| accumulation in marine sponge grafts of the mrna encoding the main proteins of the cell adhesion system. | specific cell adhesion in the marine sponge microciona prolifera is mediated by an extracellular aggregation factor complex, whose main protein component, termed mafp3, is highly polymorphic. we have now identified mafp4, an approximately 400-kda protein, from the aggregation factor that is translated from the same mrna as mafp3. the existence of multiple potential sites for n-glycosylation and calcium binding suggests a direct involvement of mafp4 in the species-specific aggregation of sponge c ... | 1998 | 9792663 |
| characterization of mutations that allow p-aminobenzoyl-glutamate utilization by escherichia coli. | an escherichia coli strain deficient in p-aminobenzoate synthesis was mutagenized, and derivatives were selected for growth on folic acid. supplementation was shown to be due to p-aminobenzoyl-glutamate present as a breakdown product in commercial folic acid preparations. two classes of mutations characterized by the minimum concentration of p-aminobenzoyl-glutamate that could support growth were obtained. both classes of mutations were genetically and physically mapped to about 30 min on the e. ... | 1998 | 9829935 |
| 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 |
| 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 |
| carbamoylation of azorhizobial nod factors is mediated by nodu. | lipochitooligosaccharides (lcos) synthesized by azorhizobium caulinodans ors571 are substituted at the nonreducing-terminal residue with a 6-o-carbamoyl group. lco biosynthesis in a. caulinodans is dependent on the nodabcsuijznoec operon. until now, the role of the nodulation protein nodu in the synthesis of azorhizobial lcos remained unclear. based on sequence similarities and structural analysis of lcos produced by a nodu mutant, a complemented nodu mutant, and escherichia coli dh5 alpha expre ... | 1999 | 9885196 |
| genes involved in the formation and assembly of rhizobial cytochromes and their role in symbiotic nitrogen fixation. | rhizobia fix nitrogen in a symbiotic association with leguminous plants and this occurs in nodules. a low-oxygen environment is needed for nitrogen fixation, which paradoxically has a requirement for rapid respiration to produce atp. these conflicting demands are met by control of oxygen flux and production of leghaemoglobin (an oxygen carrier) by the plant, coupled with the expression of a high-affinity oxidase by the nodule bacteria (bacteroids). many of the bacterial genes encoding cytochrome ... | 1998 | 9889979 |
| accumulation of ppgpp in symbiotic and free-living nitrogen-fixing bacteria following amino acid starvation | following amino acid or ammonium starvation, ppgpp is accumulated by rhizobium meliloti strain 1021 but not by r. meliloti strain 41 or rhizobium tropici. azorhizobium caulinodans ors571 produced ppgpp following amino acid deprivation; however, the free-living nitrogen-fixing bacteria azotobacter vinelandii and azomonas agilis did not produce ppgpp. western blot analysis using anti-rela antibody demonstrated that r. meliloti strain 1021, azotobacter vinelandii and azorhizobium caulinodans cross- ... | 1999 | 9914311 |
| the signal transduction protein glnk is required for nifl-dependent nitrogen control of nif gene expression in klebsiella pneumoniae. | in klebsiella pneumoniae, transcription of the nitrogen fixation (nif) genes is regulated in response to molecular oxygen or availability of fixed nitrogen by the coordinated activities of the nifa and nifl gene products. nifa is a nif-specific transcriptional activator, the activity of which is inhibited by interaction with nifl. nitrogen control of nifl occurs at two levels: transcription of the nifla operon is regulated by the global ntr system, and the inhibitory activity of nifl is controll ... | 1999 | 9973341 |
| identification and cloning of an erwinia carotovora subsp. carotovora bacteriocin regulator gene by insertional mutagenesis. | avirulent erwinia carotovora subsp. carotovora cge234-m403 produces two types of bacteriocin. for the purpose of cloning the bacteriocin genes of strain cge234m403, a spontaneous rifampin-resistant mutant of this strain, m-rif-11-2, was isolated. by tn5 insertional mutagenesis using m-rif-11-2, a mutant, tm01a01, which produces the high-molecular-weight bacteriocin but not the low-molecular-weight bacteriocin was obtained. by thermal asymmetric interlaced pcr, the dna sequence from the tn5 inser ... | 1999 | 10074096 |
| coproporphyrin excretion by azorhizobium caulinodans under micro-aerobic conditions. | azorhizobium caulinodans ors571 was found to excrete moderate amounts of a fluorescent pigment into the culture medium in response to dissolved oxygen tensions below 1.0 kpa. the pigment was identified as coproporphyrin, on the basis of its optical and fluorescence spectra. fixlj and fixk mutant derivatives of ors571 were found to excrete 25-fold higher amounts of coproporphyrin under micro-aerobic conditions than the wild type strain. these observations suggest that a. caulinodans switches from ... | 1998 | 10081584 |
| characterization of mdcr, a regulatory gene of the malonate catabolic system in klebsiella pneumoniae. | the klebsiella pneumoniae mdcr gene, which encodes a lysr-type regulator, was overexpressed in escherichia coli. purified mdcr was found to bind specifically to the control region of either the malonate decarboxylase (mdc) genes or mdcr. we have also demonstrated that mdcr is an activator of the expression of the mdc genes, whereas it represses the transcription of the putative control region of mdcr, pmdcr, indicating a negative autoregulatory control. | 1999 | 10094715 |
| ligand specificity of a high-affinity binding site for lipo-chitooligosaccharidic nod factors in medicago cell suspension cultures. | rhizobial lipo-chitooligosaccharides (lcos) are signaling molecules involved in host-range recognition for the establishment of the symbiosis with leguminous plants. the major lco of rhizobium meliloti, the symbiont of medicago plants contains four or five n-acetylglucosamines, o-acetylated and n-acylated with a c16:2 fatty acid on the terminal nonreducing sugar and o-sulfated on the reducing sugar. in this paper, the ligand specificity of a high-affinity binding site (nod factor binding site 2 ... | 1999 | 10200326 |
| the global nitrogen regulator ntca regulates transcription of the signal transducer pii (glnb) and influences its phosphorylation level in response to nitrogen and carbon supplies in the cyanobacterium synechococcus sp. strain pcc 7942. | the pii protein is encoded by a unique glnb gene in synechococcus sp. strain pcc 7942. its expression has been analyzed in the wild type and in ntca-null mutant cells grown under different conditions of nitrogen and carbon supply. rna-dna hybridization experiments revealed the presence of one transcript species 680 nucleotides long, whatever the nutrient conditions tested. a second transcript species, 620 nucleotides long, absent in the ntca null mutant, was observed in wild-type cells that were ... | 1999 | 10217756 |
