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chitosan modification and pharmaceutical/biomedical applications.chitosan has received much attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine. our recent efforts focused on the chemical and biological modification of chitosan in order to increase its solubility in aqueous solutions and absorbability in the in vivo system, thus for a better use of chitosan. this review summarizes chitosan modification and its pharmaceutical/biomedical applications based on our achievements as well as the domestic and overse ...201020714418
classification, prediction, and verification of the regioselectivity of fungal polyketide synthase product template domains.the fungal iterative nonreducing polyketide synthases (nrpkss) synthesize aromatic polyketides, many of which have important biological activities. the product template domains (pt) embedded in the multidomain nrpkss mediate the regioselective cyclization of the highly reactive polyketide backbones and dictate the final structures of the products. understanding the sequence-activity relationships of different pt domains is therefore an important step toward the prediction of polyketide structure ...201020479000
the importance of nodule co2 fixation for the efficiency of symbiotic nitrogen fixation in pea at vegetative growth and during pod formation.nodule co2 fixation is of pivotal importance for n2 fixation. the process provides malate for bacteroids and oxaloacetate for nitrogen assimilation. the hypothesis of the present paper was that grain legume nodules would adapt to higher plant n demand and more restricted carbon availability at pod formation through increased nodule co2 fixation and a more efficient n2 fixation. growth, n2 fixation, and nodule composition during vegetative growth and at pod formation were studied in pea plants (p ...201020363863
the vibrio cholerae type vi secretion system: evaluating its role in the human disease cholera.vibrio cholerae, the marine bacterium responsible for the diarrheal disease cholera, utilizes a multitude of virulence factors to cause disease. the importance of two of these factors, the toxin co-regulated pilus (tcp) and cholera toxin (ct), has been well documented for pandemic o1 and epidemic o139 serogroups. in contrast, endemic non-o1 and non-o139 serogroups can cause localized outbreaks of cholera-like illness, often in the absence of tcp and ct. one virulence mechanism used by these stra ...201021607085
type vi secretion: not just for pathogenesis anymore.type vi secretion systems (t6ss) have been studied primarily in the context of pathogenic bacteria-host interactions. recent data suggest, however, that these versatile secretion systems may also function to promote commensal or mutualistic relationships between bacteria and eukaryotes or to mediate cooperative or competitive interactions between bacteria.201020638635
functional promiscuity of homologues of the bacterial arsa atpases.the arsa atpase of e. coli plays an essential role in arsenic detoxification. published evidence implicates arsa in the energization of as(iii) efflux via the formation of an oxyanion-translocating complex with arsb. in addition, eukaryotic arsa homologues have several recognized functions unrelated to arsenic resistance. by aligning arsa homologues, constructing phylogenetic trees, examining arsa encoding operons, and estimating the probable coevolution of these homologues with putative transpo ...201020981284
comparative study of wild and transformed salt tolerant bacterial strains on triticum aestivum growth under salt stress.eleven salt tolerant bacteria isolated from different sources (soil, plants) and their transformed strains were used to study their influence on triticum aestivum var. inqlab-91 growth under salt (100 mm nacl) stress. salt stress caused reduction in germination (19.4%), seedling growth (46%) and fresh weight (39%) in non-inoculated plants. in general, both wild and transformed strains stimulated germination, seedling growth and fresh weight in salt free and salt stressed conditions. at 100 mm na ...201024031574
structural basis of acyl-homoserine lactone-dependent signaling. 201021125993
structural basis of acyl-homoserine lactone-dependent signaling. 201021125993
total (bio)synthesis: strategies of nature and of chemists.the biosynthetic pathways to a number of natural products have been reconstituted in vitro using purified enzymes. many of these molecules have also been synthesized by organic chemists. here we compare the strategies used by nature and by chemists to reveal the underlying logic and success of each total synthetic approach for some exemplary molecules with diverse biosynthetic origins.201021495259
rtx proteins: a highly diverse family secreted by a common mechanism.repeats-in-toxin (rtx) exoproteins of gram-negative bacteria form a steadily growing family of proteins with diverse biological functions. their common feature is the unique mode of export across the bacterial envelope via the type i secretion system and the characteristic, typically nonapeptide, glycine- and aspartate-rich repeats binding ca(2+) ions. in this review, we summarize the current state of knowledge on the organization of rtx loci and on the biological and biochemical activities of t ...201020528947
marine metagenomics: new tools for the study and exploitation of marine microbial metabolism.the marine environment is extremely diverse, with huge variations in pressure and temperature. nevertheless, life, especially microbial life, thrives throughout the marine biosphere and microbes have adapted to all the divergent environments present. large scale dna sequence based approaches have recently been used to investigate the marine environment and these studies have revealed that the oceans harbor unprecedented microbial diversity. novel gene families with representatives only within su ...201020411118
analysis and comparison of the pan-genomic properties of sixteen well-characterized bacterial genera.the increasing availability of whole genome sequences allows the gene or protein content of different organisms to be compared, leading to burgeoning interest in the relatively new subfield of pan-genomics. however, while several studies have analyzed protein content relationships in specific groups of bacteria, there has yet to be a study that provides a general characterization of protein content relationships in a broad range of bacteria.201020942950
genomic and evolutionary comparisons of diazotrophic and pathogenic bacteria of the order rhizobiales.species belonging to the rhizobiales are intriguing and extensively researched for including both bacteria with the ability to fix nitrogen when in symbiosis with leguminous plants and pathogenic bacteria to animals and plants. similarities between the strategies adopted by pathogenic and symbiotic rhizobiales have been described, as well as high variability related to events of horizontal gene transfer. although it is well known that chromosomal rearrangements, mutations and horizontal gene tra ...201020144182
response to flavonoids as a factor influencing competitiveness and symbiotic activity of rhizobium leguminosarum.flavonoids play a crucial role as signal molecules in promoting the formation of nodules by symbiotic bacteria commonly known as rhizobia. the early interaction between flavonoids and nodd regulatory protein activates nod gene transcription and the synthesis of nod factor that initiates nodule primordium. in this study, we assessed response to flavonoids as factors influencing competitiveness of rhizobia and their symbiotic activity. rhizobium leguminosarum nodule isolates belonging to three bio ...201018678476
