| hydrogenase genes are uncommon and highly conserved in rhizobium leguminosarum bv. viciae. | a screening for hydrogen uptake (hup) genes in rhizobium leguminosarum bv. viciae isolates from different locations within spain identified no hup+ strains, confirming the scarcity of the hup trait in r. leguminosarum. however, five new hup+ strains were isolated from ni-rich soils from italy and germany. the hup gene variability was studied in these strains and in six available strains isolated from north america. sequence analysis of three regions within the hup cluster showed an unusually hig ... | 2005 | 16216440 |
| evolutionary, structural and functional relationships revealed by comparative analysis of syntenic genes in rhizobiales. | comparative genomics has provided valuable insights into the nature of gene sequence variation and chromosomal organization of closely related bacterial species. however, questions about the biological significance of gene order conservation, or synteny, remain open. moreover, few comprehensive studies have been reported for rhizobial genomes. | 2005 | 16229745 |
| an expression-driven approach to the prediction of carbohydrate transport and utilization regulons in the hyperthermophilic bacterium thermotoga maritima. | comprehensive analysis of genome-wide expression patterns during growth of the hyperthermophilic bacterium thermotoga maritima on 14 monosaccharide and polysaccharide substrates was undertaken with the goal of proposing carbohydrate specificities for transport systems and putative transcriptional regulators. saccharide-induced regulons were predicted through the complementary use of comparative genomics, mixed-model analysis of genome-wide microarray expression data, and examination of upstream ... | 2005 | 16237010 |
| identification of the rcta gene, which is required for repression of conjugative transfer of rhizobial symbiotic megaplasmids. | an analysis of the conjugative transfer of pretcfn42d, the symbiotic plasmid (psym) of rhizobium etli, has revealed a novel gene, rcta, as an essential element of a regulatory system for silencing the conjugative transfer of r. etli psym by repressing the transcription of conjugal transfer genes in standard laboratory media. the rcta gene product lacks sequence conservation with other proteins of known function but may belong to the winged-helix dna-binding subfamily of transcriptional regulator ... | 2005 | 16237017 |
| dissimilatory metabolism of nitrogen oxides in bacteria: comparative reconstruction of transcriptional networks. | bacterial response to nitric oxide (no) is of major importance since no is an obligatory intermediate of the nitrogen cycle. transcriptional regulation of the dissimilatory nitric oxides metabolism in bacteria is diverse and involves fnr-like transcription factors hcpr, dnr, and nnrr; two-component systems narxl and narqp; no-responsive activator norr; and nitrite-sensitive repressor nsrr. using comparative genomics approaches, we predict dna-binding motifs for these transcriptional factors and ... | 2005 | 16261196 |
| gene expression patterns and catalytic properties of udp-d-glucose 4-epimerases from barley (hordeum vulgare l.). | uge (udp-glc 4-epimerase or udp-gal 4-epimerase; ec 5.1.3.2) catalyses the interconversion of udp-gal and udp-glc. both nucleotide sugars act as activated sugar donors for the biosynthesis of cell wall polysaccharides such as cellulose, xyloglucans, (1,3;1,4)-beta-d-glucan and pectins, together with other biologically significant compounds including glycoproteins and glycolipids. three members of the hvuge (barley uge) gene family, designated hvuge1, hvuge2 and hvuge3, have been characterized. q ... | 2006 | 16266295 |
| novel 4-chlorophenol degradation gene cluster and degradation route via hydroxyquinol in arthrobacter chlorophenolicus a6. | arthrobacter chlorophenolicus a6, a previously described 4-chlorophenol-degrading strain, was found to degrade 4-chlorophenol via hydroxyquinol, which is a novel route for aerobic microbial degradation of this compound. in addition, 10 open reading frames exhibiting sequence similarity to genes encoding enzymes involved in chlorophenol degradation were cloned and designated part of a chlorophenol degradation gene cluster (cph genes). several of the open reading frames appeared to encode enzymes ... | 2005 | 16269679 |
| impact of bt corn on rhizospheric and soil eubacterial communities and on beneficial mycorrhizal symbiosis in experimental microcosms. | a polyphasic approach has been developed to gain knowledge of suitable key indicators for the evaluation of environmental impact of genetically modified bt 11 and bt 176 corn lines on soil ecosystems. we assessed the effects of bt corn (which constitutively expresses the insecticidal toxin from bacillus thuringiensis, encoded by the truncated cry1ab gene) and non-bt corn plants and their residues on rhizospheric and bulk soil eubacterial communities by means of denaturing gradient gel electropho ... | 2005 | 16269702 |
| novel dna sequences from natural strains of the nitrogen-fixing symbiotic bacterium sinorhizobium meliloti. | variation in genome size and content is common among bacterial strains. identifying these naturally occurring differences can accelerate our understanding of bacterial attributes, such as ecological specialization and genome evolution. in this study, we used representational difference analysis to identify potentially novel sequences not present in the sequenced laboratory strain rm1021 of the nitrogen-fixing bacterium sinorhizobium meliloti. using strain rm1021 as the driver and the type strain ... | 2005 | 16269751 |
| ascending migration of endophytic rhizobia, from roots to leaves, inside rice plants and assessment of benefits to rice growth physiology. | rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. we examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. the results indicated a dynamic infection process beginning with surface col ... | 2005 | 16269768 |
| proof that burkholderia strains form effective symbioses with legumes: a study of novel mimosa-nodulating strains from south america. | twenty mimosa-nodulating bacterial strains from brazil and venezuela, together with eight reference mimosa-nodulating rhizobial strains and two other beta-rhizobial strains, were examined by amplified rrna gene restriction analysis. they fell into 16 patterns and formed a single cluster together with the known beta-rhizobia, burkholderia caribensis, burkholderia phymatum, and burkholderia tuberum. the 16s rrna gene sequences of 15 of the 20 strains were determined, and all were shown to belong t ... | 2005 | 16269788 |
| symbiotic hydrogenase activity in bradyrhizobium sp. (vigna) increases nitrogen content in vigna unguiculata plants. | bradyrhizobium sp. (lupinus) and bradyrhizobium sp. (vigna) mutants in which hydrogenase (hup) activity was affected were constructed and analyzed. vigna unguiculata plants inoculated with the bradyrhizobium sp. (vigna) hup mutant showed reduced nitrogenase activity and also a significant decrease in nitrogen content, suggesting a relevant contribution of hydrogenase activity to plant yield. | 2005 | 16269797 |
| evidence for horizontal transfer of 1-aminocyclopropane-1-carboxylate deaminase genes. | pcr was used to rapidly identify and isolate 1-aminocyclopropane-1-carboxylate (acc) deaminase genes from bacteria. the shimodaira-hasegawa test was used to assess whether phylogenetically anomalous gene placements suggestive of horizontal gene transfer (hgt) were significantly favored over vertical transmission. the best maximum likelihood (ml) acc deaminase tree was significantly more likely than four alternative ml trees, suggesting hgt. | 2005 | 16269802 |