| enhanced nitrogen fixation in a rhizobium etli ntrc mutant that overproduces the bradyrhizobium japonicum symbiotic terminal oxidase cbb3 | the ntrc gene codes for a transcriptional activator protein that modulates gene expression in response to nitrogen. the cytochrome production pattern of a rhizobium etli ntrc mutant (cfn2012) was studied. co difference spectral analysis of membranes showed that cfn2012 produced a terminal oxidase similar to the symbiotic terminal oxidase of bacteroids in free-living cells under aerobic conditions, with a characteristic trough at 553 nm. cfn2012 produced two c-type cytochromes with molecular mass ... | 1999 | 10223993 |
| occurrence of choline and glycine betaine uptake and metabolism in the family rhizobiaceae and their roles in osmoprotection | the role of glycine betaine and choline in osmoprotection of various rhizobium, sinorhizobium, mesorhizobium, agrobacterium, and bradyrhizobium reference strains which display a large variation in salt tolerance was investigated. when externally provided, both compounds enhanced the growth of rhizobium tropici, sinorhizobium meliloti, sinorhizobium fredii, rhizobium galegae, agrobacterium tumefaciens, mesorhizobium loti, and mesorhizobium huakuii, demonstrating their utilization as osmoprotectan ... | 1999 | 10224003 |
| nodule-inducing activity of synthetic sinorhizobium meliloti nodulation factors and related lipo-chitooligosaccharides on alfalfa. importance of the acyl chain structure. | sinorhizobium meliloti nodulation factors (nfs) elicit a number of symbiotic responses in alfalfa (medicago sativa) roots. using a semiquantitative nodulation assay, we have shown that chemically synthesized nfs trigger nodule formation in the same range of concentrations (down to 10(-10) m) as natural nfs. the absence of o-sulfate or o-acetate substitutions resulted in a decrease in morphogenic activity of more than 100-fold and approximately 10-fold, respectively. to address the question of th ... | 1999 | 10318686 |
| increase in alfalfa nodulation, nitrogen fixation, and plant growth by specific dna amplification in sinorhizobium meliloti. | to improve symbiotic nitrogen fixation on alfalfa plants, sinorhizobium meliloti strains containing different average copy numbers of a symbiotic dna region were constructed by specific dna amplification (sda). a dna fragment containing a regulatory gene (nodd1), the common nodulation genes (nodabc), and an operon essential for nitrogen fixation (nifn) from the nod regulon region of the symbiotic plasmid psyma of s. meliloti was cloned into a plasmid unable to replicate in this organism. the pla ... | 1999 | 10347066 |
| pas domains: internal sensors of oxygen, redox potential, and light. | pas domains are newly recognized signaling domains that are widely distributed in proteins from members of the archaea and bacteria and from fungi, plants, insects, and vertebrates. they function as input modules in proteins that sense oxygen, redox potential, light, and some other stimuli. specificity in sensing arises, in part, from different cofactors that may be associated with the pas fold. transduction of redox signals may be a common mechanistic theme in many different pas domains. pas pr ... | 1999 | 10357859 |
| analysis of a capsular polysaccharide biosynthesis locus of bacteroides fragilis. | a major clinical manifestation of infection with bacteroides fragilis is the formation of intra-abdominal abscesses, which are induced by the capsular polysaccharides of this organism. transposon mutagenesis was used to locate genes involved in the synthesis of capsular polysaccharides. a 24,454-bp region was sequenced and found to contain a 15,379-bp locus (designated wcf) with 16 open reading frames (orfs) encoding products similar to those encoded by genes of other bacterial polysaccharide bi ... | 1999 | 10377135 |
| identification and sequencing of beta-myrcene catabolism genes from pseudomonas sp. strain m1. | the m1 strain, able to grow on beta-myrcene as the sole carbon and energy source, was isolated by an enrichment culture and identified as a pseudomonas sp. one beta-myrcene-negative mutant, called n22, obtained by transposon mutagenesis, accumulated (e)-2-methyl-6-methylen-2,7-octadien-1-ol (or myrcen-8-ol) as a unique beta-myrcene biotransformation product. this compound was identified by gas chromatography-mass spectrometry. we cloned and sequenced the dna regions flanking the transposon and u ... | 1999 | 10388678 |
| purification and characterization of an alpha-glucosidase from rhizobium sp. (robinia pseudoacacia l.) strain usda 4280. | a novel alpha-glucosidase with an apparent subunit mass of 59 +/- 0. 5 kda was purified from protein extracts of rhizobium sp. strain usda 4280, a nodulating strain of black locust (robinia pseudoacacia l), and characterized. after purification to homogeneity (475-fold; yield, 18%) by ammonium sulfate precipitation, cation-exchange chromatography, hydrophobic chromatography, dye chromatography, and gel filtration, this enzyme had a pi of 4.75 +/- 0.05. the enzyme activity was optimal at ph 6.0 t ... | 1999 | 10388682 |
| photosynthetic bradyrhizobia from aeschynomene spp. are specific to stem-nodulated species and form a separate 16s ribosomal dna restriction fragment length polymorphism group. | we obtained nine bacterial isolates from root or collar nodules of the non-stem-nodulated aeschynomene species a. elaphroxylon, a. uniflora, or a. schimperi and 69 root or stem nodule isolates from the stem-nodulated aeschynomene species a. afraspera, a. ciliata, a. indica, a. nilotica, a. sensitiva, and a. tambacoundensis from various places in senegal. these isolates, together with 45 previous isolates from various aeschynomene species, were studied for host-specific nodulation within the genu ... | 1999 | 10388707 |
| production of o-acetylated and sulfated chitooligosaccharides by recombinant escherichia coli strains harboring different combinations of nod genes. | high cell density cultivation of recombinant escherichia coli strains harboring the nodbc genes (encoding chitooligosaccharide synthase and chitooligosaccharide n-deacetylase, respectively) from azorhizobium caulinodans has been previously described as a practical method for the preparation of gram-scale quantities of penta-n-acetyl-chitopentaose and tetra-n-acetylchitopentaose (samain, e., drouillard, s., heyraud, a., driguez, h., geremia, r.a., 1997. carbohydr. res. 30, 235-242). we have now e ... | 1999 | 10406097 |
| phaseolus vulgaris recognizes azorhizobium caulinodans nod factors with a variety of chemical substituents. | phaseolus vulgaris is a promiscuous host plant that can be nodulated by many different rhizobia representing a wide spectrum of nod factors. in this study, we introduced the rhizobium tropici cfn299 nod factor sulfation genes nodhpq into azorhizobium caulinodans. the a. caulinodans transconjugants produce nod factors that are mostly if not all sulfated and often with an arabinosyl residue as the reducing end glycosylation. using a. caulinodans mutant strains, affected in reducing end decorations ... | 1999 | 10494633 |
| activity of the molybdopterin-containing xanthine dehydrogenase of rhodobacter capsulatus can be restored by high molybdenum concentrations in a moea mutant defective in molybdenum cofactor biosynthesis. | during the screening for rhodobacter capsulatus mutants defective in xanthine degradation, one tn5 mutant which was able to grow with xanthine as a sole nitrogen source only in the presence of high molybdate concentrations (1 mm), a phenotype resembling escherichia coli moga mutants, was identified. unexpectedly, the corresponding tn5 insertion was located within the moea gene. partial dna sequence analysis and interposon mutagenesis of regions flanking r. capsulatus moea revealed that no furthe ... | 1999 | 10498704 |
