| biofilms on indwelling urethral catheters produce quorum-sensing signal molecules in situ and in vitro. | acylated homoserine lactones (ahls) are chemical signals that mediate population density-dependent (quorum-sensing) gene expression in numerous gram-negative bacteria. in this study, gram-negative bacilli isolated from catheters were screened for ahl production by a cross-feeding assay utilizing an ahl-responsive agrobacterium tumefaciens reporter strain. positive reactions were obtained from 14 isolates of pseudomonas aeruginosa; negative or weakly positive reactions were recorded for isolates ... | 1998 | 9726901 |
| aerobic anoxygenic phototrophic bacteria. | the aerobic anoxygenic phototrophic bacteria are a relatively recently discovered bacterial group. although taxonomically and phylogenetically heterogeneous, these bacteria share the following distinguishing features: the presence of bacteriochlorophyll a incorporated into reaction center and light-harvesting complexes, low levels of the photosynthetic unit in cells, an abundance of carotenoids, a strong inhibition by light of bacteriochlorophyll synthesis, and the inability to grow photosynthet ... | 1998 | 9729607 |
| expression of the yeast fre genes in transgenic tobacco. | two yeast genes, fre1 and fre2 (encoding fe(iii) reductases) were placed under the control of the cauliflower mosaic virus 35s promoter and introduced into tobacco (nicotiana tabacum l.) via agrobacterium tumefaciens-mediated transformation. homozygous lines containing fre1, fre2, or fre1 plus fre2 were generated. northern-blot analyses revealed mrna of two different sizes in fre1 lines, whereas all fre2 lines had mrna only of the expected length. fe(iii) reduction, chlorophyll contents, and fe ... | 1998 | 9733525 |
| the h+-sucrose cotransporter ntsut1 is essential for sugar export from tobacco leaves | in many species translocation of sucrose from the mesophyll to the phloem is carrier mediated. a sucrose/h+-symporter cdna, ntsut1, was isolated from tobacco (nicotiana tabacum) and shown to be highly expressed in mature leaves and at low levels in other tissues, including floral organs. to study the in vivo function of ntsut1, tobacco plants were transformed with a sut1 antisense construct under control of the cauliflower mosaic virus 35s promoter. upon maturation, leaves of transformants expre ... | 1998 | 9733526 |
| expression patterns conferred by tyrosine/dihydroxyphenylalanine decarboxylase promoters from opium poppy are conserved in transgenic tobacco. | opium poppy (papaver somniferum) contains a large family of tyrosine/dihydroxyphenylalanine decarboxylase (tydc) genes involved in the biosynthesis of benzylisoquinoline alkaloids and cell wall-bound hydroxycinnamic acid amides. eight members from two distinct gene subfamilies have been isolated, tydc1, tydc4, tydc6, tydc8, and tydc9 in one group and tydc2, tydc3, and tydc7 in the other. the tydc8 and tydc9 genes were located 3.2 kb apart on one genomic clone, suggesting that the family is clust ... | 1998 | 9733527 |
| characterization of lemir, a root-knot nematode-induced gene in tomato with an encoded product secreted from the root. | a tomato gene that is induced early after infection of tomato (lycopersicon esculentum mill.) with root-knot nematodes (meloidogyne javanica) encodes a protein with 54% amino acid identity to miraculin, a flavorless protein that causes sour substances to be perceived as sweet. this gene was therefore named lemir (l. esculentum miraculin). sequence similarity places the encoded protein in the soybean trypsin-inhibitor family (kunitz). lemir mrna is found in root, hypocotyl, and flower tissues, wi ... | 1998 | 9733543 |
| isolation and characterization of a histidine biosynthetic gene in arabidopsis encoding a polypeptide with two separate domains for phosphoribosyl-atp pyrophosphohydrolase and phosphoribosyl-amp cyclohydrolase. | phosphoribosyl-atp pyrophosphohydrolase (pra-ph) and phosphoribosyl-amp cyclohydrolase (pra-ch) are encoded by his4 in yeast and by hisie in bacteria and catalyze the second and the third step, respectively, in the histidine biosynthetic pathway. by complementing a hisi mutation of escherichia coli with an arabidopsis cdna library, we isolated an arabidopsis cdna (at-ie) that possesses these two enzyme activities. the at-ie cdna encodes a bifunctional protein of 281 amino acids with a calculated ... | 1998 | 9733547 |
| plaque formation by and plaque cloning of chlamydia trachomatis biovar trachoma. | a new technique for the induction of plaque formation by chlamydia trachomatis biovar trachoma applicable to the titration of infectivity and cloning of biovar trachoma was established. three novel strains were cloned and confirmed to be free of glycogen inclusions. the lack of glycogen accumulation correlated with the absence of a 7.5-kb plasmid, which is highly conserved in other strains of c. trachomatis. although the growth efficiency of these plasmid-free strains was slightly lower than tha ... | 1998 | 9738059 |
| genetic engineering for high methionine grain legumes. | methionine (met) is the primary limiting essential amino acid in grain legumes. the imbalance in amino acid composition restricts their biological value (bv) to 55 to 75% of that of animal protein. so far improvement of the bv could not be achieved by conventional breeding. therefore, genetic engineering was employed by several laboratories to resolve the problem. three strategies have been followed. a) engineering for increased free met levels; b) engineering of endogenous storage proteins with ... | 1998 | 9739551 |
| agrobacterium tumefaciens-mediated transformation of filamentous fungi. | agrobacterium tumefaciens transfers part of its ti plasmid, the t-dna, to plant cells during tumorigenesis. it is routinely used for the genetic modification of a wide range of plant species. we report that a. tumefaciens can also transfer its t-dna efficiently to the filamentous fungus aspergillus awamori, demonstrating dna transfer between a prokaryote and a filamentous fungus. we transformed both protoplasts and conidia with frequencies that were improved up to 600-fold as compared with conve ... | 1998 | 9743116 |
| a second two-component regulatory system of bordetella bronchiseptica required for bacterial resistance to oxidative stress, production of acid phosphatase, and in vivo persistence. | random minitransposon mutagenesis was used to identify genes involved in the survival of bordetella bronchiseptica within eukaryotic cells. one of the mutants which exhibited a reduced ability to survive intracellularly harbored a minitransposon insertion in a locus (ris) which displays a high degree of homology to two-component regulatory systems. this system exhibited less than 25% amino acid sequence homology to the only other two-component regulatory system described in bordetella spp., the ... | 1998 | 9746560 |
| a new class of caulobacter crescentus flagellar genes. | eight caulobacter crescentus flagellar genes, flma, flmb, flmc, flmd, flme, flmf, flmg, and flmh, have been cloned and characterized. these eight genes are clustered in pairs (flmab, flmcd, flmef, and flmgh) that appear to be structurally organized as operons. homology comparisons suggest that the proteins encoded by the flm genes may be involved in posttranslational modification of flagellins or proteins that interact with flagellin monomers prior to their assembly into a flagellar filament. ex ... | 1998 | 9748431 |
| limonene-1,2-epoxide hydrolase from rhodococcus erythropolis dcl14 belongs to a novel class of epoxide hydrolases. | an epoxide hydrolase from rhodococcus erythropolis dcl14 catalyzes the hydrolysis of limonene-1,2-epoxide to limonene-1,2-diol. the enzyme is induced when r. erythropolis is grown on monoterpenes, reflecting its role in the limonene degradation pathway of this microorganism. limonene-1,2-epoxide hydrolase was purified to homogeneity. it is a monomeric cytoplasmic enzyme of 17 kda, and its n-terminal amino acid sequence was determined. no cofactor was required for activity of this colorless enzym ... | 1998 | 9748436 |
