Publications

regulation of soybean nodulation independent of ethylene signaling	leguminous plants regulate the number of bradyrhizobium- or rhizobium-infected sites that develop into nitrogen-fixing root nodules. ethylene has been implicated in the regulation of nodule formation in some species, but this role has remained in question for soybean (glycine max). the present study used soybean mutants with decreased responsiveness to ethylene, soybean mutants with defective regulation of nodule number, and ag+ inhibition of ethylene perception to examine the role of ethylene i ...	1999	10069833
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
characterization of the pyoluteorin biosynthetic gene cluster of pseudomonas fluorescens pf-5.	ten genes (plt) required for the biosynthesis of pyoluteorin, an antifungal compound composed of a bichlorinated pyrrole linked to a resorcinol moiety, were identified within a 24-kb genomic region of pseudomonas fluorescens pf-5. the deduced amino acid sequences of eight plt genes were similar to the amino acid sequences of genes with known biosynthetic functions, including type i polyketide synthases (pltb, pltc), an acyl coenzyme a (acyl-coa) dehydrogenase (plte), an acyl-coa synthetase (pltf ...	1999	10094695
genes coding for phosphotransacetylase and acetate kinase in sinorhizobium meliloti are in an operon that is inducible by phosphate stress and controlled by phob.	recent work in this laboratory has shown that the gene coding for acetate kinase (acka) in sinorhizobium meliloti is up-regulated in response to phosphate limitation. characterization of the region surrounding acka revealed that it is adjacent to pta, which codes for phosphotransacetylase, and that these two genes are part of an operon composed of at least two additional genes in the following order: an open reading frame (orfa), pta, acka, and the partial sequence of a gene with an inferred pep ...	1999	10094701
isolation and characterization of alfalfa-nodulating rhizobia present in acidic soils of central argentina and uruguay	we describe the isolation and characterization of alfalfa-nodulating rhizobia from acid soils of different locations in central argentina and uruguay. a collection of 465 isolates was assembled, and the rhizobia were characterized for acid tolerance. growth tests revealed the existence of 15 acid-tolerant (at) isolates which were able to grow at ph 5.0 and formed nodules in alfalfa with a low rate of nitrogen fixation. analysis of those isolates, including partial sequencing of the genes encodin ...	1999	10103231
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
a phosphotransferase that generates phosphatidylinositol 4-phosphate (ptdins-4-p) from phosphatidylinositol and lipid a in rhizobium leguminosarum. a membrane-bound enzyme linking lipid a and ptdins-4-p biosynthesis.	membranes of rhizobium leguminosarum contain a 3-deoxy-d-manno-octulosonic acid (kdo)-activated lipid a 4'-phosphatase required for generating the unusual phosphate-deficient lipid a found in this organism. the enzyme has been solubilized with triton x-100 and purified 80-fold. as shown by co-purification and thermal inactivation studies, the 4'-phosphatase catalyzes not only the hydrolysis of (kdo)2-[4'-32p]lipid iva but also the transfer the 4'-phosphate of kdo2-[4'-32p]lipid iva to the inosit ...	1999	10196199
a deacylase in rhizobium leguminosarum membranes that cleaves the 3-o-linked beta-hydroxymyristoyl moiety of lipid a precursors.	lipid a from the nitrogen-fixing bacterium rhizobium leguminosarum displays many structural differences compared with lipid a of escherichia coli. r. leguminosarum lipid a lacks the usual 1- and 4'-phosphate groups but is derivatized with a galacturonic acid substituent at position 4'. r. leguminosarum lipid a often contains an aminogluconic acid moiety in place of the proximal glucosamine 1-phosphate unit. striking differences also exist in the secondary acyl chains attached to e. coli versus r ...	1999	10196200
kdgrecc negatively regulates genes for pectinases, cellulase, protease, harpinecc, and a global rna regulator in erwinia carotovora subsp. carotovora.	erwinia carotovora subsp. carotovora produces extracellular pectate lyase (pel), polygalacturonase (peh), cellulase (cel), and protease (prt). the concerted actions of these enzymes largely determine the virulence of this plant-pathogenic bacterium. e. carotovora subsp. carotovora also produces harpinecc, the elicitor of the hypersensitive reaction. we document here that kdgrecc (kdg, 2-keto-3-deoxygluconate; kdgr, general repressor of genes involved in pectin and galacturonate catabolism), a ho ...	1999	10198003
azospirillum irakense produces a novel type of pectate lyase.	the pela gene from the n2-fixing plant-associated bacterium azospirillum irakense, encoding a pectate lyase, was isolated by heterologous expression in escherichia coli. nucleotide sequence analysis of the region containing pela indicated an open reading frame of 1,296 bp, coding for a preprotein of 432 amino acids with a typical amino-terminal signal peptide of 24 amino acids. n-terminal amino acid sequencing confirmed the processing of the protein in e. coli at the signal peptidase cleavage si ...	1999	10198006
differential regulation of two divergent sinorhizobium meliloti genes for hpii-like catalases during free-living growth and protective role of both catalases during symbiosis.	two catalases, kata and katb, have been detected in sinorhizobium meliloti growing on rich medium. here we characterize a new catalase gene encoding a third catalase (katc). katc activity was detectable only at the end of the stationary phase in s. meliloti growing in minimum medium, whereas kata activity was found during the exponential phase. analysis with a katc-lacz fusion demonstrated that katc expression is mainly regulated at the transcription level. an increase of catalase activity corre ...	1999	10198032
