| novel genes coding for lithotrophic sulfur oxidation of paracoccus pantotrophus gb17. | the gene region coding for lithotrophic sulfur oxidation of paracoccus pantotrophus gb17 is located on a 13-kb insert of plasmid peg12. upstream of the previously described six open reading frames (orfs) soxabcdef with a partial sequence of soxa and soxf (c. wodara, f. bardischewsky, and c. g. friedrich, j. bacteriol. 179:5014-5023, 1997), 4,350 bp were sequenced. the sequence completed soxa, and uncovered six new orfs upstream of soxa, designated orf1, orf2, and orf3, and soxxyz. orf1 could enc ... | 2000 | 10940005 |
| mutations in each of the tol genes of pseudomonas putida reveal that they are critical for maintenance of outer membrane stability. | the outer membrane of gram-negative bacteria functions as a permeability barrier that protects cells against a large number of antibacterial agents. oprl protein of pseudomonas putida has been shown to be crucial to maintain the stability of this cell component (j. j. rodríguez-herva, m.-i. ramos-gonzález, and j. l. ramos. j. bacteriol. 178:1699-1706, 1996). in the present study we cloned and mutagenized the orf1, tolq, tolr, tola, and tolb genes from p. putida kt2440, which were located upstrea ... | 2000 | 10940016 |
| a homologue of an operon required for dna transfer in agrobacterium is required in brucella abortus for virulence and intracellular multiplication. | as part of a brucella abortus 2308 genome project carried out in our laboratory, we identified, cloned, and sequenced a genomic dna fragment containing a locus (virb) highly homologous to bacterial type iv secretion systems. the b. abortus virb locus is a collinear arrangement of 13 open reading frames (orfs). between virb1 and virb2 and downstream of orf12, two degenerated, palindromic repeat sequences characteristic of brucella intergenic regions were found. gene reporter studies demonstrated ... | 2000 | 10940027 |
| a family of six flagellin genes contributes to the caulobacter crescentus flagellar filament. | the caulobacter crescentus flagellar filament is assembled from multiple flagellin proteins that are encoded by six genes. the amino acid sequences of the fljj and fljl flagellins are divergent from those of the other four flagellins. since these flagellins are the first to be assembled in the flagellar filament, one or both might have specialized to facilitate the initiation of filament assembly. | 2000 | 10940048 |
| glycine betaine transport in the obligate halophilic archaeon methanohalophilus portucalensis. | transport of the osmoprotectant glycine betaine was investigated using the glycine betaine-synthesizing microbe methanohalophilus portucalensis (strain fdf1), since solute uptake for this class of obligate halophilic methanogenic archaea has not been examined. betaine uptake followed a michaelis-menten relationship, with an observed k(t) of 23 microm and a v(max) of 8 nmol per min per mg of protein. the transport system was highly specific for betaine: choline, proline, and dimethylglycine did n ... | 2000 | 10940053 |
| characterization of porphyromonas gingivalis insertion sequence-like element ispg5. | porphyromonas gingivalis, a black-pigmented, gram-negative anaerobe, is found in periodontitis lesions, and its presence in subgingival plaque significantly increases the risk for periodontitis. in contrast to many bacterial pathogens, p. gingivalis strains display considerable variability, which is likely due to genetic exchange and intragenomic changes. to explore the latter possibility, we have studied the occurrence of insertion sequence (is)-like elements in p. gingivalis w83 by utilizing a ... | 2000 | 10948151 |
| receptor-mediated increase in cytoplasmic free calcium required for activation of pathogen defense in parsley. | transient influx of ca(2+) constitutes an early element of signaling cascades triggering pathogen defense responses in plant cells. treatment with the phytophthora sojae-derived oligopeptide elicitor, pep-13, of parsley cells stably expressing apoaequorin revealed a rapid increase in cytoplasmic free calcium ([ca(2+)](cyt)), which peaked at approximately 1 microm and subsequently declined to sustained values of 300 nm. activation of this biphasic [ca(2+)](cyt) signature was achieved by elicitor ... | 2000 | 10948260 |
| plasmid-located pathogenicity determinants of serratia entomophila, the causal agent of amber disease of grass grub, show similarity to the insecticidal toxins of photorhabdus luminescens. | serratia entomophila and serratia proteamaculans cause amber disease in the grass grub costelytra zealandica (coleoptera: scarabaeidae), an important pasture pest in new zealand. larval disease symptoms include cessation of feeding, clearance of the gut, amber coloration, and eventual death. a 115-kb plasmid, padap, identified in s. entomophila is required for disease causation and, when introduced into escherichia coli, enables that organism to cause amber disease. a 23-kb fragment of padap tha ... | 2000 | 10960097 |
| cloning and characterization of the glucooligosaccharide catabolic pathway beta-glucan glucohydrolase and cellobiose phosphorylase in the marine hyperthermophile thermotoga neapolitana. | characterization in thermotoga neapolitana of a catabolic gene cluster encoding two glycosyl hydrolases, 1,4-beta-d-glucan glucohydrolase (ggha) and cellobiose phosphorylase (cbpa), and the apparent absence of a cellobiohydrolase (cbh) suggest a nonconventional pathway for glucan utilization in thermotogales. ggha purified from t. neapolitana is a 52.5-kda family 1 glycosyl hydrolase with optimal activity at ph 6.5 and 95 degrees c. ggha releases glucose from soluble glucooligomers, with a prefe ... | 2000 | 10960102 |
| the nosx and nirx proteins of paracoccus denitrificans are functional homologues: their role in maturation of nitrous oxide reductase. | the nos (nitrous oxide reductase) operon of paracoccus denitrificans contains a nosx gene homologous to those found in the nos operons of other denitrifiers. nosx is also homologous to nirx, which is so far unique to p. denitrificans. single mutations of these genes did not result in any apparent phenotype, but a double nosx nirx mutant was unable to reduce nitrous oxide. promoter-lacz assays and immunoblotting against nitrous oxide reductase showed that the defect was not due to failure of expr ... | 2000 | 10960107 |
| the flagellar filament of rhodobacter sphaeroides: ph-induced polymorphic transitions and analysis of the flic gene. | flagellar motility in rhodobacter sphaeroides is notably different from that in other bacteria. r. sphaeroides moves in a series of runs and stops produced by the intermittent rotation of the flagellar motor. r. sphaeroides has a single, plain filament whose conformation changes according to flagellar motor activity. conformations adopted during swimming include coiled, helical, and apparently straight forms. this range of morphological transitions is larger than that in other bacteria, where fi ... | 2000 | 10960108 |
| molecular analysis of diazotroph diversity in the rhizosphere of the smooth cordgrass, spartina alterniflora. | n(2) fixation by diazotrophic bacteria associated with the roots of the smooth cordgrass, spartina alterniflora, is an important source of new nitrogen in many salt marsh ecosystems. however, the diversity and phylogenetic affiliations of these rhizosphere diazotrophs are unknown. denaturing gradient gel electrophoresis (dgge) of pcr-amplified nifh sequence segments was used in previous studies to examine the stability and dynamics of the spartina rhizosphere diazotroph assemblages in the north ... | 2000 | 10966395 |
