| inactivation of a beta-glucosidase through the accumulation of a stable 2-deoxy-2-fluoro-alpha-d-glucopyranosyl-enzyme intermediate: a detailed investigation. | the inactivation of glycosidases by 2-deoxy-2-fluoroglycosides has been shown previously to occur via the accumulation of a covalent 2-deoxy-2-fluoro-alpha-d-glucopyranosyl enzyme intermediate [withers, s. g., & street, i. p. (1988) j. am. chem. soc. 110, 8551]. further characterization of this process with agrobacterium beta-glucosidase is described, and the range of glycosides engaging in this behavior is examined. inactivation is shown to be accompanied by the release of a stoichiometric "bur ... | 1992 | 1390781 |
| multiple ocs-like elements required for efficient transcription of the mannopine synthase gene of t-dna in maize protoplasts. | regulatory elements controlling transcriptional activity of the mannopine synthase 2' promoter (mas 2') were defined by analysis of deletion mutants in transient expression assays in maize protoplasts. deletion of the region between -305 and -290 containing sequence similarity to the octopine synthase (ocs) promoter element reduced activity by 67% compared to wild type activity. less than 1% of the activity remained in 5' deletions downstream of -153. inclusion of various heterologous enhancer-l ... | 1992 | 1391767 |
| a succinate transport mutant of bradyrhizobium japonicum forms ineffective nodules on soybeans. | biochemical evidence has shown that dicarboxylic acids actively support symbiotic nitrogen fixation by both fast- and slow-growing rhizobium. mutants defective in the active uptake of succinate have been previously described only in species of the fast-growing rhizobium. this article is a report on the isolation of mutants defective in dicarboxylate transport in a slow-growing species of rhizobium, bradyrhizobium japonicum. one of these presumptive dicarboxylate transport mutants, gts, was chara ... | 1992 | 1393826 |
| solution conformation and properties of the galactoglucan from rhizobium meliloti strain ye-2(s1). | the physicochemical solution properties of the galactoglucan excreted by rhizobium meliloti strain ye-2(s1) have been investigated by capillary viscometry, potentiometric titration, isothermal mixing microcalorimetry, and circular dichroism. potentiometric and chiro-optical data, as a function of the degree of ionisation, indicate the absence of a co-operative conformational transition. solution properties, as a function of ionic strength and temperature, suggest that the galactoglucan adopts a ... | 1992 | 1394308 |
| cyclic (1----2)-beta-d-glucans (cyclosophorans) produced by agrobacterium and rhizobium species. | neutral and acidic cyclic (1----2)-beta-d-glucans (cyclosophorans), obtained from culture filtrates and cells of agrobacterium and rhizobiun, are synthesised on the cell surface and then secreted. eight cyclosophorans with dp 17-24 were isolated; all of the strains of agrobacterium showed almost the same distribution pattern, whereas there were three other distribution patterns for the strains of rhizobium. | 1992 | 1394310 |
| the "pseudo double-helical" structure of the gel-forming capsular polysaccharide from rhizobium trifolii. | x-ray diffraction analysis of oriented fibers of the gel-forming, neutral, doubly branched, galactoserich capsular polysaccharide from rhizobium trifolii has been used to determine and refine the molecular structure to a final r value of 0.28. the polysaccharide forms a 2-fold single helix of pitch 20.2 a, is stabilized by a series of hydrogen bonds that involve the side chains, and has the appearance of a double helix. packing calculations reveal that the short-range ordering of these "pseudo d ... | 1992 | 1394313 |
| the lipo-oligosaccharidic symbiotic signals of rhizobium meliloti. | | 1992 | 1397613 |
| stable incorporation of genetic material into the chromosome of rhizobium meliloti 41: construction of an integrative vector system. | an integrative vector system has been developed from the site-specific recombination elements of temperate phage 16-3. the system can be used for highly efficient stable introduction of genetic material into the chromosome of the symbiotic nitrogen-fixing organism, rhizobium meliloti 41 (rm41) at the attb site. vectors carrying the phage-borne attachment site were constructed, and helper phages providing the site-specific recombination functions in trans were isolated. other possible application ... | 1992 | 1398094 |