characterization of two novel type i ribosome-inactivating proteins from the storage roots of the andean crop mirabilis expansa.	two novel type i ribosome-inactivating proteins (rips) were found in the storage roots of mirabilis expansa, an underutilized andean root crop. the two rips, named me1 and me2, were purified to homogeneity by ammonium sulfate precipitation, cation-exchange perfusion chromatography, and c4 reverse-phase chromatography. the two proteins were found to be similar in size (27 and 27.5 kd) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their isoelectric points were determined to be ...	1999	10198104
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 fhu genes of rhizobium leguminosarum, specifying siderophore uptake proteins: fhudcb are adjacent to a pseudogene version of fhua.	a mutant of rhizobium leguminosarum was isolated which fails to take up the siderophore vicibactin. the mutation is in a homologue of fhub, which in escherichia coli specifies an inner-membrane protein of the ferric hydroxamate uptake system. in rhizobium, fhub is in an operon fhudcb, which specifies the cytoplasmic membrane and periplasmic proteins involved in siderophore uptake. fhudcb mutants make vicibactin when grown in fe concentrations that inhibit its production in the wild-type. nodules ...	1999	10217493
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
activation and inactivation of pseudomonas stutzeri methylbenzene catabolism pathways mediated by a transposable element.	the arrangement of the genes involved in o-xylene, m-xylene, and p-xylene catabolism was investigated in three pseudomonas stutzeri strains: the wild-type strain ox1, which is able to grow on o-xylene but not on the meta and para isomers; the mutant m1, which grows on m-xylene and p-xylene but is unable to utilize the ortho isomer; and the revertant r1, which can utilize all the three isomers of xylene. a 3-kb insertion sequence (is) termed isps1, which inactivates the m-xylene and p-xylene cata ...	1999	10223973
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
the pssb gene product of rhizobium leguminosarum bv. trifolii is homologous to a family of inositol monophosphatases.	the rhizobium leguminosarum bv. trifolii region encoding pssa and pssb genes was cloned. the pssb gene located upstream of the pssa encoded a 28.36-kda protein which displayed 97.5% identity with the pssb of r. leguminosarum bv. viciae. inactivation of the pssb gene by insertion of the lacz-gmr cassette resulted in the significant increased production of exopolysaccharide in comparison to the wild-type level. a mutant strain was also defective in nitrogen fixation suggesting a regulatory role of ...	1999	10227162
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
growth of azospirillum irakense kbc1 on the aryl beta-glucoside salicin requires either sala or salb.	the rhizosphere nitrogen-fixing bacterium azospirillum irakense kbc1 is able to grow on pectin and beta-glucosides such as cellobiose, arbutin, and salicin. two adjacent genes, sala and salb, conferring beta-glucosidase activity to escherichia coli, have been identified in a cosmid library of a. irakense dna. the sala and salb enzymes preferentially hydrolyzed aryl beta-glucosides. a delta(sala-salb) a. irakense mutant was not able to grow on salicin but could still utilize arbutin, cellobiose, ...	1999	10321999
identification of genetic determinants for the hemolytic activity of streptococcus agalactiae by iss1 transposition.	streptococcus agalactiae is a poorly transformable bacterium and studies of molecular mechanisms are difficult due to the limitations of genetic tools. employing the novel pgh9:iss1 transposition vector we generated plasmid-based mutant libraries of s. agalactiae strains o90r and ac475 by random chromosomal integration. a screen for mutants with a nonhemolytic phenotype on sheep blood agar led to the identification of a genetic locus harboring several genes that are essential for the hemolytic f ...	1999	10322024
molecular characterization of a brucella species large dna fragment deleted in brucella abortus strains: evidence for a locus involved in the synthesis of a polysaccharide.	a brucella melitensis 16m dna fragment of 17,119 bp, which contains a large region deleted in b. abortus strains and dna flanking one side of the deletion, has been characterized. in addition to the previously identified omp31 gene, 14 hypothetical genes have been identified in the b. melitensis fragment, most of them showing homology to genes involved in the synthesis of a polysaccharide. considering that 10 of the 15 genes are missing in b. abortus and that all the polysaccharides described in ...	1999	10338472
primary structure of the dna polymerase i gene of an alpha-proteobacterium, rhizobium leguminosarum, and comparison with other family a dna polymerases.	the structural gene for dna polymerase i of rhizobium leguminosarum was determined. the rhizobium dna polymerase i consists of 1016 amino acid residues with a calculated molecular weight of 111,491 dalton. the amino acid sequence comparison with e. coli dna polymerase i, thermus aquaticus dna polymerase i, and rickettsia prowazekii dna polymerase i showed that, although 5'-nuclease and dna polymerase domains are highly conserved, 3' to 5' exonuclease domains are much less conserved. while both r ...	1999	10341077
earthworm egg capsules as vectors for the environmental introduction of biodegradative bacteria.	earthworm egg capsules (cocoons) may acquire bacteria from the environment in which they are produced. we found that ralstonia eutropha (pjp4) can be recovered from eisenia fetida cocoons formed in soil inoculated with this bacterium. plasmid pjp4 contains the genes necessary for 2,4-dichlorophenoxyacetic acid (2,4-d) and 2, 4-dichlorophenol (2,4-dcp) degradation. in this study we determined that the presence of r. eutropha (pjp4) within the developing earthworm cocoon can influence the degradat ...	1999	10347016
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
high-efficiency transformation of rhizobium leguminosarum by electroporation.	electrotransformation of rhizobium leguminosarum was successfully carried out with a 15.1-kb plasmid, pmp154 (cmr), containing a nodabc-lacz fusion by electroporation. the maximum transformation efficiency, 10(8) transformants/microg of dna, was achieved at a field strength of 14 kv/cm with a pulse of 7.3 ms (186 omega). the number of transformants was found to increase with increasing cell density, with no sign of saturation. in relation to dna dosage, the maximum transformation efficiency (5.8 ...	1999	10347085