the impact of window functions on nmr-based paramagnetic relaxation enhancement measurements in membrane proteins.though challenging, solution nmr spectroscopy allows fundamental interrogation of the structure and dynamics of membrane proteins. one major technical hurdle in studies of helical membrane proteins by nmr is the difficulty of obtaining sufficient long range noes to determine tertiary structure. for this reason, long range distance information is sometimes sought through measurement of paramagnetic relaxation enhancements (pre) of nmr nuclei as a function of distance from an introduced paramagnet ...201019751702
the impact of window functions on nmr-based paramagnetic relaxation enhancement measurements in membrane proteins.though challenging, solution nmr spectroscopy allows fundamental interrogation of the structure and dynamics of membrane proteins. one major technical hurdle in studies of helical membrane proteins by nmr is the difficulty of obtaining sufficient long range noes to determine tertiary structure. for this reason, long range distance information is sometimes sought through measurement of paramagnetic relaxation enhancements (pre) of nmr nuclei as a function of distance from an introduced paramagnet ...201019751702
how does sulphur availability modify n acquisition of white clover (trifolium repens l.)?the role of s in legume growth, n uptake, and n2 fixation was investigated using white clover (trifolium repens l.) as a model species. we examined whether the effect of sulphate addition on n fixation resulted from a stimulation of host plant growth, a specific effect of s on nodulation, or a specific effect of s on nodule metabolism. clones of white clover, inoculated with rhizobium leguminosarum, were grown for 140 d in a hydroponic system with three levels of sulphate concentration (0 mm, 0. ...201019933318
how does sulphur availability modify n acquisition of white clover (trifolium repens l.)?the role of s in legume growth, n uptake, and n2 fixation was investigated using white clover (trifolium repens l.) as a model species. we examined whether the effect of sulphate addition on n fixation resulted from a stimulation of host plant growth, a specific effect of s on nodulation, or a specific effect of s on nodule metabolism. clones of white clover, inoculated with rhizobium leguminosarum, were grown for 140 d in a hydroponic system with three levels of sulphate concentration (0 mm, 0. ...201019933318
pantothenate kinase from the thermoacidophilic archaeon picrophilus torridus.pantothenate kinase (coaa) catalyzes the first step of the coenzyme a (coa) biosynthetic pathway and controls the intracellular concentrations of coa through feedback inhibition in bacteria. an alternative enzyme found in archaea, pantoate kinase, is missing in the order thermoplasmatales. the pto0232 gene from picrophilus torridus, a thermoacidophilic euryarchaeon, is shown to be a distant homologue of the prokaryotic type i coaa. the cloned gene clearly complements the poor growth of the tempe ...201019854913
pantothenate kinase from the thermoacidophilic archaeon picrophilus torridus.pantothenate kinase (coaa) catalyzes the first step of the coenzyme a (coa) biosynthetic pathway and controls the intracellular concentrations of coa through feedback inhibition in bacteria. an alternative enzyme found in archaea, pantoate kinase, is missing in the order thermoplasmatales. the pto0232 gene from picrophilus torridus, a thermoacidophilic euryarchaeon, is shown to be a distant homologue of the prokaryotic type i coaa. the cloned gene clearly complements the poor growth of the tempe ...201019854913
characterization of a two-component regulatory system that regulates succinate-mediated catabolite repression in sinorhizobium meliloti.when they are available, sinorhizobium meliloti utilizes c(4)-dicarboxylic acids as preferred carbon sources for growth while suppressing the utilization of some secondary carbon sources such as α- and β-galactosides. the phenomenon of using succinate as the sole carbon source in the presence of secondary carbon sources is termed succinate-mediated catabolite repression (smcr). genetic screening identified the gene sma0113 as needed for strong smcr when s. meliloti was grown in succinate plus la ...201020817764
membrane topology mapping of the o-antigen flippase (wzx), polymerase (wzy), and ligase (waal) from pseudomonas aeruginosa pao1 reveals novel domain architectures.biosynthesis of b-band lipopolysaccharide (lps) in pseudomonas aeruginosa follows the wzy-dependent pathway, requiring the integral inner membrane proteins wzx (o-antigen [o-ag] flippase), wzy (o-ag polymerase), and waal (o-ag ligase). for an important first step in deciphering the mechanisms of lps assembly, we set out to map the membrane topology of these proteins. random and targeted 3'wzx, wzy, and waal truncations were fused to a phoa-laczalpha dual reporter capable of displaying both alkal ...201020824106
comparing symbiotic efficiency between swollen versus nonswollen rhizobial bacteroids.symbiotic rhizobia differentiate physiologically and morphologically into nitrogen-fixing bacteroids inside legume host nodules. the differentiation is apparently terminal in some legume species, such as peas (pisum sativum) and peanuts (arachis hypogaea), likely due to extreme cell swelling induced by the host. in other legume species, such as beans (phaseolus vulgaris) and cowpeas (vigna unguiculata), differentiation into bacteroids, which are similar in size and shape to free-living rhizobia, ...201020837702
symbiotic legume nodules employ both rhizobial exo- and endo-hydrogenases to recycle hydrogen produced by nitrogen fixation.in symbiotic legume nodules, endosymbiotic rhizobia (bacteroids) fix atmospheric n(2), an atp-dependent catalytic process yielding stoichiometric ammonium and hydrogen gas (h(2)). while in most legume nodules this h(2) is quantitatively evolved, which loss drains metabolic energy, certain bacteroid strains employ uptake hydrogenase activity and thus evolve little or no h(2). rather, endogenous h(2) is efficiently respired at the expense of o(2), driving oxidative phosphorylation, recouping atp u ...201020838423
genotypic and phenotypic diversity of rhizobia isolated from lathyrus japonicus indigenous to japan.sixty-one rhizobial strains from lathyrus japonicus nodules growing on the seashore in japan were characterized and compared to two strains from canada. the pcr-based method was used to identify test strains with novel taxonomic markers that were designed to discriminate between all known lathyrus rhizobia. three genomic groups (i, ii, and iii) were finally identified using rapd, rflp, and phylogenetic analyses. strains in genomic group i (related to rhizobium leguminosarum) were divided into tw ...201020851546
engineered polyketide biosynthesis and biocatalysis in escherichia coli.polyketides are important bioactive natural products biosynthesized by bacteria, fungi, and plants. the enzymes that synthesize polyketides are collectively referred to as polyketide synthases (pkss). because many of the natural hosts that produce polyketides are difficult to culture or manipulate, establishing a universal heterologous host that is genetically tractable has become an important goal toward the engineered biosynthesis of polyketides and analogues. here, we summarize the recent pro ...201020853106