| characterization of mext, the regulator of the mexe-mexf-oprn multidrug efflux system of pseudomonas aeruginosa. | we investigated the regulation of the mexef-oprn multidrug efflux system of pseudomonas aeruginosa, which is overexpressed in nfxc-type mutants and confers resistance to quinolones, chloramphenicol and trimethoprim. sequencing of the dna region upstream of the mexef-oprn operon revealed the presence of an open reading frame (orf) of 304 amino acids encoding a lysr-type transcriptional activator, termed mext. by using t7-polymerase, a 34-kda protein was expressed in escherichia coli from a plasmi ... | 1999 | 10515918 |
| purification of p(ii) and p(ii)-ump and in vitro studies of regulation of glutamine synthetase in rhodospirillum rubrum. | the p(ii) protein from rhodospirillum rubrum was fused with a histidine tag, overexpressed in escherichia coli, and purified by ni(2+)-chelating chromatography. the uridylylated form of the p(ii) protein could be generated in e. coli. the effects on the regulation of glutamine synthetase by p(ii), p(ii)-ump, glutamine, and alpha-ketoglutarate were studied in extracts from r. rubrum grown under different conditions. p(ii) and glutamine were shown to stimulate the atp-dependent inactivation (adeny ... | 1999 | 10515945 |
| expression of p(ii) and glutamine synthetase is regulated by p(ii), the ntrbc products, and processing of the glnba mrna in rhodospirillum rubrum. | we have studied the transcription of the glnb and glna genes in rhodospirillum rubrum with firefly luciferase as a reporter enzyme. under nh(4)(+) and n(2) conditions, glnba was cotranscribed from a weak and a strong promoter. in nitrogen-fixing cultures, activity of the latter was highly enhanced by ntrc, but transcription from both promoters occurred under both conditions. there is no promoter controlling transcription of glna alone, supporting our proposal that the glna mrna is produced by pr ... | 1999 | 10515946 |
| biosynthesis of trehalose from maltooligosaccharides in rhizobia. | previously, the enzymes for trehalose synthesis that are present in escherichia coli were demonstrated in bradyrhizobium japonicum and b. elkanii. an alternative mechanism recently reported for the synthesis of trehalose from maltooligosaccharides was considered based on the fact that high concentrations of sugars in liquid culture stimulated the accumulation of trehalose. an assay for the synthesis of trehalose from maltooligosaccharides using crude, gel-filtered protein preparations was develo ... | 1999 | 10528404 |
| identification, sequencing and structural analysis of a nifa-like gene of acetobacter diazotrophicus. | a recombinant plasmid, pad101, containing a dna fragment of acetobacter diazotrophicus strain pal5 was isolated by its ability to restore nif+ phenotype to a nifa- ntrc- double mutant of azotobacter vinelandii. hybridization with the nifa genes of azospirillum brasilense located the nifa gene more precisely to specific fragments of pad101. dna sequencing of appropriate subclones of pad101 revealed that the nifa gene was adjacent to the nifb gene in a. diazotrophicus, and the 5' end of the nifb g ... | 1999 | 10530336 |
| relationships of bradyrhizobia from the legumes apios americana and desmodium glutinosum. | multilocus enzyme electrophoresis, partial 23s rrna sequences, and nearly full-length 16s rrna sequences all indicated high genetic similarity among root-nodule bacteria associated with apios americana, desmodium glutinosum, and amphicarpaea bracteata, three common herbaceous legumes whose native geographic ranges in eastern north america overlap extensively. a total of 19 distinct multilocus genotypes (electrophoretic types [ets]) were found among the 35 a. americana and 33 d. glutinosum isolat ... | 1999 | 10543803 |
| the basis of ammonium release in nifl mutants of azotobacter vinelandii. | in azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifla. certain mutations in nifl result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve nifa, the activator of nif gene transcription. we have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium releas ... | 1999 | 10572141 |
| hbar, a 4-hydroxybenzoate sensor and fnr-crp superfamily member, regulates anaerobic 4-hydroxybenzoate degradation by rhodopseudomonas palustris. | under anaerobic conditions, structurally diverse aromatic compounds are catabolized by bacteria to form benzoyl-coenzyme a (benzoyl-coa), the starting compound for a central reductive pathway for aromatic ring degradation. the structural genes required for the conversion of 4-hydroxybenzoate (4-hba) to benzoyl-coa by rhodopseudomonas palustris have been identified. here we describe a regulatory gene, hbar, that is part of the 4-hba degradation gene cluster. an hbar mutant that was constructed wa ... | 2000 | 10613868 |
| mutagenesis and functional characterization of the glnb, glna, and nifa genes from the photosynthetic bacterium rhodospirillum rubrum. | nitrogen fixation is tightly regulated in rhodospirillum rubrum at two different levels: transcriptional regulation of nif expression and posttranslational regulation of dinitrogenase reductase by reversible adp-ribosylation catalyzed by the drat-drag (dinitrogenase reductase adp-ribosyltransferase-dinitrogenase reductase-activating glycohydrolase) system. we report here the characterization of glnb, glna, and nifa mutants and studies of their relationship to the regulation of nitrogen fixation. ... | 2000 | 10648524 |
| extracellular glycanases of rhizobium leguminosarum are activated on the cell surface by an exopolysaccharide-related component. | rhizobium leguminosarum secretes two extracellular glycanases, plya and plyb, that can degrade exopolysaccharide (eps) and carboxymethyl cellulose (cmc), which is used as a model substrate of plant cell wall cellulose polymers. when grown on agar medium, cmc degradation occurred only directly below colonies of r. leguminosarum, suggesting that the enzymes remain attached to the bacteria. unexpectedly, when a plya-plyb-secreting colony was grown in close proximity to mutants unable to produce or ... | 2000 | 10671451 |
| the xylem of rice (oryza sativa) is colonized by azorhizobium caulinodans. | following inoculation with azorhizobium caulinodans ors571 (pxlgd4), lateral root development of rice and colonization of lateral root cracks by bacteria were shown to be stimulated by the flavonoid naringenin. rice seedlings growing aseptically in the presence of naringenin were inoculated with ors571 (pxlgd4), carrying the lacz reporter gene. by microscopic analysis of sections of inoculated rice roots, it has been demonstrated that the xylem of rice roots can be colonized by azorhizobium caul ... | 2000 | 10687813 |
| azorhizobium caulinodans pii and glnk proteins control nitrogen fixation and ammonia assimilation. | we herein report that azorhizobium caulinodans pii and glnk are not necessary for glutamine synthetase (gs) adenylylation whereas both proteins are required for complete gs deadenylylation. the disruption of both glnb and glnk resulted in a high level of gs adenylylation under the condition of nitrogen fixation, leading to ammonium excretion in the free-living state. pii and glnk also controlled nif gene expression because nifa activated nifh transcription and nitrogenase activity was derepresse ... | 1999 | 10198037 |