the physiological contribution of acinetobacter pcak, a transport system that acts upon protocatechuate, can be masked by the overlapping specificity of vank.	vank is the fourth member of the ubiquitous major facilitator superfamily of transport proteins to be identified that, together with pcak, benk, and muck, contributes to aromatic catabolism in acinetobacter sp. strain adp1. vank and pcak have overlapping specificity for p-hydroxybenzoate and, most clearly, for protocatechuate: inactivation of both proteins severely impairs growth with protocatechuate, and the activity of either protein alone can mask the phenotype associated with inactivation of ...	1999	10348864
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 quorum-sensing-dependent control of rhizosphere-expressed (rhi) genes in rhizobium leguminosarum bv. viciae.	the rhi genes of rhizobium leguminosarum biovar viciae are expressed in the rhizosphere and play a role in the interaction with legumes, such as the pea. previously (k. m. gray, j. p. pearson, j. a. downie, b. e. a. boboye, and e. p. greenberg, j. bacteriol. 178:372-376, 1996) the rhiabc operon had been shown to be regulated by rhir and to be induced by added n-(3-hydroxy-7-cis-tetradecenoyl)-l-homoserine lactone (3oh, c14:1-hsl). mutagenesis of a cosmid carrying the rhiabc and rhir gene region ...	1999	10368158
structural and putative regulatory genes involved in cellulose synthesis in rhizobium leguminosarum bv. trifolii.	six genes involved in cellulose synthesis in rhizobium leguminosarum bv. trifolii were identified using tn5 mutagenesis. four of them displayed homology to the previously cloned and sequenced agrobacterium tumefaciens cellulose genes cela, celb, celc and cele. these genes are organized similarly in r. leguminosarum bv. trifolii. in addition, there were strong indications that two tandemly located genes, celr1 and celr2, probably organized as one operon, are involved in the regulation of cellulos ...	1999	10376842
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
interaction of azospirillum lipoferum with wheat germ agglutinin stimulates nitrogen fixation.	in vitro, the nitrogen fixation capability of a. lipoferum is efficiently increased in the presence of wheat germ agglutinin (wga). a putative wga-binding receptor, a 32-kda protein, was detected in the cell capsule. the stimulatory effect required n-acetyl-d-glucosamine dimer (glcnacdi) terminated sugar side chains of the receptor and was dependent on the number of glcnacdi links involved in receptor-wga interface. binding to the primary sugar binding sites on wga had a larger stimulatory effec ...	1999	10383962
cloning and characterization of a rhizobium leguminosarum gene encoding a bacteriocin with similarities to rtx toxins.	a 3-kb region containing the determinant for bacteriocin activity from rhizobium leguminosarum 248 was isolated and characterized by tn5 insertional mutagenesis and dna sequencing. southern hybridizations showed that this bacteriocin was encoded on the plasmid prl1ji and that homologous loci were not found in other unrelated r. leguminosarum strains. tn5 insertional mutagenesis showed that mutations in the c-terminal half of the bacteriocin open reading frame apparently did not abolish bacterioc ...	1999	10388672
quantification of chemotaxis to naphthalene by pseudomonas putida g7.	the capillary assay was used to quantify the chemotactic response of pseudomonas putida g7 to naphthalene. experiments were conducted in which the cell concentration in the assay chamber, the naphthalene concentration in the capillary, or the incubation time was varied. data from these experiments were evaluated with a model that accounted for the effect of diffusion on the distribution of substrate and the transport of cells from the chamber through the capillary orifice. by fitting a numerical ...	1999	10388674
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
brucella outer membrane lipoproteins share antigenic determinants with bacteria of the family rhizobiaceae.	brucellae have been reported to be phylogenetically related to bacteria of the family rhizobiaceae. in the present study, we used a panel of monoclonal antibodies (mabs) to brucella outer membrane proteins (omps) to determine the presence of common omp epitopes in some representative bacteria of this family, i.e., ochrobactrum anthropi, phyllobacterium rubiacearum, rhizobium leguminosarum, and agrobacterium tumefaciens, and also in bacteria reported to serologically cross-react with brucella, i. ...	1999	10391877
a novel sinorhizobium meliloti operon encodes an alpha-glucosidase and a periplasmic-binding-protein-dependent transport system for alpha-glucosides.	the most abundant carbon source transported into legume root nodules is photosynthetically produced sucrose, yet the importance of its metabolism by rhizobia in planta is not yet known. to identify genes involved in sucrose uptake and hydrolysis, we screened a sinorhizobium meliloti genomic library and discovered a segment of s. meliloti dna which allows ralstonia eutropha to grow on the alpha-glucosides sucrose, maltose, and trehalose. tn5 mutagenesis localized the required genes to a 6.8-kb re ...	1999	10400573
characterization of the serogroup o11 o-antigen locus of pseudomonas aeruginosa pa103.	we previously cloned a genomic dna fragment from the serogroup o11 pseudomonas aeruginosa strain pa103 that contained all genes necessary for o-antigen synthesis and directed the expression of serogroup o11 antigen on recombinant escherichia coli and salmonella. to elucidate the pathway of serogroup o11 antigen synthesis, the nucleotide sequence of the biosynthetic genes was determined. eleven open reading frames likely to be involved in serogroup o11 o-antigen biosynthesis were identified and a ...	1999	10400585