| starvation improves survival of bacteria introduced into activated sludge. | a phenol-degrading bacterium, ralstonia eutropha e2, was grown in luria-bertani (lb) medium or in an inorganic medium (called mp) supplemented with phenol and harvested at the late-exponential-growth phase. phenol-acclimated activated sludge was inoculated with the e2 cells immediately after harvest or after starvation in mp for 2 or 7 days. the densities of the e2 populations in the activated sludge were then monitored by quantitative pcr. the e2 cells grown on phenol and starved for 2 days (p- ... | 2000 | 10966407 |
| genotypic characterization of bradyrhizobium strains nodulating small senegalese legumes by 16s-23s rrna intergenic gene spacers and amplified fragment length polymorphism fingerprint analyses. | we examined the genotypic diversity of 64 bradyrhizobium strains isolated from nodules from 27 native leguminous plant species in senegal (west africa) belonging to the genera abrus, alysicarpus, bryaspis, chamaecrista, cassia, crotalaria, desmodium, eriosema, indigofera, moghania, rhynchosia, sesbania, tephrosia, and zornia, which play an ecological role and have agronomic potential in arid regions. the strains were characterized by intergenic spacer (between 16s and 23s rrna genes) pcr and res ... | 2000 | 10966419 |
| response of a soil bacterial community to grassland succession as monitored by 16s rrna levels of the predominant ribotypes. | the composition of predominant soil bacteria during grassland succession was investigated in the dutch drentse a area. five meadows, taken out of agricultural production at different time points, and one currently fertilized plot represented different stages of grassland succession. since fertilization and agricultural production were stopped, the six plots showed a constant decline in the levels of nutrients and vegetation changes. the activity of the predominant bacteria was monitored by direc ... | 2000 | 10966420 |
| plant genome complexity may be a factor limiting in situ the transfer of transgenic plant genes to the phytopathogen ralstonia solanacearum. | the development of natural competence by bacteria in situ is considered one of the main factors limiting transformation-mediated gene exchanges in the environment. ralstonia solanacearum is a plant pathogen that is also a naturally transformable bacterium that can develop the competence state during infection of its host. we have attempted to determine whether this bacterium could become the recipient of plant genes. we initially demonstrated that plant dna was released close to the infecting ba ... | 2000 | 10966449 |
| fine tuning bacterial chemotaxis: analysis of rhodobacter sphaeroides behaviour under aerobic and anaerobic conditions by mutation of the major chemotaxis operons and chey genes. | rhodobacter sphaeroides chemotaxis is significantly more complex than that of enteric bacteria. rhodobacter sphaeroides has multiple copies of chemotaxis genes (two chea, one cheb, two cher, three chew, five chey but no chez), controlling a single 'stop-start' flagellum. the growth environment controls the level of expression of different groups of genes. tethered cell analysis of mutants suggests that chey(4) and chey(5) are the motor-binding response regulators. the histidine protein kinase ch ... | 2000 | 10970853 |
| promoter opening by sigma(54) and sigma(70) rna polymerases: sigma factor-directed alterations in the mechanism and tightness of control. | transcription control at the melting step is not yet understood. here, band shift, cross-linking, and transcription experiments on diverse dna probes were used with two bacterial rna polymerase holoenzymes that differ in how they regulate melting. data indicated that both sigma(54) and sigma(70) holoenzymes assume a default closed form that cannot establish single-strand binding. upon activation the enzymes are converted to an open form that can bind simultaneously to the upstream fork junction ... | 2000 | 10970887 |
| inactivation of the gene for phospholipid n-methyltransferase in sinorhizobium meliloti: phosphatidylcholine is required for normal growth. | in phosphatidylcholine (pc)-containing prokaryotes, only the methylation pathway of pc biosynthesis was thought to occur. however, a second choline-dependent pathway for pc formation, the pc synthase (pcs) pathway, exists in sinorhizobium (rhizobium) meliloti in which choline is condensed with cdp-diacylglyceride. here, we characterize the methylation pathway of pc biosynthesis in s. meliloti. a mutant deficient in phospholipid n-methyltransferase (pmt) was complemented with a s. meliloti gene b ... | 2000 | 10972799 |
| the sinorhizobium meliloti expe1 protein secreted by a type i secretion system involving expd1 and expd2 is required for biosynthesis or secretion of the exopolysaccharide galactoglucan. | in sinorhizobium meliloti the biosynthesis of the exopolysaccharide galactoglucan (eps ii) is directed by the exp genes. the expd1 and expd2 gene products are homologous to components of type i secretion systems. expe1, the gene of which is located adjacent to expd1 and expd2, was detected in s. meliloti cells and culture supernatants. expd1 and expd2 were required for the secretion of expe1, indicating that expe1 is secreted by a type i secretion system involving expd1 and expd2. expe1 contains ... | 2000 | 10974111 |
| proteome analysis of differentially displayed proteins as a tool for the investigation of symbiosis. | two-dimensional gel electrophoresis was used to identify differentially displayed proteins expressed during the symbiotic interaction between the bacterium sinorhizobium meliloti strain 1021 and the legume melilotus alba (white sweetclover). our aim was to characterize novel symbiosis proteins and to determine how the two symbiotic partners alter their respective metabolisms as part of the interaction, by identifying gene products that are differentially present between the symbiotic and non-sym ... | 2000 | 10975656 |
| variation of microbial rhizosphere communities in response to crop species, soil origin, and inoculation with sinorhizobium meliloti l33. | a greenhouse study with soil-plant microcosms was conducted in order to compare the effect of crop species, soil origin, and a bacterial inoculant on the establishment of microbial communities colonizing plant roots. two crop species, alfalfa (medicago sativa) and rye (secale cereale), were grown separately in two soils collected from agricultural fields at different locations and with differing histories of leguminous crop rotation. a subset of microcosms was inoculated at 10(6) cfu g(-1) soil ... | 2000 | 10977876 |
| a critical role for ania in energy-carbon flux and symbiotic nitrogen fixation in sinorhizobium meliloti. | during free-living reproductive growth, sinorhizobium meliloti accumulates poly-beta-hydroxybutyrate (phb) and glycogen, and produces and excretes exopolysaccharides and beta-1,2-glucan. in previous investigations, phb-minus mutants of s. meliloti 41 were obtained and studied; and the genes for phb biosynthesis, phaab and phac, were described. in this work, the role of an open reading frame (orf) upstream of phaab is studied. this orf is designated ania because the gene was found to be expressed ... | 2000 | 10985741 |
| varying the abundance of o antigen in rhizobium etli and its effect on symbiosis with phaseolus vulgaris. | judged by migration of its lipopolysaccharide (lps) in gel electrophoresis, the o antigen of rhizobium etli mutant strain ce166 was apparently of normal size. however, its lps sugar composition and staining of the lps bands after electrophoresis indicated that the proportion of its lps molecules that possessed o antigen was only 40% of the wild-type value. its lps also differed from the wild type by lacking quinovosamine (2-amino-2,6-dideoxyglucose). both of these defects were due to a single ge ... | 2000 | 10986232 |