| the nodd protein does not bind to the promoters of inducible nodulation genes in extracts of bacteroids of rhizobium leguminosarum biovar viciae. | in a previous study, we showed that in bacteroids, transcription of the inducible nod genes does not occur and expression of nodd is decreased by 65% (h. r. m. schlaman, b. horvath, e. vijgenboom, r.j.h. okker, and b. j. j. lugtenberg, j. bacteriol. 173:4277-4287, 1991). in the present study, we show, using gel retardation, that in crude extracts of bacteroids of rhizobium leguminosarum biovar (bv.) viciae, nodd protein does not bind to the nodf, nodm, and nodo box and that it binds only weakly ... | 1992 | 1400160 |
| the orit region of the agrobacterium tumefaciens ti plasmid ptic58 shares dna sequence identity with the transfer origins of rsf1010 and rk2/rp4 and with t-region borders. | ti plasmids of agrobacterium tumefaciens are conjugal elements whose transfer is induced by certain opines secreted from crown galls. on transmissible plasmids, dna transfer initiates within a cis-acting site, the origin of conjugal transfer, or orit. we have localized an orit on the a. tumefaciens plasmid ptic58 to a region containing the conjugal transfer loci trai and traii and acc, which is the locus encoding catabolism of the two conjugal opines, agrocinopines a and b. the smallest function ... | 1992 | 1400174 |
| synthesis of cyclic beta-(1,2)-glucans by rhizobium leguminosarum biovar trifolii ta-1: factors influencing excretion. | the synthesis of cyclic beta-(1,2)-glucans from udp-[14c]glucose by a crude membrane preparation and whole cells of rhizobium leguminosarum bv. trifolii ta-1 was investigated. the crude membrane system needed mn2+, atp, and nad+ for optimal activity. hardly any difference in biosynthetic activity between membrane fractions of ta-1 cells grown in the presence (200 mm) or absence of nacl was observed. whole ta-1 cells grown in the presence of nacl excreted labeled, neutral cyclic beta-(1,2)-glucan ... | 1992 | 1400186 |
| rhodobacter sphaeroides rdxa, a homolog of rhizobium meliloti fixg, encodes a membrane protein which may bind cytoplasmic [4fe-4s] clusters. | in the photosynthetic bacterium rhodobacter sphaeroides, a chromosomal gene, rdxa, which encodes a 52-kda protein, was found to be homologous to fixg, the first gene of a rhizobium meliloti nitrogen fixation operon on the psym plasmid (d. kahn, m. david, o. domergue, m.-l. daveran, j. ghai, p. r. hirsch, and j. batut, j. bacteriol. 171:929-939, 1989). the deduced amino acid sequences of rdxa and fixg are 53% identical and 73% similar; sequence analyses suggested that each has five transmembrane ... | 1992 | 1400197 |
| functional roles assigned to the periplasmic, linker, and receiver domains of the agrobacterium tumefaciens vira protein. | vira and virg activate the agrobacterium tumefaciens vir regulon in response to phenolic compounds, monosaccharides, and acidity released from plant wound sites. vira contains an amino-terminal periplasmic domain and three cytoplasmic domains: a linker, a protein kinase, and a phosphoryl receiver. we constructed internal deletions of vira that truncate one or more domains and tested the ability of the resulting proteins to mediate environmentally responsive vir gene activation in vivo. the perip ... | 1992 | 1400253 |
| altered-function mutations of the transcriptional regulatory gene virg of agrobacterium tumefaciens. | three point mutations were isolated in the agrobacterium tumefaciens virg gene by screening for vir gene expression in the absence of added phenolic inducing compounds. all three mutations were localized in the predicted amino-terminal phosphoryl receiver domain of the protein. one mutant (n54d) bypasses the requirement for vira and phenolic inducers both for transcriptional activation of all tested vir promoters and for plant tumorigenesis. this mutant also activates vir gene expression efficie ... | 1992 | 1400254 |
| role of integration host factor in stimulating transcription from the sigma 54-dependent nifh promoter. | in a wide variety of nitrogen-fixing organisms among the purple bacteria (large division of gram-negative bacteria) the nitrogen fixation (nif) operons are transcribed by an alternative holoenzyme form of rna polymerase, sigma 54-holoenzyme. transcription depends on the activator protein nifa (nitrogen fixation protein a), which catalyzes isomerization of closed complexes between this polymerase and a promoter to transcriptionally productive open complexes. nifa-mediated activation of transcript ... | 1992 | 1404379 |
