Publications

evidence for plasmid- and chromosome-borne multiple nif genes in rhizobium fredii.	rhizobium fredii is a fast-growing rhizobium isolated from the primitive chinese soybean cultivar peking and from the wild soybean glycine soja. this rhizobium harbors nif genes on 150- to 200-megadalton plasmids. by passage on acridine orange plates, we obtained a mutant of r. fredii usda 206 cured of the 197-megadalton plasmid (usda 206c) which carries both nif and nod genes. this strain, however, has retained its symbiotic effectiveness. probing ecori digests of wild-type and cured plasmid dn ...	1985	2992376
isolation and characterization of the dna region encoding nodulation functions in bradyrhizobium japonicum.	the dna region encoding early nodulation functions of bradyrhizobium japonicum 3i1b110 (i110) was isolated by its homology to the functionally similar region from rhizobium meliloti. isolation of a number of overlapping recombinant clones from this region allowed the construction of a restriction map of the region. the identified nodulation region of b. japonicum shows homology exclusively to those regions of r. meliloti and rhizobium leguminosarum dna known to encode early nodulation functions. ...	1985	2999080
effect of sym plasmid curing on symbiotic effectiveness in rhizobium fredii.	a mutant, usda 206c, of rhizobium fredii usda 206 was obtained by passage on acridine plates. this mutant was cured of its 197-megadalton sym plasmid but retained its symbiotic effectiveness. multiple plasmid and chromosomally borne nif gene copies have previously been shown in r. fredii usda 206. hindiii and ecori restriction enzyme digests of plasmid and total dna showed that at least two nif gene copies are probably missing in usda 206c. to compare the symbiotic effectiveness of usda 206 and ...	1985	16346803
symbiotic effectiveness and host-strain interactions of rhizobium fredii usda 191 on different soybean cultivars.	nodulation, acetylene reduction activity, dry matter accumulation, and total nitrogen accumulation by nodulated plants growing in a nitrogen-free culture system were used to compare the symbiotic effectiveness of the fast-growing rhizobium fredii usda 191 with that of the slow-growing bradyrhizobium japonicum usda 110 in symbiosis with five soybean (glycine max (l.) merr.) cultivars. measurement of the amount of nitrogen accumulated during a 20-day period of vegetative growth (28 to 48 days afte ...	1986	16347066
growth of fast- and slow-growing rhizobia on ethanol.	free-living soybean rhizobia and bradyrhizobium spp. (lupine) have the ability to catabolize ethanol. of the 30 strains of rhizobia examined, only the fast- and slow-growing soybean rhizobia and the slow-growing bradyrhizobium sp. (lupine) were capable of using ethanol as a sole source of carbon and energy for growth. two strains from each of the other rhizobium species examined (r. meliloti, r. loti, and r. leguminosarum biovars phaseoli, trifolii, and viceae) failed to grow on ethanol. one rhi ...	1986	16347190
two indirect methods for detecting ureide synthesis by nodulated legumes.	two methods were developed for the detection of altered ureide metabolism in legume nodules. both techniques are based on the positive correlation between the presence of high xanthine dehydrogenase (ec 1.2.1.37) specific activity in nodules and the ability of those nodules to produce the ureides, allantoin and allantoic acid. in the first method, nodulated legumes are treated for 2 weeks with a soil drench of allopurinol. after allopurinol treatment, leaves of n(2)-fed, ureide-producing legumes ...	1986	16664857
mobilization of tn5 insertions from rhizobium fredii by pjb3ji.	techniques for in vivo cloning were used with the fast-growing nitrogen-fixing soybean microsymbiont r. fredii usda 191. selection for transfer of tn5 insertions from r. fredii usda 191 containing the gene-mobilizing plasmid pjb3ji provided recombinants at up to 400 times the background mutation level. these techniques may be useful for future genetic analysis of r. fredii.	1986	3015025
molecular cloning and expression of rhizobium fredii usda 193 nodulation genes: extension of host range for nodulation.	dna hybridization with the cloned nodulation region of rhizobium meliloti as a probe revealed dna homology with four hindiii fragments, 12.5, 6.8, 5.2, and 0.3 kilobases (kb) in size, of the symbiotic plasmid prjausda193. both hybridization and complementation studies suggest that the common nodulation genes nodabc and nodd of r. fredii usda 193 are present on the 5.2-kb hindiii and 2.8-kb ecori fragments, respectively, of the sym plasmid. both fragments together could confer nodulation ability ...	1986	3782034
enzymes of the beta-ketoadipate pathway are inducible in rhizobium and agrobacterium spp. and constitutive in bradyrhizobium spp.	protocatechuate is a universal growth substrate for members of the family rhizobiaceae, and these bacteria utilize the aromatic compound via the beta-ketoadipate pathway. this report describes transcriptional controls exercised by different subgroups of the rhizobiaceae over five enzymes that catalyze consecutive reactions in the pathway: protocatechuate oxygenase (ec 1.13.11.3), beta-carboxy-cis,cis-muconate lactonizing enzyme (ec 5.5.1.2), gamma-carboxymuconolactone decarboxylase (ec 4.1.1.44) ...	1986	3941043
isolation of competition-defective mutants of rhizobium fredii.	we coupled tn5 mutagenesis with a competition assay to isolate mutants of rhizobium fredii usda 257 that are defective in competition for nodulation of soybeans. two mutants with single tn5 inserts in the chromosome showed reduced competitiveness in vermiculite but were identical to the wild-type strain in symbiotic properties when inoculated alone. recombination of tn5 and flanking genomic regions cloned from the mutants into the parent strain showed that tn5 was responsible for the mutant phen ...	1987	3025184
regulation of nodulation in the soybean-rhizobium symbiosis : strain and cultivar variability.	double inoculation (15 h apart) of the soybean cultivar williams with bradyrhizobium japonicum i-110ars reveals a rapid regulatory plant response that inhibits nodulation of distal portions of the primary root (m pierce, wd bauer 1984 plant physiol 73: 286-290). only living, homologous rhizobia elicit the response. we conducted similar double inoculation experiments to test the hypothesis that this is a universal phenomenon in soybean symbioses. we investigated interactions of the cultivar mccal ...	1987	16665616
serological relatedness of rhizobium fredii to other rhizobia and to the bradyrhizobia.	several isolates of rhizobium fredii were examined for their serological relatedness to each other, to bradyrhizobium japonicum, and to other fast- and slow-growing rhizobia. immunofluorescence, agglutination, and immunodiffusion analyses indicated that r. fredii contains at least three separate somatic serogroups, usda 192, usda 194, and usda 205. there was no cross-reaction between any of the r. fredii isolates and 13 of the 14 b. japonicum somatic serogroups tested. cross-reactions were obtai ...	1987	16347404
conservation of a symbiotic dna region in soybean root nodule bacteria.	bradyrhizobium japonicum usda 3i1b110 contains a dna region in which symbiotic genes and many repeated sequences are closely linked. hybridization analysis revealed that this region was highly conserved in some b. japonicum strains (usda 24, usda 122, usda 123, atcc 10324, 61a24) but not in others (usda 76, 61a76, 61a101). the genomic presence of multiple copies of one of the repeated sequences (rsalpha) appeared to be specifically characteristic for soybean root nodule bacteria, including the f ...	1987	16347446