| orit-directed cloning of defined large regions from bacterial genomes: identification of the sinorhizobium meliloti pexo megaplasmid replicator region. | we have developed a procedure to directly clone large fragments from the genome of the soil bacterium sinorhizobium meliloti. specific regions to be cloned are first flanked by parallel copies of an origin of transfer (orit) together with a plasmid replication origin capable of replicating large clones in escherichia coli but not in the target organism. supplying transfer genes in trans specifically transfers the orit-flanked region, and in this process, site-specific recombination at the orit s ... | 2000 | 10986253 |
| role of the rna polymerase alpha subunits in metr-dependent activation of mete and meth: important residues in the c-terminal domain and orientation requirements within rna polymerase. | many transcription factors activate by directly interacting with rna polymerase (rnap). the c terminus of the rnap alpha subunit (alphactd) is a common target of activators. we used both random mutagenesis and alanine scanning to identify alphactd residues that are crucial for metr-dependent activation of mete and meth. we found that these residues localize to two distinct faces of the alphactd. the first is a complex surface consisting of residues important for alpha-dna interactions, activatio ... | 2000 | 10986259 |
| identification of brucella abortus oxyr and its role in control of catalase expression. | we report the cloning and sequencing of the brucella abortus oxyr homolog and provide evidence that the transcription product of this gene binds to the b. abortus catalase promoter region. a gene replacement/deletion brucella oxyr mutant exhibits increased sensitivity to prolonged exposure to h(2)o(2) and is unable to adapt to h(2)o(2) in the environment. | 2000 | 10986275 |
| is1414, an escherichia coli insertion sequence with a heat-stable enterotoxin gene embedded in a transposase-like gene. | enteroaggregative escherichia coli (eaec) heat-stable enterotoxin 1 (east1) was originally discovered in eaec but has also been associated with enterotoxigenic e. coli (etec). multiple genomic restriction fragments from each of three etec strains of human origin showed homology with an east1 gene probe. a single hybridizing fragment was detected on the plasmid of etec strain 27d that also encodes heat-stable enterotoxin ib and colonization factor antigen i. we isolated and characterized this fra ... | 2000 | 10992475 |
| identification and characterization of the brucella abortus phosphoglucomutase gene: role of lipopolysaccharide in virulence and intracellular multiplication. | smooth lipopolysaccharide (lps) of brucella abortus has been reported to be an important virulence factor, although its precise role in pathogenesis is not yet clear. while the protective properties of lps against complement are well accepted, there is still some controversy about the capacity of rough mutants to replicate intracellularly. the b. abortus phosphoglucomutase gene (pgm) was cloned, sequenced, and disrupted. the gene has a high index of identity to agrobacterium tumefaciens pgm but ... | 2000 | 10992476 |
| keys to symbiotic harmony. | | 2000 | 11004160 |
| effects of nonpolar mutations in each of the seven bacillus subtilis mrp genes suggest complex interactions among the gene products in support of na(+) and alkali but not cholate resistance. | the bacillus subtilis mrp (multiple resistance and ph) operon supports na(+) and alkali resistance via an na(+)/h(+) antiport, as well as cholate efflux and resistance. among the individual mutants with nonpolar mutations in each of the seven mrp genes, only the mrpf mutant exhibited cholate sensitivity and a cholate efflux defect that were complemented by expression of the deleted gene in trans. expression of mrpf in the mrp null (vkn1) strain also restored cholate transport and increased na(+) ... | 2000 | 11004162 |
| transcriptional regulation of the cpr gene cluster in ortho-chlorophenol-respiring desulfitobacterium dehalogenans. | to characterize the expression and possible regulation of reductive dehalogenation in halorespiring bacteria, a 11.5-kb genomic fragment containing the o-chlorophenol reductive dehalogenase-encoding cprba genes of the gram-positive bacterium desulfitobacterium dehalogenans was subjected to detailed molecular characterization. sequence analysis revealed the presence of eight designated genes with the order cprtkzebacd and with the same polarity except for cprt. the deduced cprc and cprk gene prod ... | 2000 | 11004165 |
| four genes of medicago truncatula controlling components of a nod factor transduction pathway. | rhizobium nodulation (nod) factors are lipo-chitooligosaccharides that act as symbiotic signals, eliciting several key developmental responses in the roots of legume hosts. using nodulation-defective mutants of medicago truncatula, we have started to dissect the genetic control of nod factor transduction. mutants in four genes (dmi1, dmi2, dmi3, and nsp) were pleiotropically affected in nod factor responses, indicating that these genes are required for a nod factor-activated signal transduction ... | 2000 | 11006338 |
| generation of new hydrogen-recycling rhizobiaceae strains by introduction of a novel hup minitransposon. | hydrogen evolution by nitrogenase is a source of inefficiency for the nitrogen fixation process by the rhizobium-legume symbiosis. to develop a strategy to generate rhizobial strains with h(2)-recycling ability, we have constructed a tn5 derivative minitransposon (tnhb100) that contains the ca. 18-kb h(2) uptake (hup) gene cluster from rhizobium leguminosarum bv. viciae upm791. bacteroids from tnhb100-containing strains of r. leguminosarum bv. viciae pre, bradyrhizobium japonicum, r. etli, and m ... | 2000 | 11010872 |
| identification and analysis of the polyhydroxyalkanoate-specific beta-ketothiolase and acetoacetyl coenzyme a reductase genes in the cyanobacterium synechocystis sp. strain pcc6803. | synechocystis sp. strain pcc6803 possesses a polyhydroxyalkanoate (pha)-specific beta-ketothiolase encoded by phaa(syn) and an acetoacetyl-coenzyme a (coa) reductase encoded by phab(syn). a similarity search of the entire synechocystis genome sequence identified a cluster of two putative open reading frames (orfs) for these genes, slr1993 and slr1994. sequence analysis showed that the orfs encode proteins having 409 and 240 amino acids, respectively. the two orfs are colinear and most probably c ... | 2000 | 11010896 |
| phenylacetyl-coenzyme a is the true inducer of the phenylacetic acid catabolism pathway in pseudomonas putida u. | aerobic degradation of phenylacetic acid in pseudomonas putida u is carried out by a central catabolism pathway (phenylacetyl-coenzyme a [coa] catabolon core). induction of this route was analyzed by using different mutants specifically designed for this objective. our results revealed that the true inducer molecule is phenylacetyl-coa and not other structurally or catabolically related aromatic compounds. | 2000 | 11010921 |
| growth promoting effect of two sinorhizobium meliloti strains (a wild type and its genetically modified derivative) on a non-legume plant species in specific interaction with two arbuscular mycorrhizal fungi. | in the present study, we have investigated whether the ubiquitous rhizosphere soil organism sinorhizobium meliloti has a plant growth promoting (pgp) effect on non-leguminous plant species. such pgp activity was investigated for both a wild type strain and its genetically modified (gm) derivative, which had an enhanced biofertilizer capability. the pgp effect of these rhizobial strains was tested in interaction with two arbuscular-mycorrhizal (am) fungi: g. mosseae or g. intraradices on lettuce ... | 2000 | 11011093 |