| molecular basis of symbiotic promiscuity. | eukaryotes often form symbioses with microorganisms. among these, associations between plants and nitrogen-fixing bacteria are responsible for the nitrogen input into various ecological niches. plants of many different families have evolved the capacity to develop root or stem nodules with diverse genera of soil bacteria. of these, symbioses between legumes and rhizobia (azorhizobium, bradyrhizobium, mesorhizobium, and rhizobium) are the most important from an agricultural perspective. nitrogen- ... | 2000 | 10704479 |
| effects of glucosinolates and flavonoids on colonization of the roots of brassica napus by azorhizobium caulinodans ors571. | plants of brassica napus were assessed quantitatively for their susceptibility to lateral root crack colonization by azorhizobium caulinodans ors571(pxlgd4) (a rhizobial strain carrying the lacz reporter gene) and for the concentration of glucosinolates in their roots by high-pressure liquid chromatography (hplc). high- and low-glucosinolate-seed (hgs and lgs) varieties exhibited a relatively low and high percentage of colonized lateral roots, respectively. hplc showed that roots of hgs plants c ... | 2000 | 10788398 |
| nod factor requirements for efficient stem and root nodulation of the tropical legume sesbania rostrata. | azorhizobium caulinodans ors571 synthesizes mainly pentameric nod factors with a household fatty acid, an n-methyl, and a 6-o-carbamoyl group at the nonreducing-terminal residue and with a d-arabinosyl, an l-fucosyl group, or both at the reducing-terminal residue. nodulation on sesbania rostrata was carried out with a set of bacterial mutants that produce well characterized nod factor populations. purified nod factors were tested for their capacity to induce root hair formation and for their sta ... | 2000 | 10821846 |
| microbial relatives of the seed storage proteins of higher plants: conservation of structure and diversification of function during evolution of the cupin superfamily. | this review summarizes the recent discovery of the cupin superfamily (from the latin term "cupa," a small barrel) of functionally diverse proteins that initially were limited to several higher plant proteins such as seed storage proteins, germin (an oxalate oxidase), germin-like proteins, and auxin-binding protein. knowledge of the three-dimensional structure of two vicilins, seed proteins with a characteristic beta-barrel core, led to the identification of a small number of conserved residues a ... | 2000 | 10704478 |
| the common nodulation genes of astragalus sinicus rhizobia are conserved despite chromosomal diversity. | the nodulation genes of mesorhizobium sp. (astragalus sinicus) strain 7653r were cloned by functional complementation of sinorhizobium meliloti nod mutants. the common nod genes, nodd, noda, and nodbc, were identified by heterologous hybridization and sequence analysis. the noda gene was found to be separated from nodbc by approximately 22 kb and was divergently transcribed. the 2. 0-kb noddbc region was amplified by pcr from 24 rhizobial strains nodulating a. sinicus, which represented differen ... | 2000 | 10877796 |
| identification of brucella suis genes affecting intracellular survival in an in vitro human macrophage infection model by signature-tagged transposon mutagenesis. | bacteria of the genus brucella are facultative intracellular pathogens which have developed the capacity to survive and multiply in professional and nonprofessional phagocytes. the genetic basis of this aspect of brucella virulence is still poorly understood. to identify new virulence factors, we have adapted signature-tagged transposon mutagenesis, which has been used essentially in animal models, to an in vitro human macrophage infection model. a library of 1,152 brucella suis 1330 tagged mini ... | 2000 | 10678941 |
| the serotype of type ia and iii group b streptococci is determined by the polymerase gene within the polycistronic capsule operon. | streptococcus agalactiae is a primary cause of neonatal morbidity and mortality. essential to the virulence of this pathogen is the production of a type-specific capsular polysaccharide (cps) that enables the bacteria to evade host immune defenses. the identification, cloning, sequencing, and functional characterization of seven genes involved in type iii capsule production have been previously reported. here, we describe the cloning and sequencing of nine additional adjacent genes, cps(iii)fghi ... | 2000 | 10913080 |
| bacteria in the leaf ecosystem with emphasis on pseudomonas syringae-a pathogen, ice nucleus, and epiphyte. | the extremely large number of leaves produced by terrestrial and aquatic plants provide habitats for colonization by a diversity of microorganisms. this review focuses on the bacterial component of leaf microbial communities, with emphasis on pseudomonas syringae-a species that participates in leaf ecosystems as a pathogen, ice nucleus, and epiphyte. among the diversity of bacteria that colonize leaves, none has received wider attention than p. syringae, as it gained notoriety for being the firs ... | 2000 | 10974129 |
| in vitro antimicrobial properties of recombinant asabf, an antimicrobial peptide isolated from the nematode ascaris suum. | asabf is a csalphabeta-type antimicrobial peptide that contains four intramolecular disulfide bridges (y. kato and s. komatsu, j. biol. chem. 271:30493-30498, 1996). in the present study, a recombinant asabf was produced by using a yeast expression system, and its antimicrobial activity was characterized in detail. the recombinant asabf was active against all gram-positive bacteria tested (7 of 7; minimum bactericidal concentration [mbc], 0.03 to 1 microg/ml) except leuconostoc mesenteroides, so ... | 2000 | 10991847 |
| 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 |
| 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 |
| 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 |
| effect of bradyrhizobium photosynthesis on stem nodulation of aeschynomene sensitiva. | some leguminous species of the genus aeschynomene are specifically stem-nodulated by photosynthetic bradyrhizobia. to study the effect of bacterial photosynthesis during symbiosis, we generated a photosynthesis-negative mutant of the bradyrhizobium sp. strain ors278 symbiont of aeschynomene sensitiva. the presence of a functional photosynthetic unit in bacteroids and the high expression of the photosynthetic genes observed in stem nodules demonstrate that the bacteria are photosynthetically acti ... | 2000 | 11114184 |
| 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 |
| 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 |
| differentiation of o-acetyl and o-carbamoyl esters of n-acetyl-glucosamine by decomposition of their oxonium ions. application to the structure of the nonreducing terminal residue of nod factors. | nod factors are substituted n-acyl chito-oligomers secreted by plant symbiotic bacteria of the rhizobium family. substitutions on the oligosaccharide core specify their recognition by host plants. a method using tandem mass spectrometry is proposed to locate the o-acetyl and o-carbamoyl substituents on the nonreducing terminal residue of the chito-oligomers. as model compounds, all the positional isomers of monoacetyl and monocarbamoyl esters of 1-o-methyl-n-acetyl-alpha-d-glucosamine were synth ... | 2000 | 10757166 |