complete genome and comparative analysis of the chemolithoautotrophic bacterium oligotropha carboxidovorans om5.oligotropha carboxidovorans om5 t. (dsm 1227, atcc 49405) is a chemolithoautotrophic bacterium capable of utilizing co (carbon monoxide) and fixing co2 (carbon dioxide). we previously published the draft genome of this organism and recently submitted the complete genome sequence to genbank.201020863402
membrane topology and identification of critical amino acid residues in the wzx o-antigen translocase from escherichia coli o157:h4.wzx belongs to a family of membrane proteins involved in the translocation of isoprenoid lipid-linked glycans, which is loosely related to members of the major facilitator superfamily. despite wzx homologs performing a conserved function, it has been difficult to pinpoint specific motifs of functional significance in their amino acid sequences. here, we elucidate the topology of the escherichia coli o157 wzx (wzx(eco157)) by a combination of bioinformatics and substituted cysteine scanning mutag ...201020870764
[the nadph oxidase activity of pea seedling roots in rhizobial infection depending on abiotic and biotic factors].the changes in nadph activity was studied in the roots of 3-4-day-old etiolated pea (cultivar aksaiskii usatyi) seedlings depending on plant inoculation with rhizobium leguminosarum bv. viceae (strain ciam 1026), adverse environmental factors (low temperature and high dose of a mineral nitrogen fertilizer), chemical substances (sodium nitroprusside and methyl viologen, or paraquat), and a biotic factor--the bacterium escherichia coli (strain xl-1 blue). it was demonstrated that all exogenous fac ...201020873175
evolution and multiplicity of arginine decarboxylases in polyamine biosynthesis and essential role in bacillus subtilis biofilm formation.arginine decarboxylases (adcs; ec 4.1.1.19) from four different protein fold families are important for polyamine biosynthesis in bacteria, archaea, and plants. biosynthetic alanine racemase fold (ar-fold) adc is widespread in bacteria and plants. we report the discovery and characterization of an ancestral form of the ar-fold adc in the bacterial chloroflexi and bacteroidetes phyla. the ancestral ar-fold adc lacks a large insertion found in escherichia coli and plant ar-fold adc and is more sim ...201020876533
n-acylation during glidobactin biosynthesis by the tridomain nonribosomal peptide synthetase module glbf.glidobactins are hybrid nrps-pks natural products that function as irreversible proteasome inhibitors. a variety of medium chain 2(e),4(e)-diene fatty acids n-acylate the peptidolactam core and contribute significantly to the potency of proteasome inhibition. we have expressed the initiation nrps module glbf (c-a-t) in escherichia coli and observe soluble active protein only on coexpression with the 8 kda mbth-like protein, glbe. following adenylation and installation of thr as a t-domain thioes ...201021035730
rhizobium leguminosarum bv. trifolii rosr is required for interaction with clover, biofilm formation and adaptation to the environment.rhizobium leguminosarum bv. trifolii is a symbiotic nitrogen-fixing bacterium that elicits nodules on roots of host plants trifolium spp. bacterial surface polysaccharides are crucial for establishment of a successful symbiosis with legumes that form indeterminate-type nodules, such as trifolium, pisum, vicia, and medicago spp. and aid the bacterium in withstanding osmotic and other environmental stresses. recently, the r. leguminosarum bv. trifolii rosr regulatory protein which controls exopoly ...201021070666
characterisation of source-separated household waste intended for composting.large-scale composting of source-separated household waste has expanded in recent years in the nordic countries. one problem can be low ph at the start of the process. incoming biowaste at four composting plants was characterised chemically, physically and microbiologically. the ph of food waste ranged from 4.7 to 6.1 and organic acid concentration from 24 to 81 mmol kg(-1). the bacterial diversity in the waste samples was high, with all samples dominated by gammaproteobacteria, particularly pse ...201021075618
role of symbiotic auxotrophy in the rhizobium-legume symbioses.rhizobium leguminosarum bv. viciae mutants unable to transport branched-chain amino acids via the two main amino acid abc transport complexes aapjqmp and bradefgc produce a nitrogen starvation phenotype when inoculated on pea (pisum sativum) plants [1], [2]. bacteroids in indeterminate pea nodules have reduced abundance and a lower chromosome number. they reduce transcription of pathways for branched-chain amino acid biosynthesis and become dependent on their provision by the host. this has been ...201021085630
o-acetylation of peptidoglycan is required for proper cell separation and s-layer anchoring in bacillus anthracis.o-acetylation of the murnac moiety of peptidoglycan is typically associated with bacterial resistance to lysozyme, a muramidase that serves as a central component of innate immunity. here, we report that the peptidoglycan of bacillus anthracis, the etiological agent of anthrax, is o-acetylated and that, unusually, this modification is produced by two unrelated families of o-acetyltransferases. also, in contrast to other bacteria, o-acetylation of b. anthracis peptidoglycan is combined with n-dea ...201021135105
o-acetylation of peptidoglycan is required for proper cell separation and s-layer anchoring in bacillus anthracis.o-acetylation of the murnac moiety of peptidoglycan is typically associated with bacterial resistance to lysozyme, a muramidase that serves as a central component of innate immunity. here, we report that the peptidoglycan of bacillus anthracis, the etiological agent of anthrax, is o-acetylated and that, unusually, this modification is produced by two unrelated families of o-acetyltransferases. also, in contrast to other bacteria, o-acetylation of b. anthracis peptidoglycan is combined with n-dea ...201021135105
a c subunit of the plant nuclear factor nf-y required for rhizobial infection and nodule development affects partner selection in the common bean-rhizobium etli symbiosis.legume plants are able to interact symbiotically with soil bacteria to form nitrogen-fixing root nodules. although specific recognition between rhizobia and legume species has been extensively characterized, plant molecular determinants that govern the preferential colonization by different strains within a single rhizobium species have received little attention. we found that the c subunit of the heterotrimeric nuclear factor nf-y from common bean (phaseolus vulgaris) nf-yc1 plays a key role in ...201021139064
quinone-dependent d-lactate dehydrogenase dld (cg1027) is essential for growth of corynebacterium glutamicum on d-lactate.corynebacterium glutamicum is able to grow with lactate as sole or combined carbon and energy source. quinone-dependent l-lactate dehydrogenase lldd is known to be essential for utilization of l-lactate by c. glutamicum. d-lactate also serves as sole carbon source for c. glutamicum atcc 13032.201021159175