| isolation of phosphorylation-deficient mutants of the rhizobium meliloti two-component regulatory protein, fixj. | rhizobium meliloti fixl and fixj are members of a symbiotically essential two-component system that regulates nitrogen-fixation genes in response to environmental oxygen concentrations. fixl is a membrane protein that is thought to relay information about oxygen availability to fixj via a phosphotransfer mechanism. fixj increases expression of the nifa and fixk genes by activating transcription of the nifa and fixk promoters (p-nifa and p-fixk, respectively). in this study, we examined the relat ... | 1992 | 1406247 |
| isolation and characterization of an ndvb locus from rhizobium fredii. | a gene (ndvb) in rhizobium meliloti that is essential for nodule development in medicago sativa (alfalfa), specifies synthesis of a large membrane protein. this protein appears to be an intermediate in beta-1,2-glucan synthesis by the microsymbiont. southern hybridization analysis showed strong homology between an ndvb (chvb) probe and genomic dna of r. fredii but not from bradyrhizobium japonicum. a cosmid clone containing the putative ndvb locus was isolated from a rhizobium fredii gene librar ... | 1992 | 1406255 |
| ammonia regulation of the rhizobium meliloti nitrogenase structural and regulatory genes under free-living conditions: involvement of the fixl gene product? | the expression under microaerobic conditions of the rhizobium meliloti nifa and consequently the nifhdk genes was found to be negatively regulated by ammonia and nitrate. assimilation of the ammonia to glutamate and glutamine is not required for this regulation to occur. this indicates that ammonia itself, and not a product of its metabolism, may be regulating nif expression. unlike the situation in klebsiella pneumoniae, ntrc is apparently not involved in mediating the ammonia effect on nifa ex ... | 1992 | 1406587 |
| a defined amino acid exchange close to the putative nucleotide binding site is responsible for an oxygen-tolerant variant of the rhizobium meliloti nifa protein. | in rhizobium meliloti the nifa protein plays a central role in the expression of genes involved in nitrogen fixation. the r. meliloti nifa protein has been found to be oxygen sensitive and therefore acts as a transcriptional activator only under microaerobic conditions. in order to generate oxygen-tolerant variants of the nifa protein a plasmid carrying the r. meliloti nifa gene was mutagenized in vitro with hydroxylamine. about 70 mutated nifa genes were isolated which mediated up to 12-fold in ... | 1992 | 1406589 |
| [pea (pisum sativum) genes, participating in symbiosis with nitrogen-fixing bacteria. iii. study of the structure of the enod12 early nodulin gene for various types of peas using the polymerase chain reaction (pcr)]. | we have determined the length of early noduline gene enod12 in various varieties and lines of pea (pisum sativum) using the polymerase chain reaction (pcr). it was demonstrated that promoter regions of enod12a and enod12b genes in line 2150 (afghanistan) are longer than these in variety "feltham first". the disparity is 14 bp. when studying these genes in 7 different lines and varieties of pea it was found that enod12a gene is more variable in size than the enod12b gene. we showed the possibilit ... | 1992 | 1406614 |
| cellulose-binding domains: potential for purification of complex proteins. | the endoglucanase cena and the exoglucanase cex from cellulomonas fimi each contain a discrete cellulose-binding domain (cbd), at the amino-terminus or carboxyl-terminus respectively. the gene fragment encoding the cbd can be fused to the gene of a protein of interest. using this approach hybrid proteins can be engineered which bind reversibly to cellulose and exhibit the biological activity of the protein partner. alkaline phosphatase (phoa) from escherichia coli, and a beta-glucosidase (abg) f ... | 1992 | 1409557 |
| agroinfection as an alternative to insects for infecting plants with beet western yellows luteovirus. | beet western yellows luteovirus, like other luteoviruses, cannot be transmitted to host plants by mechanical inoculation but requires an aphid vector, a feature that has heretofore presented a serious obstacle to the study of such viruses. in this paper we describe use of agroinfection to infect hosts with beet western yellows virus without recourse to aphids. agroinfection is a procedure for introducing a plant virus into a host via agrobacterium tumefaciens harboring a ti plasmid, which can ef ... | 1992 | 1409615 |