| enhanced symbiotic performance by rhizobium tropici glycogen synthase mutants. | we isolated a tn5-induced rhizobium tropici mutant that has enhanced capacity to oxidize n,n-dimethyl-p-phenylendiamine (dmpd) and therefore has enhanced respiration via cytochrome oxidase. the mutant had increased levels of the cytochromes c(1) and cycm and a small increase in the amount of cytochrome aa(3). in plant tests, the mutant increased the dry weight of phaseolus vulgaris plants by 20 to 38% compared with the control strain, thus showing significantly enhanced symbiotic performance. th ... | 2001 | 11208782 |
| preferential occurrence of diazotrophic endophytes, azoarcus spp., in wild rice species and land races of oryza sativa in comparison with modern races. | several diazotrophic species of azoarcus spp. occur as endophytes in the pioneer plant kallar grass. the purpose of this study was to screen asian wild rice and cultivated oryza sativa varieties for natural association with these endophytes. populations of culturable diazotrophs in surface-sterilized roots were characterized by 16s rdna sequence analysis, and azoarcus species were identified by genomic fingerprints. a. indigens and azoarcus sp. group c were detected only rarely, whereas azoarcus ... | 2000 | 11220300 |
| p(ii) signal transduction proteins, pivotal players in microbial nitrogen control. | the p(ii) family of signal transduction proteins are among the most widely distributed signal proteins in the bacterial world. first identified in 1969 as a component of the glutamine synthetase regulatory apparatus, p(ii) proteins have since been recognized as playing a pivotal role in control of prokaryotic nitrogen metabolism. more recently, members of the family have been found in higher plants, where they also potentially play a role in nitrogen control. the p(ii) proteins can function in t ... | 2001 | 11238986 |
| a functional myo-inositol dehydrogenase gene is required for efficient nitrogen fixation and competitiveness of sinorhizobium fredii usda191 to nodulate soybean (glycine max [l.] merr.). | inositol derivative compounds provide a nutrient source for soil bacteria that possess the ability to degrade such compounds. rhizobium strains that are capable of utilizing certain inositol derivatives are better colonizers of their host plants. we have cloned and determined the nucleotide sequence of the myo-inositol dehydrogenase gene (idha) of sinorhizobium fredii usda191, the first enzyme responsible for inositol catabolism. the deduced idha protein has a molecular mass of 34,648 da and sho ... | 2001 | 11274120 |
| endophytic colonization of rice by a diazotrophic strain of serratia marcescens. | six closely related n2-fixing bacterial strains were isolated from surface-sterilized roots and stems of four different rice varieties. the strains were identified as serratia marcescens by 16s rrna gene analysis. one strain, irbg500, chosen for further analysis showed acetylene reduction activity (ara) only when inoculated into media containing low levels of fixed nitrogen (yeast extract). diazotrophy of irbg500 was confirmed by measurement of 15n2 incorporation and by sequence analysis of the ... | 2001 | 11274124 |
| rhesus factors and ammonium: a function in efflux? | completion of fungal, plant and human genomes paved the way to the identification of erythrocytic rhesus proteins and their kidney homologs as ammonium transporters. | 2001 | 11276430 |
| case of localized recombination in 23s rrna genes from divergent bradyrhizobium lineages associated with neotropical legumes. | enzyme electrophoresis and rrna sequencing were used to analyze relationships of bradyrhizobium sp. nodule bacteria from four papilionoid legumes (clitoria javitensis, erythrina costaricensis, rhynchosia pyramidalis, and desmodium axillare) growing on barro colorado island (bci), panama. bacteria with identical multilocus allele profiles were commonly found in association with two or more legume genera. among the 16 multilocus genotypes (electrophoretic types [ets]) detected, six ets formed a cl ... | 2001 | 11319084 |
| structural and functional analysis of the phosphonoacetate hydrolase (phna) gene region in pseudomonas fluorescens 23f. | the pseudomonas fluorescens 23f phosphonoacetate hydrolase gene (phna) encodes a novel carbon-phosphorus bond cleavage enzyme whose expression is independent of the phosphate status of the cell. analysis of the regions adjacent to the phosphonoacetate hydrolase structural gene (phna) indicated the presence of five open reading frames (orfs). these include one (phnr) whose putative product shows high levels of homology to the lysr family of positive transcriptional regulators. its presence was sh ... | 2001 | 11344133 |
| rhizobial nodl o-acetyl transferase and nods n-methyl transferase functionally interfere in production of modified nod factors. | the products of the rhizobial nodulation genes are involved in the biosynthesis of lipochitin oligosaccharides (lcos), which are host-specific signal molecules required for nodule formation. the presence of an o-acetyl group on c-6 of the nonreducing n-acetylglucosamine residue of lcos is due to the enzymatic activity of nodl. here we show that transfer of the nodl gene into four rhizobial species that all normally produce lcos that are not modified on c-6 of the nonreducing terminal residue res ... | 2001 | 11344149 |
| role of a ferredoxin gene cotranscribed with the nifhdk operon in n(2) fixation and nitrogenase "switch-off" of azoarcus sp. strain bh72. | the endophytic diazotroph azoarcus sp. strain bh72 is capable of infecting rice roots and of expressing the nitrogenase (nif) genes there. in order to study the genetic background for nitrogen fixation in strain bh72, the structural genes of nitrogenase (nifhdk) were cloned and sequenced. the sequence analysis revealed an unusual gene organization: downstream of nifhdk, a ferredoxin gene (fdxn; 59% amino acid sequence identity to r. capsulatus fdxn) and open reading frames showing 52 and 36% ami ... | 2001 | 11371540 |
| the sinorhizobium meliloti nutrient-deprivation-induced tyrosine degradation gene hmga is controlled by a novel member of the arsr family of regulatory genes. | the regulation of the nutrient-deprivation-induced sinorhizobium meliloti homogentisate dioxygenase (hmga) gene, involved in tyrosine degradation, was examined. hmga expression was found to be independent of the canonical nitrogen regulation (ntr) system. to identify regulators of hmga, secondary mutagenesis of an s. meliloti strain harboring a hmga-luxab reporter gene fusion (n4) was carried out using transposon tn1721. two independent tn1721 insertions were found to be located in a positive re ... | 2001 | 11375175 |
| burkholderia, a genus rich in plant-associated nitrogen fixers with wide environmental and geographic distribution. | the genus burkholderia comprises 19 species, including burkholderia vietnamiensis which is the only known n(2)-fixing species of this bacterial genus. the first isolates of b. vietnamiensis were recovered from the rhizosphere of rice plants grown in a phytotron, but its existence in natural environments and its geographic distribution were not reported. in the present study, most n(2)-fixing isolates recovered from the environment of field-grown maize and coffee plants cultivated in widely separ ... | 2001 | 11375196 |