species-specific and inhibitor-dependent conformations of lpxc: implications for antibiotic design.lpxc is an essential enzyme in the lipid a biosynthetic pathway in gram-negative bacteria. several promising antimicrobial lead compounds targeting lpxc have been reported, though they typically display a large variation in potency against different gram-negative pathogens. we report that inhibitors with a diacetylene scaffold effectively overcome the resistance caused by sequence variation in the lpxc substrate-binding passage. compound binding is captured in complex with representative lpxc or ...201021167751
species-specific and inhibitor-dependent conformations of lpxc: implications for antibiotic design.lpxc is an essential enzyme in the lipid a biosynthetic pathway in gram-negative bacteria. several promising antimicrobial lead compounds targeting lpxc have been reported, though they typically display a large variation in potency against different gram-negative pathogens. we report that inhibitors with a diacetylene scaffold effectively overcome the resistance caused by sequence variation in the lpxc substrate-binding passage. compound binding is captured in complex with representative lpxc or ...201021167751
cytochrome c4 is required for siderophore expression by legionella pneumophila, whereas cytochromes c1 and c5 promote intracellular infection.a panel of cytochrome c maturation (ccm) mutants of legionella pneumophila displayed a loss of siderophore (legiobactin) expression, as measured by both the chrome azurol s assay and a legionella-specific bioassay. these data, coupled with the finding that ccm transcripts are expressed by wild-type bacteria grown in deferrated medium, indicate that the ccm system promotes siderophore expression by l. pneumophila. to determine the basis of this newfound role for ccm, we constructed and tested a s ...201021178169
control of lipopolysaccharide biosynthesis by ftsh-mediated proteolysis of lpxc is conserved in enterobacteria but not in all gram-negative bacteria.despite the essential function of lipopolysaccharides (lps) in gram-negative bacteria, it is largely unknown how the exact amount of this molecule in the outer membrane is controlled. the first committed step in lps biosynthesis is catalyzed by the lpxc enzyme. in escherichia coli, the cellular concentration of lpxc is adjusted by the only essential protease in this organism, the membrane-anchored metalloprotease ftsh. turnover of e. coli lpxc requires a length- and sequence-specific c-terminal ...201021193611
control of lipopolysaccharide biosynthesis by ftsh-mediated proteolysis of lpxc is conserved in enterobacteria but not in all gram-negative bacteria.despite the essential function of lipopolysaccharides (lps) in gram-negative bacteria, it is largely unknown how the exact amount of this molecule in the outer membrane is controlled. the first committed step in lps biosynthesis is catalyzed by the lpxc enzyme. in escherichia coli, the cellular concentration of lpxc is adjusted by the only essential protease in this organism, the membrane-anchored metalloprotease ftsh. turnover of e. coli lpxc requires a length- and sequence-specific c-terminal ...201021193611
syntheses, structures and antibiotic activities of lpxc inhibitors based on the diacetylene scaffold.compounds inhibiting lpxc in the lipid a biosynthetic pathway are promising leads for novel antibiotics against multidrug-resistant gram-negative pathogens. we report the syntheses and structural and biochemical characterizations of lpxc inhibitors based on a diphenyl-diacetylene (1,4-diphenyl-1,3-butadiyne) threonyl-hydroxamate scaffold. these studies provide a molecular interpretation for the differential antibiotic activities of compounds with a substituted distal phenyl ring as well as the a ...201021194954
syntheses, structures and antibiotic activities of lpxc inhibitors based on the diacetylene scaffold.compounds inhibiting lpxc in the lipid a biosynthetic pathway are promising leads for novel antibiotics against multidrug-resistant gram-negative pathogens. we report the syntheses and structural and biochemical characterizations of lpxc inhibitors based on a diphenyl-diacetylene (1,4-diphenyl-1,3-butadiyne) threonyl-hydroxamate scaffold. these studies provide a molecular interpretation for the differential antibiotic activities of compounds with a substituted distal phenyl ring as well as the a ...201021194954
deletion of the signalling molecule synthase scba has pleiotropic effects on secondary metabolite biosynthesis, morphological differentiation and primary metabolism in streptomyces coelicolor a3(2).streptomycetes have high biotechnological relevance as producers of diverse metabolites widely used in medical and agricultural applications. the biosynthesis of these metabolites is controlled by signalling molecules, γ-butyrolactones, that act as bacterial hormones. in streptomyces coelicolor, a group of signalling molecules called scbs (s. coelicolorbutanolides) regulates production of the pigmented antibiotics coelicolor polyketide (cpk), actinorhodin and undecylprodigiosin. the γ-butyrolact ...201021342469
the extracellular proteome of rhizobium etli ce3 in exponential and stationary growth phase.abstract:201020942974
what is type vi secretion doing in all those bugs?the identification of bacterial secretion systems capable of translocating substrates into eukaryotic cells via needle-like appendages has opened fruitful and exciting areas of microbial pathogenesis research. the recent discovery of the type vi secretion system (t6ss) was met with early speculation that it too acts as a 'needle' that pathogens aim at host cells. new reports demonstrate that certain t6sss are potent mediators of interbacterial interactions. in light of these findings, we examine ...201020961764
complete genome sequence of rhizobium leguminosarum bv trifolii strain wsm2304, an effective microsymbiont of the south american clover trifolium polymorphum.rhizobium leguminosarum bv trifolii is the effective nitrogen fixing microsymbiont of a diverse range of annual and perennial trifolium (clover) species. strain wsm2304 is an aerobic, motile, non-spore forming, gram-negative rod, isolated from trifolium polymorphum in uruguay in 1998. this microsymbiont predominated in the perennial grasslands of glencoe research station, in uruguay, to competitively nodulate its host, and fix atmospheric nitrogen. here we describe the basic features of wsm2304, ...201021304679
complete genome sequence of rhizobium leguminosarum bv. trifolii strain wsm1325, an effective microsymbiont of annual mediterranean clovers.rhizobium leguminosarum bv trifolii is a soil-inhabiting bacterium that has the capacity to be an effective nitrogen fixing microsymbiont of a diverse range of annual trifolium (clover) species. strain wsm1325 is an aerobic, motile, non-spore forming, gram-negative rod isolated from root nodules collected in 1993 from the greek island of serifos. wsm1325 is produced commercially in australia as an inoculant for a broad range of annual clovers of mediterranean origin due to its superior attribute ...201021304718
differential expression of pathogenicity- and virulence-related genes of xanthomonas axonopodis pv. citri under copper stress.in this study, we used real-time quantitative pcr (rt-qpcr) to evaluate the expression of 32 genes of xanthomonas axonopodis pv. citri related to pathogenicity and virulence that are also involved in copper detoxification. nearly all of the genes were up-regulated, including copa and copb. two genes homologous to members of the type ii secretion system (xcsh and xcsc) and two involved in the degradation of plant cell wall components (pgla and pel) were the most expressed in response to an elevat ...201021637493
