganisms, and lactic acid bacterial starter culture activity. aerobic mesophilic bacterial counts in raw milk decreased from an initial 1.4 x 10(6) to 3.9 x 10(2) cfu/ml after pasteurization. during uf, counts increased from 3.9 x 10(2) cfu/ml uf, counts increased from 3.9 x 10(2) cfu/ml in pasteurized milk to 1.4 x 10(3), 1.4 x 10(4), ... | 1991 | 1744259 |