| mutation analysis of pobr and pcau, closely related transcriptional activators in acinetobacter. | acinetobacter pobr and pcau are transcriptional activators that closely resemble each other in primary structure, dna-binding sites, metabolic modulators, and physiological function. pobr responds to the inducer-metabolite p-hydroxybenzoate and activates transcription of poba, the structural gene for the enzyme that converts p-hydroxybenzoate to protocatechuate. this compound, differing from p-hydroxybenzoate only in that it contains an additional oxygen atom, binds to pcau and thereby specifica ... | 1998 | 9748437 |
| succinoglycan is required for initiation and elongation of infection threads during nodulation of alfalfa by rhizobium meliloti. | rhizobium meliloti rm1021 must be able to synthesize succinoglycan in order to invade successfully the nodules which it elicits on alfalfa and to establish an effective nitrogen-fixing symbiosis. using r. meliloti cells that express green fluorescent protein (gfp), we have examined the nature of the symbiotic deficiency of exo mutants that are defective or altered in succinoglycan production. our observations indicate that an exoy mutant, which does not produce succinoglycan, is symbiotically de ... | 1998 | 9748453 |
| molecular characterization of the virulence gene virg of ptiku 12. | the virulence (vir) genes of agrobacterium tumefaciens ku12, a korean strain, were not induced by acetosyringone and the strain showed weak tumor forming ability and broad plant host ranges. we identified complete nucleotide sequence of virg of ptiku12, an octopine ti plasmid of this strain. when it was compared with those of other ti plasmids, ptiku12 virg contained an open reading frame (orf) of 726 nucleotides which showed much lower homology (about 77%) than those (above 98%) already known a ... | 1998 | 9749525 |
| plasmids responsible for horizontal transfer of naphthalene catabolism genes between bacteria at a coal tar-contaminated site are homologous to pdtg1 from pseudomonas putida ncib 9816-4 | the presence of a highly conserved nahac allele among phylogenetically diverse bacteria carrying naphthalene-catabolic plasmids provided evidence for in situ horizontal gene transfer at a coal tar-contaminated site (j. b. herrick, k. g. stuart-keil, w. c. ghiorse, and e. l. madsen, appl. environ. microbiol. 63:2330-2337, 1997). the objective of the present study was to identify and characterize the different-sized naphthalene-catabolic plasmids in order to determine the probable mechanism of hor ... | 1998 | 9758778 |
| comparison of paenibacillus azotofixans strains isolated from rhizoplane, rhizosphere, and non-root-associated soil from maize planted in two different brazilian soils | paenibacillus azotofixans is a nitrogen-fixing bacterium often found in soil and in the rhizospheres of different grasses. in this study, two brazilian clay soils were planted with cross-hybrid maize (br-201) and four stages of plant growth were analyzed to characterize the p. azotofixans populations present in the rhizoplanes, rhizospheres, and non-root-associated soils (herein called nonrhizospheres). a total of 106 strains were isolated and identified as p. azotofixans with an api 50ch kit, b ... | 1998 | 9758811 |
| bacterial stress responses to 1-megahertz pulsed ultrasound in the presence of microbubbles. | members of a panel of stress-responsive biosensors have been used to study the effect of megahertz frequency ultrasound on escherichia coli. insonification causes acoustic cavitation, the collapse of oscillating microbubbles in solution, which can damage bacterial cells. a focused 1-mhz ultrasound transducer, capable of generating a spatial peak pulse average intensity of 500 w/cm2, was used to treat liquid bacterial cultures. stress-responsive promoters fused to luxcdabe allowed the continuous ... | 1998 | 9758821 |
| construction of a range of derivatives of the biological control strain agrobacterium rhizogenes k84: a study of factors involved in biological control of crown gall disease | the biological control strain agrobacterium rhizogenes k84 is an effective agent in the control of agrobacterium pathogens, the causative agents of crown gall disease. a number of factors are thought to play a role in the control process, including production of the specific agrocins 84 and 434, which differ in the spectra of pathogenic strains that they inhibit in vitro. a range of derivatives of strain k84 has been developed with every combination of the three resident plasmids, pagk84, pagk43 ... | 1998 | 9758829 |
| molecular diversity of rhizobia occurring on native shrubby legumes in southeastern australia | the structure of rhizobial communities nodulating native shrubby legumes in open eucalypt forest of southeastern australia was investigated by a molecular approach. twenty-one genomic species were characterized by small-subunit ribosomal dna pcr-restriction fragment length polymorphism and phylogenetic analyses, among 745 rhizobial strains isolated from nodules sampled on 32 different legume host species at 12 sites. among these rhizobial genomic species, 16 belonged to the bradyrhizobium subgro ... | 1998 | 9758831 |
| developmental regulation of intercellular protein trafficking through plasmodesmata in tobacco leaf epidermis | plasmodesmata mediate direct cell-to-cell communication in plants. one of their significant features is that primary plasmodesmata formed at the time of cytokinesis often undergo structural modifications, by the de novo addition of cytoplasmic strands across cell walls, to become complex secondary plasmodesmata during plant development. whether such modifications allow plasmodesmata to gain special transport functions has been an outstanding issue in plant biology. here we present data showing t ... | 1998 | 9765523 |
| arabidopsis rho-related gtpases: differential gene expression in pollen and polar localization in fission yeast. | the rho small gtp-binding proteins are versatile, conserved molecular switches in eukaryotic signal transduction. plants contain a unique subfamily of rho-gtpases called rop (rho-related gtpases from plants). our previous studies involving injection of antibodies indicated that the pea rop gtpase rop1ps is critical for pollen tube growth. in this study we show that overexpression of an apparent arabidopsis ortholog of rop1ps, rop1at, induces isotropic cell growth in fission yeast (schizosaccharo ... | 1998 | 9765526 |
| overexpression of an arabidopsis cdna encoding a sterol-c24(1)-methyltransferase in tobacco modifies the ratio of 24-methyl cholesterol to sitosterol and is associated with growth reduction. | higher plants synthesize 24-methyl sterols and 24-ethyl sterols in defined proportions. as a first step in investigating the physiological function of this balance, an arabidopsis cdna encoding an s-adenosyl-l-methionine 24-methylene lophenol-c24(1)-methyltransferase, the typical plant enzyme responsible for the production of 24-ethyl sterols, was expressed in tobacco (nicotiana tabacum l.) under the control of a constitutive promoter. transgenic plants displayed a novel 24-alkyl-delta5-sterol p ... | 1998 | 9765531 |
| manipulation of glutathione and amino acid biosynthesis in the chloroplast | poplars (populus tremula x populus alba) were transformed to overexpress escherichia coli gamma-glutamylcysteine synthetase (gamma-ecs) or glutathione synthetase in the chloroplast. five independent lines of each transformant strongly expressed the introduced gene and possessed markedly enhanced activity of the gene product. glutathione (gsh) contents were unaffected by high chloroplastic glutathione synthetase activity. enhanced chloroplastic gamma-ecs activity markedly increased gamma-glutamyl ... | 1998 | 9765532 |