distribution of cepacian biosynthesis genes among environmental and clinical burkholderia strains and role of cepacian exopolysaccharide in resistance to stress conditions.the genus burkholderia includes strains pathogenic to animals and plants, bioremediators, or plant growth promoters. genome sequence analyses of representative burkholderia cepacia complex (bcc) and non-bcc strains for the presence of the bce-i gene cluster, directing the biosynthesis of the exopolysaccharide (eps) cepacian, further extended this previously described cluster by another 9 genes. the genes in the bce-ii cluster were named bcem to bceu and encode products putatively involved in nuc ...201019948863
distribution of cepacian biosynthesis genes among environmental and clinical burkholderia strains and role of cepacian exopolysaccharide in resistance to stress conditions.the genus burkholderia includes strains pathogenic to animals and plants, bioremediators, or plant growth promoters. genome sequence analyses of representative burkholderia cepacia complex (bcc) and non-bcc strains for the presence of the bce-i gene cluster, directing the biosynthesis of the exopolysaccharide (eps) cepacian, further extended this previously described cluster by another 9 genes. the genes in the bce-ii cluster were named bcem to bceu and encode products putatively involved in nuc ...201019948863
characterization of a gene family of outer membrane proteins (ropb) in rhizobium leguminosarum bv. viciae vf39sm and the role of the sensor kinase chvg in their regulation.the outer membrane of gram-negative bacteria represents the interface between the bacterium and its external environment. it has a critical role as a protective barrier against harmful substances and is also important in host-bacteria interactions representing the initial physical point of contact between the host cell and bacterial cell. ropb is a previously identified outer membrane protein from rhizobium leguminosarum bv. viciae that is present in free-living cells but absent in bacteroids (h ...201020023026
characterization of a gene family of outer membrane proteins (ropb) in rhizobium leguminosarum bv. viciae vf39sm and the role of the sensor kinase chvg in their regulation.the outer membrane of gram-negative bacteria represents the interface between the bacterium and its external environment. it has a critical role as a protective barrier against harmful substances and is also important in host-bacteria interactions representing the initial physical point of contact between the host cell and bacterial cell. ropb is a previously identified outer membrane protein from rhizobium leguminosarum bv. viciae that is present in free-living cells but absent in bacteroids (h ...201020023026
rhizobium leguminosarum hupe encodes a nickel transporter required for hydrogenase activity.synthesis of the hydrogen uptake (hup) system in rhizobium leguminosarum bv. viciae requires the function of an 18-gene cluster (hupslcdefghijk-hypabfcdex). among them, the hupe gene encodes a protein showing six transmembrane domains for which a potential role as a nickel permease has been proposed. in this paper, we further characterize the nickel transport capacity of hupe and that of the translated product of hupe2, a hydrogenase-unlinked gene identified in the r. leguminosarum genome. hupe2 ...201020023036
rhizobium leguminosarum hupe encodes a nickel transporter required for hydrogenase activity.synthesis of the hydrogen uptake (hup) system in rhizobium leguminosarum bv. viciae requires the function of an 18-gene cluster (hupslcdefghijk-hypabfcdex). among them, the hupe gene encodes a protein showing six transmembrane domains for which a potential role as a nickel permease has been proposed. in this paper, we further characterize the nickel transport capacity of hupe and that of the translated product of hupe2, a hydrogenase-unlinked gene identified in the r. leguminosarum genome. hupe2 ...201020023036
functional role of bradyrhizobium japonicum trehalose biosynthesis and metabolism genes during physiological stress and nodulation.trehalose, a disaccharide accumulated by many microorganisms, acts as a protectant during periods of physiological stress, such as salinity and desiccation. previous studies reported that the trehalose biosynthetic genes (otsa, tres, and trey) in bradyrhizobium japonicum were induced by salinity and desiccation stresses. functional mutational analyses indicated that disruption of otsa decreased trehalose accumulation in cells and that an otsa trey double mutant accumulated an extremely low level ...201020023090
functional role of bradyrhizobium japonicum trehalose biosynthesis and metabolism genes during physiological stress and nodulation.trehalose, a disaccharide accumulated by many microorganisms, acts as a protectant during periods of physiological stress, such as salinity and desiccation. previous studies reported that the trehalose biosynthetic genes (otsa, tres, and trey) in bradyrhizobium japonicum were induced by salinity and desiccation stresses. functional mutational analyses indicated that disruption of otsa decreased trehalose accumulation in cells and that an otsa trey double mutant accumulated an extremely low level ...201020023090
identification of a novel abc transporter required for desiccation tolerance, and biofilm formation in rhizobium leguminosarum bv. viciae 3841.rhizobium leguminosarum is a soil bacterium with the ability to form nitrogen-fixing nodules on the roots of leguminous plants. soil-dwelling, free-living r. leguminosarum often encounters desiccation stress, which impacts its survival within the soil. the mechanisms by which soil bacteria resist the effects of desiccation stress have been described. however, the role of the cell envelope in the desiccation tolerance mechanisms of rhizobia is relatively uncharacterized. using a transposon mutage ...201020030718
identification of a novel abc transporter required for desiccation tolerance, and biofilm formation in rhizobium leguminosarum bv. viciae 3841.rhizobium leguminosarum is a soil bacterium with the ability to form nitrogen-fixing nodules on the roots of leguminous plants. soil-dwelling, free-living r. leguminosarum often encounters desiccation stress, which impacts its survival within the soil. the mechanisms by which soil bacteria resist the effects of desiccation stress have been described. however, the role of the cell envelope in the desiccation tolerance mechanisms of rhizobia is relatively uncharacterized. using a transposon mutage ...201020030718
multidrug efflux pump mdtbc of escherichia coli is active only as a b2c heterotrimer.rnd (resistance-nodulation-division) family transporters in gram-negative bacteria frequently pump out a wide range of inhibitors and often contribute to multidrug resistance to antibiotics and biocides. an archetypal rnd pump of escherichia coli, acrb, is known to exist as a homotrimer, and this construction is essential for drug pumping through the functionally rotating mechanism. mdtbc, however, appears different because two pump genes coexist within a single operon, and genetic deletion data ...201020038594