| rhizobium leguminosarum biovar viciae symbiotic hydrogenase activity and processing are limited by the level of nickel in agricultural soils. | analysis of levels of hydrogenase processing and activity in rhizobium leguminosarum biovar viciae bacteroids from pea (pisum sativum) plants showed that the oxidation of nitrogenase-evolved hydrogen is limited by the availability of nickel in agricultural soils. this limitation was overcome by using an inoculant strain engineered for higher hydrogenase expression. | 2005 | 16269813 |
| induction of fungal disease resistance in vicia faba by dual inoculation with rhizobium leguminosarum and vesicular-arbuscular mycorrhizal fungi. | infection of vicia faba with bothytis fabae causes significant decreases in growth vigour, total nitrogen content, number of nodules and nutrient accumulation. na-uptake and phenolics concentration increased compared to that of noninfected plants. in contrast, dual inoculation of rhizobium and va mycorrhizae increased all above parameters suggesting a distinct improvement of the plants. the results also revealed that an inverse correlation may exist between phenolic, calcium, magnesium and zinc ... | 1998 | 16284861 |
| a role for shoot protein in shoot-root dry matter allocation in higher plants. | it is stated in many recent publications that nitrate (no3-) acts as a signal to regulate dry matter partitioning between the shoot and root of higher plants. here we challenge this hypothesis and present evidence for the viewpoint that no3- and other environmental effects on the shoot:root dry weight ratio (s:r) of higher plants are often related mechanistically to changes in shoot protein concentration. | 2006 | 16299006 |
| four-helix bundle: a ubiquitous sensory module in prokaryotic signal transduction. | motivation: transmembrane chemoreceptors in escherichia coli utilize ligand-binding domains for detecting various external signals. the structure of this domain in the e.coli aspartate receptor, tar, is known and its signal transduction mechanism is under investigation. current domain models for this important sensory module are inaccurate and, therefore, cannot reveal the distribution of this domain within the current genomic landscape. results: we carried out sensitive and exhaustive psi-blast ... | 2005 | 16306392 |
| a wide host-range metagenomic library from a waste water treatment plant yields a novel alcohol/aldehyde dehydrogenase. | using dna obtained from the metagenome of an anaerobic digestor in a waste water treatment plant, we constructed a gene library cloned in the wide host-range cosmid plafr3. one cosmid enabled rhizobium leguminosarum to grow on ethanol as sole carbon and energy source, this being due to the presence of a gene, termed adhemeta. the adhemeta protein most closely resembles the adhe alcohol dehydrogenase of clostridium acetobutylicum, where it catalyses the formation of ethanol and butanol in a two-s ... | 2005 | 16309390 |
| screening a wide host-range, waste-water metagenomic library in tryptophan auxotrophs of rhizobium leguminosarum and of escherichia coli reveals different classes of cloned trp genes. | a metagenomic cosmid library was constructed, in which the insert dna was derived from bacteria in a waste-water treatment plant and the vector was the wide host-range cosmid plafr3. the library was screened for clones that could correct defined tryptophan auxotrophs of the alpha-proteobacterium rhizobium leguminosarum and of escherichia coli. a total of 26 different cosmids that corrected at least one trp mutant in one or both of these species were obtained. several cosmids corrected the auxotr ... | 2005 | 16309391 |
| long-term effects of crop management on rhizobium leguminosarum biovar viciae populations. | little is known about factors that affect the indigenous populations of rhizobia in soils. we compared the abundance, diversity and genetic structure of rhizobium leguminosarum biovar viciae populations in soils under different crop managements, i.e., wheat and maize monocultures, crop rotation, and permanent grassland. rhizobial populations were sampled from nodules of pea- or vetch plants grown in soils collected at three geographically distant sites in france, each site comprising a plot unde ... | 2004 | 16329858 |
| rhizoplane colonisation of peas by rhizobium leguminosarum bv. viceae and a deleterious pseudomonas putida. | pseudomonas putida strain a313, a deleterious rhizosphere bacterium, reduced pea nitrogen content when inoculated alone or in combination with rhizobium leguminosarum bv. viceae on plants in the presence of soil under greenhouse conditions. when plants were grown gnotobiotically in liquid media, mixed inocula of a313 and rhizobia gave a higher proportion of small evenly distributed nodules when compared with a single rhizobial inoculation. in addition, the rhizobial root establishment was reduce ... | 2004 | 16329894 |
| effect of elevated tropospheric ozone on the structure of bacterial communities inhabiting the rhizosphere of herbaceous plants native to germany. | current elevated concentrations of ozone in the atmosphere, as they are observed during summer seasons, can cause severe effects on plant vegetation. this study was initiated to analyze whether ozone-stressed plants also transfer signals below ground and thereby alter the bacterial community composition in their rhizospheres. herbaceous plants, native to germany, with tolerance (anthoxanthum odoratum, achillea millefolium, poa pratensis, rumex acetosa, and veronica chamaedrys) and sensitivity (m ... | 2005 | 16332747 |
| impact of the microscale distribution of a pseudomonas strain introduced into soil on potential contacts with indigenous bacteria. | soil bioaugmentation is a promising approach in soil bioremediation and agriculture. nevertheless, our knowledge of the fate and activity of introduced bacteria in soil and thus of their impact on the soil environment is still limited. the microscale spatial distribution of introduced bacteria has rarely been studied, although it determines the encounter probability between introduced cells and any components of the soil ecosystem and thus plays a role in the ecology of introduced bacteria. for ... | 2005 | 16332794 |
| the manganese-responsive repressor mur of rhizobium leguminosarum is a member of the fur-superfamily that recognizes an unusual operator sequence. | the manganese uptake regulator mur of rhizobium leguminosarum is a close homologue of the global iron regulatory protein fur. mur represses the sitabcd operon, which encodes a mn2+ transport system, specifically in response to mn2+ but not fe2+. in previous work the authors mapped the 5' ends of two sit operon transcripts, termed ts1 and ts2, which were co-ordinately regulated by mn2+-mur, but this paper now shows that only ts1 is a primary transcript. dnase i protection analyses showed that pur ... | 2005 | 16339952 |
| diversity of rhizobium leguminosarum in the palouse of eastern washington. | serology, antibiotic resistance, litmus milk reaction, and ability to fix nitrogen in peas were methods employed in studying the diversity of rhizobium leguminosarum. the two serogroups identified were related to the position on the soil slope where isolated were taken. | 1978 | 16345331 |
| promotion of infection thread formation by substances from rhizobium. | an extrinsic substance (es-6000) was isolated from the periplasmic space of rhizobium trifolii (strain 4s) cells by osmotic shock, using a high-density sucrose solution. this substance promoted infection thread formation in root hairs of white clover when inoculated together with the infectious strain (4s). however, es-6000 obtained from another rhizobial species and from strain a1, which is a noninfectious mutant strain obtained from strain 4s, did not have this effect. the promoter in the es-6 ... | 1980 | 16345501 |