cloning, sequencing, and characterization of the cgmb gene of sinorhizobium meliloti involved in cyclic beta-glucan biosynthesis.	periplasmic cyclic beta-glucans of rhizobium species provide important functions during plant infection and hypo-osmotic adaptation. in sinorhizobium meliloti (also known as rhizobium meliloti), these molecules are highly modified with phosphoglycerol and succinyl substituents. we have previously identified an s. meliloti tn5 insertion mutant, s9, which is specifically impaired in its ability to transfer phosphoglycerol substituents to the cyclic beta-glucan backbone (m. w. breedveld, j. a. hadl ...	1999	10419956
mgatp binding and hydrolysis determinants of ntrc, a bacterial enhancer-binding protein.	when phosphorylated, the dimeric form of nitrogen regulatory protein c (ntrc) of salmonella typhimurium forms a larger oligomer(s) that can hydrolyze atp and hence activate transcription by the sigma(54)-holoenzyme form of rna polymerase. studies of mg-nucleoside triphosphate binding using a filter-binding assay indicated that phosphorylation is not required for nucleotide binding but probably controls nucleotide hydrolysis per se. studies of binding by isothermal titration calorimetry indicated ...	1999	10419963
[effect of the addition of specific lectin on the symbiosis of rhizobium leguminosarum and phaseolus vulgaris].	the effect of specific lectin addition on rhizobium leguminosarum-phaseolus vulgaris symbiosis characteristics was studied. two alternatives were selected for comparison: a) p. vulgaris seedling roots treated with lectin were inoculated with r. leguminosarum and b) p. vulgaris seedling roots were inoculated with r. leguminosarum incubated with lectin for 3 h and 72 h. the following parameters were evaluated: number and dry weight of nodules and dry matter and nitrogen content of shoot. in lectin ...	1999	10425662
genetic structure of natural populations of escherichia coli in wild hosts on different continents.	current knowledge of genotypic and phenotypic diversity in the species escherichia coli is based almost entirely on strains recovered from humans or zoo animals. in this study, we analyzed a collection of 202 strains obtained from 81 mammalian species representing 39 families and 14 orders in australia and the americas, as well as several reference strains; we also included a strain from a reptile and 10 from different families of birds collected in mexico. the strains were characterized genotyp ...	1999	10427022
the viable-but-nonculturable condition is induced by copper in agrobacterium tumefaciens and rhizobium leguminosarum.	many bacteria respond to changes in environmental conditions by entering the viable-but-nonculturable state. we have determined that copper can induce nutrient-starved agrobacterium tumefaciens and rhizobium leguminosarum cells to become viable but nonculturable. this is the first report of a chemical inducer of this condition.	1999	10427081
genome signature comparisons among prokaryote, plasmid, and mitochondrial dna.	our basic observation is that each genome has a characteristic "signature" defined as the ratios between the observed dinucleotide frequencies and the frequencies expected if neighbors were chosen at random (dinucleotide relative abundances). the remarkable fact is that the signature is relatively constant throughout the genome; i.e. , the patterns and levels of dinucleotide relative abundances of every 50-kb segment of the genome are about the same. comparison of the signatures of different gen ...	1999	10430917
the pseudomonas aeruginosa exotoxin a regulatory gene, ptxs: evidence for negative autoregulation.	we have previously described a pseudomonas aeruginosa gene, ptxr, which enhances exotoxin a production at the transcriptional level. we have also described another gene, ptxs, which is transcribed divergently from ptxr and interferes with the enhancement of exotoxin a synthesis by ptxr. however, the mechanisms through which ptxr and/or ptxs are regulated is not known. in this study, we attempted (by using the dna gel shift assay) to determine if p. aeruginosa contains a potential regulatory prot ...	1999	10438759
identification and characterization of hupt, a gene involved in negative regulation of hydrogen oxidation in bradyrhizobium japonicum.	the bradyrhizobium japonicum hupt gene was sequenced, and its gene product was found to be homologous to ntrb-like histidine kinases. a hupt mutant expresses higher levels of hydrogenase activity than the wild-type strain under hydrogenase-inducing conditions (i.e., microaerobiosis plus hydrogen, or symbiosis), whereas in noninduced hupt cells, hupsl expression is derepressed but does not lead to hydrogenase activity. we conclude that hupt is involved in the repression of hupsl synthesis at the ...	1999	10438783
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
mutations affecting motifs of unknown function in the central domain of nitrogen regulatory protein c.	the positive control function of the bacterial enhancer-binding protein ntrc resides in its central domain, which is highly conserved among activators of sigma54 holoenzyme. previous studies of a small set of mutant forms specifically defective in transcriptional activation, called ntrc repressor [ntrc(rep)] proteins, had enabled us to locate various functional determinants in the central domain. in this more comprehensive survey, the dna encoding a major portion of the central domain was random ...	1999	10464219
characterization of a pseudomonas aeruginosa fatty acid biosynthetic gene cluster: purification of acyl carrier protein (acp) and malonyl-coenzyme a:acp transacylase (fabd).	a dna fragment containing the pseudomonas aeruginosa fabd (encoding malonyl-coenzyme a [coa]:acyl carrier protein [acp] transacylase), fabg (encoding beta-ketoacyl-acp reductase), acpp (encoding acp), and fabf (encoding beta-ketoacyl-acp synthase ii) genes was cloned and sequenced. this fab gene cluster is delimited by the plsx (encoding a poorly understood enzyme of phospholipid metabolism) and pabc (encoding 4-amino-4-deoxychorismate lyase) genes; the fabf and pabc genes seem to be translation ...	1999	10464226