induction of bradyrhizobium japonicum common nod genes by isoflavones isolated from glycine max.	the early events in legume nodulation by rhizobium spp. involve a conserved gene cluster known as the common nod region. a broad-host-range plasmid (pea2-21) containing a bradyrhizobium japonicum noddabc-lacz translational fusion was constructed and used to monitor nod gene expression in response to soybean root extract. two inducing compounds were isolated and identified. analysis using ultraviolet absorption spectra, proton nuclear magnetic resonance, and mass spectrometry showed that the two ...	1987	16593884
induction of symbiotically defective auxotrophic mutants of rhizobium fredii hh303 by transposon mutagenesis.	symbiotically defective auxotrophic mutants were isolated by transposon tn5 mutagenesis of rhizobium fredii hh303, a fast-growing microsymbiont of north american commercial soybean cultivars such as glycine max cv. williams. three different tn5-carrying suicide vectors, pblk1-2, psup1011, and pgs9, were used for mutagenesis with transposition frequencies of 4 x 10, 3 x 10, and 1 x 10, respectively, while the frequency of background mutation resistant to 500 mug of kanamycin per ml was 1 x 10. fr ...	1988	16347555
influence of glycine spp. on competitiveness of bradyrhizobium japonicum and rhizobium fredii.	the displacement of indigenous bradyrhizobium japonicum in soybean nodules with more effective strains offers the possibility of enhanced n(2) fixation in soybean (glycine max (l.) merr.). our objective was to determine whether the wild soybean (g. soja sieb. & zucc.) genotype pi 468397 would cause reduced competitiveness of important indigenous b. japonicum strains usda 31, 76, and 123 and thereby permit nodulation by rhizobium fredii, the fast-growing microsymbiont of soybean. in an initial ex ...	1988	16347589
nodulation and nitrogen fixation efficacy of rhizobium fredii with phaseolus vulgaris genotypes.	phaseolus plant introduction (pi) genotypes (consisting of 684 p. vulgaris, 26 p. acutifolius, 39 p. lunatus, and 5 p. coccineus accessions) were evaluated for their ability to form effective symbioses with strains of six slow-growing (bradyrhizobium) and four fast-growing (rhizobium fredii) soybean rhizobia. of the 684 p. vulgaris genotypes examined, three pis were found to form effective nitrogen-fixing symbioses with the r. fredii strains. while none of the bradyrhizobium strains nodulated an ...	1988	16347705
two host-inducible genes of rhizobium fredii and characterization of the inducing compound.	random transcription fusions with mu d1(kan lac) generated three mutants in rhizobium fredii (strain usda 201) which showed induction of beta-galactosidase when grown in root exudate of the host plants glycine max, phaseolus vulgaris, and vigna ungliculata. two genes were isolated from a library of total plasmid dna of one of the mutants, 3f1. these genes, present in tandem on a 4.2-kilobase hindiii fragment, appear in one copy each on the symbiotic plasmid and do not hybridize to the rhizobium ...	1988	2447061
influence of soil variables on in situ plasmid transfer from escherichia coli to rhizobium fredii.	a model system was established to determine whether intergeneric plasmid transfer occurs in soil and how various soil variables affect the rate of plasmid transfer. the donor bacterium, escherichia coli hb101 carrying plasmid pblk1-2 (prk2073::tn5), and the recipient bacterium, rhizobium fredii usda 201, were inoculated into a sterile adelphia fine-sandy-loam soil. transconjugants were enumerated by direct plating on antibiotic-amended hm [n-2-hydroxyethylpiperazine-n'-2-ethanesulfonic acid; 2-( ...	1989	2669634
relationship of the presence and copy number of plasmids to exopolysaccharide production and symbiotic effectiveness in rhizobium fredii usda 206.	rhizobium fredii usda 206 harbors four large plasmids, one of which carries nodulation and nitrogen fixation genes. previously isolated groups of plasmid-cured derivatives of strain usda 206 were compared with each other to determine possible plasmid functions. mutant strain 206cans was isolated as a nonmucoid (muc) derivative of strain 206ca, a mutant that was cured of two plasmids. the muc phenotype of 206cans was only expressed when the strain was grown on certain media, particularly those wi ...	1989	16347890
exopolysaccharide-deficient mutants of rhizobium fredii hh303 which are symbiotically effective.	nineteen tn5-induced mutants of rhizobium fredii hh303 defective in acidic exopolysaccharide synthesis were isolated by screening for lack of calcofluor fluorescence. they were grouped by complementation analysis by using rhizobium meliloti cosmids carrying exo genes. all of the 19 mutants were symbiotically effective or partially effective, indicating that the major bacterial acidic exopolysaccharide of this strain of r. fredii may not be required for symbiotic development in the soybean.	1989	16347980
cadmium resistance screening in nitrilotriacetate-buffered minimal media.	media used to determine the mics of heavy metals for bacteria are unreliable because organic components in the media bind or chelate most of the metal being studied. to define specific metal activity in media and to maintain metal activity at a constant level, hepes-mes [n-2-hydroxyethylpiperazine-n' -2-ethanesulfonic acid-2-(n-morpholine)ethanesulfonic acid] salts medium with arabinose medium was modified, and the modified medium was used to examine the mic of cadmium for rhizobium fredii usda ...	1989	16348000
modulation of host gene expression during initiation and early growth of nodules in cowpea, vigna unguiculata (l.) walp.	inoculation of 2-day-old cowpea (vigna unguiculata [l.] walp.) seedlings with rhizobium fredii usda257 results in proficient nodulation of the tap root. the most abundant nodulation occurs in a region roughly corresponding to the position of the root tip at the time of inoculation. we have examined plant gene expression in this region, after inoculation with either usda257 or a nonnodulating mutant, 257b3. after isolation of mrna and in vitro translation, the protein products were separated by t ...	1990	16667410
nodulation of soybean by a transposon-mutant of rhizobium fredii usda257 is subject to competitive nodulation blocking by other rhizobia.	rhizobium fredii usda257 fails to nodulate the improved soybean [glycine max (l.)merr.] cultivar mccall in plastic growth pouches. mutant 257dh4, which was derived from usda257 by transposon mutagenesis, forms nitrogen fixing nodules under these conditions. if usda257 is present in inocula containing the mutant, most infections are arrested prior to organization of the nodule meristem, and nodule number is reduced by 95%. the improved cultivars essex, harosoy, hodgson 78, and viçoja, as well as ...	1990	16667829
cultivar-specific interactions of soybean with rhizobium fredii are regulated by the genotype of the root.	rhizobium fredii usda257 forms nitrogen-fixing nodules on soybean cultivar peking, but not on cultivar mccall. this pattern of nodulation persists when mccall and peking seedlings are cultivated together in plastic growth pouches. reciprocal grafting experiments confirm that the root genotype, and not that of the shoot, regulates such cultivar specificity. when peking roots are grafted onto mccall seedlings, the nodulation responses of roots similarly remain unaffected. transposon-mutant 257dh4, ...	1990	16667934