| natural genetic transformation by agrobacterium rhizogenes . annual flowering in two biennials, belgian endive and carrot | genetic transformation of belgian endive (cichorium intybus) and carrot (daucus carota) by agrobacterium rhizogenes resulted in a transformed phenotype, including annual flowering. back-crossing of transformed (r1) endive plants produced a line that retained annual flowering in the absence of the other traits associated with a. rhizogenes transformation. annualism was correlated with the segregation of a truncated transferred dna (t-dna) insertion. during vegetative growth, carbohydrate reserves ... | 1998 | 9765539 |
| characterization of transgenic tobacco with an increased alpha-linolenic acid level | microsomal omega-3 fatty acid desaturase catalyzes the conversion of 18:2 (linoleic acid) to 18:3 (alpha-linolenic acid) in phospholipids, which are the main constituents of extrachloroplast membranes. transgenic tobacco (nicotiana tabacum) plants with increased 18:3 contents (designated siin plants) were produced through the introduction of a construct with the tobacco microsomal omega-3 fatty acid desaturase gene under the control of the highly efficient promoter containing the e12omega sequen ... | 1998 | 9765545 |
| domain structure of the atp-binding-cassette protein malk of salmonella typhimurium as assessed by coexpressed half molecules and lack'-'malk chimeras. | atp-binding-cassette (abc) subunit malk of the binding protein-dependent transport system for maltose of salmonella typhimurium and escherichia coli is crucial to the transport process but also exhibits a repressing activity on other genes of the maltose regulon. the latter function has been attributed to a carboxy-terminal extension by which malk differs in length from a prototype abc protein. in order to define the boundaries of putative functional domains of malk, we have analyzed pairs of n- ... | 1998 | 9765559 |
| analogs of the autoinducer 3-oxooctanoyl-homoserine lactone strongly inhibit activity of the trar protein of agrobacterium tumefaciens. | the trar and trai proteins of agrobacterium tumefaciens mediate cell-density-dependent expression of the ti plasmid tra regulon. trai synthesizes the autoinducer pheromone n-(3-oxooctanoyl)-l-homoserine lactone (3-oxo-c8-hsl), while trar is an 3-oxo-c8-hsl-responsive transcriptional activator. we have compared the abilities of 3-oxo-c8-hsl and 32 related compounds to activate expression of a trar-regulated promoter. in a strain that expresses wild-type levels of trar, only 3-oxo-c8-hsl was stron ... | 1998 | 9765571 |
| a chemotaxis cluster from agrobacterium tumefaciens. | we report the dna sequence of a 9.6-kb region of the agrobacterium tumefaciens chromosome containing a putative 8-kb chemotaxis operon. the putative operon begins with orf1, whose predicted protein product shows strong sequence identity to methyl-accepting chemotaxis proteins (mcps), followed by orf2, chey1, chea, cher, cheb, chey2, orf9, orf10. all of the identified homologues show a high degree of sequence conservation with their counterparts in the che operons from sinorhizobium meliloti and ... | 1998 | 9767126 |
| identification of brucella by ribosomal-spacer-region pcr and differentiation of brucella canis from other brucella spp. pathogenic for humans by carbohydrate profiles. | molecular and chemical characteristics often provide complementary information in the differentiation of closely related organisms. the genus brucella consists of a highly conserved group of organisms. identification of the four species pathogenic in humans (brucella melitensis, brucella abortus, brucella suis, and brucella canis) is problematic for many clinical laboratories that depend primarily on serology and phenotypic characteristics to differentiate species. pcr amplification of the 16s-2 ... | 1998 | 9774568 |
| the radioprotective effect of a new aminothiol (20-pra). | we examined the radioprotective effect of aminothiol 2-n-propylamine-cyclo-hexanethiol (20-pra) on a human leukemic cell line (k562) following various radiation doses (5, 7.5 and 20 gy) using a source of 60co gamma-rays. at 5 gy and 1 nm 20-pra, a substantial protective effect (58%) was seen 24 h after irradiation, followed by a decrease at 48 h (11%). at the high radiation dose (20 gy) a low protective effect was also seen (35%). in addition, the antitumorigenic potential of 10 nm 20-pra was sh ... | 1998 | 9777017 |
| [formation of deletional derivatives of the ti-plasmid pgv3850 in a conjugative transfer from agrobacterium tumefaciens to escherichia coli]. | the process of the transfer of the ti-plasmid vector pgv3850 with the plasmid pbr322 inserted into the t-dna region from agrobacterium tumefaciens to a non-plasmid strain of escherichia coli was studied. the transferred ti-plasmid was found to be exposed to deletions and formed a wide range of derivatives with a size ranging from 3-4 kb to 50 kb, maintained in e. coli due to cole1-replicon. the ti-plasmid is also inserted into the chromosome of the recipient bacterium with at least a 100-fold lo ... | 1998 | 9777352 |
| the construction and use of a pcr internal control. | an example of the application and contruction of a polymerase chain reaction (pcr) internal control is presented. the internal control is synthesized in one pcr reaction. the primers used in this reaction possess 5' over-hanging ends which are identical to the primers used in the diagnostic reaction, whereas their 3' ends are complementary to a predetermined dna sequence (puc19 in this case) of defined length and sequence. as the sequence of the control except for primer sites, is not homologous ... | 1998 | 9778450 |
| symbiotic mutants deficient in nodule establishment identified after t-dna transformation of lotus japonicus. | nitrogen-fixing root nodules develop on legumes as a result of an interaction between host plants and soil bacteria collectively referred to as rhizobia. the organogenic process resulting in nodule development is triggered by the bacterial microsymbiont, but genetically controlled by the host plant genome. using t-dna insertion as a tool to identify novel plant genes that regulate nodule ontogeny, we have identified two putatively tagged symbiotic loci, ljsym8 and ljsym13, in the diploid legume ... | 1998 | 9790598 |
| molecular genetic analysis of phosphite and hypophosphite oxidation by pseudomonas stutzeri wm88. | the first molecular and genetic characterization of a biochemical pathway for oxidation of the reduced phosphorus (p) compounds phosphite and hypophosphite is reported. the pathway was identified in pseudomonas stutzeri wm88, which was chosen for detailed studies from a group of organisms isolated based on their ability to oxidize hypophosphite (+1 valence) and phosphite (+3 valence) to phosphate (+5 valence). the genes required for oxidation of both compounds by p. stutzeri wm88 were cloned on ... | 1998 | 9791102 |
| domain analysis of the flim protein of escherichia coli. | the flim protein of escherichia coli is required for the assembly and function of flagella. genetic analyses and binding studies have shown that flim interacts with several other flagellar proteins, including flin, flig, phosphorylated chey, other copies of flim, and possibly mota and flif. here, we examine the effects of a set of linker insertions and partial deletions in flim on its binding to flin, flig, chey, and phospho-chey and on its functions in flagellar assembly and rotation. the resul ... | 1998 | 9791106 |
| the phenolic recognition profiles of the agrobacterium tumefaciens vira protein are broadened by a high level of the sugar binding protein chve. | the formation of crown gall tumors by agrobacterium tumefaciens requires that the virulence (vir) genes be induced by chemical signals which consist of specific phenolic compounds and monosaccharides, synthesized at plant wound sites. signal transduction in the activation of these genes is mediated by the vira-virg two-component regulatory system, together with chve, a glucose-galactose binding protein which interacts with vira. we have previously presented genetic evidence that vira senses phen ... | 1998 | 9791112 |