| interaction between a non-nodulating and an ineffective mutant of rhizobium trifolli resulting in effective (nitrogen-fixing) nodulation. | a noninvasive (non-nodulating) mutant of rhizobium trifolii when mixed with an ineffective (non-nitrogen-fixing) mutant gives rise to effective (nitrogen-fixing) nodules. | 1980 | 16345518 |
| use of two-dimensional polyacrylamide electrophoresis to demonstrate that putative rhizobium cross-inoculation mutants actually are contaminants. | two-dimensional polyacrylamide electrophoresis was used to determine that mutants of rhizobium trifolii dt6, claimed to be capable of effectively nodulating soybeans, were actually rhizobium japonicum 110 contaminants isolated from the parent dt6 culture. | 1980 | 16345520 |
| scanning electron microscopy of rhizobium trifolii infection sites on root hairs of white clover. | white clover root hairs which were inoculated with rhizobium trifolii 4s (infectious strain) contained infection threads which were observed by light microscopy and scanning electron microscopy. three morphological types of root hairs retaining infection threads were recognized. the bacteria were strongly attached between the surfaces of two plant cell walls as follows: between surfaces of a root hair tip curled back on itself, between a protuberance from a root hair and its cell surface, or bet ... | 1980 | 16345672 |
| succinate-induced morphology of rhizobium trifolii 0403 resembles that of bacteroids in clover nodules. | morphological changes which accompany nutrient enrichment of rhizobium trifolii 0403 were studied. assays of cell number and size coupled with scanning electron microscopy and immunofluorescence microscopy showed that succinate induces cells to stop dividing in vitro and to swell either in the cell center or at one cell pole. the extent and frequency of in vitro cell swelling were in direct relation to the concentration of succinate added to the enrichment medium. the in vitro swelling of cells ... | 1982 | 16346058 |
| growth-related substituent changes in exopolysaccharides of fast-growing rhizobia. | pyruvic acid and o-acetyl groups are the major noncarbohydrate substituents in exopolysaccharides (eps) produced by fast-growing species of rhizobium. eps substituent variations were observed among strains of the same species. the amounts of these substituents also varied with culture age; pyruvic acid increased in the eps of all four species, whereas o-acetyl increased in rhizobium trifolii and r. leguminosarum eps, decreased in r. meliloti eps, and remained constant in r. phaseoli eps. the use ... | 1982 | 16346062 |
| alteration of the trifoliin a-binding capsule of rhizobium trifolii 0403 by enzymes released from clover roots. | the effect of white clover root exudate on capsules of rhizobium trifolii 0403 was examined. the clover lectin trifoliin a was detected in root exudate of two clover varieties by indirect immunofluorescence with antibody against this lectin purified from clover seed. trifoliin a bound uniformly to encapsulated, heat-fixed cells during 1 h of incubation with root exudate. after 4 to 8 h of incubation, trifoliin a was only bound to one pole of the cells. transmission electron microscopy showed tha ... | 1982 | 16346081 |
| quantitative study of nodulation competitiveness in rhizobium strains. | we compared the nodulation competitiveness of three strains of rhizobium leguminosarum by counting the number of nodules formed on faba bean plants after the application at sowing time of different concentrations of the strains to soils already containing rhizobium strains of the same species. a relationship of type y = ax was found to exist between the ratio of the nodules formed by the applied inoculum strain to the nodules formed by the soil strains and the ratio of rhizobium cells in the ino ... | 1982 | 16346089 |
| competitiveness of rhizobium trifolii strains associated with red clover (trifolium pratense l.) in mississippi soils. | five strains of rhizobium trifolii were evaluated in competition with indigenous populations in nodulating red clover (trifolium pratense l.) cv. kenland in two different soils in mississippi. double antibiotic resistance acquisition was used to measure the proportion of nodules occupied by the introduced mutant strains. in vertisol soil, strains rp113-7, 162bb1, lm1, and 162p17 were recovered in at least 94% of the assayed nodules, whereas ta1 was found in 83.8% of the nodules. at an ultisol lo ... | 1982 | 16346130 |
| congo red absorption by rhizobium leguminosarum. | congo red absorption is generally considered a contraindication of rhizobium. however, r. leguminosarum takes up the dye on yeast extract-mannitol agar. the uptake of congo red varies among strains of r. leguminosarum, as shown elsewhere with strains of r. trifolii and r. meliloti. congo red absorption does not distinguish rhizobia from other bacteria, but may be useful as a strain marker. | 1983 | 16346177 |
| production of antimicrobial and bacteriocin-like substances by rhizobium trifolii. | rhizobium trifolii strains iari and rel-1 produced substances with broad and narrow activity spectra, respectively. reproducible inhibitory zones of various sizes produced by r. trifolii iari (2 to 14 mm) and r. trifolii rel-1 (2 to 6 mm) were detected, depending upon the indicator organism used. the maximum production of these substances by both strains of r. trifolii was observed on l-arabinose agar. a preliminary characterization of the antimicrobial substance produced by strain iari showed r ... | 1983 | 16346202 |
| hydrogen recycling by rhizobium leguminosarum isolates and growth and nitrogen contents of pea plants (pisum sativum l.). | the ability to recycle h(2) evolved by nitrogenase is thought to be of importance in increasing the efficiency of n(2) fixation and to be a factor in increasing plant yield in symbiotic systems. to determine whether this ability is a significant factor in the rhizobium leguminosarum-pisum sativum l. system, plants were inoculated with r. leguminosarum isolates which differed in their ability to oxidize h(2) and in their relative efficiency of n(2) fixation. these plants were grown at three level ... | 1983 | 16346248 |
| competition among rhizobium leguminosarum strains for nodulation of lentils (lens esculenta). | thirty-one cultures of rhizobium leguminosarum were screened for effectiveness (c(2)h(2) reduction) on lentils (lens esculenta). fluorescent antibodies prepared against three of the most effective strains (hawaii 5-0, nitragin 92a3, and nitragin 128a12) exhibited a high degree of strain specificity; the antibodies reacted strongly with their homologous rhizobia in culture and with bacteroids in nodules. they did not cross-react with one another, and only weakly with 5 of the 47 other r. legumino ... | 1983 | 16346257 |
| interaction of agromyces ramosus with other bacteria in soil. | agromyces ramosus occurs in very high numbers in most soils and, based on studies of laboratory isolates, does not require host cells for growth. nevertheless, it attacked and destroyed most of the gram-positive and gram-negative bacterial species tested as possible host organisms. a. ramosus also attacked and destroyed saccharomyces cerevisiae. the possibility of attack on fungi was unclear. among the bacteria serving as hosts were the important soil species azotobacter vinelandii, rhizobium le ... | 1983 | 16346402 |
