PMID(sorted descending)
membrane topology of the sodium ion-dependent citrate carrier of klebsiella pneumoniae. evidence for a new structural class of secondary transporters.the predicted secondary structure model of the sodium ion-dependent citrate carrier of klebsiella pneumoniae (cits) presents the 12-transmembrane helix motif observed for many secondary transporters. biochemical evidence presented in this paper is not consistent with this model. n-terminal and c-terminal fusions of cits with the biotin acceptor domain of the oxaloacetate decarboxylase of k. pneumoniae catalyze citrate transport, showing the correct folding of the cits part of the fusion proteins ...19968810332
sequence analysis and identification of the pyrkdbf operon from lactococcus lactis including a novel gene, pyrk, involved in pyrimidine biosynthesis.three genes encoding enzymes involved in the biosynthesis of pyrimidines have been found to constitute an operon in lactococcus lactis. two of the genes are the well-known pyr genes pyrdb and pyrf, encoding dihydroorotate dehydrogenase and orotidine monophosphate decarboxylase, respectively. the third gene encodes a protein which was shown to be necessary for the activity of the pyrdb-encoded dihydroorotate dehydrogenase; we propose to name the gene pyrk. the pyrk-encoded protein is homologous t ...19968759867
[isolation and reassociation of acetogen and methanogen in a syntrophobic coculture degrading butyrate anaerobically].anaerobic coculture bf2 which degraded butyrate into acetate and produced methane was isolated from granular methanogenic sludge. the coculture is associated syntrophically the syntrophomonas subsp. saponavida strain cf2 with methanobacterium formicicum strain mf2 and appeared to degraded c4 approximately c18 fatty acids including isobutyrate. the optimal temperature and ph for growth was 37 degrees c and 7.7 respectively. the strain cf2 was obtained in pure culture with crotonate as substrate a ...19958745550
nucleotide sequence and analysis of pwc1, a pc194-type rolling circle replicon in lactococcus lactis.a 2.8-kb cryptic plasmid showing no homology to either pfx3 (rolling circle, pe194-type) or pci305 (theta-type) lactococcal replicons was identified in lactococcus lactis subsp. cremoris 2204. the plasmid, pwc1, was compatible with both pci3340 (a pci305 derivative) and pfx3 in l. lactis subsp. cremoris 2204. sequence analysis of pwc1 showed one major orf encoding a protein with a deduced size of 316 amino acids (aa). database comparisons showed that the protein was distinct from the pfx- and pc ...19968700966
nisin z, mutant nisin z and lacticin 481 interactions with anionic lipids correlate with antimicrobial activity. a monolayer study.monomolecular layers of lipids at the air/water interface have been used as a model membrane to study membrane interactions of the lantibiotic nisin. the natural lantibiotics nisin a and nisin z proved to have a high affinity for the anionic lipids phosphatidylglycerol and bis(phosphatidyl)glycerol (cardiolipin). the interaction with zwitterionic phopholipids or neutral lipids is very low at surface pressures higher than 32 mn/m. nisin, nisin mutants and lacticin 481 show a remarkable correlatio ...19968631341
identical transcriptional control of the divergently transcribed prtp and prtm genes that are required for proteinase production in lactococcus lactis sk11.we have investigated transcriptional regulation of the divergently transcribed genes required for proteinase production (prtp and prtm) of lactococcus lactis sk11. their promoters partially overlap and are arranged in a face-to-face configuration. the medium-dependent activities of both prtp and prtm promoters were analyzed by quantitative primer extension studies and beta-glucuronidase assays with l. lactis mg1363 cells harboring transcriptional gene fusions of each promoter with the promoterle ...19968626277
the ribonucleotide reductase system of lactococcus lactis. characterization of an nrdef enzyme and a new electron transport protein.escherichia coli contains the genetic information for three separate ribonucleotide reductases. two of them (class i enzymes), coded by the nrdab and nrdef genes, respectively, contain a tyrosyl radical, whose generation requires oxygen. the nrdab enzyme is physiologically active. the function of the nrdef gene is not known. the third enzyme (class iii), coded by nrddg, operates during anaerobiosis. the dna of lactococcus lactis contains sequences homologous to the nrddg genes. surprisingly, an ...19968621514
the reca gene of lactococcus lactis: characterization and involvement in oxidative and thermal stress.the role of reca in lactococcus lactis, a microaerophilic fermenting organism, was examined by constructing a reca-disrupted strain. this single alteration had a surprisingly pleiotropic effect. in addition to its roles in homologous recombination and dna repair, reca is also involved in responses to oxygen and heat stresses. we found that oxygen stress induced by aeration causes reductions in growth and stationary-phase survival of the reca strain. toxicity is a consequence of hydroxyl radical ...19958594331