| wound-released chemical signals may elicit multiple responses from an agrobacterium tumefaciens strain containing an octopine-type ti plasmid. | the vir regions of octopine-type and nopaline-type ti plasmids direct the transfer of oncogenic t-dna from agrobacterium tumefaciens to the nuclei of host plant cells. previous studies indicate that at least two genetic loci at the left ends of these two vir regions are sufficiently conserved to form heteroduplexes visible in the electron microscope. to initiate an investigation of these genetic loci, we determined the dna sequences of these regions of both ti plasmids and identified both conser ... | 1998 | 9791116 |
| a cytochrome cbb3 (cytochrome c) terminal oxidase in azospirillum brasilense sp7 supports microaerobic growth. | spectral analysis indicated the presence of a cytochrome cbb3 oxidase under microaerobic conditions in azospirillum brasilense sp7 cells. the corresponding genes (cytnoqp) were isolated by using pcr. these genes are organized in an operon, preceded by a putative anaerobox. the phenotype of an a. brasilense cytn mutant was analyzed. under aerobic conditions, the specific growth rate during exponential phase (mu(e)) of the a. brasilense cytn mutant was comparable to the wild-type specific growth r ... | 1998 | 9791120 |
| an abc transporter plays a developmental aggregation role in myxococcus xanthus. | myxococcus xanthus is a gram-negative bacterium which has a complex life cycle. autochemotaxis, a process whereby cells release a self-generated signaling molecule, may be the principal mechanism facilitating directed motility in both the vegetative swarming and developmental aggregation stages of this life cycle. the process requires the frz signal transduction system, including frzz, a protein which is composed of two domains, both showing homology to the enteric chemotaxis response regulator ... | 1998 | 9791121 |
| alpha-galactoside uptake in rhizobium meliloti: isolation and characterization of agpa, a gene encoding a periplasmic binding protein required for melibiose and raffinose utilization. | rhizobium meliloti can occupy at least two distinct ecological niches; it is found in the soil as a free-living saprophyte, and it also lives as a nitrogen-fixing intracellular symbiont in root nodules of alfalfa and related legumes. one approach to understanding how r. meliloti alters its physiology in order to become an integral part of a developing nodule is to identify and characterize genes that are differentially expressed by bacteria living inside nodules. we used a screen to identify gen ... | 1998 | 9791127 |
| identification and quantification of toxic chemicals by use of escherichia coli carrying lux genes fused to stress promoters. | the luxcdabe bioluminescence genes of the vibrio fischeri lux system have been used as a reporter system for different stress and regulatory promoters of escherichia coli. selected e. coli strains carrying lux genes fused to different promoters were exposed to various toxic chemicals, and the recorded luminescence was used for the characterization of the biologic signature of each compound. analysis of these data with the aid of a proper algorithm allowed quantitative and qualitative assessment ... | 1998 | 9797288 |
| engineering of a single-chain variable-fragment (scfv) antibody specific for the stolbur phytoplasma (mollicute) and its expression in escherichia coli and tobacco plants | from a hybridoma cell line (2a10) producing an immunoglobulin g1 directed against the major membrane protein of the stolbur phytoplasma, we have engineered scfv (single-chain variable-fragment) antibodies from the variable heavy (vh) and light (vl) domains of the immunoglobulin. the scfv gene was cloned and expressed in escherichia coli. the expressed protein of 30 kda could be recovered from the periplasmic fraction of the bacterial cells and was shown to be fully functional toward its phytopla ... | 1998 | 9797323 |
| a novel screening method for isolating exopolysaccharide-deficient mutants. | a screening method based on differential staining of the wild type and exopolysaccharide-deficient mutants of rhizobium (sinorhizobium) meliloti by the lipophilic dye sudan black b is described. mutants defective in the production of either succinoglycan or eps ii (galactoglucan) were isolated by using this method, which might also prove useful for isolating exopolysaccharide-defective derivatives of other bacteria. | 1998 | 9797329 |
| use of the cell division protein ftsz as a means of differentiating among bartonella species. | genes coding for homologs of the highly conserved cell division protein ftsz were isolated from bartonella henselae and bartonella quintana, the causative agents of cat scratch disease and trench fever, respectively. dna fragments coding for the ftsz open reading frames (orfs) were cloned into escherichia coli following pcr amplification with primers based on the ftsz sequence of the closely related species bartonella bacilliformis. the amino acid sequences predicted from the cloned b. henselae ... | 1998 | 9801332 |
| production of acyl-homoserine lactone quorum-sensing signals by gram-negative plant-associated bacteria. | many gram-negative bacteria regulate expression of specialized gene sets in response to population density. this regulatory mechanism, called autoinduction or quorum-sensing, is based on the production by the bacteria of a small, diffusible signal molecule called the autoinducer. in the most well-studied systems the autoinducers are n-acylated derivatives of l-homoserine lactone (acyl-hsl). signal specificity is conferred by the length, and the nature of the substitution at c-3, of the acyl side ... | 1998 | 9805399 |
| agrobacterium tumefaciens transformation of the radiation hypersensitive arabidopsis thaliana mutants uvh1 and rad5. | the arabidopsis thaliana mutants uvh1 and rad5, originally identified as radiation hypersensitive, were reported to be deficient in t-dna integration based on the relative efficiencies of stable transformation and t-dna transfer. we reassessed these mutants for susceptibility to transformation by agrobacterium tumefaciens. the mutant rad5 showed a significant reduction in the efficiency of transient as well as stable transformation, compared with its wild-type progenitor. these data indicate tha ... | 1998 | 9805401 |
| opposite effects on spodoptera littoralis larvae of high expression level of a trypsin proteinase inhibitor in transgenic plants | this work illustrates potential adverse effects linked with the expression of proteinase inhibitor (pi) in plants used as a strategy to enhance pest resistance. tobacco (nicotiana tabacum l. cv xanthi) and arabidopsis [heynh.] ecotype wassilewskija) transgenic plants expressing the mustard trypsin pi 2 (mti-2) at different levels were obtained. first-instar larvae of the egyptian cotton worm (spodoptera littoralis boisd.) were fed on detached leaves of these plants. the high level of mti-2 expre ... | 1998 | 9808744 |
| role of the parcba operon of the broad-host-range plasmid rk2 in stable plasmid maintenance. | the par region of the stably maintained broad-host-range plasmid rk2 is organized as two divergent operons, parcba and parde, and a cis-acting site. parde encodes a postsegregational killing system, and parcba encodes a resolvase (para), a nuclease (parb), and a protein of unknown function (parc). the present study was undertaken to further delineate the role of the parcba region in the stable maintenance of rk2 by first introducing precise deletions in the three genes and then assessing the abi ... | 1998 | 9811663 |