transfer of the pea symbiotic plasmid pjb5ji in nonsterile soil.	transfer of the pea (pisum sativum l.) symbiotic plasmid pjb5ji between strains of rhizobia was examined in sterile and nonsterile silt loam soil. sinorhizobium fredii usda 201 and hh003 were used as plasmid donors, and symbiotic plasmid-cured rhizobium leguminosarum 6015 was used as the recipient. the plasmid was carried but not expressed in s. fredii strains, whereas transfer of the plasmid to r. leguminosarum 6015 rendered the recipient capable of nodulating pea plants. confirmation of plasmi ...	1991	16348589
occurrence of lipid a variants with 27-hydroxyoctacosanoic acid in lipopolysaccharides from members of the family rhizobiaceae.	lipopolysaccharides (lpss) isolated from several strains of rhizobium, bradyrhizobium, agrobacterium, and azorhizobium were screened for the presence of 27-hydroxyoctacosanoic acid. the lpss from all strains, with the exception of azorhizobium caulinodans, contained various amounts of this long-chain hydroxy fatty acid in the lipid a fractions. analysis of the lipid a sugars revealed three types of backbones: those containing glucosamine (as found in rhizobium meliloti and rhizobium fredii), tho ...	1991	2007543
isoflavonoid-inducible resistance to the phytoalexin glyceollin in soybean rhizobia.	the antibacterial effect of the soybean phytoalexin glyceollin was assayed using a liquid microculture technique. log-phase cells of bradyrhizobium japonicum and sinorhizobium fredii were sensitive to glyceollin. as revealed by growth rates and survival tests, these species were able to tolerate glyceollin after adaptation. incubation in low concentrations of the isoflavones genistein and daidzein induced resistance to potentially bactericidal concentrations of glyceollin. this inducible resista ...	1991	2045365
phylogeny of fast-growing soybean-nodulating rhizobia support synonymy of sinorhizobium and rhizobium and assignment to rhizobium fredii.	we determined the sequences for a 260-base segment amplified by the polymerase chain reaction (corresponding to positions 44 to 337 in the escherichia coli 16s rrna sequence) from seven strains of fast-growing soybean-nodulating rhizobia (including the type strains of rhizobium fredii chemovar fredii, rhizobium fredii chemovar siensis, sinorhizobium fredii, and sinorhizobium xinjiangensis) and broad-host-range rhizobium sp. strain ngr 234. these sequences were compared with the corresponding pre ...	1992	1371066
hyperreiterated dna regions are conserved among bradyrhizobium japonicum serocluster 123 strains.	we have identified and cloned two dna regions which are highly reiterated in bradyrhizobium japonicum serocluster 123 strains. while one of the reiterated dna regions, pfr2503, is closely linked to the b. japonicum common and genotype-specific nodulation genes in strain usda 424, the other, pmap9, is located next to a tn5 insertion site in a host-range extension mutant of b. japonicum usda 438. the dna cloned in pfr2503 and pmap9 are reiterated 18 to 21 times, respectively, in the genomes of b. ...	1992	1622264
characterization of rfrs9, a second member of the rhizobium fredii repetitive sequence family from the nitrogen-fixing symbiont r. fredii usda257.	the genome of the nitrogen-fixing symbiont, rhizobium fredii usda257, contains nine copies of repetitive sequences known as the r. fredii repetitive sequence (rfrs) family. we previously sequenced rfrs3, which is linked to symbiosis plasmid-borne nodulation genes of this organism and has substantial homology to the t-dna of agrobacterium rhizogenes and lesser homology to reiterated sequences of bradyrhizobium japonicum. here we characterize a second family member, rfrs9. the ecori fragment conta ...	1993	8382462
rhizobium fredii and rhizobium meliloti produce 3-deoxy-d-manno-2-octulosonic acid-containing polysaccharides that are structurally analogous to group ii k antigens (capsular polysaccharides) found in escherichia coli.	the polysaccharide components from cultured cells of rhizobium fredii usda205 and rhizobium meliloti ak631 were extracted with hot phenol-water and separated by repetitive gel filtration chromatography. polyacrylamide gel electrophoresis, nuclear magnetic resonance spectrometry, and gas chromatography analyses showed that both of these bacterial species produce unique polysaccharides that contain a high proportion of 3-deoxy-d-manno-2-octulosonic acid (kdo). these polysaccharides, which constitu ...	1993	8501061
effects of ph and osmotic stress on cellular polyamine contents in the soybean rhizobia rhizobium fredii p220 and bradyrhizobium japonicum a1017.	homospermidine is a polyamine present in its highest concentrations in root nodule bacteria. by using the soybean rhizobia rhizobium fredii p220 and bradyrhizobium japonicum a1017, the effects of the ph and osmolarity of the medium on rhizobial growth and cellular polyamine contents were investigated. elevation of medium ph repressed the growth of slowly growing b. japonicum a1017 and resulted in a slight increase in cellular putrescine, while homospermidine content was not significantly affecte ...	1993	16348911
tellurium and selenium resistance in rhizobia and its potential use for direct isolation of rhizobium meliloti from soil.	forty-eight rhizobium and bradyrhizobium strains were screened for resistance to tellurite, selenite, and selenate. high levels of resistance to the metals were observed only in rhizobium meliloti and rhizobium fredii strains; the mics were 2 to 8 mm for te(iv), >200 mm for se(vi), and 50 to 100 mm for se(iv). incorporation of se and te into growth media permitted us to directly isolate r. meliloti strains from soil. mutant strains of rhizobia having decreased levels of se and te resistance were ...	1994	16349263
rhizobia catabolize nod gene-inducing flavonoids via c-ring fission mechanisms.	gas chromatographic and mass spectrometric analyses of derivatized culture medium extracts were used to identify the products of flavonoid metabolism by rhizobia. a number of rhizobium species and biovars degraded their nod gene-inducing flavonoids by mechanisms which originated in a cleavage of the c-ring of the molecule and which yielded conserved a- and b-ring products among the metabolites. in contrast, pseudomonas putida degraded quercetin via an initial fission in its a-ring, and agrobacte ...	1994	8071218
infection of soybean and pea nodules by rhizobium spp. purine auxotrophs in the presence of 5-aminoimidazole-4-carboxamide riboside.	purine auxotrophs of various rhizobium species are symbiotically defective, usually unable to initiate or complete the infection process. earlier studies demonstrated that, in the rhizobium etli-bean symbiosis, infection by purine auxotrophs is partially restored by supplementation of the plant medium with 5-amino-imidazole-4-carboxamide (aica) riboside, the unphosphorylated form of the purine biosynthetic intermediate aicar. the addition of purine to the root environment does not have this effe ...	1994	8195084
suppression of the fix- phenotype of rhizobium meliloti exob mutants by lpsz is correlated to a modified expression of the k polysaccharide.	the rhizobial production of extracellular polysaccharide (eps) is generally required for the symbiotic infection of host plants that form nodules with an apical meristem (indeterminate nodules). one exception is rhizobium meliloti ak631, an exob mutant of rm41, which is deficient in eps production yet infects and fixes nitrogen (i.e., is fix+) on alfalfa, an indeterminate nodule-forming plant. a mutation of lpsz in ak631 results in a fix- strain with altered phage sensitivity, suggesting that a ...	1995	7635814