multidrug efflux pump mdtbc of escherichia coli is active only as a b2c heterotrimer.rnd (resistance-nodulation-division) family transporters in gram-negative bacteria frequently pump out a wide range of inhibitors and often contribute to multidrug resistance to antibiotics and biocides. an archetypal rnd pump of escherichia coli, acrb, is known to exist as a homotrimer, and this construction is essential for drug pumping through the functionally rotating mechanism. mdtbc, however, appears different because two pump genes coexist within a single operon, and genetic deletion data ...201020038594
complete genome sequence of the fire blight pathogen erwinia pyrifoliae dsm 12163t and comparative genomic insights into plant pathogenicity.erwinia pyrifoliae is a newly described necrotrophic pathogen, which causes fire blight on asian (nashi) pear and is geographically restricted to eastern asia. relatively little is known about its genetics compared to the closely related main fire blight pathogen e. amylovora.201020047678
the helicobacter pylori groes cochaperonin hspa functions as a specialized nickel chaperone and sequestration protein through its unique c-terminal extension.the transition metal nickel plays a central role in the human gastric pathogen helicobacter pylori because it is required for two enzymes indispensable for colonization, the nickel metalloenzyme urease and [nife] hydrogenase. to sustain nickel availability for these metalloenzymes while providing protection from the metal's harmful effects, h. pylori is equipped with several specific nickel-binding proteins. among these, h. pylori possesses a particular chaperone, hspa, that is a homolog of the ...201020061471
identification and functional analysis of type iii effector proteins in mesorhizobium loti.mesorhizobium loti maff303099, a microsymbiont of the model legume lotus japonicus, possesses a cluster of genes (tts) that encode a type iii secretion system (t3ss). in the presence of heterologous nodd from rhizobium leguminosarum and a flavonoid naringenin, we observed elevated expression of the tts genes and secretion of several proteins into the culture medium. inoculation experiments with wild-type and t3ss mutant strains revealed that the presence of the t3ss affected nodulation at a spec ...201020064065
phenotypic and genetic diversity in sinorhizobium meliloti and s. medicae from drought and salt affected regions of morocco.sinorhizobium meliloti and s. medicae are symbiotic nitrogen fixing bacteria in root nodules of forage legume alfalfa (medicago sativa l.). in morocco, alfalfa is usually grown in marginal soils of arid and semi-arid regions frequently affected by drought, extremes of temperature and soil ph, soil salinity and heavy metals, which affect biological nitrogen fixing ability of rhizobia and productivity of the host. this study examines phenotypic diversity for tolerance to the above stresses and gen ...201020089174
genome-wide detection of predicted non-coding rnas in rhizobium etli expressed during free-living and host-associated growth using a high-resolution tiling array.non-coding rnas (ncrnas) play a crucial role in the intricate regulation of bacterial gene expression, allowing bacteria to quickly adapt to changing environments. in the past few years, a growing number of regulatory rna elements have been predicted by computational methods, mostly in well-studied gamma-proteobacteria but lately in several alpha-proteobacteria as well. here, we have compared an extensive compilation of these non-coding rna predictions to intergenic expression data of a whole-ge ...201020089193
a type vi secretion system of pseudomonas aeruginosa targets a toxin to bacteria.the functional spectrum of a secretion system is defined by its substrates. here we analyzed the secretomes of pseudomonas aeruginosa mutants altered in regulation of the hcp secretion island-i-encoded type vi secretion system (h1-t6ss). we identified three substrates of this system, proteins tse1-3 (type six exported 1-3), which are coregulated with the secretory apparatus and secreted under tight posttranslational control. the tse2 protein was found to be the toxin component of a toxin-immunit ...201020114026
identification of a bifunctional udp-4-keto-pentose/udp-xylose synthase in the plant pathogenic bacterium ralstonia solanacearum strain gmi1000, a distinct member of the 4,6-dehydratase and decarboxylase family.the udp-sugar interconverting enzymes involved in udp-glca metabolism are well described in eukaryotes but less is known in prokaryotes. here we identify and characterize a gene (rsu4kpxs) from ralstonia solanacearum str. gmi1000, which encodes a dual function enzyme not previously described. one activity is to decarboxylate udp-glucuronic acid to udp-beta-l-threo-pentopyranosyl-4''-ulose in the presence of nad(+). the second activity converts udp-beta-l-threo-pentopyranosyl-4''-ulose and nadh t ...201020118241
ligands of boron in pisum sativum nodules are involved in regulation of oxygen concentration and rhizobial infection.boron (b) is an essential nutrient for n(2)-fixing legume-rhizobia symbioses, and the capacity of borate ions to bind and stabilize biomolecules is the basis of any b function. we used a borate-binding-specific resin and immunostaining techniques to identify b ligands important for the development of pisum sativum-rhizobium leguminosarum 3841 symbiotic nodules. arabinogalactan-extensin (agpe), recognized by mac 265 antibody, appeared heavily bound to the resin in extracts derived from b-sufficie ...201020132519
an efficient, multiply promiscuous hydrolase in the alkaline phosphatase superfamily.we report a catalytically promiscuous enzyme able to efficiently promote the hydrolysis of six different substrate classes. originally assigned as a phosphonate monoester hydrolase (pmh) this enzyme exhibits substantial second-order rate accelerations ((k(cat)/k(m))/k(w)), ranging from 10(7) to as high as 10(19), for the hydrolyses of phosphate mono-, di-, and triesters, phosphonate monoesters, sulfate monoesters, and sulfonate monoesters. this substrate collection encompasses a range of substra ...201020133613
genome-wide investigation and functional characterization of the beta-ketoadipate pathway in the nitrogen-fixing and root-associated bacterium pseudomonas stutzeri a1501.soil microorganisms are mainly responsible for the complete mineralization of aromatic compounds that usually originate from plant products or environmental pollutants. in many cases, structurally diverse aromatic compounds can be converted to a small number of structurally simpler intermediates, which are metabolized to tricarboxylic acid intermediates via the beta-ketoadipate pathway. this strategy provides great metabolic flexibility and contributes to increased adaptation of bacteria to thei ...201020137101
myxococcus xanthus viability depends on groel supplied by either of two genes, but the paralogs have different functions during heat shock, predation, and development.myxococcus xanthus dk1622 contains two paralogous groel gene loci that possess both different sequences and different organizations within the genome. deletion of either one of these two genes alone does not affect cell viability. however, deletion of both groel genes results in cell death unless a complemented groel1 or groel2 gene is present. the groel1 gene was determined to be essential for cell survival under heat shock conditions; a strain with mutant groel2 caused cells to be more sensiti ...201020139189