| the carboxyl terminus of protein trad adds specificity and efficiency to f-plasmid conjugative transfer. | we isolated and characterized trad mutants with an altered specificity of interaction with relaxosomes of various conjugative (f and r388) and mobilizable (rsf1010 and cole1) plasmids. the change in specificity was due to a loss of some amino acids in the carboxyl terminus of trad that resulted in a broadening of the range of mobilizable relaxosomes at the expense of a decrease in the efficiency of f-plasmid transfer. | 1998 | 9811665 |
| three replicons of rhizobium sp. strain ngr234 harbor symbiotic gene sequences. | rhizobium sp. strain ngr234 contains three replicons: the symbiotic plasmid or pngr234a, a megaplasmid (pngr234b), and the chromosome. symbiotic gene sequences not present in pngr234a were analyzed by hybridization. dna sequences homologous to the genes fixljknopqghis were found on the chromosome, while sequences homologous to nodpq and exobdflk were found on pngr234b. | 1998 | 9811668 |
| amino acids in the capsid protein of tomato yellow leaf curl virus that are crucial for systemic infection, particle formation, and insect transmission. | a functional capsid protein (cp) is essential for host plant infection and insect transmission in monopartite geminiviruses. we studied two defective genomic dnas of tomato yellow leaf curl virus (tylcv), sic and sicrcv. sic, cloned from a field-infected tomato, was not infectious, whereas sicrcv, which spontaneously originated from sic, was infectious but not whitefly transmissible. a single amino acid change in the cp was found to be responsible for restoring infectivity. when the amino acid s ... | 1998 | 9811744 |
| synthesis of medium-chain-length polyhydroxyalkanoates in arabidopsis thaliana using intermediates of peroxisomal fatty acid beta-oxidation. | polyhydroxyalkanoate (pha) is a family of polymers composed primarily of r-3-hydroxyalkanoic acids. these polymers have properties of biodegradable thermoplastics and elastomers. medium-chain-length phas (mcl-phas) are synthesized in bacteria by using intermediates of the beta-oxidation of alkanoic acids. to assess the feasibility of producing mcl-phas in plants, arabidopsis thaliana was transformed with the phac1 synthase from pseudomonas aeruginosa modified for peroxisome targeting by addition ... | 1998 | 9811811 |
| the vibrio cholerae genome contains two unique circular chromosomes. | vibrio cholerae, the etiologic agent of the diarrheal disease cholera, is a gram-negative bacterium that belongs to the gamma subdivision of the family proteobacteriaceae. the physical map of the genome has been reported, and the genome has been described as a single 3.2-mb chromosome [majumder, r., et al. (1996) j. bacteriol. 178, 1105-1112]. by using pulsed-field gel electrophoresis of genomic dna immobilized in agarose plugs and digested with the restriction enzymes i-ceui, sfii, and noti, we ... | 1998 | 9826723 |
| characterization of proteus mirabilis precocious swarming mutants: identification of rsba, encoding a regulator of swarming behavior. | proteus mirabilis swarming behavior is characterized by the development of concentric rings of growth that are formed as cyclic events of swarmer cell differentiation, swarming migration, and cellular differentiation are repeated during colony translocation across a surface. this cycle produces the bull's-eye colony often associated with cultures of p. mirabilis. how the cells communicate with one another to coordinate these perfectly synchronized rings is presently unknown. we report here the i ... | 1998 | 9829920 |
| genetic and sequence analysis of the ptic58 trb locus, encoding a mating-pair formation system related to members of the type iv secretion family. | conjugal transfer of ptic58 requires two regions, tra which contains the orit and several genes involved in dna processing and a region of undefined size and function that is located at the 2-o'clock position of the plasmid. using transposon mutagenesis with tn3hoho1 and a binary transfer system, we delimited this second region, called trb, to an 11-kb interval between the loci for vegetative replication and nopaline catabolism. dna sequence analysis of this region identified 13 significant open ... | 1998 | 9829924 |
| characterization of corr, a transcriptional activator which is required for biosynthesis of the phytotoxin coronatine. | coronatine (cor) is a plasmid-encoded phytotoxin synthesized by several pathovars of phytopathogenic pseudomonas syringae. the cor biosynthetic gene cluster in p. syringae pv. glycinea pg4180 is encoded by a 32-kb region which contains both the structural and regulatory genes needed for cor synthesis. the regulatory region contains three genes: corp, cors, and corr. cors is thought to function as a histidine protein kinase, whereas corp and corr show relatedness to response regulators of the two ... | 1998 | 9829934 |
| mutational analysis of the rhizobium etli reca operator. | based upon our earlier studies (a. tapias, a. r. fernández de henestrosa, and j. barbé, j. bacteriol. 179:1573-1579, 1997) we hypothesized that the regulatory sequence of the rhizobium etli reca gene was ttgn11caa. however, further detailed analysis of the r. etli reca operator described in the present work suggests that it may in fact be gaacn7gtac. this new conclusion is based upon pcr mutagenesis analysis carried out in the r. etli reca operator, which indicates that the gaac and gtac submoti ... | 1998 | 9829943 |
| effect of canavanine from alfalfa seeds on the population biology of bacillus cereus | bacillus cereus uw85 suppresses diseases of alfalfa seedlings, although alfalfa seed exudate inhibits the growth of uw85 in culture (j. l. milner, s. j. raffel, b. j. lethbridge, and j. handelsman, appl. microbiol. biotechnol. 43:685-691, 1995). in this study, we determined the chemical basis for and biological role of the inhibitory activity. all of the alfalfa germ plasm tested included seeds that released inhibitory material. we purified the inhibitory material from one alfalfa cultivar and i ... | 1998 | 9835549 |
| psychrotolerant bacteria isolated from arctic soil that degrade polychlorinated biphenyls at low temperatures | psychrotolerant polychlorinated biphenyl (pcb)-degrading bacteria were isolated at 7 degreesc from pcb-contaminated arctic soil by using biphenyl as the sole organic carbon source. these isolates were distinguished from each other by differences in substrates that supported growth and substrates that were oxidized. 16s ribosomal dna sequences suggest that these isolates are most closely related to the genus pseudomonas. total removal of aroclor 1242, and rates of removal of selected pcb congener ... | 1998 | 9835569 |
| a new approach to utilize pcr-single-strand-conformation polymorphism for 16s rrna gene-based microbial community analysis. | single-strand-conformation polymorphism (sscp) of dna, a method widely used in mutation analysis, was adapted to the analysis and differentiation of cultivated pure-culture soil microorganisms and noncultivated rhizosphere microbial communities. a fragment (approximately 400 bp) of the bacterial 16s rrna gene (v-4 and v-5 regions) was amplified by pcr with universal primers, with one primer phosphorylated at the 5' end. the phosphorylated strands of the pcr products were selectively digested wit ... | 1998 | 9835576 |
| genetic diversity and phylogeny of rhizobia that nodulate acacia spp. in morocco assessed by analysis of rrna genes | forty rhizobia nodulating four acacia species (a. gummifera, a. raddiana, a. cyanophylla, and a. horrida) were isolated from different sites in morocco. these rhizobia were compared by analyzing both the 16s rrna gene (rdna) and the 16s-23s rrna spacer by pcr with restriction fragment length polymorphism (rflp) analysis. analysis of the length of 16s-23s spacer showed a considerable diversity within these microsymbionts, but rflp analysis of the amplified spacer revealed no additional heterogene ... | 1998 | 9835582 |