conservation of pcaq, a transcriptional activator of pca genes for catabolism of phenolic compounds, in agrobacterium tumefaciens and rhizobium species.	in agrobacterium tumefaciens a348, control of five genes for catabolism of the phenolic compound protocatechuate to beta-ketoadipate is exerted by the gene pcaq. the product of pcaq is a transcriptional activator which is distinct from regulators of the beta-ketoadipate pathway characterized in other bacterial groups. an investigation of whether pcaq is present and conserved in related rhizobium species employed southern hybridization and an agrobacterial pcad::lacz promoter probe plasmid. these ...	1996	8655573
sinorhizobium medicae sp. nov., isolated from annual medicago spp.	the taxonomic position of isolates of a new genomic species (designated genomic species 2) obtained from several annual medicago species and originating from different geographical locations was established through the results of phenotypic tests (including the results of auxanographic and biochemical tests and symbiotic properties) and 16s rrna phylogenetic inferences. a comparison of the complete 16s rrna sequence of a representative of genomic species 2 (strain a 321t [t = type strain]) with ...	1996	8863426
the soybean cultivar specificity gene nolx is present, expressed in a nodd-dependent manner, and of symbiotic significance in cultivar-nonspecific strains of rhizobium (sinorhizobium) fredii.	rhizobium (now sinorhizobium) fredii is a symbiotic nitrogen-fixing bacterium that can nodulate soybean in a cultivar-specific manner. this process is governed by a set of negatively acting nodulation genes termed nolxwbtuv. these genes prevent r. fredii strain usda257 from infecting soybean cultivars such as mccall, but they do not block nodulation of cultivar peking. r. fredii strain usda191 contains dna sequences that hybridize to nolxwbtuv, yet it forms normal nitrogen-fixing nodules on both ...	1997	9141700
structural characterization of the k antigens from rhizobium fredii usda257: evidence for a common structural motif, with strain-specific variation, in the capsular polysaccharides of rhizobium spp.	rhizobium fredii participates in a nitrogen-fixing symbiosis with soybeans, in a strain-cultivar-specific interaction, and past studies have shown that the cell surface and extracellular polysaccharides of rhizobia function in the infection process that leads to symbiosis. the structural analysis of the capsular polysaccharides (k antigens) from strain usda257 was performed in this study. the k antigens were extracted from cultured cells with hot phenol-water and purified by size exclusion chrom ...	1997	9286989
rapid identification of medicago nodulating strains by using two oligonucleotide probes complementary to 16s rdna sequences.	symbiotic bacteria associated with the medicago genus are separated into two closely related species named sinorhizobium meliloti and sinorhizobium medicae. to discriminate rapidly between these two bacterial species, two 15-base dna probes, 16smfs and 16smed, were designed from the alignment of 16s rdna sequences to differentiate s. meliloti from s. medicae. their specificities were evaluated by dot-blot hybridization experiments on 25 reference strains representing 13 species of rhizobium and ...	1997	9336948
isrf1, a transposable insertion sequence from sinorhizobium fredii.	sinorhizobium fredii strain hh103, a nitrogen-fixing bacterial symbiont of plants, contains an insertion sequence (is) that can transpose into plasmid pmus248 and activate a promoterless tcr gene that is normally not expressed. we have cloned and characterized this element, which we designate isrf1. the is is 1002 bp in length, contains a single 513-bp open reading frame (orf), is flanked by imperfect 36-bp terminal inverted repeats, and creates 5-bp target duplications. two copies of isrf1 are ...	1997	9434166
three phylogenetic groups of noda and nifh genes in sinorhizobium and mesorhizobium isolates from leguminous trees growing in africa and latin america.	the diversity and phylogeny of noda and nifh genes were studied by using 52 rhizobial isolates from acacia senegal, prosopis chilensis, and related leguminous trees growing in africa and latin america. all of the strains had similar host ranges and belonged to the genera sinorhizobium and mesorhizobium, as previously determined by 16s rrna gene sequence analysis. the restriction patterns and a sequence analysis of the noda and nifh genes divided the strains into the following three distinct grou ...	1998	9464375
exopolysaccharide ii production is regulated by salt in the halotolerant strain rhizobium meliloti efb1.	the halotolerant strain rhizobium meliloti efb1 modifies the production of extracellular polysaccharides in response to salt. efb1 colonies grown in the presence of 0.3 m nacl show a decrease in mucoidy, and in salt-supplemented liquid medium this organism produces 40% less exopolysaccharides. we isolated transposon-induced mutant that, when grown in the absence of salt, had a colony morphology (nonmucoid) similar to the colony morphology of the wild type grown in the presence of salt. calcofluo ...	1998	9501442
characterization of rhizobium leguminosarum exopolysaccharide glycanases that are secreted via a type i exporter and have a novel heptapeptide repeat motif.	the prsde genes encode a type i protein secretion system required for the secretion of the nodulation protein nodo and at least three other proteins from rhizobium leguminosarum bv. viciae. at least one of these proteins was predicted to be a glycanase involved in processing of bacterial exopolysaccharide (eps). two strongly homologous genes (plya and plyb) were identified as encoding secreted proteins with polysaccharide degradation activity. both plya and plyb degrade eps and carboxymethyl cel ...	1998	9537364
unconventional genomic organization in the alpha subgroup of the proteobacteria.	pulsed-field gel electrophoresis was used to analyze the genomic organization of 16 bacteria belonging or related to the family rhizobiaceae of the alpha subgroup of the class proteobacteria. the number and sizes of replicons were determined by separating nondigested dna. hybridization of an rrn gene probe was used to distinguish between chromosomes and plasmids. members of the genus agrobacterium all possess two chromosomes, and each biovar has a specific genome size. as previously demonstrated ...	1998	9573163
the atzabc genes encoding atrazine catabolism are located on a self-transmissible plasmid in pseudomonas sp. strain adp.	pseudomonas sp. strain adp initiates atrazine catabolism via three enzymatic steps, encoded by atza, -b, and -c, which yield cyanuric acid, a nitrogen source for many bacteria. in-well lysis, southern hybridization, and plasmid transfer studies indicated that the atza, -b, and -c genes are localized on a 96-kb self-transmissible plasmid, padp-1, in pseudomonas sp. strain adp. high-performance liquid chromatography analyses showed that cyanuric acid degradation was not encoded by padp-1. padp-1 w ...	1998	9603862
type iii protein secretion systems in bacterial pathogens of animals and plants.	various gram-negative animal and plant pathogens use a novel, sec-independent protein secretion system as a basic virulence mechanism. it is becoming increasingly clear that these so-called type iii secretion systems inject (translocate) proteins into the cytosol of eukaryotic cells, where the translocated proteins facilitate bacterial pathogenesis by specifically interfering with host cell signal transduction and other cellular processes. accordingly, some type iii secretion systems are activat ...	1998	9618447