altered lipid a structures and polymyxin hypersensitivity of rhizobium etli mutants lacking the lpxe and lpxf phosphatases.the lipid a of rhizobium etli, a nitrogen-fixing plant endosymbiont, displays significant structural differences when compared to that of escherichia coli. an especially striking feature of r. etli lipid a is that it lacks both the 1- and 4'-phosphate groups. the 4'-phosphate moiety of the distal glucosamine unit is replaced with a galacturonic acid residue. the dephosphorylated proximal unit is present as a mixture of the glucosamine hemiacetal and an oxidized 2-aminogluconate derivative. disti ...201020153447
requirements for construction of a functional hybrid complex of photosystem i and [nife]-hydrogenase.the development of cellular systems in which the enzyme hydrogenase is efficiently coupled to the oxygenic photosynthesis apparatus represents an attractive avenue to produce h(2) sustainably from light and water. here we describe the molecular design of the individual components required for the direct coupling of the o(2)-tolerant membrane-bound hydrogenase (mbh) from ralstonia eutropha h16 to the acceptor site of photosystem i (ps i) from synechocystis sp. pcc 6803. by genetic engineering, th ...201020154103
a new small regulatory protein, hmup, modulates haemin acquisition in sinorhizobium meliloti.sinorhizobium meliloti has multiple systems for iron acquisition, including the use of haem as an iron source. haem internalization involves the shmr haem outer membrane receptor and the hmutuv locus, which participates in haem transport across the cytoplasmic membrane. previous studies have demonstrated that expression of the shmr gene is negatively regulated by iron through rira. here, we identify hmup in a genetic screen for mutants that displayed aberrant control of shmr. the normal inductio ...201020167620
role of the sinorhizobium meliloti global regulator hfq in gene regulation and symbiosis.the rna-binding protein hfq is a global regulator which controls diverse cellular processes in bacteria. to begin understanding the role of hfq in the sinorhizobium meliloti-medicago truncatula nitrogen-fixing symbiosis, we defined free-living and symbiotic phenotypes of an hfq mutant. over 500 transcripts were differentially accumulated in the hfq mutant of s. meliloti rm1021 when grown in a shaking culture. consistent with transcriptome-wide changes, the hfq mutant displayed dramatic alteratio ...201020192823
evolution and multifarious horizontal transfer of an alternative biosynthetic pathway for the alternative polyamine sym-homospermidine.polyamines are small flexible organic polycations found in almost all cells. they likely existed in the last universal common ancestor of all extant life, and yet relatively little is understood about their biological function, especially in bacteria and archaea. unlike eukaryotes, where the predominant polyamine is spermidine, bacteria may contain instead an alternative polyamine, sym-homospermidine. we demonstrate that homospermidine synthase (hss) has evolved vertically, primarily in the alph ...201020194510
regulation of flagellar, motility and chemotaxis genes in rhizobium leguminosarum by the visn/r-rem cascade.in this paper, we describe the regulatory roles of visn, visr and rem in the expression of flagellar, motility and chemotaxis genes in rhizobium leguminosarum biovar viciae strains vf39sm and 3841. individual mutations in the genes encoding these proteins resulted in a loss of motility and an absence of flagella, indicating that these regulatory genes are essential for flagellar synthesis and function. transcriptional experiments involving gusa-gene fusions in wild-type and mutant backgrounds we ...201020203055
the sinorhizobium meliloti rna chaperone hfq influences central carbon metabolism and the symbiotic interaction with alfalfa.the bacterial hfq protein is able to interact with diverse rna molecules, including regulatory small non-coding rnas (srnas), and thus it is recognized as a global post-transcriptional regulator of gene expression. loss of hfq has an extensive impact in bacterial physiology which in several animal pathogens influences virulence. sinorhizobium meliloti is a model soil bacterium known for its ability to establish a beneficial nitrogen-fixing intracellular symbiosis with alfalfa. despite the predic ...201020205931
udp xylose synthase 1 is required for morphogenesis and histogenesis of the craniofacial skeleton.udp-xylose synthase (uxs1) is strongly conserved from bacteria to humans, but because no mutation has been studied in any animal, we do not understand its roles in development. furthermore, no crystal structure has been published. uxs1 synthesizes udp-xylose, which initiates glycosaminoglycan attachment to a protein core during proteoglycan formation. crystal structure and biochemical analyses revealed that an r233h substitution mutation in zebrafish uxs1 alters an arginine buried in the dimer i ...201020226781
mutation in the pssm gene encoding ketal pyruvate transferase leads to disruption of rhizobium leguminosarum bv. viciae-pisum sativum symbiosis.to study the question whether acidic exopolysaccharide (eps) modification, e.g. pyruvylation, plays any role in the development of rhizobium leguminosarum/pisum sativum symbiosis.201020233262
heme-responsive dna binding by the global iron regulator irr from rhizobium leguminosarum.heme, a physiologically crucial form of iron, is a cofactor for a very wide range of proteins and enzymes. these include dna regulatory proteins in which heme is a sensor to which an analyte molecule binds, effecting a change in the dna binding affinity of the regulator. given that heme, and more generally iron, must be carefully regulated, it is surprising that there are no examples yet in bacteria in which heme itself is sensed directly by a reversibly binding dna regulatory protein. here we s ...201020233710
quorum-sensing regulation of a copper toxicity system in pseudomonas aeruginosa.the lasr/lasi quorum-sensing system in pseudomonas aeruginosa influences global gene expression and mediates pathogenesis. in this study, we show that the quorum-sensing system activates, via the transcriptional regulator pa4778, a copper resistance system composed of 11 genes. the quorum-sensing global regulator lasr was recently shown to directly activate transcription of pa4778, a cuer homolog and a merr-type transcriptional regulator. using molecular genetic methods and bioinformatics, we ve ...201020233934
glnb/glnk pii proteins and regulation of the sinorhizobium meliloti rm1021 nitrogen stress response and symbiotic function.the sinorhizobium meliloti rm1021 delta glnd-sm2 mutant, which is predicted to make a glnd nitrogen sensor protein truncated at its amino terminus, fixes nitrogen in symbiosis with alfalfa, but the plants cannot use this nitrogen for growth (s. n. yurgel and m. l. kahn, proc. natl. acad. sci. u. s. a. 105:18958-18963, 2008). the mutant also has a generalized nitrogen stress response (nsr) defect. these results suggest a connection between glnd, symbiotic metabolism, and the nsr, but the nature o ...201020304991
symbiotic functioning and bradyrhizobial biodiversity of cowpea (vigna unguiculata l. walp.) in africa.cowpea is the most important food grain legume in sub-saharan africa. however, no study has so far assessed rhizobial biodiversity and/or nodule functioning in relation to strain igs types at the continent level. in this study, 9 cowpea genotypes were planted in field experiments in botswana, south africa and ghana with the aim of i) trapping indigenous cowpea root-nodule bacteria (cowpea "rhizobia") in the 3 countries for isolation, molecular characterisation using pcr-rflp analysis, and sequen ...201020331875