| effect of acidity on the composition of an indigenous soil population of rhizobium trifolii found in nodules of trifolium subterraneum l. | acidity affected which members of an indigenous soil population of rhizobium trifolii nodulated trifolium subterraneum l. cv. mt. barker. in three experiments involving plants grown either in mineral salts agar adjusted to ph 4.8 or 6.8 and inoculated with a soil suspension or grown directly in samples of unamended soil (ph 4.8) or soil amended with caco(3) (ph 6.4), 121 of 151 isolates of r. trifolii were placed into four serogroups. seventy-nine of these isolates were placed into two serogroup ... | 1983 | 16346425 |
| effect of plasmid pij1008 from rhizobium leguminosarum on symbiotic function of rhizobium meliloti. | plasmid pij1008, which carries determinants for uptake hydrogenase (hup) activity, was transferred from rhizobium leguminosarum to rhizobium meliloti without impairing the capacity of the latter species to form root nodules on alfalfa. the plasmid was still present in rhizobia reisolated from the root nodules of 12 different alfalfa cultivars, but only low levels of hup activity were detected in alfalfa. | 1984 | 16346527 |
| fine structure of succinate-swollen rhizobium trifolii 0403. | transmission electron micrographs of glutaraldehyde- oso(4)-fixed rhizobium trifolii 0403 before and after cells were treated with 16.6 mm succinate showed that treated cells increased in mass by increasing cytoplasmic volume. the morphology of succinate-treated cells was identical to that of bacteroids, and the appearances of the envelope and periplasmic space were similar. the primary difference was in inclusion number and type. | 1984 | 16346547 |
| root hair deformation, bacterial attachment, and plant growth in wheat-azospirillum associations. | seven azospirillum strains induced more deformation of root hairs of wheat than did strains of rhizobium leguminosarum, azotobacter chroococcum, or escherichia coli. azospirillum sp. strain sp245 caused the most deformation. strain sp245 (isolated from surface sterile roots of wheat) and strain sp7 (isolated from the rhizosphere of a forage grass) were compared with regard to their effects on root hair deformation, their attachment to roots, and their effects on the growth of four wheat cultivar ... | 1984 | 16346680 |
| underexpression of ap from r-plasmids in fast-growing rhizobium species. | the presence of the plasmid rp1 in the cells of rhizobium leguminosarum strains rld1, 300, and 248, r. phaseoli 1233, r. trifolii strains t1 and 6661, and r. meliloti 4013 was found to appreciably increase bacterial resistance toward kanamycin and tetracycline but not toward ampicillin. the presence of 16 other r-plasmids in r. leguminosarum was also found to either not increase or only marginally increase bacterial resistance toward ampicillin. it appears now that underexpression of the plasmid ... | 1984 | 16346686 |
| root hair deformations associated with fractionated extracts from rhizobium trifolii. | components from culture fluid and whole cells of rhizobium trifolii were examined for effects on root hair morphology of white clover seedlings (trifolium repens var. ladino). cell-free culture fluid, exopolysaccharides, supernatant fluid from the precipitation of the exopolysaccharides, capsular polysaccharides, lipopolysaccharides, and a protein fraction from culture fluids were assayed for morphogenetic effects on the root hairs of axenically grown clover seedlings. crude fractions were chrom ... | 1985 | 16346709 |
| possible involvement of phage-like structures in antagonism of cowpea rhizobia by rhizobium trifolii. | a reduction in the viability of cowpea rhizobia was observed when rhizobium trifolii iari and cowpea rhizobium strain 3824 were inoculated together in soil. the reduction in number of cowpea rhizobia in soil was found to be associated with the reduction in number of nodules per plant and retardation in plant growth. an antimicrobial substance was isolated from r. trifolii which, on electron microscopic investigation, demonstrated the presence of several phage-like structures. | 1985 | 16346736 |
| inoculant maturity influences survival of rhizobia on seed. | survival of rhizobium trifolii on seeds of arrowleaf clover (trifolium versiculosum savi) and subclover (trifolium subterraneum l.) was affected by the maturity of peat-, vermiculite-, and charcoal-based inoculants. ten times more rhizobia survived on seed 4 days after inoculation when inoculants were stored (cured) before being utilized as compared with uncured inoculants. increasing the curing time of inoculants beyond 4 weeks had little effect on increasing survival of seed-applied rhizobia. | 1985 | 16346738 |
| studies on the inoculation and competitiveness of a rhizobium leguminosarum strain in soils containing indigenous rhizobia. | the competitiveness of a rhizobium leguminosarum strain was investigated at two separate locations in field inoculation studies on commercially grown peas. the soil at each location (sites i and ii) contained an indigenous r. leguminosarum population of ca. 3 x 10 rhizobia per g of soil. at site i it was necessary to use an inoculum concentration as large as 4 x 10 cfu ml (2 x 10 bacteria seed) to establish the inoculum strain in the majority of nodules (73%). however, at site ii the inoculum st ... | 1985 | 16346769 |
| influence of azospirillum strains on the nodulation of clovers by rhizobium strains. | mixed cultures of several azospirillum and rhizobium trifolii strains caused either an inhibition or stimulation of nodule formation on plant hosts as compared with nodulation of plants inoculated with r. trifolii alone. azospirillum strains affected the nodulation process at a precise cell ratio (r. trifolii/azospirillum cells) and time of inoculation. all azospirillum strains used showed a variation in their ability to inhibit or enhance nodulation by r. trifolii strains. when nonviable cell p ... | 1985 | 16346772 |
| interaction of azospirillum and rhizobium strains leading to inhibition of nodulation. | rhizobium-azospirillum interactions during establishment of rhizobium-clover symbiosis were studied. when mixed cultures of azospirillum and rhizobium trifolii strains were simultaneously inoculated onto clover plants, no nodulation by r. trifolii was observed. r. trifolii anu1030, which nodulated clover plants without attacking root hairs, i.e., does not cause root hair curling (hac), did not show inhibition of nodulation when inoculated together with azospirillum strains. isolation of bacteria ... | 1985 | 16346773 |
| conserved nodulation genes in rhizobium meliloti and rhizobium trifolii. | plasmids which contained wild-type or mutated rhizobium meliloti nodulation (nod) genes were introduced into nodr. trifolii mutants anu453 and anu851 and tested for their ability to nodulate clover. cloned wild-type and mutated r. meliloti nod gene segments restored anu851 to nod, with the exception of nodd mutants. similarly, wild-type and mutant r. meliloti nod genes complemented anu453 to nod, except for nodcii mutants. thus, anu851 identifies the equivalent of the r. meliloti nodd genes, and ... | 1985 | 16346809 |
| association of rhizobium strains with roots of trifolium repens. | two techniques were used to assess the binding of rhizobia to clover roots: indirect counting after radiolabeling the bacteria and direct counting by using phase-contrast microscopy. microscopic observations revealed a large variability in the number of bacteria associated with individual root hairs. this variability made unbiased counting by microscopy difficult. systematic examination of all visible root hairs and "blind" counting of coded strains and treatments were adopted to minimize observ ... | 1985 | 16346819 |