release of flavonoids by the soybean cultivars mccall and peking and their perception as signals by the nitrogen-fixing symbiont sinorhizobium fredii	sinorhizobium fredii strain usda191 forms n-fixing nodules on the soybean (glycine max l. merr.) cultivars (cvs) mccall and peking, but s. fredii strain usda257 nodulates only cv peking. we wondered whether specificity in this system is conditioned by the release of unique flavonoid signals from one of the cultivars or by differential perception of signals by the strains. we isolated flavonoids and used nodc and nolx, which are nod-box-dependent and -independent nod genes, respectively, to deter ...	1998	9625713
differential regulation of rhizobium etli rpon2 gene expression during symbiosis and free-living growth.	the rhizobium etli rpon1 gene, encoding the alternative sigma factor sigma54 (rpon), was recently characterized and shown to be involved in the assimilation of several nitrogen and carbon sources during free-living aerobic growth (j. michiels, t. van soom, i. d'hooghe, b. dombrecht, t. benhassine, p. de wilde, and j. vanderleyden, j. bacteriol. 180:1729-1740, 1998). we identified a second rpon gene copy in r. etli, rpon2, encoding a 54.0-kda protein which displays 59% amino acid identity with th ...	1998	9658006
the succinyl and acetyl modifications of succinoglycan influence susceptibility of succinoglycan to cleavage by the rhizobium meliloti glycanases exok and exsh.	in rhizobium meliloti (sinorhizobium meliloti) cultures, the endo-1, 3-1,4-beta-glycanases exok and exsh depolymerize nascent high-molecular-weight (hmw) succinoglycan to yield low-molecular-weight (lmw) succinoglycan. we report here that the succinyl and acetyl modifications of succinoglycan influence the susceptibility of succinoglycan to cleavage by these glycanases. it was previously shown that exoh mutants, which are blocked in the succinylation of succinoglycan, exhibit a defect in the pro ...	1998	9696768
genetic characterization of a mutant of sinorhizobium fredii strain usda208 with enhanced competitive ability for nodulation of soybean, glycine max (l.) merr.	sinorhizobium fredii strain usda208 is a nitrogen-fixing bacterium that forms nodules on roots of soybean and other legume plants. we previously found that the tn5-containing mutant 208t3, which was derived from strain usda208, is both deficient in production of exopolysaccharides and more competitive than the wild-type strain in competing against other rhizobia for nodulation of soybean. we now demonstrate that the transposon insertion of the mutant lies in a locus that is highly homologous to ...	1998	9711859
characterization of the hrpc and hrprs operons of pseudomonas syringae pathovars syringae, tomato, and glycinea and analysis of the ability of hrpf, hrpg, hrcc, hrpt, and hrpv mutants to elicit the hypersensitive response and disease in plants.	the species pseudomonas syringae encompasses plant pathogens with differing host specificities and corresponding pathovar designations. p. syringae requires the hrp (type iii protein secretion) system, encoded by a 25-kb cluster of hrp and hrc genes, in order to elicit the hypersensitive response (hr) in nonhosts or to be pathogenic in hosts. dna sequence analysis of the hrpc and hrprs operons of p. syringae pv. syringae 61 (brown spot of beans), p. syringae pv. glycinea u1 (bacterial blight of ...	1998	9721291
structural determination of a 5-o-methyl-deaminated neuraminic acid (kdn)-containing polysaccharide isolated from sinorhizobium fredii.	the structure of a polysaccharide from sinorhizobium fredii svq293, a thiamine auxotrophic mutant of s. fredii hh103, has been determined. this polysaccharide was isolated following the protocol for lipopolysaccharide extraction. on the basis of monosaccharide analysis, methylation analysis, fast atom bombardment ms, collision-induced dissociation tandem ms, one-dimensional 1h and 13c nmr and two-dimensional nmr experiments, the structure was shown to consist of the following trisaccharide repea ...	1998	9729466
characterization of a novel acyl carrier protein, rkpf, encoded by an operon involved in capsular polysaccharide biosynthesis in sinorhizobium meliloti.	rhizobial capsular polysaccharides (rkps) play an important role in the development of a nitrogen-fixing symbiosis with the plant host and in sinorhizobium meliloti ak631 functional rkpabcdef genes are required for the production of rkps. after cloning the rkpf gene, we overexpressed and purified the derived protein product (rkpf) in escherichia coli. like acyl carrier protein (acp), the rkpf protein can be labeled in vivo with radioactive beta-alanine added to the growth medium. if homogeneous ...	1998	9733701
intracellular changes in ions and organic solutes in halotolerant brevibacterium sp. strain jcm 6894 after exposure to hyperosmotic shock	in the present study we aimed to observe the intracellular responses when there was a hyperosmotic shock with a large shift in ionic strength in nutrient-rich and nutrient-poor external environments in order to clarify the availability of substrates. to do this, we used the halotolerant organism brevibacterium sp. strain jcm 6894, which is able to grow in the presence of a wide range of salt concentrations. hyperosmotic shock was induced by transferring cells in the late exponential phase of gro ...	1998	9758779
a new genetic locus in sinorhizobium meliloti is involved in stachydrine utilization	stachydrine, a betaine released by germinating alfalfa seeds, functions as an inducer of nodulation genes, a catabolite, and an osmoprotectant in sinorhizobium meliloti. two stachydrine-inducible genes were found in s. meliloti 1021 by mutation with a tn5-luxab promoter probe. both mutant strains (s10 and s11) formed effective alfalfa root nodules, but neither grew on stachydrine as the sole carbon and nitrogen source. when grown in the absence or presence of salt stress, s10 and s11 took up [14 ...	1998	9758825
molecular diversity of rhizobia occurring on native shrubby legumes in southeastern australia	the structure of rhizobial communities nodulating native shrubby legumes in open eucalypt forest of southeastern australia was investigated by a molecular approach. twenty-one genomic species were characterized by small-subunit ribosomal dna pcr-restriction fragment length polymorphism and phylogenetic analyses, among 745 rhizobial strains isolated from nodules sampled on 32 different legume host species at 12 sites. among these rhizobial genomic species, 16 belonged to the bradyrhizobium subgro ...	1998	9758831
novel rkp gene clusters of sinorhizobium meliloti involved in capsular polysaccharide production and invasion of the symbiotic nodule: the rkpk gene encodes a udp-glucose dehydrogenase.	the production of exopolysaccharide (eps) was shown to be required for the infection process by rhizobia that induce the formation of indeterminate nodules on the roots of leguminous host plants. in sinorhizobium meliloti (also known as rhizobium meliloti) rm41, a capsular polysaccharide (kps) analogous to the group ii k antigens of escherichia coli can replace eps during symbiotic nodule development and serve as an attachment site for the strain-specific bacteriophage phi16-3. the rkpa to -j ge ...	1998	9765575