| xylem colonization of tomato by azorhizobium caulinodans ors571. | tomato seedlings growing aseptically in murashige and skoog medium were inoculated with azorhizobium caulinodans ors571 (pxlgd4), carrying the lacz reporter gene. by microscopic analyses of inoculated tomato roots, it has been demonstrated that the xylem of tomato roots can be colonized by azorhizobium. we discuss whether this colonization of the xylem of tomato roots by diazotrophic azorhizobia might provide a suitable niche for endophytic nitrogen fixation. | 2001 | 11426852 |
| knockout of an azorhizobial dtdp-l-rhamnose synthase affects lipopolysaccharide and extracellular polysaccharide production and disables symbiosis with sesbania rostrata. | a nonpolar mutation was made in the oac2 gene of azorhizobium caulinodans. oac2 is an ortholog of the salmonella typhimurium rfbd gene that encodes a dtdp-l-rhamnose synthase. the knockout of oac2 changed the lipopolysaccharide (lps) pattern and affected the extracellular polysaccharide production but had no effect on bacterial hydrophobicity. upon hot phenol extraction, the wild-type lps partitioned in the phenol phase. the lps fraction of ors571-oac2 partitioned in the water phase and had a re ... | 2001 | 11437259 |
| extracellular polysaccharide production by azorhizobium caulinodans from stem nodules of leguminous emergent hydrophyte aeschynomene aspera. | the azorhizobium caulinodans isolated from the stem nodules of a leguminous emergent hydrophyte, aeschynomene aspera, produced a large amount of extracellular polysaccharides (eps) in yeast extract basal medium. maximum eps production was at the stationary phase of growth. eps production was increased by 919% over control when the medium was supplemented with sucrose (1.5%), d-biotin (1 microgram/ml) and casamino acid (0.1%). eps contained rhamnose and arabinose. possible role of the azorhizobia ... | 2001 | 11480212 |
| analysis of the chromosome sequence of the legume symbiont sinorhizobium meliloti strain 1021. | sinorhizobium meliloti is an alpha-proteobacterium that forms agronomically important n(2)-fixing root nodules in legumes. we report here the complete sequence of the largest constituent of its genome, a 62.7% gc-rich 3,654,135-bp circular chromosome. annotation allowed assignment of a function to 59% of the 3,341 predicted protein-coding orfs, the rest exhibiting partial, weak, or no similarity with any known sequence. unexpectedly, the level of reiteration within this replicon is low, with onl ... | 2001 | 11481430 |
| azorhizobium caulinodans pyruvate dehydrogenase activity is dispensable for aerobic but required for microaerobic growth. | azorhizobium caulinodans mutant 62004 carries a null allele of pdhb, encoding the e1beta subunit of pyruvate dehydrogenase, which converts pyruvate to acetyl-coa. this pdhb mutant completely lacks pyruvate oxidation activities yet grows aerobically on c(4) dicarboxylates (succinate, l-malate) as sole energy source, albeit slowly, and displays pleiotropic growth defects consistent with physiological acetyl-coa limitation. temperature-sensitive (ts), conditional-lethal derivatives of the pdhb muta ... | 2001 | 11496000 |
| a critical evaluation of differential display as a tool to identify genes involved in legume nodulation: looking back and looking forward. | screening for differentially expressed genes is a straightforward approach to study the molecular basis of a biological system. in the last 10 years, differential screening technology has evolved rapidly and currently high-throughput tools for genome-wide transcript profiling, such as expressed sequence tags and microarray analysis, are becoming widely available. here, an overview of this (r)evolution is given with emphasis on the differential display method, which for many years has been the pr ... | 2001 | 11522814 |
| dual control of the noda operon of azorhizobium caulinodans ors571 by a nod box and a nifa-sigma54-type promoter. | earlier studies have shown that the azorhizohium caulinodans noda promoter is controlled by a host plant-derived flavonoid signal via the transcription activator nodd. here, we report that the transcription of the noda operon is also under the control of nifa-rpon. a nifa-sigma54-type promoter, p2noda, is present upstream of the nod-box consensus motif of the noda gene and directs expression of a noda-uida reporter gene both in free-living bacteria under nitrogen fixation conditions and in bacte ... | 2001 | 11523777 |
| cloning and functional analysis of the pbr lead resistance determinant of ralstonia metallidurans ch34. | the lead resistance operon, pbr, of ralstonia metallidurans (formerly alcaligenes eutrophus) strain ch34 is unique, as it combines functions involved in uptake, efflux, and accumulation of pb(ii). the pbr lead resistance locus contains the following structural resistance genes: (i) pbrt, which encodes a pb(ii) uptake protein; (ii) pbra, which encodes a p-type pb(ii) efflux atpase; (iii) pbrb, which encodes a predicted integral membrane protein of unknown function; and (iv) pbrc, which encodes a ... | 2001 | 11544228 |
| srchi24, a chitinase homolog lacking an essential glutamic acid residue for hydrolytic activity, is induced during nodule development on sesbania rostrata. | the interaction between the tropical legume sesbania rostrata and the bacterium azorhizobium caulinodans results in the formation of nodules on both stem and roots. stem nodulation was used as a model system to isolate early markers by differential display. one of them, srchi24 is a novel early nodulin whose transcript level increased already 4 h after inoculation. this enhancement depended on nod factor-producing bacteria. srchi24 transcript levels were induced also by exogenous cytokinins. in ... | 2001 | 11553736 |
| detection and enumeration of methanotrophs in acidic sphagnum peat by 16s rrna fluorescence in situ hybridization, including the use of newly developed oligonucleotide probes for methylocella palustris. | two 16s rrna-targeted oligonucleotide probes, mcell-1026 and mcell-181, were developed for specific detection of the acidophilic methanotroph methylocella palustris using fluorescence in situ hybridization (fish). the fluorescence signal of probe mcell-181 was enhanced by its combined application with the oligonucleotide helper probe h158. mcell-1026 and mcell-181, as well as 16s rrna oligonucleotide probes with reported group specificity for either type i methanotrophs (probes m-84 and m-705) o ... | 2001 | 11571193 |
| azide-resistant mutants of azorhizobium caulinodans with enhanced symbiotic effectiveness. | azide-resistant mutants of azorhizobium caulinodans strains sb3, s78, srr13 and srs8 were isolated and screened for nitrate reductase activity. selected nitrate reductase negative mutants were inoculated on sesbania bispinosa and s. rostrata under sterile conditions in chillum jars to study their symbiotic behavior. azide-resistant mutants exhibited either similar or higher symbiotic effectiveness than the parent strain after 30 d of plant growth. nodule mass, nitrogenase activity and uptake hyd ... | 2001 | 11702406 |