| uptake hydrogenase activity determined by plasmid prl6ji in rhizobium leguminosarum does not increase symbiotic nitrogen fixation. | six mutants of rhizobium leguminosarum 3855 lacking uptake hydrogenase activity (hup phenotype) as a result of tn5-mob mutagenesis of the hup-containing plasmid prl6ji were tested for symbiotic performance on pisum sativum l. and vicia benghalensis l. three pea cultivars and one vetch line, which induce four different levels of hup activity in strain 3855, were grown to flowering under microbiologically controlled conditions in the absence of combined n. direct kjeldahl n measurements showed tha ... | 1985 | 16346912 |
| production and use of monoclonal antibodies for identification of strains of rhizobium trifolii. | we produced a monoclonal antibody against rhizobium trifolii 162x95. this antibody in cell culture supernatant was used in an indirect enzyme-linked immunosorbent assay to differentiate strain 162x95 from naturalized strains in the appalachian region. nodules crushed in 0.1 to 0.2 ml of phosphate-buffered saline and used to charge enzyme-linked immunosorbent assay plates gave strong absorbance readings. heat-inactivated and noninactivated portions of 162x95 cultures were strongly reactive, indic ... | 1986 | 16347098 |
| role of pili (fimbriae) in attachment of bradyrhizobium japonicum to soybean roots. | pili (fimbriae) were observed on cells of each of the five strains of bradyrhizobium japonicum and the one strain of rhizobium trifolii examined. pili on b. japonicum were about 4 nm in diameter and polarly expressed. piliated cells were estimated by transmission electron microscopy and hydrophobic attachment to polystyrene to constitute only a small percentage of the total population. the proportion of piliated cells in these populations was dependent on culture age in some strains. piliated b. ... | 1986 | 16347100 |
| autecology in rhizospheres and nodulating behavior of indigenous rhizobium trifolii. | indigenous serotype 1-01 of rhizobium trifolii occupied significantly fewer nodules (6%) on plants of soil-grown noninoculated subterranean clover (trifolium subterraneum l.) cv. woogenellup than on cv. mt. barker (36%) sampled at the flowering stage of growth. occupancy by indigenous serotype 2-01, was not significantly different on the two cultivars (16 and 26%). serotype-specific, fluorescent-antibody conjugates were synthesized and used to enumerate the indigenous serotypes in host (clovers) ... | 1986 | 16347198 |
| interstrain competition between representatives of indigenous serotypes of rhizobium trifolii. | the symbiotic characteristics of rhizobium trifolii strains 1-01 and 2-01 were evaluated both individually and in various combinations on two cultivars (mt. barker and woogenellup) of subterranean clover (trifolium subterraneum l.). nodules were observed on day 8 independent of cultivar or strain. cultivar differences were measured in nodulating efficiency by 1-01 since 54% of the primary nodules were formed on cv. mt. barker and only 15% were formed on cv. woogenellup in the zone above, or 1 cm ... | 1986 | 16347199 |
| rhizobium trifolii 0403 is capable of growth in the absence of combined nitrogen. | rhizobium trifolii 0403 was treated with 16.6 mm succinate and other nutrients and thereby induced to grow in nitrogen-free medium. the organism grew microaerophilically on either semisolid or liquid medium, fixing atmospheric nitrogen to meet metabolic needs. nitrogen fixation was measured via n incorporation (18% n enrichment in 1.5 doublings) and acetylene reduction. nitrogen-fixing cells had a k(m) for acetylene of 0.07 atm (ca. 7.09 kpa), required about 3% oxygen for optimum growth in liqui ... | 1986 | 16347203 |
| rhizobium population genetics: enzyme polymorphism in rhizobium leguminosarum from plants and soil in a pea crop. | a population of rhizobium leguminosarum biovar viceae symbiotic on the roots of a commercial pea (pisum sativum cv. maro) crop was sampled by extracting a total of 249 isolates from root nodules on nine plants. another 104 isolates were obtained by using soil from the same site to inoculate test plants, and a further 86 isolates were similarly obtained from soil 20 m distant within the crop. each isolate was characterized for mobility variants of the enzymes glucose-6-phosphate dehydrogenase, su ... | 1987 | 16347287 |
| influence of soil and nonsoil environments on nodulation by rhizobium trifolii. | indigenous serotypes 1-01 and 2-02 of rhizobium trifolii occupied similar percentages (18 to 23%) of root nodules on soil-grown subclover (trifolium subterraneum l.) and were virtually absent (4.5%) from nodules of soil-grown white clover (trifolium repens l.). in contrast (with the exception of one dilution [10]), serotype 1-01 occupied a substantial portion of nodules (16 to 40%) on white clover seedlings grown on mineral salts agar and exposed to samples of the same soil in the form of a 10-f ... | 1987 | 16347307 |
| environmental factors influencing numbers of rhizobium leguminosarum biovar trifolii and its bacteriophages in two field soils. | fluctuations in numbers of rhizobium leguminosarum biovar trifolii and its bacteriophages in two fields with different soil types were followed during a 17-month period in 1981 and 1982. mean levels of both phage and rhizobia varied significantly (p < 0.05) on different occasions, with rhizobial levels varying from 1.6 x 10 to 2.0 x 10 cell per g of soil and phage from 0 to 1.7 x 10 pfu/g of soil. multivariate regression analysis showed rhizobial levels to be significantly and positively related ... | 1987 | 16347339 |
| split-root assays using trifolium subterraneum show that rhizobium infection induces a systemic response that can inhibit nodulation of another invasive rhizobium strain. | subterranean clover plants possessing two equally infectible and robust lateral root systems ("split roots") were used in conjunction with several specific mutant strains (derived from rhizobium trifolii anu843) to investigate a systemic plant response induced by infective rhizobium strains. this plant response controls and inhibits subsequent nodulation on the plant. when strain anu843 was inoculated onto both root systems simultaneously or 24, 48, 72, or 96 h apart, an inhibitory response occu ... | 1987 | 16347390 |
| influence of lime and phosphate on nodulation of soil-grown trifolium subterraneum l. by indigenous rhizobium trifolii. | previous research had identified four serogroups of rhizobium trifolii indigenous to the acidic abiqua soil (fine, mixed, mesic cumulic ultic haploxeroll). nodulation of subterranean clover (trifolium subterraneum l.) by two of the serogroups, 6 and 36, was differentially influenced by an application of caco(3) which raised the ph of the soil from 5.0 to 6.5. these studies were designed to characterize this phenomenon more comprehensively. liming the soil with either caco(3), ca(oh)(2), mgo, or ... | 1987 | 16347431 |
| influence of phosphate on the growth and nodulation characteristics of rhizobium trifolii. | the growth and nodulating characteristics of rhizobium trifolii 6 and 36 differed under different external phosphate conditions. under growth conditions designed to deplete the internal phosphate content of the rhizobia, strain 6 maintained a generation time of 5 h during the exponential phase over two cycles of growth in phosphate-depleted medium. in contrast, the generation time of strain 36 was extended from 3.5 to 9.8 h over two cycles of phosphate-depleted growth, although the organism even ... | 1987 | 16347432 |