purification, crystallization, and preliminary x-ray analysis of pepx, an x-prolyl dipeptidyl aminopeptidase from lactococcus lactis.the x-prolyl dipeptidyl aminopeptidase pepx, a serine peptidase isolated originally from lactococcus lactis subsp lactis ncdo 763, was cloned and overproduced in escherichia coli. the enzyme was isolated in its active form in two purification steps. crystals of pepx were grown by the hanging drop vapor diffusion method using polyethyleneglycol 4000 as precipitant at ph 5.0. the crystals are orthorhombic with cell dimensions a = 92.8 a, b = 102.6 a, and c = 101.6 a, space group p2(1)2(1)2, and pr ...19958592708
reca gene involvement in oxidative and thermal stress in lactococcus lactis.the reca gene is best known for its effects on homologous recombination and dna repair via sos induction. there is gathering evidence that reca also affects expression of genes associated with different types of stress. we studied reca properties in lactococcus lactis by generating a reca-disrupted mutant of mg1363 and comparing it with the wild type strain. reca appears to have an important role in cell survival upon oxygen or thermal stress, in addition to its conserved role in dna repair. oxy ...19958586217
two genes present on a transposon-like structure in lactococcus lactis are involved in a clp-family proteolytic activity.the lactose-protease plasmid pucl22 of lactococcus lactis subsp. lactis strain cnrz270 contained two inverted copies of is 1076 flanking a region of 3.7 kb. this internal region was sequenced and found to contain two large open reading frames, orf1 and orfp in opposite orientations. orf1 consists of 2289 bp; the deduced 763-amino-acid sequence is similar to the atpases of the clpa family. it contains two well-conserved consensus atp-binding sites. it was named clpl. orfp consists of 930 bp encod ...19938387149
sequence analysis of the lysin gene region of the prolate lactococcal bacteriophage c2.approximately 80% of the genome of the prolate-headed lactococcal bacteriophage c2 was cloned into shuttle vectors psa3 and pfx3 in escherichia coli and transferred to lactococcus lactis. a 1.67-kilobase ecorv fragment containing the gene for the phage lysin was identified and the position and orientation of the phage lysin gene in the physical map of the phage were determined. the phage lysin was expressed in e. coli and its sequence was determined and compared with the sequences of other bacte ...19938221377
the di- and tripeptide transport protein of lactococcus lactis. a new type of bacterial peptide transporter.lactococcus lactis takes up di- and tripeptides via a proton motive force-dependent carrier protein. the gene (dtpt) encoding the di-tripeptide transport protein of l. lactis was cloned by complementation of a dipeptide transport-deficient and proline auxotrophic escherichia coli strain. functional expression of the dipeptide transport gene was demonstrated by uptake studies of alanyl-[14c]glutamate and other peptides in e. coli cells. the di-tripeptide transport protein catalyzes proton motive ...19948157671
identification and characterization of genes involved in excision of the lactococcus lactis conjugative transposon tn5276.the 70-kb transposon tn5276, originally detected in lactococcus lactis nizo r5 and carrying the genes for nisin production and sucrose fermentation, can be conjugally transferred to other l. lactis strains. sequence analysis and complementation studies showed that the right end of tn5276 contains two genes, designated xis and int, which are involved in excision. the 379-amino-acid int gene product shows high (up to 50%) similarity with various integrases, including that of the tn916-related conj ...19948157585
two different dihydroorotate dehydrogenases in lactococcus lactis.the pyrimidine de novo biosynthesis pathway has been characterized for a number of organisms. the general pathway consists of six enzymatic steps. in the characterization of the pyrimidine pathway of lactococcus lactis, two different pyrd genes encoding dihydroorotate dehydrogenase were isolated. the nucleotide sequences of the two genes, pyrda and pyrdb, have been determined. one of the deduced amino acid sequences has a high degree of homology to the saccharomyces cerevisiae dihydroorotate deh ...19948021180
cloning, sequencing and characterization of the pepip gene encoding a proline iminopeptidase from lactobacillus delbrueckii subsp. bulgaricus cnrz 397.the proline iminopeptidase (pepip) of lactobacillus delbrueckii subsp. bulgaricus is a major peptidase located in the cell envelope. its structural gene (pepip) has been cloned into puc18 and expressed at a very high level in escherichia coli to give a pepip activity 15,000-fold higher than that found in l. delbrueckii subsp. bulgaricus. the nucleotide sequence of the pepip gene revealed an open reading frame of 295 codons encoding a protein with a predicted m(r) of 33,006, which is consistent w ...19948012575