different phenotypic classes of sinorhizobium meliloti mutants defective in synthesis of k antigen.	for sinorhizobium meliloti (also known as rhizobium meliloti) ak631 to establish effective symbiosis with alfalfa, it must be able to synthesize a symbiotically active form of its k antigen, a capsular polysaccharide containing a kdo (3-deoxy-d-manno-octulosonic acid) derivative. previously isolated mutants defective in the synthesis of k antigen are resistant to bacteriophage phi16-3. by screening ca. 100,000 tn5-mutagenized r. meliloti bacteria for resistance to bacteriophage phi16-3, we isola ...	1998	9765576
genetic diversity and phylogeny of rhizobia that nodulate acacia spp. in morocco assessed by analysis of rrna genes	forty rhizobia nodulating four acacia species (a. gummifera, a. raddiana, a. cyanophylla, and a. horrida) were isolated from different sites in morocco. these rhizobia were compared by analyzing both the 16s rrna gene (rdna) and the 16s-23s rrna spacer by pcr with restriction fragment length polymorphism (rflp) analysis. analysis of the length of 16s-23s spacer showed a considerable diversity within these microsymbionts, but rflp analysis of the amplified spacer revealed no additional heterogene ...	1998	9835582
sinorhizobium fredii and sinorhizobium meliloti produce structurally conserved lipopolysaccharides and strain-specific k antigens.	lipopolysaccharides (lps) and capsular polysaccharides (k antigens) may influence the interaction of rhizobia with their specific hosts; therefore, we conducted a comparative analysis of sinorhizobium fredii and sinorhizobium meliloti, which are genetically related, yet symbiotically distinct, nitrogen-fixing microsymbionts of legumes. we found that both species typically produce strain-specific k antigens that consist of 3-deoxy-d-manno-2-octulosonic acid (kdo), or other 1-carboxy-2-keto-3-deox ...	1998	9835585
the virulence plasmid of yersinia, an antihost genome.	the 70-kb virulence plasmid enables yersinia spp. (yersinia pestis, y. pseudotuberculosis, and y. enterocolitica) to survive and multiply in the lymphoid tissues of their host. it encodes the yop virulon, an integrated system allowing extracellular bacteria to disarm the cells involved in the immune response, to disrupt their communications, or even to induce their apoptosis by the injection of bacterial effector proteins. this system consists of the yop proteins and their dedicated type iii sec ...	1998	9841674
effects of ionic and osmotic strength on the glucosyltransferase of rhizobium meliloti responsible for cyclic beta-(1,2)-glucan biosynthesis.	the cyclic beta-(1,2)-glucans of rhizobium meliloti and agrobacterium tumefaciens play an important role during hypoosmotic adaptation, and the synthesis of these compounds is osmoregulated. glucosyltransferase, the enzyme responsible for cyclic beta-(1,2)-glucan biosynthesis, is present constitutively, suggesting that osmotic regulation of the biosynthesis of these glucans occurs through modulation of enzyme activity. in this study, we examined regulation of cyclic glucan biosynthesis in vitro ...	1998	16349538
insertion sequences.	insertion sequences (iss) constitute an important component of most bacterial genomes. over 500 individual iss have been described in the literature to date, and many more are being discovered in the ongoing prokaryotic and eukaryotic genome-sequencing projects. the last 10 years have also seen some striking advances in our understanding of the transposition process itself. not least of these has been the development of various in vitro transposition systems for both prokaryotic and eukaryotic e ...	1998	9729608
analysis of stable low-molecular-weight rna profiles of members of the family rhizobiaceae.	staircase electrophoresis in polyacrylamide gels was used to analyze the stable low-molecular-weight (lmw) rna profiles of 24 type strains belonging to the family rhizobiaceae. this new electrophoretic technique results in good separation of the molecules forming the lmw rna profiles. differences in the number and distribution of the rna bands in these profiles allowed us to identify differences among the 24 strains assayed. species assignments based on lmw rnas proved to be consistent with the ...	1998	9575134
infection by heterodera glycines elevates isoflavonoid production and influences soybean nodulation.	high-performance liquid chromatography and sinorhizobium fredii usda191 nodc-lacz gene fusion were used to monitor changes in the isoflavonoid content of soybean roots infected with heterodera glycines isolate tn1. isoflavonoid concentrations in infected roots of both h. glycines-resistant hartwig and susceptible essex soybean were two to four-fold higher than those of uninfected roots 2 and 3 days after inoculation. the isoflavonoids produced activated the transcription of nodc-lacz fusion. the ...	1999	19270906
noll of rhizobium sp. strain ngr234 is required for o-acetyltransferase activity.	following (iso)flavonoid induction, nodulation genes of the symbiotic nitrogen-fixing bacterium rhizobium sp. strain ngr234 elaborate a large family of lipooligosaccharidic nod factors (nodngr factors). when secreted into the rhizosphere of compatible legumes, these signal molecules initiate root hair deformation and nodule development. the nonreducing glucosamine residue of nodngr factors are n acylated, n methylated, and mono- or biscarbamoylated, while position c-6 of the reducing extremity i ...	1999	9922261
a 55-kilodalton immunodominant antigen of porphyromonas gingivalis w50 has arisen via horizontal gene transfer.	a 55-kda outer membrane protein of porphyromonas gingivalis w50 is a significant target of the serum immunoglobulin g antibody response of periodontal disease patients and hence may play an important role in host-bacterium interactions in periodontal disease. the gene encoding the 55-kda antigen (ragb, for receptor antigen b) was isolated on a 9.5-kb partial sau3ai fragment of p. gingivalis w50 chromosomal dna in puc18 by immunoscreening with a monoclonal antibody to this antigen. the 1.6-kb ope ...	1999	10024556
the bradyrhizobium japonicum nola gene encodes three functionally distinct proteins.	examination of nola revealed that nola can be uniquely translated from three atg start codons. translation from the first atg (atg1) predicts a protein (nola1) having an n-terminal, helix-turn-helix dna-binding motif similar to the dna-binding domains of the merr-type regulatory proteins. translation from atg2 and atg3 would give the n-terminally truncated proteins nola2 and nola3, respectively, lacking the dna-binding domain. consistent with this, immunoblot analyses of bradyrhizobium japonicum ...	1999	10049387
polynucleotide probes that target a hypervariable region of 16s rrna genes to identify bacterial isolates corresponding to bands of community fingerprints.	temperature gradient gel electrophoresis (tgge) is well suited for fingerprinting bacterial communities by separating pcr-amplified fragments of 16s rrna genes (16s ribosomal dna [rdna]). a strategy was developed and was generally applicable for linking 16s rdna from community fingerprints to pure culture isolates from the same habitat. for this, digoxigenin-labeled polynucleotide probes were generated by pcr, using bands excised from tgge community fingerprints as a template, and applied in hyb ...	1999	10049861
mutation in gdp-fucose synthesis genes of sinorhizobium fredii alters nod factors and significantly decreases competitiveness to nodulate soybeans.	we mutagenized sinorhizobium fredii hh103-1 with tn5-b20 and screened about 2,000 colonies for increased beta-galactosidase activity in the presence of the flavonoid naringenin. one mutant, designated svq287, produces lipochitooligosaccharide nod factors (lcos) that differ from those of the parental strain. the nonreducing n-acetylglucosamine residues of all of the lcos of mutant svq287 lack fucose and 2-o-methylfucose substituents. in addition, svq287 synthesizes an lco with an unusually long, ...	1999	10065558