| functional analysis of chimeras derived from the sinorhizobium meliloti and mesorhizobium loti nodc genes identifies regions controlling chitin oligosaccharide chain length. | the rhizobial nodulation gene nodc encodes an n-acetylglucosaminyltransferase that is responsible for the synthesis of chitin oligosaccharides. these oligosaccharides are precursors for the synthesis of the lipo-chitin oligosaccharides that induce cell division and differentiation during the development of nitrogen-fixing root nodules in leguminous plants. the nodc proteins of mesorhizobium loti and sinorizobium meliloti yield chitinpentaose and chitintetraose as their main products, respectivel ... | 2000 | 11016835 |
| heat shock protein 60 sequence comparisons: duplications, lateral transfer, and mitochondrial evolution. | heat shock proteins 60 (groel) are highly expressed essential proteins in eubacterial genomes and in eukaryotic organelles. these chaperone proteins have been advanced as propitious marker sequences for tracing the evolution of mitochondrial (mt) genomes. similarities among hsp60 sequences based on significant segment pair alignment calculations are used to deduce associations of sequences taking into account groel functional/structural domain differences and to relate hsp60 duplications pervasi ... | 2000 | 11027334 |
| nod factors and chitooligomers elicit an increase in cytosolic calcium in aequorin-expressing soybean cells. | rhizobial nod factors (nfs) function as nodulation signals that trigger symbiotic responses of leguminous host plants. nfs consist of a chitin oligomer backbone carrying a fatty acid at the non-reducing end. depending on the rhizobial strain, nfs carry additional substituents, which may determine host specificity. transgenic suspension-cultured soybean (glycine max [l.] merr.) cells expressing aequorin have been used to record cytosolic [ca(2+)] changes upon treatment with purified nfs and chiti ... | 2000 | 11027722 |
| energy taxis is the dominant behavior in azospirillum brasilense. | energy taxis encompasses aerotaxis, phototaxis, redox taxis, taxis to alternative electron acceptors, and chemotaxis to oxidizable substrates. the signal for this type of behavior is originated within the electron transport system. energy taxis was demonstrated, as a part of an overall behavior, in several microbial species, but it did not appear as the dominant determinant in any of them. in this study, we show that most behavioral responses proceed through this mechanism in the alpha-proteobac ... | 2000 | 11029423 |
| discovery, purification, and characterization of a temperate transducing bacteriophage for bordetella avium. | we discovered and characterized a temperate transducing bacteriophage (ba1) for the avian respiratory pathogen bordetella avium. ba1 was initially identified along with one other phage (ba2) following screening of four strains of b. avium for lysogeny. of the two phage, only ba1 showed the ability to transduce via an allelic replacement mechanism and was studied further. with regard to host range, ba1 grew on six of nine clinical isolates of b. avium but failed to grow on any tested strains of b ... | 2000 | 11029434 |
| positive selection for mutations affecting bioconversion of aromatic compounds in agrobacterium tumefaciens: analysis of spontaneous mutations in the protocatechuate 3,4-dioxygenase gene. | a positive selection method for mutations affecting bioconversion of aromatic compounds was applied to a mutant strain of agrobacterium tumefaciens a348. the nucleotide sequence of the a348 pcahgb genes, which encode protocatechuate 3,4-dioxygenase (pcahg) and beta-carboxy-cis,cis-muconate cycloisomerase (pcab) for the first two steps in catabolism of the diphenolic protocatechuate, was determined. an omega element was introduced into the pcab gene of a348, creating strain ado2077. in the presen ... | 2000 | 11029436 |
| nonspecific adherence by actinobacillus actinomycetemcomitans requires genes widespread in bacteria and archaea. | the gram-negative coccobacillus, actinobacillus actinomycetemcomitans, is the putative agent for localized juvenile periodontitis, a particularly destructive form of periodontal disease in adolescents. this bacterium has also been isolated from a variety of other infections, notably endocarditis. fresh clinical isolates of a. actinomycetemcomitans form tenacious biofilms, a property likely to be critical for colonization of teeth and other surfaces. here we report the identification of a locus o ... | 2000 | 11029439 |
| pseudobactin biogenesis in the plant growth-promoting rhizobacterium pseudomonas strain b10: identification and functional analysis of the l-ornithine n(5)-oxygenase (psba) gene. | pseudobactin(b10), the fluorescent siderophore produced by the rhizobacterium pseudomonas strain b10, contains the hydroxamate ligand d-n(5)-hydroxyornithine (d-n(5)-oh-orn). we cloned the l-orn n(5)-oxygenase (psba) gene from a genomic library of pseudomonas strain b10 and demonstrated that psba is involved in the conversion of l-orn to its n(5)-oh derivative. psba shows significant similarity to microbial omega-amino acid hydroxylases containing flavin adenine dinucleotide and nadp cofactor-bi ... | 2000 | 11029447 |
| identification and mapping of sigma-54 promoters in chlamydia trachomatis. | the first sigma(54) promoters in chlamydia trachomatis l2 were mapped upstream of hypothetical proteins ct652.1 and ct683. comparative genomics indicated that these sigma(54) promoters and potential upstream activation binding sites are conserved in orthologous c. trachomatis d, c. trachomatis mouse pneumonitis strain, and chlamydia pneumoniae (cwl029 and ar39) genes. | 2000 | 11029448 |
| crystal structure of the cell division protein ftsa from thermotoga maritima. | bacterial cell division requires formation of a septal ring. a key step in septum formation is polymerization of ftsz. ftsa directly interacts with ftsz and probably targets other proteins to the septum. we have solved the crystal structure of ftsa from thermotoga maritima in the apo and atp-bound form. ftsa consists of two domains with the nucleotide-binding site in the interdomain cleft. both domains have a common core that is also found in the actin family of proteins. structurally, ftsa is m ... | 2000 | 11032797 |
| sinorhizobium meliloti associated with medicago sativa and melilotus spp. in arid saline soils in xinjiang, china. | of 42 rhizobial isolates from medicago sativa and melilotus spp. growing in arid saline fields in xinjiang, china, 40 were identified as sinorhizobium meliloti by a polyphasic approach. however, diverse groups were obtained from these isolates in numerical taxonomy and sds-page of proteins. they could grow at ph 10.5 and were tolerant to 2.5-4.0% (w/v) nacl. | 2000 | 11034500 |
| bacteroides fragilis nctc9343 produces at least three distinct capsular polysaccharides: cloning, characterization, and reassignment of polysaccharide b and c biosynthesis loci. | bacteroides fragilis produces a capsular polysaccharide complex (cpc) that is directly involved in its ability to induce abscesses. two distinct capsular polysaccharides, polysaccharide a (ps a) and ps b, have been shown to be synthesized by the prototype strain for the study of abscesses, nctc9343. both of these polysaccharides in purified form induce abscesses in animal models. in this study, we demonstrate that the cpc of nctc9343 is composed of at least three distinct capsular polysaccharide ... | 2000 | 11035722 |
| role of catalase in campylobacter jejuni intracellular survival. | the ability of campylobacter jejuni to penetrate normally nonphagocytic host cells is believed to be a key virulence determinant. recently, kinetics of c. jejuni intracellular survival have been described and indicate that the bacterium can persist and multiply within epithelial cells and macrophages in vitro. studies conducted by pesci et al. indicate that superoxide dismutase contributes to intraepithelial cell survival, as isogenic sod mutants are 12-fold more sensitive to intracellular killi ... | 2000 | 11035743 |