controlled expression and structural organization of a lactococcus lactis bacteriophage lysin encoded by two overlapping genes.the phi vml3 bacteriophage lysin is specific for lactococci and could be used to promote enzyme release during cheese manufacture. the level of lysin expression from the cloned gene using its own upstream sequences is very low. expression in escherichia coli by using a synthetic hybrid lysin gene and a series of bal 31 deletions of the original cloned dna fragment suggested that the start of the gene had previously been incorrectly assigned. reevaluation of homology between the lysin and bacillu ...19947944354
expression, purification, and characterization of thymidylate synthase from lactococcus lactis.the thymidylate synthase (ts) gene from lactococcus lactis has been highly expressed in escherichia coli. the ts protein was purified by sequential chromatography on q-sepharose and phenyl-sepharose. six grams of cell pellet yielded 140 mg of homogeneous ts. ts is a highly conserved enzyme, and several of the conserved amino acid residues that have been implicated in catalytic function are altered in l. lactis ts. by use of a 3-dimensional homology model, we have predicted covariant changes that ...19947920258
molecular cloning and nucleotide sequence of the gene encoding the major peptidoglycan hydrolase of lactococcus lactis, a muramidase needed for cell separation.a gene of lactococcus lactis subsp. cremoris mg1363 encoding a peptidoglycan hydrolase was identified in a genomic library of the strain in puc19 by screening escherichia coli transformants for cell wall lysis activity on a medium containing autoclaved, lyophilized micrococcus lysodeikticus cells. in cell extracts of l. lactis mg1363 and several halo-producing e. coli transformants, lytic bands of similar sizes were identified by denaturing sodium dodecyl sulfate (sds)-polyacrylamide gels contai ...19957883712
two lactococcus lactis genes, including lacx, cooperate to trigger an sos response in a reca-negative background.a 4.3-kb ecori fragment from a lactococcus lactis genomic library alleviates the methyl methanesulfonate, mitomycin c, and uv sensitivities of an escherichia coli reca mutant (m. novel, x. f. huang, and g. novel, fems microbiol. lett. 72:309-314, 1990). it complements reca1 and delta reca mutations but not reca13. three proteins (with molecular masses of 20, 35, and 23 kda) were produced from this fragment in a t7-directed system, and three corresponding genes were detected by dna sequencing, na ...19957814316
genes involved in immunity to the lantibiotic nisin produced by lactococcus lactis 6f3.the lantibiotic nisin is produced by several strains of lactococcus lactis. the complete gene cluster for nisin biosynthesis in l. lactis 6f3 comprises 15 kb of dna. as described previously, the structural gene nisa is followed by the genes nisb, nist, nisc, nisi, nisp, nisr, and nisk. further analysis revealed three additional open reading frames, nisf, nise, and nisg, adjacent to nisk. approximately 1 kb downstream of the nisg gene, three open reading frames in the opposite orientation have be ...19957793910
medium-dependent regulation of proteinase gene expression in lactococcus lactis: control of transcription initiation by specific dipeptides.transcriptional gene fusions with the escherichia coli beta-glucuronidase gene (gusa) were used to study the medium- and growth-dependent expression of the divergently transcribed genes involved in proteinase production (prtp and prtm) of lactococcus lactis sk11. the results show that both the prtp and prtm genes are controlled at the transcriptional level by the peptide content of the medium and, to a lesser extent, by the growth rate. a more than 10-fold regulation in beta-glucuronidase activi ...19957768792
cloning and nucleotide sequencing of l-lactate dehydrogenase gene from streptococcus thermophilus m-192.the gene encoding l-lactate dehydrogenase (ldh) was cloned from an industrial dairy strain of streptococcus thermophilus m-192 using a synthetic oligonucleotide probe based on the n-terminal amino acid sequence of the purified enzyme, and its nucleotide sequence was determined. the enzyme was deduced to have 328 amino acid residues with a molecular weight of 35,428 and found to have high sequence similarity to ldhs from other lactic acid bacteria (89.0% to streptococcus mutans, 76.3% to lactococ ...19947765475
a family of bacteriocin abc transporters carry out proteolytic processing of their substrates concomitant with export.lantibiotic and non-lantibiotic bacteriocins are synthesized as precursor peptides containing n-terminal extensions (leader peptides) which are cleaved off during maturation. most non-lantibiotics and also some lantibiotics have leader peptides of the so-called double-glycine type. these leader peptides share consensus sequences and also a common processing site with two conserved glycine residues in positions -1 and -2. the double-glycine-type leader peptides are unrelated to the n-terminal sig ...19957565085