| sinorhizobium fredii and sinorhizobium meliloti produce structurally conserved lipopolysaccharides and strain-specific k antigens. | lipopolysaccharides (lps) and capsular polysaccharides (k antigens) may influence the interaction of rhizobia with their specific hosts; therefore, we conducted a comparative analysis of sinorhizobium fredii and sinorhizobium meliloti, which are genetically related, yet symbiotically distinct, nitrogen-fixing microsymbionts of legumes. we found that both species typically produce strain-specific k antigens that consist of 3-deoxy-d-manno-2-octulosonic acid (kdo), or other 1-carboxy-2-keto-3-deox ... | 1998 | 9835585 |
| effects of bacterial antibiotic production on rhizosphere microbial communities from a culture-independent perspective | the effects of antibiotic production on rhizosphere microbial communities of field-grown phaseolus vulgaris were assessed by using ribosomal intergenic spacer analysis. inoculum strains of rhizobium etli ce3 differing only in trifolitoxin production were used. trifolitoxin production dramatically reduced the diversity of trifolitoxin-sensitive members of the alpha subdivision of the class proteobacteria with little apparent effect on most microbes. | 1998 | 9835600 |
| construction of a bioluminescent reporter strain to detect polychlorinated biphenyls | a bioluminescent reporter strain, ralstonia eutropha env307(putk60), was constructed for the detection of polychlorinated biphenyls by inserting the biphenyl promoter upstream of the bioluminescence genes. in the presence of a nonionic surfactant, which enhances the solubility of chlorinated biphenyls, bioluminescence was induced three- to fourfold over background by biphenyl, monochlorinated biphenyls, and aroclor 1242. the minimum detection limits for these compounds ranged from 0.15 mg/liter ... | 1998 | 9835601 |
| molecular genetics of the genus paracoccus: metabolically versatile bacteria with bioenergetic flexibility. | paracoccus denitrificans and its near relative paracoccus versutus (formerly known as thiobacilllus versutus) have been attracting increasing attention because the aerobic respiratory system of p. denitrificans has long been regarded as a model for that of the mitochondrion, with which there are many components (e.g., cytochrome aa3 oxidase) in common. members of the genus exhibit a great range of metabolic flexibility, particularly with respect to processes involving respiration. prominent exam ... | 1998 | 9841665 |
| a natural view of microbial biodiversity within hot spring cyanobacterial mat communities. | this review summarizes a decade of research in which we have used molecular methods, in conjunction with more traditional approaches, to study hot spring cyanobacterial mats as models for understanding principles of microbial community ecology. molecular methods reveal that the composition of these communities is grossly oversimplified by microscopic and cultivation methods. for example, none of 31 unique 16s rrna sequences detected in the octopus spring mat, yellowstone national park, matches t ... | 1998 | 9841675 |
| polyphosphate-accumulating and denitrifying bacteria isolated from anaerobic-anoxic and anaerobic-aerobic sequencing batch reactors | in this study, phosphate-accumulating bacteria achieved complete phosphate removal in two different systems: an anaerobic-anoxic sequencing batch reactor and an anaerobic-aerobic sequencing batch reactor. this result shows that phosphate-accumulating bacteria in the a2 sbr can use nitrate as terminal electron acceptor instead of oxygen. phosphate-accumulating bacteria accumulated phosphate with a rates between 30 and 70 mg p/l/h in the a/o sbr and between 15 and 32 mg p/l/h in the a2 sbr. twenty ... | 1999 | 9841775 |
| abscisic acid-dependent and -independent expression of the carrot late-embryogenesis-abundant-class gene dc3 in transgenic tobacco seedlings | we studied the expression of three promoter 5' deletion constructs (-218, -599, and -1312) of the lea (late embryogenesis abundant)-class gene dc3 fused to beta-glucuronidase (gus), where each construct value refers to the number of base pairs upstream of the transcription start site at which the deletion occurred. the dc3 gene is noted for its induction by abscisic acid (aba), but its response to other plant hormones and various environmental stresses has not been reported previously for vegeta ... | 1998 | 9847092 |
| incp plasmids are unusually effective in mediating conjugation of escherichia coli and saccharomyces cerevisiae: involvement of the tra2 mating system. | mobilizable shuttle plasmids containing the origin-of-transfer (orit) region of plasmids f (incfi), colib-p9 (inci1), and rp4/rp1 (incpalpha) were constructed to test the ability of the cognate conjugation system to mediate gene transfer from escherichia coli to saccharomyces cerevisiae. only the palpha system caused detectable mobilization to yeast, giving peak values of 5 x 10(-5) transconjugants per recipient cell in 30 min. transfer of the shuttle plasmid required carriage of orit in cis and ... | 1998 | 9851996 |
| gene organization and transcription analysis of the agrobacterium tumefaciens glycogen (glg) operon: two transcripts for the single phosphoglucomutase gene. | the gene organization and transcription of the agrobacterium glg operon differ from those in other bacteria. agrobacterium tumefaciens a348 contains a 9.1-kb gene cluster harboring genes for glycogen metabolism. the nucleotide sequence and gene organization of a region containing adp-glucose pyrophosphorylase (glgc), glycogen synthetase (glga), and phosphoglucomutase (pgm) genes have been previously described (a. uttaro and r. a. ugalde, gene 150:117-122, 1994). in this work we report that the g ... | 1998 | 9851999 |
| stability of the agrobacterium tumefaciens virb10 protein is modulated by growth temperature and periplasmic osmoadaption. | export of oncogenic t-dna from the phytopathogen agrobacterium tumefaciens is mediated by the products of the virb operon. it has recently been reported (k. j. fullner and e. w. nester, j. bacteriol. 178:1498-1504, 1996) that dna transfer does not occur at elevated temperatures; these observations correlate well with much earlier studies on the temperature sensitivity of crown gall tumor development on plants. in testing the hypothesis that this loss of dna movement reflects a defect in assembly ... | 1998 | 9852004 |
| selectivity of ferric enterobactin binding and cooperativity of transport in gram-negative bacteria. | the ligand-gated outer membrane porin fepa serves escherichia coli as the receptor for the siderophore ferric enterobactin. we characterized the ability of seven analogs of enterobactin to supply iron via fepa by quantitatively measuring the binding and transport of their 59fe complexes. the experiments refuted the idea that chirality of the iron complex affects its recognition by fepa and demonstrated the necessity of an unsubstituted catecholate coordination center for binding to the outer mem ... | 1998 | 9852016 |
| a 42 bp fragment of the pmas1' promoter containing an ocs-like element confers a developmental, wound- and chemically inducible expression pattern. | synthesis of mannopine in plant tissues infected with agrobacterium tumefaciens is controlled by a divergent promoter (pmas2' and pmas1') that in 479 bp contains all the cis-acting elements necessary to direct tissue-specific and wound-inducible expression. in this report, using transgenic tobacco plants harboring a pmas1'-beta-glucuronidase (gus) gene fusion, we investigated the developmental expression pattern directed by pmas1' in the early stages of development and the responses of pmas1' to ... | 1998 | 9862492 |