| regulation of gene expression in response to oxygen in rhizobium etli: role of fnrn in fixnoqp expression and in symbiotic nitrogen fixation. | previously, we reported finding duplicated fixnoqp operons in rhizobium etli cfn42. one of these duplicated operons is located in the symbiotic plasmid (fixnoqpd), while the other is located in a cryptic plasmid (fixnoqpf). although a novel fixl-fixkf regulatory cascade participates in microaerobic expression of both fixnoqp duplicated operons, we found that a mutation in fixl eliminates fixnoqpf expression but has only a moderate effect on expression of fixnoqpd. this suggests that there are di ... | 2001 | 11717256 |
| identification of essential amino acids in the azorhizobium caulinodans fucosyltransferase nodz. | the nodz gene, which is present in various rhizobial species, is involved in the addition of a fucose residue in an alpha 1-6 linkage to the reducing n-acetylglucosamine residue of lipo-chitin oligosaccharide signal molecules, the so-called nod factors. fucosylation of nod factors is known to affect nodulation efficiency and host specificity. despite a lack of overall sequence identity, nodz proteins share conserved peptide motifs with mammalian and plant fucosyltransferases that participate in ... | 2001 | 11717264 |
| complex i and its involvement in redox homeostasis and carbon and nitrogen metabolism in rhodobacter capsulatus. | a transposon mutant of rhodobacter capsulatus, strain mal7, that was incapable of photoautotrophic and chemoautotrophic growth and could not grow photoheterotrophically in the absence of an exogenous electron acceptor was isolated. the phenotype of strain mal7 suggested that the mutation was in some gene(s) not previously shown to be involved in co(2) fixation control. the site of transposition in strain mal7 was identified and shown to be in the gene nuof, which encodes one of the 14 subunits f ... | 2001 | 11717288 |
| polyhydroxybutyrate biosynthesis in caulobacter crescentus: molecular characterization of the polyhydroxybutyrate synthase. | caulobacter crescentus was investigated with respect to polyhydroxybutyrate (phb) biosynthesis. polyhydroxyalkanoate (pha) accumulation contributing to approximately 18% of the cell dry weight was obtained in the presence of glucose. gas chromatography-mass spectrometry and gel permeation chromatography of the purified pha showed that this polyester was solely composed of 3-hydroxybutyrate and had a weight average molar mass of 5.5 x 10(5) g mol(-1) and a polydispersity of 1.6. an orf encoding a ... | 2001 | 11739767 |
| site-specific integrative elements of rhizobiophage 16-3 can integrate into proline trna (cgg) genes in different bacterial genera. | the integrase protein of the rhizobium meliloti 41 phage 16-3 has been classified as a member of the int family of tyrosine recombinases. the site-specific recombination system of the phage belongs to the group in which the target site of integration (attb) is within a trna gene. since trna genes are conserved, we expected that the target sequence of the site-specific recombination system of the 16-3 phage could occur in other species and integration could take place if the required putative hos ... | 2002 | 11741858 |
| characterization of a family of arabidopsis genes related to xyloglucan fucosyltransferase1. | to understand primary cell wall assembly in arabidopsis, we have focused on identifying and characterizing enzymes involved in xyloglucan biosynthesis. nine genes (atfut2-10) were identified that share between 47% and 62% amino acid similarity with the xyloglucan-specific fucosyltransferase atfut1. reverse transcriptase-pcr analysis indicates that all these genes are expressed. bioinformatic analysis predicts that these family members are fucosyltransferases, and we first hypothesized that some ... | 2001 | 11743104 |
| patterns of pectin methylesterase transcripts in developing stem nodules of sesbania rostrata. | differential display was applied to the early stages of the interaction between the tropical legume sesbania rostrata and its microsymbiont azorhizobium caulinodans ors571. an upregulated clone that is similar to pectin methylesterase-encoding genes was isolated (srpmel). the full-length sequence of srpme1 was used to localize pme transcripts in situ during s. rostrata stem-nodule development. several expression patterns were distinguished, hinting at general roles in vascular tissue development ... | 2002 | 11876427 |
| the rhizobium leguminosarum prsde genes are required for secretion of several proteins, some of which influence nodulation, symbiotic nitrogen fixation and exopolysaccharide modification. | nodo is a secreted protein from rhizobium leguminosarum bv. viciae with a role in signalling during legume nodulation. a tn5-induced mutant was identified that was defective in nodo secretion. as predicted, the secretion defect decreased pea and vetch nodulation but only when the node gene was also mutated. this confirms earlier observations that nodo plays a particularly important role in nodulation when nod factors carrying c18:1 (but not c18:4) acyl groups are the primary signalling molecules ... | 1997 | 11902716 |
| distinct roles of p(ii)-like signal transmitter proteins and amtb in regulation of nif gene expression, nitrogenase activity, and posttranslational modification of nifh in azoarcus sp. strain bh72. | p(ii)-like signal transmitter proteins, found in bacteria, archaea, and plants, are known to mediate control of carbon and nitrogen assimilation. they indirectly regulate the activity of key metabolic enzymes and transcription factors by protein-protein interactions with signal transduction proteins. many proteobacteria harbor two paralogous p(ii)-like proteins, glnb and glnk, whereas a novel third p(ii) paralogue (glny) was recently identified in azoarcus sp. strain bh72, a diazotrophic endophy ... | 2002 | 11914357 |
| genetic and phenotypic analyses of the rdx locus of rhodobacter sphaeroides 2.4.1. | previously, we reported that rdxb, encoding a likely membrane-bound two [4fe-4s]-containing center, is involved in the aerobic regulation of photosystem gene expression in rhodobacter sphaeroides 2.4.1. to further investigate the role of rdxb as well as other genes of the rdxbhis operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of the rdx genes. using both puc and puf operon lacz fusions to monitor photosystem gene expression, under ... | 2000 | 10852880 |
| applications of differential-display reverse transcription-pcr to molecular pathogenesis and medical mycology. | the host-fungus interaction is characterized by changes in gene expression in both host and pathogen. differential-display reverse transcription pcr (ddrt-pcr) is a pcr-based method that allows extensive analysis of gene expression among several cell populations. several limitations and drawbacks to this procedure have now been addressed, including the large number of false-positive results and the difficulty in confirming differential expression. modifications that simplify the reaction time, a ... | 2000 | 10885984 |
| azorhizobium caulinodans ors571 colonizes the xylem of arabidopsis thaliana. | improved conditions were used for the aseptic growth of arabidopsis thaliana to investigate whether xylem colonization of a. thaliana by azorhizobium caulinodans ors571 might occur. when seedlings were inoculated with ors571 (pxlgd4) tagged with the lacz reporter gene, nearly all of the plants showed blue regions of ors571 colonization at lateral root cracks (lrc). the flavonoids naringenin and liquiritigenin significantly stimulated colonization of lrc by ors571. blue bands of ors571 (pxlgd4) b ... | 2001 | 11194878 |