| conserved plasmid hydrogen-uptake (hup)-specific sequences within huprhizobium leguminosarum strains. | thirteen rhizobium leguminosarum strains previously reported as h(2)-uptake hydrogenase positive (hup) or negative (hup) were analyzed for the presence and conservation of dna sequences homologous to cloned bradyrhizobium japonicum hup-specific dna from cosmid phu1 (m. a. cantrell, r. a. haugland, and h. j. evans, proc. natl. acad. sci. usa 80:181-185, 1983). the hup phenotype of these strains was reexamined by determining hydrogenase activity induced in bacteroids from pea nodules. five strains ... | 1987 | 16347471 |
| evidence for genetic exchange and recombination of rhizobium symbiotic plasmids in a soil population. | a soil population of 16 rhizobium leguminosarum bv. trifolii isolates was characterized by using three sym (for symbiotic) plasmid-specific dna hybridization probes: (i) an r. leguminosarum bv. trifolii-specific, repeated-sequence probe; (ii) a nifhdk gene probe, and (iii) a nod gene probe. a predominant sym plasmid family was identified among the isolates. three other unrelated sym plasmid families were also identified. the isolates were also classified either by using a chromosomal dna hybridi ... | 1987 | 16347509 |
| growth of indigenous rhizobium leguminosarum and rhizobium meliloti in soils amended with organic nutrients. | the ability of indigenous rhizobium leguminosarum and rhizobium meliloti to use organic nutrients as growth substrates in soil was assessed by indirect bacteriophage analysis. a total of 17 organic compounds, including 9 carbohydrates, 3 organic acids, and 5 amino acids, were tested (1,000 mug g) in three soils with different cropping histories. four additional soils were screened with a glucose amendment. nutrient amendments stimulated growth of indigenous rhizobia, allowing subsequent replicat ... | 1988 | 16347530 |
| ecological indicators of native rhizobia in tropical soils. | the relationship between environment and abundance of rhizobia was described by determining the populations of root nodule bacteria at 14 diverse sites on the island of maui. mean annual rainfall at the sites ranged from 320 to 1,875 mm, elevation from 37 to 1,650 m, and soil ph from 4.6 to 7.9. four different soil orders were represented in this study: inceptisols, mollisols, ultisols, and an oxisol. the rhizobial populations were determined by plant infection counts of five legumes (trifolium ... | 1988 | 16347624 |
| numerical taxonomic analysis of some strains of rhizobium spp. that uses a qualitative coding of immunodiffusion reactions. | antigenic relationships among seven strains of bradyrhizobium japonicum were examined by immunodiffusion reactions, in which cells of each strain were reacted against each of the seven corresponding antisera. similar analyses were performed with rhizobium trifolii (28 strains), rhizobium meliloti (9 strains), and rhizobia of the cowpea miscellany (13 strains). antigens and antisera were reacted within each species only; serological interspecies cross-reactions were not performed. the results, sc ... | 1988 | 16347692 |
| expression of nodulation genes in rhizobium leguminosarum biovar trifolii is affected by low ph and by ca and al ions. | early stages in the infection of leguminous plants by rhizobium spp. are restricted at low ph and are further influenced by the presence of ca and al ions. in the experiments reported here, transcriptional and translational fusions of the escherichia coli lacz gene to rhizobium leguminosarum biovar trifolii nodulation (nod) genes were used to investigate the effects of ph and of ca and al ions on nod gene expression. the regulatory nodd gene in r. leguminosarum biovar trifolii was constitutively ... | 1988 | 16347761 |
| identification and characterization of a bacteroid-specific dehydrogenase complex in rhizobium leguminosarum pre. | in membranes of rhizobium leguminosarum bacteroids isolated from nitrogen-fixing pea root nodules, two different protein complexes with nadh dehydrogenase activity were detected. one of these complexes, with a molecular mass of 110 kilodaltons, was also found in membranes of free-living rhizobia, but the other, with a molecular mass of 550 kilodaltons, appeared to be present only in bacteroids. the bacteroid-specific complex, referred to as dh1, probably consists of at least four different subun ... | 1988 | 16347793 |
| diversity within serogroups of rhizobium leguminosarum biovar viceae in the palouse region of eastern washington as indicated by plasmid profiles, intrinsic antibiotic resistance, and topography. | serology, plasmid profiles, and intrinsic antibiotic resistance (iar) were determined for 192 isolates of rhizobium leguminosarum biovar viceae from nodules of peas (pisum sativum l.) grown on the south slope and bottomland topographic positions in eastern washington state. a total of 3 serogroups and 18 plasmid profile groups were identified. nearly all isolates within each plasmid profile group were specific for one of the three serogroups. cluster analysis of iar data showed that individual c ... | 1989 | 16347814 |
| use of the chrome azurol s agar plate technique to differentiate strains and field isolates of rhizobium leguminosarum biovar trifolii. | identification of rhizobium and bradyrhizobium strains and especially of indigenous isolates continues to be one of the major difficulties associated with competition studies. because there is no universally accepted method, the method of choice depends on preference, experience, and equipment. here, an agar plate technique was used to distinguish strains and field isolates of rhizobium leguminosarum biovar trifolii to provide a basis for identifying nodule occupants in further competition studi ... | 1989 | 16347877 |
| population size and distribution of rhizobium leguminosarum bv. trifolii in relation to total soil bacteria and soil depth. | bacterial cells small enough to pass through 0.4-mum-pore-size filters made up 5 to 9% of the indigenous bacterial population in 0- to 20-cm-depth samples of abiqua silty clay loam. within the same soil samples, cells of a similar dimension were stained with fluorescent antibodies specific to each of four antigenically distinct indigenous serogroups of rhizobium leguminosarum bv. trifolii and made up 22 to 34% of the soil population of the four serogroups. despite the extensive contribution of s ... | 1989 | 16347896 |
| expression by soil bacteria of nodulation genes from rhizobium leguminosarum biovar trifolii. | gram-negative, rod-shaped bacteria from the soil of white clover-ryegrass pastures were screened for their ability to nodulate white clover (trifolium repens) cultivar grasslands huia and for dna homology with genomic dna from rhizobium leguminosarum biovar trifolii icmp2668 (nzp582). of these strains, 3.2% were able to hybridize with strain icmp2668 and nodulate white clover and approximately 19% hybridized but were unable to nodulate. strains which nodulated but did not hybridize with strain i ... | 1989 | 16347936 |
| competition among strains of rhizobium leguminosarum biovar trifolii and use of a diallel analysis in assessing competition. | competition between indigenous rhizobium leguminosarum biovar trifolii strains and inoculant strains or between mixtures of inoculant strains was assessed in field and growth-room studies. strain effectiveness under competition was compared with strain performance in the absence of competition. field inoculation trials were conducted at elora, ontario, canada, with soil containing indigenous r. leguminosarum biovar trifolii. the indirect fluorescent-antibody technique was used for the identifica ... | 1989 | 16347952 |