| genetic and biochemical characterization of a 2-pyrone-4, 6-dicarboxylic acid hydrolase involved in the protocatechuate 4, 5-cleavage pathway of sphingomonas paucimobilis syk-6. | sphingomonas paucimobilis syk-6 is able to grow on a wide variety of dimeric lignin compounds with guaiacyl moieties, which are converted into protocatechuate by the actions of lignin degradation enzymes in this strain. protocatechuate is a key metabolite in the syk-6 degradation of lignin compounds with guaiacyl moieties, and it is thought that it degrades to pyruvate and oxaloacetate via the protocatechuate 4,5-cleavage pathway. in a 10.5-kb ecori fragment carrying the protocatechuate 4,5-diox ... | 1999 | 9864312 |
| psa causes oncogenic suppression of agrobacterium by inhibiting vire2 protein export. | when coresident with the ti (tumor-inducing) plasmid, the 21-kda product of the osa gene of the plasmid psa can suppress crown gall tumorigenesis incited by agrobacterium tumefaciens. neither t-dna processing nor vir (virulence) gene induction is affected by the presence of osa in the bacterium. we used arabidopsis thaliana root segments and tobacco leaf discs to demonstrate that osa inhibits a. tumefaciens from transforming these plants to the stable phenotypes of tumorigenesis, kanamycin resis ... | 1999 | 9864329 |
| extracellular products as mediators of the formation and detachment of pseudomonas fluorescens biofilms. | pseudomonas fluorescens b52 produces substantial biofilms at the air/liquid/solid interface of glass coverslips clamped vertically and partly submerged in liquid medium at 21 degrees c. biofilm formation was maximal ca. 20-50 h after inoculation of the liquid medium and as indicated by environmental scanning electron microscopy (esem), contained large numbers of bacterial cells that were embedded within an extensive exopolymeric matrix. incubation beyond 50 h led to reductions in biofilm which e ... | 1998 | 9867469 |
| thermal gradient gel electrophoresis analysis of bioprotection from pollutant shocks in the activated sludge microbial community. | we used a culture-independent approach, namely, thermal gradient gel electrophoresis (tgge) analysis of ribosomal sequences amplified directly from community dna, to determine changes in the structure of the microbial community following phenol shocks in the highly complex activated sludge ecosystem. parallel experimental model sewage plants were given shock loads of chlorinated and methylated phenols and simultaneously were inoculated (i) with a genetically engineered microorganism (gem) able t ... | 1999 | 9872766 |
| new mobilizable vectors suitable for gene replacement in gram-negative bacteria and their use in mapping of the 3' end of the xanthomonas campestris pv. campestris gum operon. | we describe useful vectors to select double-crossover events directly in site-directed marker exchange mutagenesis in gram-negative bacteria. these vectors contain the gusa marker gene, providing colorimetric screens to identify bacteria harboring those sequences. the applicability of these vectors was shown by mapping the 3' end of the xanthomonas campestris gum operon, involved in biosynthesis of xanthan. | 1999 | 9872790 |
| purification and properties of the chloroplastic form of biotin holocarboxylase synthetase from arabidopsis thaliana overexpressed in escherichia coli. | holocarboxylase synthetases (hcss) are key enzymes in biotin utilisation in both prokaryotes and eukaryotes. in a previous study, we demonstrated that, in plants, hcs activity is localised in cytosol, chloroplasts and mitochondria. we also described the cloning and sequencing of a full-length cdna encoding an arabidopsis thaliana hcs isoform with a putative organelle-transit peptide. in the study reported here, this cdna was used to construct an overproducing escherichia coli strain. the recombi ... | 1998 | 9874227 |
| the lateral suppressor (ls) gene of tomato encodes a new member of the vhiid protein family. | the ability of the shoot apical meristem to multiply and distribute its meristematic potential through the formation of axillary meristems is essential for the diversity of forms and growth habits of higher plants. in the lateral suppressor mutant of tomato the initiation of axillary meristems is prevented, thus offering the unique opportunity to study the molecular mechanisms underlying this important function of the shoot apical meristem. we report here the isolation of the lateral suppressor ... | 1999 | 9874811 |
| overexpression of glutathione synthetase in indian mustard enhances cadmium accumulation and tolerance | an important pathway by which plants detoxify heavy metals is through sequestration with heavy-metal-binding peptides called phytochelatins or their precursor, glutathione. to identify limiting factors for heavy-metal accumulation and tolerance, and to develop transgenic plants with an increased capacity to accumulate and/or tolerate heavy metals, the escherichia coli gshii gene encoding glutathione synthetase (gs) was overexpressed in the cytosol of indian mustard (brassica juncea). the transge ... | 1999 | 9880348 |
| dynamics of cytokinins in apical shoot meristems of a day-neutral tobacco during floral transition and flower formation | this study considered cytokinin distribution in tobacco (nicotiana tabacum l.) shoot apices in distinct phases of development using immunocytochemistry and quantitative tandem mass spectrometry. in contrast to vegetative apices and flower buds, we detected no free cytokinin bases (zeatin, dihydrozeatin, or isopentenyladenine) in prefloral transition apices. we also observed a 3-fold decrease in the content of cytokinin ribosides (zeatin riboside, dihydrozeatin riboside, and isopentenyladenosine) ... | 1999 | 9880352 |
| a conserved acidic motif in the n-terminal domain of nitrate reductase is necessary for the inactivation of the enzyme in the dark by phosphorylation and 14-3-3 binding. | it has previously been shown that the n-terminal domain of tobacco (nicotiana tabacum) nitrate reductase (nr) is involved in the inactivation of the enzyme by phosphorylation, which occurs in the dark (l. nussaume, m. vincentz, c. meyer, j.p. boutin, and m. caboche [1995] plant cell 7: 611-621). the activity of a mutant nr protein lacking this n-terminal domain was no longer regulated by light-dark transitions. in this study smaller deletions were performed in the n-terminal domain of tobacco nr ... | 1999 | 9880364 |
| rhizobium (sinorhizobium) meliloti phn genes: characterization and identification of their protein products. | in escherichia coli, the phn operon encodes proteins responsible for the uptake and breakdown of phosphonates. the c-p (carbon-phosphorus) lyase enzyme encoded by this operon which catalyzes the cleavage of c-p bonds in phosphonates has been recalcitrant to biochemical characterization. to advance the understanding of this enzyme, we have cloned dna from rhizobium (sinorhizobium) meliloti that contains homologues of the e. coli phng, -h, -i, -j, and -k genes. we demonstrated by insertional mutag ... | 1999 | 9882650 |
| heat-induced synthesis of sigma32 in escherichia coli: structural and functional dissection of rpoh mrna secondary structure. | the heat shock response in escherichia coli depends primarily on the increased synthesis and stabilization of otherwise scarce and unstable sigma32 (rpoh gene product), which is required for the transcription of heat shock genes. the heat-induced synthesis of sigma32 occurs at the level of translation, and genetic evidence has suggested the involvement of a secondary structure at the 5' portion (nucleotides -19 to +247) of rpoh mrna in regulation. we now present evidence for the mrna secondary s ... | 1999 | 9882652 |
| cloning and characterization of a tetracycline resistance determinant present in agrobacterium tumefaciens c58. | agrobacterium tumefaciens c58 and its derivatives give rise to spontaneous mutants resistant to tetracycline at a high frequency. we observed that a mutation affecting a trna processing function significantly affected the emergence of such mutants, suggesting that c58 contained a positively acting gene conferring resistance to tetracycline. a cosmid clone conferring resistance to tetracycline in escherichia coli and agrobacterium was isolated from a genomic bank of one such mutant. subcloning, t ... | 1999 | 9882678 |