the cellular location and effect on nisin immunity of the nisi protein from lactococcus lactis n8 expressed in escherichia coli and l. lactis.lactococcus lactis cells secreting the lantibiotic nisin, commercially used for food preservation, must protect their cell membrane against the pore-forming activity of extracellular nisin. the nisi gene product has been suggested to be a lipoprotein, which due to the location on the extracellular surface would be an ideal candidate for an immunity protein. in vivo labelling of nisi from l. lactis n8 expressed in escherichia coli proved that nisi is a lipoprotein. expression of nisi in the nisin ...19957557313
transformation of lactococcus by electroporation. 19957550735
evidence for a large dispensable segment in the subtilisin-like catalytic domain of the lactococcus lactis cell-envelope proteinase.the lactococcus lactis sk11 cell-envelope proteinase contains various inserts, located in external loops of the catalytic domain compared with related subtilisins. in this study, protein engineering was employed to determine the function of the largest loop insertion (residues 238-388) relative to the subtilisin structure. by site-directed mutagenesis we have deleted the fragment of the proteinase gene encoding these 151 residues and analyzed the mutant delta 238-388 proteinase for activity, (au ...19947528919
physiological and genetic regulation of rrna synthesis in lactococcus.the macromolecular composition of lactococcus was regulated by growth rate in the same general way as that of less fastidious bacteria such as escherichia coli and salmonella typhimurium. the ratios of rna:dna and rna:protein increased approximately threefold over a 13.5-fold increase in growth rate, whereas the ratio of dna:protein remained approximately constant. using reporter genes fused to a dna fragment of a cloned lactococcal rrna operon, promoter activity was located upstream of the 16s ...19937504067
improvement of solubility and stability of the antimicrobial peptide nisin by protein engineering.nisin is a 3.4-kda antimicrobial peptide that, as a result of posttranslational modifications, contains unsaturated amino acids and lanthionine residues. it is applied as a preservative in various food products. the solubility and stability of nisin and nisin mutants have been studied. it is demonstrated that nisin mutants can be produced with improved functional properties. the solubility of nisin a is highest at low ph values and gradually decreases by almost 2 orders of magnitude when the ph ...19957487019
radiosensitization of hypoxic bacterial cells by nitroimidazoles of low lipophilicity: steady-state and rapid-mix studies. 19816782616
evaluation of the direct epifluorescent filter technique for assessing the hygienic condition of milking equipment.the hygienic condition of 6 milking installations, 3 sanitized by circulation cleaning (cc) with chlorine-based chemicals and 3 by flushing with acidified boiling water (abw), was tested using rinses of quarter strength ringer's solution. the bacterial content of the rinses was determined using both colony counts and the direct epifluorescent filter technique (deft). a comparison of testing methods gave correlation coefficients between colony count and deft of 0.82 for plants using cc and 0.46 f ...19836341424
[laboratory diagnosis of mastitis]. 19724628197
comparative resistance of nonsporogenic bacteria to low-temperature gamma irradiation.a total of 36 microorganisms, comprising 19 species of 11 genera, were screened for radiation resistance with (60)co gamma rays at a radiation temperatore of -80 +/- 2 c in phosphate buffer (ph 7.0) under vacuum. micrococcus radiodurans was the most resistant organism. an initial population of 2.8 x 10(5) cells per dose of this species survived 2.4 but not 2.7 mrad. of the remaining 18 species with initial populations of about 10(6) cells per dose, streptococcus faecium survived 0.9 to 1.5 mrad, ...19734572982
herd incidence of bovine mastitis in four danish dairy districts. i. the prevalence and mastitogenic effect of micro-organisms in the mammary glands of cows. 19744213559
molecular and genetic characterization of lactose-metabolic genes of streptococcus cremoris.lac+ plasmid dna from streptococcus cremoris h2 was subcloned with an escherichia coli vector on a 3.5-kilobase-pair psti-avai fragment. genetic analysis of the cloned dna was possible because linear lac+ dna fragments were productive in the s. sanguis transformation system. complementation of s. sanguis lac-mutants showed that the 3.5-kilobase-pair fragment included the structural gene for 6-phospho-beta-d-galactosidase and either enzyme ii-lac or factor iii-lac of the lactose-specific phosphoe ...19863091581
cloning, expression and location of the streptococcus lactis gene for phospho-beta-d-galactosidase.genes for lactose catabolism and proteinase production in streptococcus lactis 712 are encoded by a 56.5 kb metabolic plasmid, plp712. a lactose mini-plasmid of only 23.7 kb, pmg820, was constructed by introducing two deletions into plp712, and was cloned as two segments of dna into the escherichia coli vector pat153 using restriction endonuclease psti. the lactose genetic region of plp712, which has been defined by deletion and restriction mapping, was cut into two parts by this process. when t ...19863086494