identification of nodulation promoter (nod-box) regions of rhizobium galegae.	a hybridisation analysis of a genomic clone library of rhizobium galegae hambi 1174 located four ecori fragments homologous to the nod-box promoter sequence of sinorhizobium meliloti in two separate gene regions. two of the five nod-boxes detected in the r. galegae genome were carried on a single cosmid clone, prg30, upstream from the nodabcij and nodf genes, whereas the other three nod-boxes were carried on a different cosmid clone, prg10. hybridisations with various nod gene probes from s. mel ...	1999	10474187
metabolism and genetics of helicobacter pylori: the genome era.	the publication of the complete sequence of helicobacter pylori 26695 in 1997 and more recently that of strain j99 has provided new insight into the biology of this organism. in this review, we attempt to analyze and interpret the information provided by sequence annotations and to compare these data with those provided by experimental analyses. after a brief description of the general features of the genomes of the two sequenced strains, the principal metabolic pathways are analyzed. in particu ...	1999	10477311
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
inactivation and regulation of the aerobic c(4)-dicarboxylate transport (dcta) gene of escherichia coli.	the gene (dcta) encoding the aerobic c(4)-dicarboxylate transporter (dcta) of escherichia coli was previously mapped to the 79-min region of the linkage map. the nucleotide sequence of this region reveals two candidates for the dcta gene: f428 at 79.3 min and the o157a-o424-o328 (or orfqmp) operon at 79.9 min. the f428 gene encodes a homologue of the sinorhizobium meliloti and rhizobium leguminosarum h(+)/c(4)-dicarboxylate symporter, dcta, whereas the orfqmp operon encodes homologues of the aer ...	1999	10482502
positive transcriptional feedback controls hydrogenase expression in alcaligenes eutrophus h16.	the protein hoxa is the central regulator of the alcaligenes eutrophus h16 hox regulon, which encodes two hydrogenases, a nickel permease and several accessory proteins required for hydrogenase biosynthesis. expression of the regulatory gene hoxa was analyzed. screening of an 8-kb region upstream of hoxa with a promoter probe vector localized four promoter activities. one of these was found in the region immediately 5' of hoxa; the others were correlated with the nickel metabolism genes hypa1, h ...	1999	10482509
involvement of the cis/trans isomerase cti in solvent resistance of pseudomonas putida dot-t1e.	pseudomonas putida dot-t1e is a solvent-resistant strain that is able to grow in the presence of high concentrations of toluene. we have cloned and sequenced the cti gene of this strain, which encodes the cis/trans isomerase, termed cti, that catalyzes the cis-trans isomerization of esterified fatty acids in phospholipids, mainly cis-oleic acid (c(16:1,9)) and cis-vaccenic acid (c(18:1,11)), in response to solvents. to determine the importance of this cis/trans isomerase for solvent resistance a ...	1999	10482510
identification of a functional fur gene in bradyrhizobium japonicum.	the recent identification of the iron response regulator (irr) in bradyrhizobium japonicum raised the question of whether the global regulator fur is present in that organism. a fur gene homolog was isolated by the functional complementation of an escherichia coli fur mutant. the b. japonicum fur bound to a fur box dna element in vitro, and a fur mutant grown in iron-replete medium was derepressed for iron uptake activity. thus, b. japonicum expresses at least two regulators of iron metabolism.	1999	10482529
flavan-containing cells delimit frankia-infected compartments in casuarina glauca nodules.	we investigated the involvement of polyphenols in the casuarina glauca-frankia symbiosis. histological analysis revealed a cell-specific accumulation of phenolics in c. glauca nodule lobes, creating a compartmentation in the cortex. histochemical and biochemical analyses indicated that these phenolic compounds belong to the flavan class of flavonoids. we show that the same compounds were synthesized in nodules and uninfected roots. however, the amount of each flavan was dramatically increased in ...	1999	10482666
effects of calcium and protons on the secondary structure of the nodulation protein nodo from rhizobium leguminosarum biovar viciae.	nodo, a 30-kda nodulation protein secreted by rhizobium leguminosarum biovar viciae, belongs to a family of proteins produced by gram-negative bacteria containing a variable number of glycine/aspartates nonapeptides. in some instances, these are organized into a parallel beta-roll structure and bind ca(2+) (one ion per repeat). to gain insight into nodo's secondary and tertiary structures, and their dependence upon ca(2+) binding, we performed fluorescence experiments and ftir spectroscopy. we f ...	1999	10491324
rsmc of the soft-rotting bacterium erwinia carotovora subsp. carotovora negatively controls extracellular enzyme and harpin(ecc) production and virulence by modulating levels of regulatory rna (rsmb) and rna-binding protein (rsma).	previous studies have shown that the production of extracellular enzymes (pectate lyase [pel], polygalacturonase [peh], cellulase [cel], and protease [prt]) and harpin(ecc) (the elicitor of hypersensitive reaction) in erwinia carotovora subsp. carotovora is regulated by rsma, an rna-binding protein, and rsmb, a regulatory rna (rsm stands for regulator of secondary metabolites) (y. liu et al., mol. microbiol. 29:219-234, 1998). we have cloned and characterized a novel regulatory gene, rsmc, that ...	1999	10498717
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
opening the iron box: transcriptional metalloregulation by the fur protein.		1999	10515908
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
functional analysis of glycosyltransferase genes from lactococcus lactis and other gram-positive cocci: complementation, expression, and diversity.	sixteen exopolysaccharide (eps)-producing lactococcus lactis strains were analyzed for the chemical compositions of their epss and the locations, sequences, and organization of the eps genes involved in eps biosynthesis. this allowed the grouping of these strains into three major groups, representatives of which were studied in detail. previously, we have characterized the eps gene cluster of strain nizo b40 (group i) and determined the function of three of its glycosyltransferase (gtf) genes. f ...	1999	10515924