| expression of early nodulin genes in alfalfa mycorrhizae indicates that signal transduction pathways used in forming arbuscular mycorrhizae and rhizobium-induced nodules may be conserved. | transcripts for two genes expressed early in alfalfa nodule development (msenod40 and msenod2) are found in mycorrhizal roots, but not in noncolonized roots or in roots infected with the fungal pathogen rhizoctonia solani. these same two early nodulin genes are expressed in uninoculated roots upon application of the cytokinin 6-benzylaminopurine. correlated with the expression of the two early nodulin genes, we found that mycorrhizal roots contain higher levels of trans-zeatin riboside than nonm ... | 1997 | 11038545 |
| enod40 induces dedifferentiation and division of root cortical cells in legumes. | under nitrogen-limiting conditions rhizobium meliloti can establish symbiosis with medicago plants to form nitrogen-fixing root nodules. nodule organogenesis starts with the dedifferentiation and division of root cortical cells. in these cells the early nodulin gene enod40, which encodes an unusually small peptide (12 or 13 amino acids), is induced from the beginning of this process. herein we show that enod40 expression evokes root nodule initiation. (i) nitrogen-deprived transgenic medicago tr ... | 1997 | 11038563 |
| transcription initiation-defective forms of sigma(54) that differ in ability to function with a heteroduplex dna template. | transcription by sigma(54)-rna polymerase holoenzyme requires an activator that catalyzes isomerization of the closed promoter complex to an open complex. we examined mutant forms of salmonella enterica serovar typhimurium sigma(54) that were defective in transcription initiation but retained core rna polymerase- and promoter-binding activities. four of the mutant proteins allowed activator-independent transcription from a heteroduplex dna template. one of these mutant proteins, l124p v148a, had ... | 2000 | 11053397 |
| escherichia coli tehb requires s-adenosylmethionine as a cofactor to mediate tellurite resistance. | the escherichia coli chromosomal determinant for tellurite resistance consists of two genes (teha and tehb) which, when expressed on a multicopy plasmid, confer resistance to k(2)teo(3) at 128 microg/ml, compared to the mic of 2 microg/ml for the wild type. tehb is a cytoplasmic protein which possesses three conserved motifs (i, ii, and iii) found in s-adenosyl-l-methionine (sam)-dependent non-nucleic acid methyltransferases. replacement of the conserved aspartate residue in motif i by asparagin ... | 2000 | 11053398 |
| [improvement of nitrogen fixation efficiency and plasmid stability in bradyrhizobium japonicum by the introduction of dctabd and parcba/de genes]. | a recombinant plasmid phn207 containing c4-dicarboxylic acid transport genes (dctabd) from sinorhizobium meliloti, parcba/de genes from ptr102 and reporter genes luxab from pdb30 was constructed by using plafr3 as the vector. the phn207 was then introduced into the bradyrhizobium japonicum ta11 and cb1809 by bi-parental mating. it was confirmed that parcba/de genes could increase the stability of plafr3 in the transconjugants under both free-living and symbiotic condition. the results of plant p ... | 2000 | 11055128 |
| cloning and random mutagenesis of the erwinia herbicola tyrr gene for high-level expression of tyrosine phenol-lyase. | tyrosine phenol-lyase (tpl), which can synthesize 3, 4-dihydroxyphenylalanine from pyruvate, ammonia, and catechol, is a tyrosine-inducible enzyme. previous studies demonstrated that the tpl promoter of erwinia herbicola is activated by the tyrr protein of escherichia coli. in an attempt to create a high-tpl-expressing strain, we cloned the tyrr gene of e. herbicola and then randomly mutagenized it. mutant tyrr proteins with enhanced ability to activate tpl were screened for by use of the lac re ... | 2000 | 11055921 |
| genetic diversity and dynamics of sinorhizobium meliloti populations nodulating different alfalfa cultivars in italian soils. | we analyzed the genetic diversity of 531 sinorhizobium meliloti strains isolated from nodules of medicago sativa cultivars in two different italian soils during 4 years of plant growth. the isolates were analyzed for dna polymorphism with the random amplified polymorphic dna method. the populations showed a high level of genetic polymorphism distributed throughout all the isolates, with 440 different haplotypes. analysis of molecular variance allowed us to relate the genetic structure of the sym ... | 2000 | 11055924 |
| bradyrhizobium sp. strains that nodulate the leguminous tree acacia albida produce fucosylated and partially sulfated nod factors. | we determined the structures of nod factors produced by six different bradyrhizobium sp. strains nodulating the legume tree acacia albida (syn. faidherbia albida). compounds from all strains were found to be similar, i.e., o-carbamoylated and substituted by an often sulfated methyl fucose and different from compounds produced by rhizobium-mesorhizobium-sinorhizobium strains nodulating other species of the acaciae tribe. | 2000 | 11055966 |
| genetic characterization of soybean rhizobia in paraguay. | the soybean is an exotic plant introduced in paraguay in this century; commercial cropping expanded after the 1970s. inoculation is practiced in just 15 to 20% of the cropping areas, but root nodulation occurs in most sites where soybeans grow. little is known about rhizobial diversity in south america, and no study has been performed in paraguay until this time. therefore, in this study, the molecular characterization of 78 rhizobial isolates from soybean root nodules, collected under field con ... | 2000 | 11055970 |
| an imperfect inverted repeat is critical for dna binding of the response regulator regr of bradyrhizobium japonicum. | regr is the response regulator of the regsr two-component regulatory system in bradyrhizobium japonicum. the only target known so far is the fixr-nifa operon, encoding the redox-responsive transcription factor nifa, which activates many genes required for symbiotic nitrogen fixation in soybean nodules. in previous in vivo studies, we identified a 32 bp upstream activating sequence located around position -68, which is essential for regr-dependent expression of the fixr-nifa operon. here, we used ... | 2000 | 11058113 |
| reca-independent ectopic transposition in vivo of a bacterial group ii intron. | rmint1 is a group ii intron of sinorhizobium meliloti which was initially found within the insertion sequence isrm2011-2. although the rmint1 intron-encoded protein lacks a recognizable endonuclease domain, it is able to mediate insertion of rmint1 at an intron-specific location in intronless isrm2011-2 recipient dna, a phenomenon termed homing. here we have characterized three additional insertion sites of rmint1 in the genome of s.meliloti. two of these sites are within is elements closely rel ... | 2000 | 11058141 |
| multicomponent transcriptional regulation at the complex promoter of the exopolysaccharide i biosynthetic operon of ralstonia solanacearum. | high-level transcription of eps, an operon encoding biosynthesis of an exopolysaccharide virulence factor of the phytopathogen ralstonia (pseudomonas) solanacearum, requires the products of at least seven regulatory genes (phca, phcb, xpsr, vsra-vsrd, and vsrb-vsrc), which are organized in three converging signal transduction cascades. because xpsr and the vsrb-vsrc two-component system are the most downstream cascade components required for activation of eps, we explored how these components co ... | 2000 | 11073909 |