| localization of bacteria and hemoglobin in root nodules of parasponia andersonii containing both bradyrhizobium strains and rhizobium leguminosarum biovar trifolii. | dual occupancy of parasponia andersonii nodules with different bradyrhizobium strains and rhizobium leguminosarum biovar trifolii was frequently obtained when two strains were inoculated into plants grown aseptically in tubes. since reisolates of bradyrhizobium strains from dually occupied nodules acquired the ability to nodulate trifolium repens, the spatial relationship of the two species of bacteria during nodule initiation and development was investigated and their proximity was demonstrated ... | 1989 | 16347995 |
| construction of a symbiotically effective strain of rhizobium leguminosarum bv. trifolii with increased nodulation competitiveness. | genes involved in nodulation competitiveness (tfx) were inserted by marker exchange into the genome of the effective strain rhizobium leguminosarum bv. trifolii ta1. isogenic strains of ta1 were constructed which differed only in their ability to produce trifolitoxin, an antirhizobial peptide. trifolitoxin production by the ineffective strain r. leguminosarum bv. trifolii t24 limited nodulation of clover roots by trifolitoxin-sensitive strains of r. leguminosarum bv. trifolii. the trifolitoxin-p ... | 1990 | 16348109 |
| role of microniches in protecting introduced rhizobium leguminosarum biovar trifolii against competition and predation in soil. | the importance of microniches for the survival of introduced rhizobium leguminosarum biovar trifolii cells was studied in sterilized and recolonized sterilized loamy sand and silt loam. the recolonized soils contained several species of soil microorganisms but were free of protozoa. part of these soil samples was inoculated with the flagellate bodo saltans, precultured on rhizobial cells. the introduced organisms were enumerated in different soil fractions by washing the soil, using a standardiz ... | 1990 | 16348125 |
| isolation of rhizobium leguminosarum (biovar trifolii) strains from ethiopian soils and symbiotic effectiveness on african annual clover species. | strains of rhizobium leguminosarum (biovar trifolii) isolated from two ethiopian soils or obtained from a commercial source were evaluated for symbiotic effectiveness on five african annual clover species. numerous rhizobium trifolii strains that exhibited varying levels of symbiotic effectiveness were isolated from both soils (a nitosol and a vertisol), and it was possible to identify strains that were highly effective for each clover species. the soil isolates were, as a group, superior to the ... | 1990 | 16348157 |
| purification and properties of catechol 1,2-dioxygenase from rhizobium leguminosarum biovar viceae usda 2370. | the catechol 1,2-dioxygenase of rhizobium leguminosarum biovar viceae usda 2370 was purified 296-fold, yielding a homogeneous preparation with a specific activity of 51.1 u mg of protein. the molecular weight of the native protein was 70,000, with two identical subunits of 34,500 and 1 g-atom of iron per mol. the optimum ph for catalytic activity was 9.0 to 9.5. | 1990 | 16348234 |
| new field isolates of rhizobium leguminosarum biovar viciae that nodulate the primitive pea cultivar afghanistan in addition to modern cultivars. | a collection of 13 field isolates of rhizobium leguminosarum bv. viciae that have the ability to nodulate the roots of current north american cultivars of peas as well as a "primitive" cultivar, afghanistan, was examined. these isolates originated in diverse geographical regions of the world, which indicates that this phenotype is not restricted to isolates from any one region. when subclones of the nodulation region from one plasmid were used to examine ecori-fragment-length polymorphisms in th ... | 1990 | 16348240 |
| increased bean (phaseolus vulgaris l.) nodulation competitiveness of genetically modified rhizobium strains. | rhizobium leguminosarum bv. phaseoli strain collections harbor heterogeneous groups of bacteria in which two main types of strains may be distinguished, differing both in the symbiotic plasmid and in the chromosome. we have analyzed under laboratory conditions the competitive abilities of the different types of rhizobium strains capable of nodulating phaseolus vulgaris l. bean. r. leguminosarum bv. phaseoli type i strains (characterized by nif gene reiterations and a narrow host range) are more ... | 1990 | 16348252 |
| population dynamics of rhizobium leguminosarum tn5 mutants with altered cell surface properties introduced into sterile and nonsterile soils. | the influence of cell surface properties on attachment to soil particles and on population dynamics of introduced bacteria was studied in sterilized and nonsterilized loamy sand and silt loam. rhizobium leguminosarum rbl5523 and three tn5 mutants (rbl5762, rbl5810, and rbl5811) with altered cell surface properties were used. cellulose fibrils were not produced by rbl5762. both rbl5810 and rbl5811 produced 80 to 90% less soluble exopolysaccharides and rbl5811 had, in addition, an altered lipopoly ... | 1991 | 16348432 |
| procedure for obtaining efficient root nodulation of a pea cultivar by a desired rhizobium strain and preempting nodulation by other strains. | the specificity between the sym-2 gene bred into certain cultivars of pea (pisum sativum l.) and the nodx gene, present only rarely in isolates of rhizobium leguminosarum, can be exploited to preempt competition or nodulation blocking by a rhizobium strain indigenous to a soil environment. the principle is to isolate an r. leguminosarum strain prevalent in a locale, convert it into a strain that will nodulate a desirable pea cultivar carrying sym-2 by establishing nodx in it, and then use the re ... | 1991 | 16348502 |
| degradation of the herbicide glyphosate by members of the family rhizobiaceae. | several strains of the family rhizobiaceae were tested for their ability to degrade the phosphonate herbicide glyphosate (isopropylamine salt of n-phosphonomethylglycine). all organisms tested (seven rhizobium meliloti strains, rhizobium leguminosarum, rhizobium galega, rhizobium trifolii, agrobacterium rhizogenes, and agrobacterium tumefaciens) were able to grow on glyphosate as the sole source of phosphorus in the presence of the aromatic amino acids, although growth on glyphosate was not as f ... | 1991 | 16348512 |
| construction of an acid-tolerant rhizobium leguminosarum biovar trifolii strain with enhanced capacity for nitrogen fixation. | strain anu1173 is an acid-tolerant rhizobium leguminosarum biovar trifolii strain that is able to nodulate subterranean clover plants growing in agar culture at ph 4.4 at ph 6.5, its symbiotic effectiveness in association with trifolium subterraneum cv. mt. barker was 80% relative to that of strain anu794, a sm derivative of the commercial inoculant r. leguminosarum bv. trifolii ta1. strain anu1173 contained four indigenous megaplasmids, the smallest of these being the symbiotic (sym) plasmid. t ... | 1991 | 16348523 |
| transfer of the pea symbiotic plasmid pjb5ji in nonsterile soil. | transfer of the pea (pisum sativum l.) symbiotic plasmid pjb5ji between strains of rhizobia was examined in sterile and nonsterile silt loam soil. sinorhizobium fredii usda 201 and hh003 were used as plasmid donors, and symbiotic plasmid-cured rhizobium leguminosarum 6015 was used as the recipient. the plasmid was carried but not expressed in s. fredii strains, whereas transfer of the plasmid to r. leguminosarum 6015 rendered the recipient capable of nodulating pea plants. confirmation of plasmi ... | 1991 | 16348589 |