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
genotypic and phenotypic relationships between clinical and environmental isolates of stenotrophomonas maltophilia.	while the gram-negative bacterium stenotrophomonas maltophilia is used in biotechnology (e.g., for biological control of plant pathogens and for bioremediation), the number of s. maltophilia diseases in humans has dramatically increased in recent years. a total of 40 s. maltophilia isolates from clinical and environmental sources (plant associated and water) was investigated to determine the intraspecies diversity of the group and to determine whether or not the strains could be grouped based on ...	1999	10523559
molecular characterization of the locus encoding biosynthesis of the lipopolysaccharide o antigen of escherichia coli serotype o113.	shiga toxigenic escherichia coli (stec) strains are a diverse group of organisms capable of causing severe gastrointestinal disease in humans. within the stec family, eae-positive stec strains, particularly those belonging to serogroups o157 and o111, appear to have greater virulence for humans. however, in spite of being eae negative, stec strains belonging to serogroup o113 have frequently been associated with cases of severe stec disease, including hemolytic-uremic syndrome (hus). western blo ...	1999	10531250
structural characterization of the symbiotically important low-molecular-weight succinoglycan of sinorhizobium meliloti.	the production of succinoglycan by sinorhizobium meliloti rm1021 is required for successful nodule invasion by the bacterium of its host plant, alfalfa. rm1021 produces succinoglycan, an acidic exopolysaccharide composed of an octasaccharide repeating unit modified with acetyl, succinyl, and pyruvyl moieties, in both low- and high-molecular-weight forms. low-molecular-weight (lmw) succinoglycan, previously thought to consist of monomers, trimers, and tetramers of the repeating unit, has been rep ...	1999	10542182
biochemical and genetic analyses of ferulic acid catabolism in pseudomonas sp. strain hr199.	the gene loci fcs, encoding feruloyl coenzyme a (feruloyl-coa) synthetase, ech, encoding enoyl-coa hydratase/aldolase, and aat, encoding beta-ketothiolase, which are involved in the catabolism of ferulic acid and eugenol in pseudomonas sp. strain hr199 (dsm7063), were localized on a dna region covered by two ecori fragments (e230 and e94), which were recently cloned from a pseudomonas sp. strain hr199 genomic library in the cosmid pvk100. the nucleotide sequences of parts of fragments e230 and e ...	1999	10543794
protein-mediated adhesion of the dissimilatory fe(iii)-reducing bacterium shewanella alga bry to hydrous ferric oxide.	the rate and extent of bacterial fe(iii) mineral reduction are governed by molecular-scale interactions between the bacterial cell surface and the mineral surface. these interactions are poorly understood. this study examined the role of surface proteins in the adhesion of shewanella alga bry to hydrous ferric oxide (hfo). enzymatic degradation of cell surface polysaccharides had no effect on cell adhesion to hfo. the proteolytic enzymes streptomyces griseus protease and chymotrypsin inhibited t ...	1999	10543817
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
identification of residues essential for a two-step reaction by malonyl-coa synthetase from rhizobium trifolii.	malonyl-coa synthetase (mcs) catalyses the formation of malonyl-coa in a two-step reaction consisting of the adenylation of malonate with atp followed by malonyl transfer from malonyl-amp to coa. in order to identify amino acid residues essential for each step of the enzyme, catalysis based on chemical modification and database analysis, arg-168, lys-170, and his-206 were selected for site-directed mutagenesis. glutathione-s-transferase-fused enzyme (gst-mcs) was constructed and mutagenized to m ...	1999	10548546
a putative ecf sigma factor gene, rpol, regulates siderophore production in rhizobium leguminosarum.	a cloned rhizobium leguminosarum gene, termed rpoi, when transferred to wild-type strains, caused overproduction of the siderophore vicibactin. an rpoi mutant was defective in fe uptake but was unaffected in symbiotic n2 fixation. the rpoi gene product was similar in sequence to extra-cytoplasmic sigma factors of rna polymerase. transcription of rpoi was reduced in cells grown in medium that was replete with fe.	1999	10550895
glutathione and homoglutathione synthesis in legume root nodules.	high-performance liquid chromatography (hplc) with fluorescence detection was used to study thiol metabolism in legume nodules. glutathione (gsh) was the major non-protein thiol in all indeterminate nodules examined, as well as in the determinate nodules of cowpea (vigna unguiculata), whereas homoglutathione (hgsh) predominated in soybean (glycine max), bean (phaseolus vulgaris), and mungbean (vigna radiata) nodules. all nodules had greater thiol concentrations than the leaves and roots of the s ...	1999	10557236
anaerobic growth of paracoccus denitrificans requires cobalamin: characterization of cobk and cobj genes.	a pleiotropic mutant of paracoccus denitrificans, which has a severe defect that affects its anaerobic growth when either nitrate, nitrite, or nitrous oxide is used as the terminal electron acceptor and which is also unable to use ethanolamine as a carbon and energy source for aerobic growth, was isolated. this phenotype of the mutant is expressed only during growth on minimal media and can be reversed by addition of cobalamin (vitamin b(12)) or cobinamide to the media or by growth on rich media ...	1999	10559155
a rhizobial homolog of ihf stimulates transcription of dcta in rhizobium leguminosarum but not in sinorhizobium meliloti.	sequence inspection identified several potential ihf binding sites adjacent to the rhizobium leguminosarum dcta promoter. ihf protected the -30 to -76 region from dnase i digestion, but systematic error in quantitative assays suggested that this protein dna interaction is complex. ihf stimulated dctd-mediated transcriptional activation from the r. leguminosarum dcta promoter both in vivo and in vitro. in contrast to r. leguminosarum dcta, the sinorhizobium meliloti dcta promoter region was found ...	1999	10570977