| physical map of the vitopine ti plasmid ptis4. | within the agrobacterium vitis group the vitopine strains represent a special subclass. vitopine bacteria carry ti plasmids with little or no homology with the well-characterized t-dnas of agrobacterium tumefaciens or agrobacterium rhizogenes. the 262-kb ti plasmid of the vitopine strain s4 was cloned and mapped. homology studies with the octopine ti plasmid ptiach5, the nopaline ti plasmid ptic58, and the agropine/mannopine ri plasmid prihri identified several regions of homology. the origin of ... | 1992 | 1409971 |
| biosynthesis and distribution of n-carboxyalkyl amino acids (opines) in bacteria. | | 1992 | 1410788 |
| microbial metabolism of quinoline and related compounds. xv. quinoline-4-carboxylic acid oxidoreductase from agrobacterium spec.1b: a molybdenum-containing enzyme. | the quinoline-4-carboxylic acid oxidoreductase from agrobacterium spec.1b was purified 84-fold to apparent homogeneity with 15% recovery, using ammonium sulphate precipitation, heat precipitation, hydrophobic interaction, anion exchange- and gel chromatography. the molecular mass of the native enzyme was estimated to be 320 kda by gel filtration. sds-polyacrylamide gel electrophoresis of the enzyme revealed three protein bands corresponding to 85, 35 and 21 kda. per molecule the enzyme contains ... | 1992 | 1418685 |
| characterization of genes expressed in mesophyll protoplasts of nicotiana sylvestris before the re-initiation of the dna replicational activity. | to decipher the early events preceding the re-entry of somatic cells into the cell cycle, we constructed a cdna library from 6-h-old protoplasts of nicotiana sylvestris. we characterized three mrnas, via their cdnas, that accumulate at very high levels 6 h after the beginning of the culture. two of them could be identified by comparison of the deduced amino acid sequence to databanks. 6p10 is a novel type i trypsin inhibitor, which has the peculiarity of being devoid of the pro-sequence peptide ... | 1992 | 1419848 |
| expression of desiccation-related proteins from the resurrection plant craterostigma plantagineum in transgenic tobacco. | three cdnas encoding desiccation-induced proteins from the resurrection plant craterostigma plantagineum were each ligated to a triplicated camv 35s promoter and a nopaline synthase 3'-flanking region in an agrobacterium vector and introduced into tobacco. transgenic plants expressed the encoded craterostigma proteins at high levels. this did not lead to changes in the phenotype, in the growth habit or in basic photosynthetic parameters. in tobacco, one protein was targeted to the chloroplast st ... | 1992 | 1421157 |
| effects of flavonoids released naturally from bean (phaseolus vulgaris) on nodd-regulated gene transcription in rhizobium leguminosarum bv. phaseoli. | nine flavonoid aglycones released from black bean (phaseolus vulgaris 'pi165426cs') seeds and roots induced nodc::lacz transcription in rhizobium leguminosarum bv. phaseoli strains containing extra cloned copies of the regulatory genes nodd1, nodd2, or nodd3 from that biovar. individual flavonoids generally induced highest levels of nodc::lacz transcription (imax) with extra copies of nodd2, and the concentration required for half-maximum induction (i50) was lowest with extra copies of nodd1 gen ... | 1992 | 1421508 |
| structural and functional analysis of two different nodd genes in bradyrhizobium japonicum usda110. | bradyrhizobium japonicum has two closely linked homologs of the nodulation regulatory gene, nodd; these homologs are located upstream of and in divergent orientation to the nodyabcsuij gene cluster. we report here the nucleotide sequence and mutational analyses of both nodd copies. the predicted nodd1 and nodd2 proteins shared 62% identical amino acid residues at corresponding positions and exhibited different degrees of homology with nodd proteins of other bradyrhizobium, azorhizobium, and rhiz ... | 1992 | 1421512 |
| a chimaeric antibiotic resistance gene as a selectable marker for plant cell transformation. 1983. | | 1992 | 1422041 |