further studies of the role of cyclic beta-glucans in symbiosis. an ndvc mutant of bradyrhizobium japonicum synthesizes cyclodecakis-(1-->3)-beta-glucosyl.	the cyclic beta-(1-->3),beta-(1-->6)-d-glucan synthesis locus of bradyrhizobium japonicum is composed of at least two genes, ndvb and ndvc. mutation in either gene affects glucan synthesis, as well as the ability of the bacterium to establish a successful symbiotic interaction with the legume host soybean (glycine max). b. japonicum strain ab-14 (ndvb::tn5) does not synthesize beta-glucans, and strain ab-1 (ndvc::tn5) synthesizes a cyclic beta-glucan lacking beta-(1-->6)-glycosidic bonds. we det ...	1999	10069844
disaccharides as a new class of nonaccumulated osmoprotectants for sinorhizobium meliloti.	sucrose and ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidine carboxylic acid) are very unusual osmoprotectants for sinorhizobium meliloti because these compounds, unlike other bacterial osmoprotectants, do not accumulate as cytosolic osmolytes in salt-stressed s. meliloti cells. here, we show that, in fact, sucrose and ectoine belong to a new family of nonaccumulated sinorhizobial osmoprotectants which also comprises the following six disaccharides: trehalose, maltose, cellobiose, gentiobiose, ...	1999	10103242
the periplasmic nitrate reductase in pseudomonas sp. strain g-179 catalyzes the first step of denitrification.	both membrane-bound and periplasmic nitrate reductases have been found in denitrifying bacteria. yet the role of periplasmic nitrate reductase in denitrification has not been clearly defined. to analyze the function of the periplasmic nitrate reductase in pseudomonas sp. strain g-179, the nap gene cluster was identified and found to be linked to genes involved in reduction of nitrite and nitric oxide and anaerobic heme biosynthesis. mutation in the nap region rendered the cells incapable of grow ...	1999	10217771
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
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
expression of a serratia marcescens chitinase gene in sinorhizobium fredii usda191 and sinorhizobium meliloti rcr2011 impedes soybean and alfalfa nodulation.	a gene encoding chitinase from serratia marcescens bjl200 was cloned into a broad-host-range vector (prk415) and mobilized into sinorhizobium fredii usda191. chitinolytic activity was detected in s. fredii usda191 transconjugants that carried the s. marcescens chib gene. chitinase-producing s. fredii usda191 formed nodules on soybean cultivar mccall. however, there was a delay in nodule formation and a marked decrease in the total number of nodules formed by the chitinase-producing s. fredii in ...	1999	10432638
the 102-kilobase pgm locus of yersinia pestis: sequence analysis and comparison of selected regions among different yersinia pestis and yersinia pseudotuberculosis strains.	we report the complete 119,443-bp sequence of the pgm locus from yersinia pestis and its flanking regions. sequence analysis confirms that the 102-kb unstable pgm locus is composed of two distinct parts: the pigmentation segment and a high-pathogenicity island (hpi) which carries virulence genes involved in iron acquisition (yersiniabactin biosynthetic gene cluster). within the hpi, three genes coding for proteins related to phage proteins were uncovered. they are located at both extremities ind ...	1999	10456941
reduction of adenosine-5'-phosphosulfate instead of 3'-phosphoadenosine-5'-phosphosulfate in cysteine biosynthesis by rhizobium meliloti and other members of the family rhizobiaceae.	we have cloned and sequenced three genes from rhizobium meliloti (sinorhizobium meliloti) that are involved in sulfate activation for cysteine biosynthesis. two of the genes display homology to the escherichia coli cysdn genes, which code for an atp sulfurylase (ec 2.7.7.4). the third gene has homology to the e. coli cysh gene, a 3'-phosphoadenosine-5'-phosphosulfate (paps) reductase (ec 1.8.99.4), but has greater homology to a set of genes found in arabidopsis thaliana that encode an adenosine- ...	1999	10464198
development and application of pathovar-specific monoclonal antibodies that recognize the lipopolysaccharide o antigen and the type iv fimbriae of xanthomonas hyacinthi.	the objective of this study was to develop a specific immunological diagnostic assay for yellow disease in hyacinths, using monoclonal antibodies (mabs). mice were immunized with a crude cell wall preparation (shear fraction) from xanthomonas hyacinthi and with purified type iv fimbriae. hybridomas were screened for a positive reaction with x. hyacinthi cells or fimbriae and for a negative reaction with x. translucens pv. graminis or erwinia carotovora subsp. carotovora. nine mabs recognized fim ...	1999	10473431
structural determination of a 5-acetamido-3,5,7, 9-tetradeoxy-7-(3-hydroxybutyramido)-l-glycero-l-manno-nonulos onic acid-containing homopolysaccharide isolated from sinorhizobium fredii hh103.	the structure of a polysaccharide from sinorhizobium fredii hh103 has been determined. this polysaccharide was isolated by following the protocol for lipopolysaccharide extraction. on the basis of monosaccharide analysis, methylation analysis, fast atom bombardment ms, matrix-assisted laser desorption ionization ms, electron-impact high-resolution ms, one-dimensional (1)h-nmr and (13)c-nmr and two-dimensional nmr experiments, the structure was shown to consist of a homopolymer of a 3:1 mixture o ...	1999	10477263
identification of a plasmid-borne locus in rhizobium etli kim5s involved in lipopolysaccharide o-chain biosynthesis and nodulation of phaseolus vulgaris.	screening of derivatives of rhizobium etli kim5s randomly mutagenized with mtn5ssgusa30 resulted in the identification of strain kim-g1. its rough colony appearance, flocculation in liquid culture, and ndv(-) fix(-) phenotype were indicative of a lipopolysaccharide (lps) defect. electrophoretic analysis of cell-associated polysaccharides showed that kim-g1 produces only rough lps. composition analysis of purified lps oligosaccharides from kim-g1 indicated that it produces an intact lps core tris ...	1999	10482500
halomethane:bisulfide/halide ion methyltransferase, an unusual corrinoid enzyme of environmental significance isolated from an aerobic methylotroph using chloromethane as the sole carbon source.	a novel dehalogenating/transhalogenating enzyme, halomethane:bisulfide/halide ion methyltransferase, has been isolated from the facultatively methylotrophic bacterium strain cc495, which uses chloromethane (ch(3)cl) as the sole carbon source. purification of the enzyme to homogeneity was achieved in high yield by anion-exchange chromatography and gel filtration. the methyltransferase was composed of a 67-kda protein with a corrinoid-bound cobalt atom. the purified enzyme was inactive but was act ...	1999	10508052
epitope identification for a panel of anti-sinorhizobium meliloti monoclonal antibodies and application to the analysis of k antigens and lipopolysaccharides from bacteroids.	in two published reports using monoclonal antibodies (mabs) generated against whole cells, olsen et al. showed that strain-specific antigens on the surface of cultured cells of sinorhizobium meliloti were diminished or absent in the endophytic cells (bacteroids) recovered from alfalfa nodules, whereas two common antigens were not affected by bacterial differentiation (p. olsen, m. collins, and w. rice, can. j. microbiol. 38:506-509, 1992; p. olsen, s. wright, m. collins, and w. rice, appl. envir ...	1999	10543844