| novel role for an hpt domain in stabilizing the phosphorylated state of a response regulator domain. | two-component regulatory systems that utilize a multistep phosphorelay mechanism often involve a histidine-containing phosphotransfer (hpt) domain. these hpt domains serve an essential role as histidine-phosphorylated protein intermediates during phosphoryl transfer from one response regulator domain to another. in saccharomyces cerevisiae, the ypd1 protein facilitates phosphoryl transfer from a hybrid sensor kinase, sln1, to two distinct response regulator proteins, ssk1 and skn7. because the p ... | 2000 | 11073911 |
| genetic analysis of calcium spiking responses in nodulation mutants of medicago truncatula. | the symbiotic interaction between medicago truncatula and sinorhizobium meliloti results in the formation of nitrogen-fixing nodules on the roots of the host plant. the early stages of nodule formation are induced by bacteria via lipochitooligosaccharide signals known as nod factors (nfs). these nfs are structurally specific for bacterium-host pairs and are sufficient to cause a range of early responses involved in the host developmental program. early events in the signal transduction of nfs ar ... | 2000 | 11078514 |
| dissection of nodulation signaling using pea mutants defective for calcium spiking induced by nod factors and chitin oligomers. | changes in intracellular calcium in pea root hairs responding to rhizobium leguminosarum bv. viciae nodulation (nod) factors were analyzed by using a microinjected calcium-sensitive fluorescent dye (dextran-linked oregon green). within 1-2 min after nod-factor addition, there was usually an increase in fluorescence, followed about 10 min later by spikes in fluorescence occurring at a rate of about one spike per minute. these spikes, corresponding to an increase in calcium of approximately 200 nm ... | 2000 | 11078515 |
| structure and sequence analysis of yersinia yada and moraxella uspas reveal a novel class of adhesins. | the non-fimbrial adhesins, yada of enteropathogenic yersinia species, and uspa1 and uspa2 of moraxella catarrhalis, are established pathogenicity factors. in electron micrographs, both surface proteins appear as distinct 'lollipop'-shaped structures forming a novel type of surface projection on the outer membranes. these structures, amino acid sequence analysis of these molecules and yada gene manipulation suggest a tripartite organization: an n-terminal oval head domain is followed by a putativ ... | 2000 | 11080146 |
| the acidic pin of ruva modulates holliday junction binding and processing by the ruvabc resolvasome. | holliday junctions are four-way branched dna structures formed during recombination, replication and repair. they are processed in escherichia coli by the ruva, ruvb and ruvc proteins. ruva targets the junction and facilitates loading of ruvb helicase and ruvc endonuclease to form complexes that catalyse junction branch migration (ruvab) and resolution (ruvabc). we investigated the role of ruva in these reactions and in particular the part played by the acidic pin located on its dna-binding surf ... | 2000 | 11080172 |
| localization of a nod factor-binding protein in legume roots and factors influencing its distribution and expression. | the roots of the legume dolichos biflorus contain a lectin/nucleotide phosphohydrolase (db-lnp) that binds to the nod factor signals produced by rhizobia that nodulate this plant. in this study we show that db-lnp is differentially distributed along the surface of the root axis in a pattern that correlates with the zone of nodulation of the root. db-lnp is present on the surface of young and emerging root hairs and redistributes to the tips of the root hairs in response to treatment of the roots ... | 2000 | 11080281 |
| molecular characterization of the sinorhizobium meliloti nlpd gene. | the sinorhizobium meliloti nlpd gene consists of 1,539 nucleotides and codes for 512 amino acids. expression of the nlpd gene as a histidine-tagged protein in escherichia coli resulted in the production of a 57-kda protein. the deduced polypeptide sequence of nlpd contains one unusual hexamer repeat (kvqrgq), one tetramer (tvtv) and two direct and inverted trimer repeats (kaa, aak). the n-terminal amino acid residues displayed similarity with signal peptides of secreted bacterial lipoproteins. m ... | 2000 | 11081798 |
| hemin-binding surface protein from bartonella quintana. | bartonella quintana, the agent of trench fever and a cause of endocarditis and bacillary angiomatosis in humans, has the highest reported in vitro hemin requirement for any bacterium. we determined that eight membrane-associated proteins from b. quintana bind hemin and that a approximately 25-kda protein (hbpa) was the dominant hemin-binding protein. like many outer membrane proteins, hbpa partitions to the detergent phase of a triton x-114 extract of the cell and is heat modifiable, displaying ... | 2000 | 11083791 |
| sequencing the sinorhizobium meliloti genome. | the sinorhizobium meliloti genome consists of three replicons. this bacterium forms an intricate symbiotic relationship with the roots of certain legumes and is considered as an agriculturally important nitrogen-fixer. a consortium of 6 european laboratories was organized to sequence its single chromosome (3.7 mb), whereas the other two elements (psyma 1.4 mb and psymb 1.7 mb) will be sequenced by other groups. | 2000 | 11092731 |
| molecular evolution of virulence in natural field strains of xanthomonas campestris pv. vesicatoria. | the avrbs2 avirulence gene of the bacterial plant pathogen xanthomonas campestris pv. vesicatoria triggers disease resistance in pepper plants containing the bs2 resistance gene and contributes to bacterial virulence on susceptible host plants. we studied the effects of the pepper bs2 gene on the evolution of avrbs2 by characterizing the molecular basis for virulence of 20 x. campestris pv. vesicatoria field strains that were isolated from disease spots on previously resistant bs2 pepper plants. ... | 2000 | 11092868 |
| characterization of a major cluster of nif, fix, and associated genes in a sugarcane endophyte, acetobacter diazotrophicus. | a major 30.5-kb cluster of nif and associated genes of acetobacter diazotrophicus (syn. gluconacetobacter diazotrophicus), a nitrogen-fixing endophyte of sugarcane, was sequenced and analyzed. this cluster represents the largest assembly of contiguous nif-fix and associated genes so far characterized in any diazotrophic bacterial species. northern blots and promoter sequence analysis indicated that the genes are organized into eight transcriptional units. the overall arrangement of genes is most ... | 2000 | 11092875 |
| coliform bacteria and nitrogen fixation in pulp and paper mill effluent treatment systems. | the majority of pulp and paper mills now biotreat their combined effluents using activated sludge. on the assumption that their wood-based effluents have negligible fixed n, and that activated-sludge microorganisms will not fix significant n, these mills routinely spend large amounts adding ammonia or urea to their aeration tanks (bioreactors) to permit normal biomass growth. n(2) fixation in seven eastern canadian pulp and paper mill effluent treatment systems was analyzed using acetylene reduc ... | 2000 | 11097883 |
| behavioral responses of rhodobacter sphaeroides to linear gradients of the nutrients succinate and acetate. | rhodobacter sphaeroides cells were tethered by their flagella and subjected to increasing and decreasing nutrient gradients. using motion analysis, changes in flagellar motor rotation were measured and the responses of the cells to the chemotactic gradients were determined. the steepness and concentration ranges of increasing and decreasing gradients were varied, and the bacterial responses were measured. this allowed the limits of gradients that would invoke changes in flagellar behavior to be ... | 2000 | 11097888 |