| the agrobacterium tumefaciens ti plasmid as a host vector system for introducing foreign dna in plant cells. 1980. | | 1992 | 1422043 |
| expression of chimaeric genes transferred into plant cells using a ti-plasmid-derived vector. 1983. | | 1992 | 1422044 |
| expression of ti plasmid genes in monocotyledonous plants infected with agrobacterium tumefaciens. 1984. | | 1992 | 1422045 |
| molecular signals in the interactions between plants and microbes. | the field of plant-microbe interactions has witnessed several recent breakthroughs, such as the molecular details of vir gene induction, identification of nod factors, and the cloning and characterization of avr genes. other breakthroughs, such as the cloning and characterization of r genes, appear imminent. parallels to mammalian systems are emerging in the world of plant-microbe interactions, for example, ion channels formed by rhizobium proteins, similarities of hrp genes to pathogenicity gen ... | 1992 | 1423587 |
| eight bacterial proteins, including udp-n-acetylglucosamine acyltransferase (lpxa) and three other transferases of escherichia coli, consist of a six-residue periodicity theme. | only a few prokaryotic or eukaryotic enzymes are known to consist of a tandem-repeat structure. this report describes a common hexapeptide-repeat theme in four escherichia coli transferases and in four less-characterized bacterial proteins. the proteins are the ssc protein of salmonella typhimurium (25), udp-n-acetylglucosamine acyltransferase of e. coli (24), the hypothetical proteins tms of bacillus subtilis (23) and yglm of e. coli (22), succinyldiaminopimelate aminotransferase of e. coli (14 ... | 1992 | 1427014 |
| molecular analysis of the reca gene of agrobacterium tumefaciens c58. | the complete nucleotide sequence of the agrobacterium tumefaciens reca gene was determined. a comparison of the translated open reading frame of the gene with other known reca sequences revealed significant sequence conservation. however, unlike its escherichia coli equivalent, a. tumefaciens reca lacks the upstream 'sos box', suggesting a different mechanism of regulation for this gene. | 1992 | 1427086 |
| a region of the broad-host-range plasmid rk2 causes stable in planta inheritance of plasmids in rhizobium meliloti cells isolated from alfalfa root nodules. | we demonstrate for the first time that the broad-host-range stabilization loci from plasmid rk2 cause total retention of plasmids in cells of rhizobium meliloti during symbiosis with alfalfa. two derivatives of plasmid rk2, prk290 and a 7.3-kb mini-rk2 plasmid, were stabilized in r. meliloti cells isolated from root nodules by the insertion of a 3.2-kb dna fragment or a smaller 0.8-kb dna fragment derived from the rk2 stabilization region. | 1992 | 1429472 |
| modular structure of the fixl protein of rhizobium meliloti. | fixl protein of rhizobium meliloti is a haemo-protein kinase which activates the transcription of nifa and fixk genes via the transcriptional activator protein fixj under microaerobic conditions. fixl and fixj proteins belong to the family of two-component regulatory systems for which primary sequence data predicts a modular structure. we showed, using escherichia coli as heterologous host, that fixl indeed has a modular structure. the amino-terminal hydrophobic domain is dispensable for the oxy ... | 1992 | 1435730 |
| exopolysaccharides of rhizobium leguminosarum biovar trifolii harbouring cloned exo region. | rhizobium leguminosarum bv. trifolii produces an acidic exopolysaccharide (eps) which plays an important role in the development of nitrogen-fixing nodules. tn5 mutant of r. trifolii 93 defective in eps production (exo-) forms ineffective (fix-) nodules on red clover. this exo- mutation is complemented by the parf1368 and parf25 cosmids isolated from gene bank of rhizobium trifolii ta1, but the complementation is not correlated with restoration of fix+ phenotype. furthermore, these cosmids intro ... | 1992 | 1441845 |
| inhibition of tumor induction in tobacco by agrobacterium tumefaciens and nodulation induced by rhizobium meliloti in the presence of phenothiazines and structurally related compounds. | plasmids of agrobacterium tumefaciens and rhizobium meliloti carrying kanamycin resistance genes were eliminated from 1.4 to 0.2% of the growing bacterial cultures by promethazine and imipramine. as a result of plasmid elimination, the a. tumefaciens plasmidless isolate was not able to induce crown gall tumor on tobacco plants. the plasmidless r. meliloti strain failed to induce nodule formation on alfalfa plants. the efficiency of nodulation was decreased when the bacteria were grown in the pre ... | 1992 | 1444234 |