rhizobium-legume symbiosis and nitrogen fixation under severe conditions and in an arid climate.	biological n(2) fixation represents the major source of n input in agricultural soils including those in arid regions. the major n(2)-fixing systems are the symbiotic systems, which can play a significant role in improving the fertility and productivity of low-n soils. the rhizobium-legume symbioses have received most attention and have been examined extensively. the behavior of some n(2)-fixing systems under severe environmental conditions such as salt stress, drought stress, acidity, alkalinit ...	1999	10585971
[construction of a gfp broad-host-range promoter-probe vector and its application].	the 0.9 kb dna fragment was obtained by pcr and using a pair of special designed primers from the green fluorescent protein gene(gfp). it was then cloned into an expression vector pet-11c and named as phn115. a promoferless gfp vector with sd fragment was obtained from phn115 and subcloned into sk(+), pij 2925 and finally into ptr102. a broad-hast-range and visible promoter-probe vector, phn127 was constructed and used successfully for the identification of constitutive and inducible promoters f ...	1999	12555521
[study on the improvement of plasmid stability in soybean rhizobia].	by using luxab as the report genes, 3.2 kb parcba/de gene fragment from ptr102 was inserted into plafr3 which contained a 3.7 kb enhancing fragment and deleted its cos site. recombinant plasmids phn155 and phn156 were obtained. contrasted plasmids phn157 and phn158 which contained cos site were also constructed. these four plasmids were transferred into sinorhizobium fredii hn01 by tri-parental mating, and plasmid phn155 and phn158 were introduced into bradyrhizobium japonicum ta11 by two-parent ...	2000	12548995
[subcloning and sequencing of dna fragment related to salt tolerance in sinorhizobium fredii rt19].	a 23 kb dna fragment related to salt tolerance was obtained from the gene library of s. fredii strain rt19. in this study, bamh i was selected to digest 23 kb dna fragment into different length of dna fragments. the resulting fragments were ligated with plasmid pml122, then the recombinant plasmids were transformed to competent cells of e. coli s17-1 on selective medium and three transformants tr were obtained. two-parental mating experiments were carried out with these transformants as donor an ...	2000	11192438
a new chemolithoautotrophic arsenite-oxidizing bacterium isolated from a gold mine: phylogenetic, physiological, and preliminary biochemical studies.	a previously unknown chemolithoautotrophic arsenite-oxidizing bacterium has been isolated from a gold mine in the northern territory of australia. the organism, designated nt-26, was found to be a gram-negative motile rod with two subterminal flagella. in a minimal medium containing only arsenite as the electron donor (5 mm), oxygen as the electron acceptor, and carbon dioxide-bicarbonate as the carbon source, the doubling time for chemolithoautotrophic growth was 7.6 h. arsenite oxidation was f ...	2000	10618208
environmental regulation of exopolysaccharide production in sinorhizobium meliloti.	exopolysaccharide production by sinorhizobium meliloti is required for invasion of root nodules on alfalfa and successful establishment of a nitrogen-fixing symbiosis between the two partners. s. meliloti wild-type strain rm1021 requires production of either succinoglycan, a polymer of repeating octasaccharide subunits, or eps ii, an exopolysaccharide of repeating dimer subunits. the reason for the production of two functional exopolysaccharides is not clear. earlier reports suggested that low-p ...	2000	10633091
structural characterization of the released polysaccharide of desiccation-tolerant nostoc commune drh-1.	the structure of the viscous extracellular polysaccharide (glycan) of desiccation-tolerant nostoc commune drh-1 was determined through chromatographic and spectroscopic methods. the polysaccharide is novel in that it possesses a 1-4-linked xylogalactoglucan backbone with d-ribofuranose and 3-o-[(r)-1-carboxyethyl]-d-glucuronic acid (nosturonic acid) pendant groups. the presence of d-ribose and nosturonic acid as peripheral groups is unusual, and their potential roles in modulating the rheologica ...	2000	10648523
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
identification of two novel hrp-associated genes in the hrp gene cluster of xanthomonas oryzae pv. oryzae.	we have cloned a hrp gene cluster from xanthomonas oryzae pv. oryzae. bacteria with mutations in the hrp region have reduced growth in rice leaves and lose the ability to elicit a hypersensitive response (hr) on the appropriate resistant cultivars of rice and the nonhost plant tomato. a 12,165-bp portion of nucleotide sequence from the presumed left end and extending through the hrpb operon was determined. the region was most similar to hrp genes from xanthomonas campestris pv. vesicatoria and r ...	2000	10714988
analysis of cellular fatty acids and phenotypic relationships of agrobacterium, bradyrhizobium, mesorhizobium, rhizobium and sinorhizobium species using the sherlock microbial identification system.	previous studies have demonstrated that cellular fatty acid analysis is a useful tool for identifying unknown strains of rhizobia and establishing taxonomic relationships between the species. in this study, the fatty acid profiles of over 600 strains belonging to the genera agrobacterium, bradyrhizobium, mesorhizobium, rhizobium and sinorhizobium were evaluated using the gaschromatography-based sherlock microbial identification system (mis). data collected with the mis showed that the three phyl ...	2000	10758890
the ++sinorhizobium meliloti lon protease is involved in regulating exopolysaccharide synthesis and is required for nodulation of alfalfa.	while screening for sinorhizobium meliloti pho regulatory mutants, a transposon mutant was isolated that constitutively expressed higher levels of acid and alkaline phosphatase enzymes. this mutant was also found to form pseudonodules on alfalfa that were delayed in appearance relative to those formed by the wild-type strain, it contained few bacteroids, and it did not fix nitrogen. sequence analysis of the transposon insertion site revealed the affected gene to have high homology to lon proteas ...	2000	10762258
genome structure of the genus azospirillum.	azospirillum species are plant-associated diazotrophs of the alpha subclass of proteobacteria. the genomes of five of the six azospirillum species were analyzed by pulsed-field gel electrophoresis. all strains possessed several megareplicons, some probably linear, and 16s ribosomal dna hybridization indicated multiple chromosomes in genomes ranging in size from 4.8 to 9.7 mbp. the nifhdk operon was identified in the largest replicon.	2000	10869094
characterization of an atrazine-degrading pseudaminobacter sp. isolated from canadian and french agricultural soils.	atrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. fourteen bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from soils obtained from two farms in canada and two farms in france. these strains were indistinguishable from each other based on repetitive extragenic palindromic pcr genomic fingerprinting performed with primers eric1r, eric2, and boxa1r. based on 16s rrna sequence analysis of one representativ ...	2000	10877767