| identification and characterization of ptlc, an essential component of the pertussis toxin secretion system. | ptlc is a member of a set of proteins necessary for the secretion of pertussis toxin (pt) from bordetella pertussis. using polyclonal antibodies specific for ptlc, we identified ptlc as a protein with an apparent molecular weight of 85,000 that localizes to the membrane fraction of bacterial cell extracts. we found that a mutant strain of b. pertussis that contains an in-frame deletion in ptlc is unable to secrete pt and that pt secretion is fully restored by expressing ptlc in trans, indicating ... | 1999 | 9916087 |
| kinetic mechanism of the enantioselective conversion of styrene oxide by epoxide hydrolase from agrobacterium radiobacter ad1. | epoxide hydrolase from agrobacterium radiobacter ad1 catalyzes the enantioselective hydrolysis of styrene oxide with an e value of 16. the (r)-enantiomer of styrene oxide is first converted with a k(cat) of 3.8 s(-1), and the conversion of the (s)-enantiomer is inhibited. the latter is subsequently hydrolyzed with a k(cat) of 10.5 s(-1). the pre-steady-state kinetic parameters were determined for both enantiomers with stopped-flow fluorescence and rapid-quench techniques. for (r)-styrene oxide a ... | 1998 | 9922181 |
| quorum sensing in burkholderia cepacia: identification of the luxri homologs cepri. | burkholderia cepacia has emerged as an important pathogen in patients with cystic fibrosis. many gram-negative pathogens regulate the production of extracellular virulence factors by a cell density-dependent mechanism termed quorum sensing, which involves production of diffusible n-acylated homoserine lactone signal molecules, called autoinducers. transposon insertion mutants of b. cepacia k56-2 which hyperproduced siderophores on chrome azurol s agar were identified. one mutant, k56-r2, contain ... | 1999 | 9922236 |
| thermoregulated expression and characterization of an nad(p)h-dependent 2-cyclohexen-1-one reductase in the plant pathogenic bacterium pseudomonas syringae pv. glycinea. | the phytopathogenic bacterium pseudomonas syringae pv. glycinea pg4180.n9 causes bacterial blight of soybeans and preferably infects its host plant during periods of cold, humid weather conditions. to identify proteins differentially expressed at low temperatures, total cellular protein fractions derived from pg4180.n9 grown at 18 and 28 degreesc were separated by two-dimensional gel electrophoresis. of several proteins which appeared to be preferentially present at 18 degreesc, a 40-kda protein ... | 1999 | 9922244 |
| poly-3-hydroxybutyrate degradation in rhizobium (sinorhizobium) meliloti: isolation and characterization of a gene encoding 3-hydroxybutyrate dehydrogenase. | we have cloned and sequenced the 3-hydroxybutyrate dehydrogenase-encoding gene (bdha) from rhizobium (sinorhizobium) meliloti. the gene has an open reading frame of 777 bp that encodes a polypeptide of 258 amino acid residues (molecular weight 27,177, pi 6.07). the r. meliloti bdh protein exhibits features common to members of the short-chain alcohol dehydrogenase superfamily. bdha is the first gene transcribed in an operon that also includes xdha, encoding xanthine oxidase/dehydrogenase. transc ... | 1999 | 9922248 |
| sequence and function of luxu: a two-component phosphorelay protein that regulates quorum sensing in vibrio harveyi. | vibrio harveyi regulates the expression of bioluminescence (lux) in response to cell density, a phenomenon known as quorum sensing. in v. harveyi, two independent quorum-sensing systems exist, and each produces, detects, and responds to a specific cell density-dependent autoinducer signal. the autoinducers are recognized by two-component hybrid sensor kinases called luxn and luxq, and sensory information from both systems is transduced by a phosphorelay mechanism to the response regulator protei ... | 1999 | 9922254 |
| topology of rbsc, a membrane component of the ribose transporter, belonging to the arah superfamily. | rbsc of escherichia coli is the hydrophobic membrane component of ribose uptake system classified as the atp-binding cassette transporter. to understand the structure and function of rbsc, its transmembrane topology was investigated by using 64 rbsc-phoa fusions isolated either specifically or randomly. in order to confirm the cytoplasmic location of the short c-terminal region (5 amino acids), inside-out or right-side-out membrane vesicles were generated, and the c-terminal region was found to ... | 1999 | 9922273 |
| sporadic distribution of trna(arg)ccu introns among alpha-purple bacteria: evidence for horizontal transmission and transposition of a group i intron. | a group i intron interrupts the trna(arg)ccu gene of the alpha-purple bacterium agrobacterium tumefaciens (b. reinhold-hurek and d. a. shub, nature [london] 357:173-176, 1992). in this study, we assess the distribution of the corresponding intron among 12 additional species of alpha-purple bacteria. of 10 newly identified trna(arg)ccu genes, we found only two that contained an intron homologous to that of the agrobacterium intron. this restricted and scattered distribution of the trna(arg)ccug i ... | 1999 | 9922276 |
| antisense-mediated depletion of a potato lipoxygenase reduces wound induction of proteinase inhibitors and increases weight gain of insect pests. | de novo jasmonic acid (ja) synthesis is required for wound-induced expression of proteinase inhibitors and other defense genes in potato and tomato. the first step in ja biosynthesis involves lipoxygenase (lox) introducing molecular oxygen at the c-13 position of linolenic acid. we previously have shown that, in potato, at least two gene families code for 13-lox proteins. we have now produced transgenic potato plants devoid of one specific 13-lox isoform (lox-h3) through antisense-mediated deple ... | 1999 | 9927708 |
| cell-specific production and antimicrobial activity of naphthoquinones in roots of lithospermum erythrorhizon | pigmented naphthoquinone derivatives of shikonin are produced at specific times and in specific cells of lithospermum erythrorhizon roots. normal pigment development is limited to root hairs and root border cells in hairy roots grown on "noninducing" medium, whereas induction of additional pigment production by abiotic (cuso4) or biotic (fungal elicitor) factors increases the amount of total pigment, changes the ratios of derivatives produced, and initiates production of pigment de novo in epide ... | 1999 | 9952436 |
| apyrase functions in plant phosphate nutrition and mobilizes phosphate from extracellular atp. | atp, which is present in the extracellular matrix of multicellular organisms and in the extracellular fluid of unicellular organisms, has been shown to function as a signaling molecule in animals. the concentration of extracellular atp (xatp) is known to be functionally modulated in part by ectoapyrases, membrane-associated proteins that cleave the gamma- and beta-phosphates on xatp. we present data showing a previously unreported (to our knowledge) linkage between apyrase and phosphate transpor ... | 1999 | 9952450 |
| use of ubiquitin fusions to augment protein expression in transgenic plants. | a major goal of plant biotechnology is the production of genetically engineered crops that express natural or foreign proteins at high levels. to enhance protein accumulation in transgenic plants, we developed a set of vectors that express proteins and peptides as c-terminal translational fusions with ubiquitin (ubq). studies of several proteins in tobacco (nicotiana tabacum) showed that: (a) proteins can be readily expressed in plants as ubq fusions; (b) by the action of endogenous ubq-specific ... | 1999 | 9952468 |