| exopolysaccharides in plant-bacterial interactions. | rhizobial plant symbionts and bacterial plant pathogens produce exopolysaccharides that often play essential roles in the plant interaction. many of these exopolysaccharides are acidic heteropolysaccharides that have repeating subunit structures with carbohydrate and noncarbohydrate substituents, while others are homopolysaccharides such as alginate, levan, cellulose, and glucan. while the homopolysaccharides are synthesized by mechanisms that vary with the particular polysaccharide, the heterop ... | 1992 | 1444258 |
| genetics of competition for nodulation of legumes. | an economically important problem in microbial ecology concerns the efficacy of rhizobial inoculants for the formation of nitrogen-fixing root nodules on legume crop plants such as soybean, alfalfa, and clover. some strains of rhizobia can increase symbiotic nitrogen fixation under controlled conditions. however, attempts to improve nitrogen fixation under agricultural conditions with such strains often fail, usually as a result of the presence of indigenous rhizobia limiting nodulation by the i ... | 1992 | 1444262 |
| signaling and host range variation in nodulation. | rhizobium, bradyrhizobium, and azorhizobium strains, collectively referred to as rhizobia, elicit on their leguminous hosts, in a specific manner, the formation of nodules in which they fix nitrogen. rhizobial nod genes, which determine host specificity, infection, and nodulation, are involved in the exchange of low molecular weight signal molecules between the plant and the bacteria as follows. transcription of the nod operons is under the control of nodd regulatory proteins, which are specific ... | 1992 | 1444265 |
| detection and enumeration of bacteria in soil by direct dna extraction and polymerase chain reaction. | in order to develop a rapid and specific detection test for bacteria in soil, we improved a method based on the polymerase chain reaction (pcr). each step of the protocol, including direct lysis of cells, dna purification, and pcr amplification, was optimized. to increase the efficiency of lysis, a step particularly critical for some microorganisms which resist classical techniques, we used small soil samples (100 mg) and various lytic treatments, including sonication, microwave heating, and the ... | 1992 | 1444380 |
| heat and cold shock protein synthesis in arctic and temperate strains of rhizobia. | we compared heat shock proteins (hsps) and cold shock proteins (csps) produced by different species of rhizobium having different growth temperature ranges. several hsps and csps were induced when cells of three arctic (psychrotrophic) and three temperate (mesophilic) strains of rhizobia were shifted from their optimal growth temperatures (arctic, 25 degrees c; temperate, 30 degrees c) to shock temperatures outside their growth temperature ranges. at heat shock temperatures, three major hsps of ... | 1992 | 1444396 |
| rhizobium meliloti elicits transient expression of the early nodulin gene enod12 in the differentiating root epidermis of transgenic alfalfa. | to study the molecular responses of the host legume during early stages of the symbiotic interaction with rhizobium, we have cloned and characterized the infection-related early nodulin gene mtenod12 from medicago truncatula. in situ hybridization experiments have shown that, within the indeterminate medicago nodule, transcription of the mtenod12 gene begins in cell layers of meristematic origin that lie ahead of the infection zone, suggesting that these cells are undergoing preparation for bact ... | 1992 | 1446169 |
| structural characterization of a novel diglycosyl diacylglyceride glycolipid from rhizobium trifolii anu843. | a novel glycolipid was isolated by chloroform-methanol extraction of rhizobium trifolii anu843 cells. compositional analysis, methylation studies, 1h nmr and spectroscopies led to the identification of a diglycosyl diacylglyceride: 1,2-di-o-acyl-3-o-[alpha-d-glucopyranosyl-(1----3)-o-alpha-d- mannopyranosyl]glycerol. iso-hexadecanoic and anteiso-heptadecanoic acids were the predominant fatty acids esterifying the glyceryl moiety, but a microheterogeneity in fatty acid composition was found, resu ... | 1992 | 1446306 |