| effect of ania (carbon flux regulator) and phac (poly-beta-hydroxybutyrate synthase) mutations on pyruvate metabolism in rhizobium etli. | the rhizobium etli poly-beta-hydroxybutyrate synthase (phac) mutant sam100 grows poorly with pyruvate as the carbon source. the inactivation of ania, encoding a global carbon flux regulator, in sam100 restores growth of the resulting double mutant (vem58) on pyruvate. pyruvate carboxylase (pyc) activity, pyc gene transcription, and holoenzyme content, which were low in sam100, were restored in strain vem58. the genetically engineered overexpression of pyc in sam100 also allowed its growth on pyr ... | 2002 | 11914362 |
| bradyrhizobia from wild phaseolus, desmodium, and macroptilium species in northern mexico. | rrna genetic markers were analyzed in 97 isolates of nodule bacteria from six legume species in chihuahua, mexico. the most common genotypes were widely shared across host species and had 16s rrna sequences identical to those of strains from an eastern north american legume (amphicarpaea) that are closely related to bradyrhizobium elkanii. | 2002 | 11916730 |
| pmh11, a tool for gene disruption and expression analysis in azorhizobium caulinodans. | tools for mutagenesis and expression analyses are needed to study the role of bacterial genes. here, we report the construction of pmh11, a small, mobilizable plasmid that replicates in escherichia coli, but not in azorhizobium caulinodans, a nodulating microsymbiont of sesbania rostrata, and that contains a unique bamhi restriction site upstream of a promoterless lacz gene. pmh11 and two derivatives with the multiple cloning site of pbluescript (ks(ii)) are useful for mutagenesis by gene disrup ... | 2002 | 11982330 |
| biochemical, molecular, and genetic analyses of the acetone carboxylases from xanthobacter autotrophicus strain py2 and rhodobacter capsulatus strain b10. | acetone carboxylase is the key enzyme of bacterial acetone metabolism, catalyzing the condensation of acetone and co(2) to form acetoacetate. in this study, the acetone carboxylase of the purple nonsulfur photosynthetic bacterium rhodobacter capsulatus was purified to homogeneity and compared to that of xanthobacter autotrophicus strain py2, the only other organism from which an acetone carboxylase has been purified. the biochemical properties of the enzymes were virtually indistinguishable, wit ... | 2002 | 12003937 |
| identification and isolation of genes involved in poly(beta-hydroxybutyrate) biosynthesis in azospirillum brasilense and characterization of a phbc mutant. | like many other prokaryotes, rhizobacteria of the genus azospirillum produce high levels of poly(beta-hydroxybutyrate) (phb) under suboptimal growth conditions. utilization of phb by bacteria under stress has been proposed as a mechanism that favors their compatible establishment in competitive environments, thus showing great potential for the improvement of bacterial inoculants for plants and soils. the three genes that are considered to be essential in the phb biosynthetic pathway, phba (beta ... | 2002 | 12039753 |
| key role of bacterial nh(4)(+) metabolism in rhizobium-plant symbiosis. | symbiotic nitrogen fixation is carried out in specialized organs, the nodules, whose formation is induced on leguminous host plants by bacteria belonging to the family rhizobiaceae: nodule development is a complex multistep process, which requires continued interaction between the two partners and thus the exchange of different signals and metabolites. nh(4)(+) is not only the primary product but also the main regulator of the symbiosis: either as ammonium and after conversion into organic compo ... | 2002 | 12040124 |
| identification and characterization of the two-component ntry/ntrx regulatory system in azospirillum brasilense. | two azospirillum brasilense open reading frames (orfs) exhibited homology with the two-component ntry/ntrx regulatory system from azorhizobium caulinodans. these a. brasilense orfs, located downstream to the nifr3ntrbc operon, were isolated, sequenced and characterized. the present study suggests that orf1 and orf2 correspond to the a. brasilense ntry and ntrx genes, respectively. the amino acid sequences of a. brasilense ntry and ntrx proteins showed high similarity to sensor/kinase and regulat ... | 2002 | 12045829 |
| biodiversity of denitrifying and dinitrogen-fixing bacteria in an acid forest soil. | isolated soil dna from an oak-hornbeam forest close to cologne, germany, was suitable for pcr amplification of gene segments coding for the 16s rrna and nitrogenase reductase (nifh), nitrous oxide reductase (nosz), cytochrome cd(1)-containing nitrite reductase (nirs), and cu-containing nitrite reductase (nirk) of denitrification. for each gene segment, diverse pcr products were characterized by cloning and sequencing. none of the 16s rrna gene sequences was identical to any deposited in the data ... | 2002 | 12147477 |
| the diversity of phaseolus-nodulating rhizobial populations is altered by liming of acid soils planted with phaseolus vulgaris l. in brazil. | pcr-mediated restriction fragment length polymorphism (rflp) analysis of the 16s-23s rrna internally transcribed spacer (its) region and the 16s rrna gene indicated that the rhizobial populations isolated from common bean (phaseolus vulgaris l.) nodules in the unlimed soil from a series of five lime rates applied 6 years previously to plots of an acidic oxisol had less diversity than those from plots with higher rates of liming. isolates affiliated with rhizobium tropici iib and rhizobium legumi ... | 2002 | 12147504 |
| predicted structure and phyletic distribution of the rna-binding protein hfq. | hfq, a bacterial rna-binding protein, was recently shown to contain the sm1 motif, a characteristic of sm and lsm proteins that function in rna processing events in archaea and eukaryotes. in this report, comparative structural modeling was used to predict a three-dimensional structure of the hfq core sequence. the predicted structure aligns with most major features of the methanobacterium thermoautotrophicum lsm protein structure. conserved residues in hfq are positioned at the same structural ... | 2002 | 12202750 |
| diversity and evolution of hydrogenase systems in rhizobia. | uptake hydrogenases allow rhizobia to recycle the hydrogen generated in the nitrogen fixation process within the legume nodule. hydrogenase (hup) systems in bradyrhizobium japonicum and rhizobium leguminosarum bv. viciae show highly conserved sequence and gene organization, but important differences exist in regulation and in the presence of specific genes. we have undertaken the characterization of hup gene clusters from bradyrhizobium sp. (lupinus), bradyrhizobium sp. (vigna), and rhizobium tr ... | 2002 | 12324339 |
| a polysaccharide deacetylase gene (pdaa) is required for germination and for production of muramic delta-lactam residues in the spore cortex of bacillus subtilis. | the predicted amino acid sequence of bacillus subtilis yfjs (renamed pdaa) exhibits high similarity to those of several polysaccharide deacetylases. beta-galactosidase fusion experiments and results of northern hybridization with sporulation sigma mutants indicated that the pdaa gene is transcribed by e(sigma)(g) rna polymerase. pdaa-deficient spores were bright by phase-contrast microscopy, and the spores were induced to germination on the addition of l-alanine. germination-associated spore dar ... | 2002 | 12374835 |