genome-wide comparative analysis of metacaspases in unicellular and filamentous cyanobacteria.cyanobacteria are an ancient group of photoautotrophic prokaryotes with wide variations in genome size and ecological habitat. metacaspases (mcas) are cysteine proteinases that have sequence homology to caspases and play essential roles in programmed cell death (pcd). mcas have been identified in several prokaryotes, fungi and plants; however, knowledge about cyanobacterial metacaspases still remains obscure. with the availability of sequenced genomes of 33 cyanobacteria, we perform a comparativ ...201020334693
toxicogenomic response of rhodospirillum rubrum s1h to the micropollutant triclosan.in the framework of the micro-ecological life support system alternative (melissa) project, a pilot study was performed to identify the effects of triclosan on the melissa carbon-mineralizing microorganism rhodospirillum rubrum s1h. triclosan is a biocide that is commonly found in human excrement and is considered an emerging pollutant in wastewater and the environment. chronic exposure to melissa-relevant concentrations (> or =25 microg liter(-1)) of triclosan resulted in a significant extensio ...201020363786
baca is essential for bacteroid development in nodules of galegoid, but not phaseoloid, legumes.baca is an integral membrane protein, the mutation of which leads to increased resistance to the antimicrobial peptides bleomycin and bac7(1-35) and a greater sensitivity to sds and vancomycin in rhizobium leguminosarum bv. viciae, r. leguminosarum bv. phaseoli, and rhizobium etli. the growth of rhizobium strains on dicarboxylates as a sole carbon source was impaired in baca mutants but was overcome by elevating the calcium level. while baca mutants elicited indeterminate nodule formation on pea ...201020363949
stress-induced synthesis of phosphatidylinositol 3-phosphate in mycobacteria.phosphoinositides play key roles in regulating membrane dynamics and intracellular signaling in eukaryotic cells. however, comparable lipid-based signaling pathways have not been identified in bacteria. here we show that mycobacterium smegmatis and other actinomycetes bacteria can synthesize the phosphoinositide, phosphatidylinositol 3-phosphate (pi3p). this lipid was transiently labeled with [(3)h]inositol. sensitivity of the purified lipid to alkaline phosphatase, headgroup analysis by high-pr ...201020364020
monomethylamine as a nitrogen source for a nonmethylotrophic bacterium, agrobacterium tumefaciens.monomethylamine can be used by nonmethylotrophs as a sole nitrogen source but not as a carbon source; however, little is known about the genes and enzymes involved. the gamma-glutamylmethylamide/n-methylglutamate pathway for monomethylamine utilization by methylotrophs has recently been resolved. we have identified genes encoding key enzymes of this pathway in nonmethylotrophs (e.g., agrobacterium tumefaciens) and demonstrated that this pathway is also involved in the utilization of monomethylam ...201020400554
bioluminescence imaging of clavibacter michiganensis subsp. michiganensis infection of tomato seeds and plants.clavibacter michiganensis subsp. michiganensis is a gram-positive bacterium that causes wilting and cankers, leading to severe economic losses in commercial tomato production worldwide. the disease is transmitted from infected seeds to seedlings and mechanically from plant to plant during seedling production, grafting, pruning, and harvesting. because of the lack of tools for genetic manipulation, very little is known regarding the mechanisms of seed and seedling infection and movement of c. mic ...201020400561
phenolic acids act as signaling molecules in plant-microbe symbioses.phenolic acids are the main polyphenols made by plants. these compounds have diverse functions and are immensely important in plant-microbe interactions/symbiosis. phenolic compounds act as signaling molecules in the initiation of legumerhizobia symbioses, establishment of arbuscular mycorrhizal symbioses and can act as agents in plant defense. flavonoids are a diverse class of polyphenolic compounds that have received considerable attention as signaling molecules involved in plant-microbe inter ...201020400851
autoinducer-2 and qsec control biofilm formation and in vivo virulence of aggregatibacter actinomycetemcomitans.biofilm formation by the periodontal pathogen aggregatibacter actinomycetemcomitans is dependent upon autoinducer-2 (ai-2)-mediated quorum sensing. however, the components that link the detection of the ai-2 signal to downstream gene expression have not been determined. one potential regulator is the qsebc two-component system, which is part of the ai-2-dependent response pathway that controls biofilm formation in escherichia coli. here we show that the expression of qsebc in a. actinomycetemcom ...201020404080
a pathobiont of the microbiota balances host colonization and intestinal inflammation.the gastrointestinal tract harbors a diverse microbiota that has coevolved with mammalian hosts. though most associations are symbiotic or commensal, some resident bacteria (termed pathobionts) have the potential to cause disease. bacterial type vi secretion systems (t6sss) are one mechanism for forging host-microbial interactions. here we reveal a protective role for the t6ss of helicobacter hepaticus, a gram-negative bacterium of the intestinal microbiota. h. hepaticus mutants with a defective ...201020413095
characterization of strains unlike mesorhizobium loti that nodulate lotus spp. in saline soils of granada, spain.lotus species are forage legumes with potential as pastures in low-fertility and environmentally constrained soils, owing to their high persistence and yield under those conditions. the aim of this work was the characterization of phenetic and genetic diversity of salt-tolerant bacteria able to establish efficient symbiosis with lotus spp. a total of 180 isolates able to nodulate lotus corniculatus and lotus tenuis from two locations in granada, spain, were characterized. molecular identificatio ...201020435777
characterization of the nifa-rpon regulon in rhizobium etli in free life and in symbiosis with phaseolus vulgaris.the nifa-rpon complex is a master regulator of the nitrogen fixation genes in alphaproteobacteria. based on the complete rhizobium etli genome sequence, we constructed an r. etli cfn42 oligonucleotide (70-mer) microarray and utilized this tool, reverse transcription (rt)-pcr analysis (transcriptomics), proteomics, and bioinformatics to decipher the nifa-rpon regulon under microaerobic conditions (free life) and in symbiosis with bean plants. the r. etli nifa-rpon regulon was determined to contai ...201020453139
disruption of the glycine cleavage system enables sinorhizobium fredii usda257 to form nitrogen-fixing nodules on agronomically improved north american soybean cultivars.the symbiosis between sinorhizobium fredii usda257 and soybean [glycine max (l.) merr.] exhibits a high degree of cultivar specificity. usda257 nodulates primitive soybean cultivars but fails to nodulate agronomically improved cultivars such as mccall. in this study we provide evidence for the involvement of a new genetic locus that controls soybean cultivar specificity. this locus was identified in usda257 by tn5 transposon mutagenesis followed by nodulation screening on mccall soybean. we have ...201020453144
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