| rhizobium nodm and nodn genes are common nod genes: nodm encodes functions for efficiency of nod signal production and bacteroid maturation. | earlier, we showed that rhizobium meliloti nodm codes for glucosamine synthase and that nodm and nodn mutants produce strongly reduced root hair deformation activity and display delayed nodulation of medicago sativa (baev et al., mol. gen. genet. 228:113-124, 1991). here, we demonstrate that nodm and nodn genes from rhizobium leguminosarum biovar viciae restore the root hair deformation activity of exudates of the corresponding r. meliloti mutant strains. partial restoration of the nodulation ph ... | 1992 | 1447128 |
| selected biological activities of saraines. | 1. the mediterranean sponge reniera sarai, pulitzeri-finali, 1969 (demospongiae: haploscleridae: renieridae) possesses in large amounts a series of unprecedented polycyclic alkaloids, saraines 1-3 and saraines a-c. 2. the structural peculiarities of saraines, their chemical-physical characteristics, along with their relevant abundance in the sponge, prompted a study aimed at investigating their biological properties. 3. saraines were assayed for their cytotoxic, antibacterial, insecticidal and p ... | 1992 | 1451440 |
| the rhizobium meliloti pmi gene encodes a new type of phosphomannose isomerase. | interspecific complementation of a xanthomonas campestris pv. campestris phosphomannose isomerase (pmi) mutant was used to isolate a cosmid from a genomic library of rhizobium meliloti 2011 carrying the pmi gene of this strain. subcloning experiments localized the coding region to a 2.0-kb sali-clai fragment. nucleotide sequence analysis of this fragment indicated the presence of two open reading frames (orfs), coding for 18- and 43-kda polypeptides. the analysis of the gene function by gene dis ... | 1992 | 1452036 |
| molecular and symbiotic characterization of exopolysaccharide-deficient mutants of rhizobium tropici strain ciat899. | we studied the symbiotic behaviour of 20 independent tn5 mutants of rhizobium tropici strain ciat899 that were deficient in exopolysaccharide (eps) production. the mutants produced non-mucoid colonies, were motile, grew in broth cultures at rates similar to those of the parent, and produced significantly less eps than did ciat899 in broth culture. a genomic library of strain ciat899, constructed in pla2917, was mobilized into all of the mutants, and cosmids that restored eps production were iden ... | 1992 | 1453954 |
| activation of a plant gene by t-dna tagging: auxin-independent growth in vitro. | a transferred dna (t-dna) tagging vector with the potential to produce dominant mutations was used with cocultured agrobacterium tumefaciens and protoplasts to tag genes involved in the action of the plant growth substance auxin. transgenic calli were selected for their ability to grow in the absence of auxin in the culture media. from one experiment, 12 calli that displayed this phenotype were recovered, of which 11 were able to regenerate into plants. in one plant studied in detail, protoplast ... | 1992 | 1455228 |
| effects of 2,4-dichlorophenoxyacetic acid on rhizobium sp. membrane fluidity. | the effects of 1 mm 2,4-dichlorophenoxyacetic acid on rhizobium sp. in pure culture was studied. in a previous work it was demonstrated that this herbicide produces an alteration on the saturated to unsaturated phospholipid acyl chains ratio. in the present paper, it was found that this alteration produces a modification on the membrane fluidity in bacteria that had achieved the stationary phase. the same results were obtained when determinations were done in liposomes from sonicated lipids of t ... | 1992 | 1456775 |
| agrobacterium tumefaciens peritonitis mimicking tuberculosis. | agrobacterium species have been previously implicated in the development of clinical disease. we report what we believe to be the first case of ascites caused by agrobacterium tumefaciens in a cirrhotic patient. since the correct diagnosis was made only after laparoscopy-guided collection of specimens from two different tissues, we suggest that agrobacterium may be an underdiagnosed pathogen in clinical situations in which tuberculosis is considered to be the cause of high-protein ascites. | 1992 | 1457664 |