| control of expression of divergent pseudomonas putida put promoters for proline catabolism. | pseudomonas putida kt2440 uses proline as the sole c and n source. utilization of this amino acid involves its uptake, which is mediated by the putp protein, and its conversion into glutamate, mediated by the puta protein. sequence analysis revealed that the puta and putp genes are transcribed divergently. expression from the putp and puta genes was analyzed at the mrna level in different host backgrounds in the absence and presence of proline. expression from the put promoters was induced by pr ... | 2000 | 11097893 |
| fatty acid competition as a mechanism by which enterobacter cloacae suppresses pythium ultimum sporangium germination and damping-off. | interactions between plant-associated microorganisms play important roles in suppressing plant diseases and enhancing plant growth and development. while competition between plant-associated bacteria and plant pathogens has long been thought to be an important means of suppressing plant diseases microbiologically, unequivocal evidence supporting such a mechanism has been lacking. we present evidence here that competition for plant-derived unsaturated long-chain fatty acids between the biological ... | 2000 | 11097912 |
| a homologue of the tryptophan-rich sensory protein tspo and fixl regulate a novel nutrient deprivation-induced sinorhizobium meliloti locus. | a nutrient deprivation-induced locus in sinorhizobium meliloti strain 1021 was identified by use of a tn5-luxab reporter gene transposon. the tagged locus is comprised of two open reading frames (orfs) designated ndia and ndib for nutrient deprivation-induced genes a and b. comparison of the deduced amino acid sequences of both ndia and ndib to the protein databases failed to reveal similarity to any known genes. the expression of the ndi locus was found to be induced by carbon and nitrogen depr ... | 2000 | 11097914 |
| detection on surfaces and in caco-2 cells of campylobacter jejuni cells transformed with new gfp, yfp, and cfp marker plasmids. | we have developed two sets of campylobacter shuttle vectors containing either the gfp (green fluorescent protein), yfp (yellow fluorescent protein), or cfp (cyan fluorescent protein) reporter gene. in one set, the reporter gene is fused to a consensus campylobacter promoter sequence (p(c)). the other set contains a puc18 multicloning site upstream of the reporter gene, allowing the construction of transcriptional fusions using known promoters or random genomic fragments. c. jejuni cells transfor ... | 2000 | 11097924 |
| photosynthetic bradyrhizobia are natural endophytes of the african wild rice oryza breviligulata. | we investigated the presence of endophytic rhizobia within the roots of the wetland wild rice oryza breviligulata, which is the ancestor of the african cultivated rice oryza glaberrima. this primitive rice species grows in the same wetland sites as aeschynomene sensitiva, an aquatic stem-nodulated legume associated with photosynthetic strains of bradyrhizobium. twenty endophytic and aquatic isolates were obtained at three different sites in west africa (senegal and guinea) from nodal roots of o. ... | 2000 | 11097925 |
| biogeography and degree of endemicity of fluorescent pseudomonas strains in soil. | fluorescent pseudomonas strains were isolated from 38 undisturbed pristine soil samples from 10 sites on four continents. a total of 248 isolates were confirmed as pseudomonas sensu stricto by fluorescent pigment production and group-specific 16s ribosomal dna (rdna) primers. these isolates were analyzed by three molecular typing methods with different levels of resolution: 16s rdna restriction analysis (ardra), 16s-23s rdna intergenic spacer-restriction fragment length polymorphism (its-rflp) a ... | 2000 | 11097926 |
| the bradyrhizobium japonicum proline biosynthesis gene proc is essential for symbiosis. | plant host-derived proline is proposed to serve as an energy source for rhizobia in the rhizosphere and in symbiotic root nodules. the bradyrhizobium japonicum proc gene was isolated, and a proc mutant strain that behaved as a strict proline auxotroph in culture was constructed. the proc strain elicited undeveloped nodules on soybeans that lacked nitrogen fixation activity and plant hemoglobin. we conclude that the proc gene is essential for symbiosis and suggest that the mutant does not obtain ... | 2000 | 11097929 |
| the chvh locus of agrobacterium encodes a homologue of an elongation factor involved in protein synthesis. | the virulence of agrobacterium tumefaciens depends on both chromosome- and ti plasmid-encoded gene products. in this study, we characterize a chromosomal locus, chvh, previously identified by tnphoa mutagenesis and shown to be required for tumor formation. through dna sequencing and comparison of the sequence with identified sequences in the database, we show that this locus encodes a protein similar in sequence to elongation factor p, a protein thought to be involved in peptide bond synthesis i ... | 2001 | 11114898 |
| identification of residues involved in catalytic activity of the inverting glycosyl transferase wbbe from salmonella enterica serovar borreze. | synthesis of the o:54 o antigen of salmonella enterica is initiated by the nonprocessive glycosyl transferase wbbe, assigned to family 2 of the glycosyl transferase enzymes (gt2). gt2 enzymes possess a characteristic n-terminal domain, domain a. based on structural data from the gt2 representative spsa (s. j. charnock and g. j. davies, biochemistry 38:6380-6385, 1999), this domain is responsible for nucleotide binding. it possesses two invariant asp residues, the first forming a hydrogen bond to ... | 2001 | 11114903 |
| rubrerythrin and rubredoxin oxidoreductase in desulfovibrio vulgaris: a novel oxidative stress protection system. | evidence is presented for an alternative to the superoxide dismutase (sod)-catalase oxidative stress defense system in desulfovibrio vulgaris (strain hildenborough). this alternative system consists of the nonheme iron proteins, rubrerythrin (rbr) and rubredoxin oxidoreductase (rbo), the product of the rbo gene (also called desulfoferrodoxin). a deltarbo strain of d. vulgaris was found to be more sensitive to internal superoxide exposure than was the wild type. unlike rbo, expression of plasmid- ... | 2001 | 11114906 |
| methylotrophic methylobacterium bacteria nodulate and fix nitrogen in symbiosis with legumes. | rhizobia described so far belong to three distinct phylogenetic branches within the alpha-2 subclass of proteobacteria. here we report the discovery of a fourth rhizobial branch involving bacteria of the methylobacterium genus. rhizobia isolated from crotalaria legumes were assigned to a new species, "methylobacterium nodulans," within the methylobacterium genus on the basis of 16s ribosomal dna analyses. we demonstrated that these rhizobia facultatively grow on methanol, which is a characterist ... | 2001 | 11114919 |
| critical protective role of bacterial superoxide dismutase in rhizobium-legume symbiosis. | in nitrogen-poor soils, rhizobia elicit nodule formation on legume roots, within which they differentiate into bacteroids that fix atmospheric nitrogen. protection against reactive oxygen species (ros) was anticipated to play an important role in rhizobium-legume symbiosis because nitrogenase is extremely oxygen sensitive. we deleted the soda gene encoding the sole cytoplasmic superoxide dismutase (sod) of sinorhizobium meliloti. the resulting mutant, deficient in superoxide dismutase, grew almo ... | 2000 | 11115110 |
| evidence for a functional similarity between the two-component regulatory systems regsr, actsr, and regba (prrba) in alpha-proteobacteria. | the symbiotic bacteria bradyrhizobium japonicum and sinorhizobium meliloti, and the purple photosynthetic bacteria rhodobacter capsulatus, rhodovulum sulfidophilum, roseobacter denitrificans and rhodobacter sphaeroides possess homologous two-component regulatory systems, namely regsr, actsr, regba and prrba. the respective response regulators of these bacteria control expression of different regulons that are involved in n2 fixation, co2 fixation, photosynthesis or acid tolerance. we therefore a ... | 2000 | 11131020 |