| genetic diversity among rhizobium leguminosarum bv. trifolii strains revealed by allozyme and restriction fragment length polymorphism analyses. | allozyme electrophoresis and restriction fragment length polymorphism (rflp) analyses were used to examine the genetic diversity of a collection of 18 rhizobium leguminosarum bv. trifolii, 1 r. leguminosarum bv. viciae, and 2 r. meliloti strains. allozyme analysis at 28 loci revealed 16 electrophoretic types. the mean genetic distance between electrophoretic types of r. leguminosarum and r. meliloti was 0.83. within r. leguminosarum, the single strain of bv. viciae differed at an average of 0.65 ... | 1991 | 16348600 |
| genetic analysis of rhizobium leguminosarum bv. phaseoli mutants defective in nodulation and nodulation suppression. | nodulation-defective rhizobia and their nodule-forming derivatives containing cloned dna from the wild type were used to study nodulation suppression in phaseolus vulgaris l. non-nitrogen-fixing derivatives which formed rhizobia-containing white nodules induced partial suppression. comparison of this with the complete suppression by fix derivatives and a fix mutant which formed rhizobia-containing pink nodules suggests that the extent of suppression may be related to successive stages of nodule ... | 1992 | 16348664 |
| extracellular polysaccharide is not responsible for aluminum tolerance of rhizobium leguminosarum bv. phaseoli ciat899. | strain uhm-5, a psym exo derivative of the aluminum-tolerant rhizobium leguminosarum bv. phaseoli strain ciat899, was equally tolerant of aluminum (al) as the parental culture. dialyzed culture supernatants of the wild-type cells grown in yem broth (10 cells ml) contained 185 mug of glucose equivalents ml whereas uhm-5 culture supernatants yielded 2 mug of glucose ml. the exo derivative and the parental strain gave essentially similar growth in medium containing from 0 to 300 mum al, indicating ... | 1992 | 16348680 |
| utilization of carbon substrates, electrophoretic enzyme patterns, and symbiotic performance of plasmid-cured clover rhizobia. | plasmids in rhizobium spp. are relatively large, numerous, and difficult to cure. except for the symbiotic plasmid, little is known about their functions. the primary objective of our investigation was to obtain plasmid-cured derivatives of rhizobium leguminosarum bv. trifolii by using a direct selection system and to determine changes in the phenotype of the cured strains. three strains of rhizobia were utilized that contained three, four, and five plasmids. phenotypic effects observed after cu ... | 1992 | 16348739 |
| involvement of genes on a megaplasmid in the acid-tolerant phenotype of rhizobium leguminosarum biovar trifolii. | the acid-tolerant rhizobium leguminosarum biovar trifolii strain anu1173 exhibited several new phenotypes when cured of its symbiotic (sym) plasmid and the second largest megaplasmid. strain p22, which has lost these two plasmids, had reduced exopolysaccharide production and cell mobility on ty medium. the parent strain anu1173 was able to grow easily in laboratory media at ph 4.5, whereas the derivative strain p22 was unable to grow in media at a ph of <4.7. the intracellular ph of strain anu11 ... | 1993 | 16348908 |
| studies of the physiological and genetic basis of acid tolerance in rhizobium leguminosarum biovar trifolii. | acid-tolerant rhizobium leguminosarum biovar trifolii anu1173 was able to grow on laboratory media at a ph as low as 4.5. transposon tn5 mutagenesis was used to isolate mutants of strain anu1173, which were unable to grow on media at a ph of less than 4.8. the acid-tolerant strain anu1173 maintained a near-neutral intracellular ph when the external ph was as low as 4.5. in contrast, the acid-sensitive mutants as25 and as28 derived from anu1173 had an acidic intracellular ph when the external ph ... | 1993 | 16348956 |
| production and excretion of nod metabolites by rhizobium leguminosarum bv. trifolii are disrupted by the same environmental factors that reduce nodulation in the field. | lipooligosaccharides (nod metabolites) have been shown to be essential for the successful nodulation of legumes. in strains of rhizobium leguminosarum bv. trifolii, nod metabolites were detected predominantly within the cell and to a lesser extent in the periplasmic space and the growth medium. the production, and in particular the excretion, of nod metabolites was restricted by a range of environmental conditions which are associated with poor nodulation in the field. lowering the medium ph fro ... | 1993 | 16349071 |
| sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein banding patterns among rhizobium leguminosarum biovar phaseoli strains isolated from the mexican bean phaseolus coccineus. | several rhizobial strains were isolated from phaseolus coccineus root nodules and were determined to be rhizobium leguminosarum biovar phaseoli strains after reinfection of the same host plant. these strains were characterized by cultural procedures (growth on different carbon sources and intrinsic antibiotic resistance) and electrophoretic procedures (sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins). our results showed that these rhizobia are very similar to each oth ... | 1993 | 16349098 |
| serological and ecological characteristics of a nodule-dominant serotype from an indigenous soil population of rhizobium leguminosarum bv. trifolii. | although at least 13 antigenically distinct serotypes of rhizobium leguminosarum bv. trifolii exist in an abiqua silty clay loam soil, one serotype, as6, occupies >/=50% of the root nodules formed on field-grown subclover and between 33 and 78% of the nodules formed on five annual clover species grown in the same soil under laboratory conditions. the dominance of subclover nodules by serotype as6 was reproducible over a 4-year sampling period and throughout the entire 200- by 100-m pasture exami ... | 1994 | 16349170 |
| genotypic and phenotypic comparisons of chromosomal types within an indigenous soil population of rhizobium leguminosarum bv. trifolii. | the relative genetic similarities of 200 isolates of rhizobium leguminosarum bv. trifolii recovered from an oregon soil were determined at 13 enzyme loci by multilocus enzyme electrophoresis (mlee). these isolates represented 13 antigenically distinct serotypes recovered from nodules formed on various clover species. the mlee-derived levels of relatedness among isolates of r. leguminosarum bv. trifolii were found to be in good agreement with the levels of relatedness established by using repetit ... | 1994 | 16349171 |
| symbiotic characteristics of rhizobium leguminosarum bv. trifolii isolates which represent major and minor nodule-occupying chromosomal types of field-grown subclover (trifolium subterraneum l.). | the symbiotic effectiveness and nodulation competitiveness of rhizobium leguminosarum bv. trifolii soil isolates were evaluated under nonsoil greenhouse conditions. the isolates which we used represented both major and minor nodule-occupying chromosomal types (electrophoretic types [ets]) recovered from field-grown subclover (trifolium subterraneum l.). isolates representing four ets (ets 2, 3, 7, and 8) that were highly successful field nodule occupants fixed between 2- and 10-fold less nitroge ... | 1994 | 16349172 |
| patterns of reactivity between a panel of monoclonal antibodies and forage rhizobium strains. | a panel of 11 monoclonal antibodies raised against vegetative cells of rhizobium leguminosarum biovar trifolii or rhizobium meliloti was tested by enzyme-linked immunosorbent assay for reactivity with 47 strains of r. leguminosarum biovar trifolii and 60 strains of r. meliloti. the goal of the study was to define the degree of specificity associated with each antibody and to gain an understanding of the amount of antigenic diversity found among the strains and between the species. each antibody ... | 1994 | 16349192 |