the cytochrome c oxidase test for the rapid detection of psychrotrophic bacteria in milk.a new, rapid, simple and cheap method for the detection of the predominant psychrotrophic bacteria in raw and pasteurized milks is described, using tetramethyl-p-phenylene-diamine dihydrochloride to detect cytochrome c oxidase which in general is not present in the non-psychrotrophic bacterial milk flora. the test is sensitive to samples containing over 10(4) organisms/ml. correlation coefficients of 0.92 and 0.84 between dye oxidation and viable counts for pasteurized and raw milk samples, resp ...19852995302
cloning and characterization of the tetracycline resistance determinant of and several promoters from within the conjugative transposon tn919.tn919 is a 15- to 16-kilobase (kb) tetracycline resistance conjugative transposon that was originally isolated from streptococcus sanguis fc1. the tetracycline resistance determinant (tet) was found on a 4.2-kb hindii fragment by in vitro deletion analysis. this fragment was subcloned to a pwv01 origin capable of directing replication in escherichia coli, bacillus subtilis, and streptococcus lactis, and expression was observed in all three genera. in all cases, expression was weaker when only th ...19882839111
functional reconstitution of prokaryote and eukaryote membrane proteins.a new strategy for the functional reconstitution of membrane proteins is described. this approach introduces a new class of protein stabilizing agents--osmolytes--whose presence at high concentration (10-20%) during detergent solubilization prevents the inactivations that normally occur when proteins are extracted from natural membranes. osmolytes that act in this way include compounds such as glycerol and higher polyols (erythritol, xylitol, sorbitol), sugars (glucose, trehalose), and certain a ...19892492790
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 ...19902389931
characterization of the lactose-specific enzymes of the phosphotransferase system in lactococcus lactis.the plasmid-encoded lactose genes of the lactococcus lactis phosphotransferase system encoding enzyme iiilac (lacf) and enzyme iilac (lace) have been identified and cloned in escherichia coli and l. lactis. nucleotide sequence and transcription analysis showed that these genes are organized into a lactose-inducible operon with the gene order lacf-lace-lacg-lacx, the latter two genes encoding phospho-beta-galactosidase and a 34-kda protein with an unknown function, respectively. the lac-operon is ...19902125052
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 ...19902123812
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 ...19902120234
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 ...19902117878
isolation, sequence and expression in escherichia coli, bacillus subtilis and lactococcus lactis of the dnase (streptodornase)-encoding gene from streptococcus equisimilis h46a.a partial library of bcli-generated chromosomal dna fragments from streptococcus equisimilis h64a (lancefield group c) was constructed in escherichia coli. clones displaying either streptokinase or deoxyribonuclease (streptodornase; sdc) activities were isolated. the gene (sdc) expressing the sdc activity was allocated on the 1.1-kb acci dna subfragment. sequence analysis of this dna fragment revealed the presence of one open reading frame, which could encode a protein of 36.8 kda. the n-termina ...19911937032
lactococcal proteinase maturation protein prtm is a lipoprotein.the production of enzymatically active proteinase by lactococci requires the joint presence of a proteinase gene, prtp, and a gene encoding a maturation protein, prtm. a 32-kda protein produced by escherichia coli upon expression of the prtm gene under the direction of the t7 rna polymerase promoter was purified and used to obtain prtm-specific antibodies. with these antibodies, immunogold labeling of lactococcal cells revealed that prtm was associated with the lactococcal cell envelope. western ...19911906066
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, ...19911685079
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, and the corresponding flanking regions were determined. the primary ...19921551842
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 ...19921514794
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 ...19921500184
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 ...19921460009
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 ...19921447185
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 ...19921406586
effect of lipophilicity of nitroimidazoles on radiosensitization of hypoxic bacterial cells in vitro.the effect of radiosensitization of hypoxic bacterial cells by 9 nitroimidazoles was measured in the bacterial strains e. coli ab 1157 and s. lactis 712. seven of these compounds were similar to misonidazole in their redox properties, but differed widely in their lipophilicites. the dependence of sensitization enhancement on reduction potential was similar to that reported in mammalian cells. the efficiency of sensitization was similar for compounds of low lipophilicity, but increased if the oct ...1979109112
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