| novel tellurite-amended media and specific chromosomal and ti plasmid probes for direct analysis of soil populations of agrobacterium biovars 1 and 2. | ecology and biodiversity studies of agrobacterium spp. require tools such as selective media and dna probes. tellurite was tested as a selective agent and a supplement of previously described media for agrobacteria. the known biodiversity within the genus was taken into account when the selectivity of k(2)teo(3) was analyzed and its potential for isolating agrobacterium spp. directly from soil was evaluated. a k(2)teo(3) concentration of 60 ppm was found to favor the growth of agrobacteria and r ... | 2001 | 11133429 |
| direct cloning from enrichment cultures, a reliable strategy for isolation of complete operons and genes from microbial consortia. | enrichment cultures of microbial consortia enable the diverse metabolic and catabolic activities of these populations to be studied on a molecular level and to be explored as potential sources for biotechnology processes. we have used a combined approach of enrichment culture and direct cloning to construct cosmid libraries with large (>30-kb) inserts from microbial consortia. enrichment cultures were inoculated with samples from five environments, and high amounts of avidin were added to the cu ... | 2001 | 11133432 |
| non-growth-associated demethylation of dimethylsulfoniopropionate by (homo)acetogenic bacteria. | the demethylation of the algal osmolyte dimethylsulfoniopropionate (dmsp) to methylthiopropionate (mtpa) by (homo)acetogenic bacteria was studied. five eubacterium limosum strains (including the type strain), sporomusa ovata dsm 2662(t), sporomusa sphaeroides dsm 2875(t), and acetobacterium woodii dsm 1030(t) were shown to demethylate dmsp stoichiometrically to mtpa. the (homo)acetogenic fermentation based on this demethylation did not result in any significant increase in biomass. the analogous ... | 2001 | 11133459 |
| small-subunit rrna genotyping of rhizobia nodulating australian acacia spp. | the structure of rhizobial communities nodulating acacia in southeastern australia from south queensland to tasmania was investigated by a molecular approach. a total of 118 isolates from nodule samples from 13 different acacia species collected at 44 sites were characterized by small-subunit (ssu) ribosomal dna (rdna) pcr-restriction fragment length polymorphism analysis. nine rhizobial genomospecies were identified, and these taxa corresponded to previously described genomospecies (b. lafay an ... | 2001 | 11133471 |
| identification of the nik gene cluster of brucella suis: regulation and contribution to urease activity. | analysis of a brucella suis 1330 gene fused to a gfp reporter, and identified as being induced in j774 murine macrophage-like cells, allowed the isolation of a gene homologous to nika, the first gene of the escherichia coli operon encoding the specific transport system for nickel. dna sequence analysis of the corresponding b. suis nik locus showed that it was highly similar to that of e. coli except for localization of the nikr regulatory gene, which lies upstream from the structural nikabcde ge ... | 2001 | 11133934 |
| the gdhb gene of pseudomonas aeruginosa encodes an arginine-inducible nad(+)-dependent glutamate dehydrogenase which is subject to allosteric regulation. | the nad(+)-dependent glutamate dehydrogenase (nad-gdh) from pseudomonas aeruginosa pao1 was purified, and its amino-terminal amino acid sequence was determined. this sequence information was used in identifying and cloning the encoding gdhb gene and its flanking regions. the molecular mass predicted from the derived sequence for the encoded nad-gdh was 182.6 kda, in close agreement with that determined from sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme (180 kda ... | 2001 | 11133942 |
| genetic and biochemical analyses of bvga interaction with the secondary binding region of the fha promoter of bordetella pertussis. | the bvga-bvgs two-component signal transduction system regulates expression of virulence factors in bordetella pertussis. the bvga response regulator activates transcription by binding to target promoters, which include those for the genes encoding filamentous hemagglutinin (fha) and pertussis toxin (ptx). we have previously shown that at both promoters the phosphorylated form of bvga binds multiple high- and low-affinity sites. specifically, at the fha promoter, we proposed that there may be hi ... | 2001 | 11133947 |
| ihfa gene of the bacterium myxococcus xanthus and its role in activation of carotenoid genes by blue light. | myxococcus xanthus responds to blue light by producing carotenoids. several regulatory genes are known that participate in the light action mechanism, which leads to the transcriptional activation of the carotenoid genes. we had already reported the isolation of a carotenoid-less, tn5-induced strain (mr508), whose mutant site was unlinked to the indicated regulatory genes. here, we show that omegamr508::tn5 affects all known light-inducible promoters in different ways. it blocks the activation o ... | 2001 | 11133949 |
| nag genes of ralstonia (formerly pseudomonas) sp. strain u2 encoding enzymes for gentisate catabolism. | ralstonia sp. strain u2 metabolizes naphthalene via gentisate to central metabolites. we have cloned and sequenced a 21.6-kb region spanning the nag genes. upstream of the pathway genes are nagy, homologous to chemotaxis proteins, and nagr, a regulatory gene of the lysr family. divergently transcribed from nagr are the genes for conversion of naphthalene to gentisate (nagaaghabacadbfcqed) (s. l. fuenmayor, m. wild, a. l. boyes, and p. a. williams, j. bacteriol. 180:2522-2530, 1998), which except ... | 2001 | 11133965 |
| temporal regulation of genes encoding the flagellar proximal rod in caulobacter crescentus. | the gram-negative bacterium caulobacter crescentus has a life cycle that includes two distinct and separable developmental stages, a motile swarmer phase and a sessile stalked phase. the cell cycle-controlled biogenesis of the single polar flagellum of the swarmer cell is the best-studied aspect of this developmental program. the flagellar regulon is arranged into a rigid trans-acting hierarchy of gene expression in which successful expression of early genes is required for the expression of gen ... | 2001 | 11133968 |
| vertical transmission of biosynthetic plasmids in aphid endosymbionts (buchnera). | this study tested for horizontal transfer of plasmids among buchnera aphidicola strains associated with ecologically and phylogenetically related aphid hosts (uroleucon species). phylogenetic congruence of buchnera plasmid (trpeg and leuabc) and chromosomal (dnan and trpb) genes supports strictly vertical long-term transmission of plasmids, which persist due to their contributions to host nutrition rather than capacity for infectious transfer. synonymous divergences indicate elevated mutation on ... | 2001 | 11133977 |
| limited genetic diversity of brucella spp. | multilocus enzyme electrophoresis (mlee) of 99 brucella isolates, including the type strains from all recognized species, revealed a very limited genetic diversity and supports the proposal of a monospecific genus. in mlee-derived dendrograms, brucella abortus and a marine brucella sp. grouped into a single electrophoretic type related to brucella neotomae and brucella ovis. brucella suis and brucella canis formed another cluster linked to brucella melitensis and related to rhizobium tropici. th ... | 2001 | 11136777 |