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
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
citrate synthase mutants of sinorhizobium meliloti are ineffective and have altered cell surface polysaccharides.	the glta gene, encoding sinorhizobium meliloti 104a14 citrate synthase, was isolated by complementing an escherichia coli glta mutant. the s. meliloti glta gene was mutated by inserting a kanamycin resistance gene and then using homologous recombination to replace the wild-type glta with the glta::kan allele. the resulting strain, csdx1, was a glutamate auxotroph, and enzyme assays confirmed the absence of a requirement for glutamate. csdx1 did not grow on succinate, malate, aspartate, pyruvate, ...	1999	10601220
production of vitamin b6 in rhizobium.	the production of vitamin b6 was studied in about 1,590 bacterial isolates from soil, and an isolate, 28-21, identified as rhizobium leguminosarum was obtained as a vitamin b6 high producer. then, the production of vitamin b6 by commercially available rhizobium strains was examined, and many of the tested strains excreted large amounts of vitamin b6 into the culture broth. the best producer of vitamin b6 was r. meliloti ifo 14782, which produced 51 mg per liter. media study for the vitamin b6 pr ...	1999	27389503
effects of hydroxylysine on the growth and morphology of rhizobium leguminosarum bv. phaseoli.	it was found that both bacteroids and free-living cells of rhizobium leguminosarum bv. phaseoli were highly susceptible to hydroxylysine (hyl) and the inhibition of rna and/or protein synthesis caused by the hydroxyl residue of hyl appeared to be responsible for the growth inhibition. the size of free-living cells was enlarged by the addition of hyl and some cells reached around 5 μm, which were close to the length of bacteroids. under the same condition, the polyhydroxybutyrate (phb) content in ...	1998	27388838
occurrence of lipopolysaccharide alterations among tn5 mutants of rhizobium leguminosarum bv. trifolii strain 24.1 with altered colony morphology.	transposon mutants of rhizobium leguminosarum bv. trifolii 24.1 showing less glossy or smaller colonies were screened for properties usually associated with lipopolysaccharide (lps) defects in r. leguminosarum, i.e. motility, growth rate, tendency to agglutination in liquid media and symbiotic efficiency. neither any of the above mutants nor the earlier isolated 24.12 strain, defective in lps, showed all these properties changed simultaneously. according to page/sodium deoxycholate analysis the ...	1998	10397346
molecular characterization and symbiotic importance of prsd gene of rhizobium leguminosarum bv. trifolii ta1.	the prsd, prse and orf3 genes of rhizobium leguminosarum bv. trifolii strain ta1 encode the proteins which are significantly related to the family of bacterial abc transporters type i secretion systems. the prsd:km(r) mutant of strain ta1 induced non-nitrogen-fixing nodules on trifolium pratense. microscopic analysis of the nodules induced by prsd mutant did not reveal major abberations in the bacteroid appearance. the exopolysaccharide of prsd mutant was produced in increased amount and its lev ...	1998	10397353
extracellular signal molecule(s) involved in the carbon starvation response of marine vibrio sp. strain s14.	the role of exogenous metabolites as putative signal molecules mediating and/or regulating the carbon starvation adaptation program in vibrio sp. strain s14 was investigated. addition of the stationary-phase supernatant extract (sse) of vibrio sp. strain s14 to logarithmic-phase cells resulted in a significant number of carbon starvation-induced proteins being up-regulated. halogenated furanones, putative antagonists of acylated homoserine lactones (ahls), inhibited the synthesis of proteins spe ...	1998	9440506
differential regulation of multiple flagellins in vibrio cholerae.	vibrio cholerae, the causative agent of the human diarrheal disease cholera, is a motile bacterium with a single polar flagellum. motility has been implicated as a virulence determinant in some animal models of cholera, but the relationship between motility and virulence has not yet been clearly defined. we have begun to define the regulatory circuitry controlling motility. we have identified five v. cholerae flagellin genes, arranged in two chromosomal loci, flaac and flaedb; all five genes hav ...	1998	9440520
expression cloning of a pseudomonas gene encoding a hydroxydecanoyl-acyl carrier protein-dependent udp-glcnac acyltransferase.	udp-n-acetylglucosamine-3-o-acyltransferase (udp-glcnac acyltransferase) catalyzes the first step of lipid a biosynthesis (m. s. anderson and c. r. h. raetz, j. biol. chem. 262:5159-5169, 1987). we here report the isolation of the lpxa gene of pseudomonas aeruginosa from a library of pseudomonas strain pao1 expressed in escherichia coli le392 (j. lightfoot and j. s. lam, j. bacteriol. 173:5624-5630, 1991). pseudomonas lpxa encodes a 10-carbon-specific udp-glcnac acyltransferase, whereas the e. c ...	1998	9440522
specific amino acid substitutions in the proline-rich motif of the rhizobium meliloti exop protein result in enhanced production of low-molecular-weight succinoglycan at the expense of high-molecular-weight succinoglycan.	the production of the acidic exopolysaccharide succinoglycan (eps i) by rhizobium meliloti exop* mutants expressing an exop protein lacking its c-terminal cytoplasmic domain and by mutants characterized by specific amino acid substitutions in the proline-rich motif (rx4px2px4spkx9ixgxmxgxg) located from positions 443 to 476 of the exop protein was analyzed. the absence of the c-terminal cytoplasmic exop domain (positions 484 to 786) and the substitution of both arginine443 by isoleucine443 and p ...	1998	9440529
assignment of biochemical functions to glycosyl transferase genes which are essential for biosynthesis of exopolysaccharides in sphingomonas strain s88 and rhizobium leguminosarum.	glycosyl transferases which recognize identical substrates (nucleotide-sugars and lipid-linked carbohydrates) can substitute for one another in bacterial polysaccharide biosynthesis, even if the enzymes originate in different genera of bacteria. this substitution can be used to identify the substrate specificities of uncharacterized transferase genes. the spsk gene of sphingomonas strain s88 and the pssde genes of rhizobium leguminosarum were identified as encoding glucuronosyl-(b1-->4)-glucosyl ...	1998	9457861
modulation of the function of the signal receptor domain of xylr, a member of a family of prokaryotic enhancer-like positive regulators.	the xylr protein controls expression from the pseudomonas putida tol plasmid upper pathway operon promoter (pu) in response to aromatic effectors. xylr-dependent stimulation of transcription from a pu::lacz fusion shows different induction kinetics with different effectors. with toluene, activation followed a hyperbolic curve with an apparent k of 0.95 mm and a maximum beta-galactosidase activity of 2,550 miller units. with o-nitrotoluene, in contrast, activation followed a sigmoidal curve with ...	1998	9457863
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
characterization of marine temperate phage-host systems isolated from mamala bay, oahu, hawaii.	to understand the ecological and genetic role of viruses in the marine environment, it is critical to know the infectivity of viruses and the types of interactions that occur between marine viruses and their hosts. we isolated four marine phages from turbid plaques by using four indigenous bacterial hosts obtained from concentrated water samples from mamala bay, oahu, hawaii. two of the rod-shaped bacterial hosts were identified as sphingomonas paucimobilis and flavobacterium sp. all of the phag ...	1998	9464390
optimization of exopolysaccharide production by lactobacillus delbrueckii subsp. bulgaricus rr grown in a semidefined medium.	the optimal fermentation temperature, ph, and bacto-casitone (difco laboratories, detroit, mich.) concentration for production of exopolysaccharide by lactobacillus delbrueckii subsp. bulgaricus rr in a semidefined medium were determined by using response surface methods. the design consisted of 20 experiments, 15 unique combinations, and five replications. all fermentations were conducted in a fermentor with a 2.5-liter working volume and were terminated when 90% of the glucose in the medium ha ...	1998	9464404
luxi- and luxr-homologous genes of rhizobium etli cnpaf512 contribute to synthesis of autoinducer molecules and nodulation of phaseolus vulgaris.	autoinduction plays an important role in intercellular communication among symbiotic and pathogenic gram-negative bacteria. we report here that a nitrogen-fixing symbiont of phaseolus vulgaris, rhizobium etli cnpaf512, produces at least seven different autoinducer molecules. one of them exhibits a growth-inhibitory effect like that of the bacteriocin small [n-(3r-hydroxy-7-cis-tetradecanoyl)-l-homoserine lactone]. at least two of the other autoinducers are synthesized by a luxi-homologous autoin ...	1998	9473034
respiratory elicitors from rhizobium meliloti affect intact alfalfa roots	molecules produced by rhizobium meliloti increase respiration of alfalfa (medicago sativa l.) roots. maximum respiratory increases, measured either as co2 evolution or as o2 uptake, were elicited in roots of 3-d-old seedlings by 16 h of exposure to living or dead r. meliloti cells at densities of 10(7) bacteria/ml. excising roots after exposure to bacteria and separating them into root-tip- and root-hair-containing segments showed that respiratory increases occurred only in the root-hair region. ...	1998	9490771
rearrangement of actin microfilaments in plant root hairs responding to rhizobium etli nodulation signals	the response of the actin cytoskeleton to nodulation (nod) factors secreted by rhizobium etli has been studied in living root hairs of bean (phaseolus vulgaris) that were microinjected with fluorescein isothiocyanate-phalloidin. in untreated control cells or cells treated with the inactive chitin oligomer, the actin cytoskeleton was organized into long bundles that were oriented parallel to the long axis of the root hair and extended into the apical zone. upon exposure to r. etli nod factors, th ...	1998	9501120
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
characterisation of the urease gene cluster in bordetella bronchiseptica.	bordetella bronchiseptica is a common ureolytic mammalian respiratory pathogen. the urease operon of this organism is encoded within an 8.9 kb dna fragment which contains the structural genes (urea, ureb and urec) and accessory genes (ured and ureg) homologous to other urease genes. uniquely, the uree and uref genes are fused to form a hybrid protein, ureef, which may result in tighter coordination of the putative functions of the individual accessory genes, nickel donation to the urease active ...	1998	9524276
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
the rhizobium etli rpon locus: dna sequence analysis and phenotypical characterization of rpon, ptsn, and ptsa mutants.	the rpon region of rhizobium etli was isolated by using the bradyrhizobium japonicum rpon1 gene as a probe. nucleotide sequence analysis of a 5,600-bp dna fragment of this region revealed the presence of four complete open reading frames (orfs), orf258, rpon, orf191, and ptsn, coding for proteins of 258, 520, 191, and 154 amino acids, respectively. the gene product of orf258 is homologous to members of the atp-binding cassette-type permeases. orf191 and ptsn are homologous to conserved orfs foun ...	1998	9537369
the active-site cysteines of the periplasmic thioredoxin-like protein ccmg of escherichia coli are important but not essential for cytochrome c maturation in vivo.	a new member of the family of periplasmic protein thiol:disulfide oxidoreductases, ccmg (also called dsbe), was characterized with regard to its role in cytochrome c maturation in escherichia coli. the ccmg protein was shown to be membrane bound, facing the periplasm with its c-terminal, hydrophilic domain. a chromosomal, nonpolar in-frame deletion in ccmg resulted in the complete absence of all c-type cytochromes. replacement of either one or both of the two cysteine residues of the predicted a ...	1998	9537397