| rhizobium meliloti genes involved in sulfate activation: the two copies of nodpq and a new locus, saa. | the nitrogen-fixing symbiont rhizobium meliloti establishes nodules on leguminous host plants. nodulation (nod) genes used for this process are located in a cluster on the psym-a megaplasmid of r. meliloti. these genes include nodp and nodq (here termed nodpq), which encode atp sulfurylase and aps kinase, enzymes that catalyze the conversion of atp and so(4)2- into the activated sulfate form 3'-phosphoadenosine 5'-phosphosulfate (paps), an intermediate in cysteine synthesis. in rhizobium, paps i ... | 1992 | 1459442 |
| introduction of a segment of rhizobium meliloti megaplasmid in escherichia coli slows down its growth in minimal medium. | | 1992 | 1459590 |
| structure and expression of a cyanobacterial ilvc gene encoding acetohydroxyacid isomeroreductase. | acetohydroxyacid isomeroreductase (ahair) is the shared second enzyme in the biosynthetic pathways leading to isoleucine and valine. ahair is encoded by the ilvc gene in bacteria. a 1,544-bp fragment of genomic dna containing the ilvc gene was cloned from the cyanobacterium synechocystis sp. strain pcc 6803, and the complete nucleotide sequence was determined. the identity of the gene was established by comparison of the nucleotide and derived peptide sequences with those of other ilvc genes. th ... | 1992 | 1459938 |
| mechanism of action of cyclic beta-1,2-glucan synthetase from agrobacterium tumefaciens: competition between cyclization and elongation reactions. | we have examined some aspects of the mechanism of cyclic beta-1,2-glucan synthetase from agrobacterium tumefaciens (235-kda protein, gene product of the chvb region). the enzyme produces cyclic beta-1,2-glucans containing 17 to 23 glucose residues from udp-glucose. in the presence of added cyclic beta-1,2-glucans (> 0.5 mg/ml) (containing 17 to 23 glucose residues), the enzyme instead synthesizes larger cyclic beta-1,2-glucans containing 24 to 30 glucose residues. this is achieved by de novo syn ... | 1992 | 1459942 |
| deletion derivatives of pagk84 and their use in the analysis of agrobacterium plasmid functions. | the 47.7-kb plasmid pagk84, present in agrobacterium radiobacter strain k84, confers production of a novel, highly specific, antiagrobacterial antibiotic called agrocin 84. strain k84 is used commercially to biocontrol crown gall caused by agrocin 84-susceptible strains of agrobacterium tumefaciens. efficient biocontrol is dependent upon production of agrocin 84 by strain k84. starting with a derivative of pagk84 containing a tn5 insertion, a series of deletion derivatives of the plasmid were is ... | 1992 | 1461939 |
| translation controls the expression level of a chimaeric reporter gene. | transcriptional and translational fusions between the reading frame of the beta-d-glucuronidase gene (gusa) and the 2' as well as the 1' promoter of mannopine synthase (mas), a tr locus of agrobacterium tumefaciens, were made. the expression of these constructs was studied in the transgenic f1 offspring of independent tobacco transformants at the protein level by assaying for gus activity and western blot analysis of the gus protein and at the steady-state mrna level. in leaves, stems and roots ... | 1992 | 1463829 |
| t-dna insertional mutagenesis in arabidopsis. | | 1992 | 1463832 |
| rhizobial lipo-oligosaccharides: answers and questions. | rhizobium bacteria produce certain lipo-oligosaccharides (modified chitin oligomers) after induction of nodulation (nod) gene transcription by the host plant. the function of the rhizobial nod genes in the biosynthesis of these lipo-oligosaccharides, focusing on their host specific aspects, is discussed. the lipo-oligosaccharides can elicit various responses in the host plants, like the formation of pre-infection threads and nodule meristems. speculating on their function in plant morphogenesis ... | 1992 | 1463833 |
| factors influencing agrobacterium-mediated transient expression of gusa in rice. | transient expression of gus in rice (oryza sativa l.) mediated by agrobacterium tumefaciens was characterized using binary vectors containing gusa genes that express minimal (pkiwi105 and pcnl1) or no (p35s-gus-int and pcnl56) gus activity in bacteria. four-day old seedlings obtained from seeds or immature embryos of rice were cut into shoot, root, and seed remnants and inoculated with various strains of a. tumefaciens. transient gus expression events were quantitated histochemically by determin ... | 1992 | 1463839 |
| mutational analysis of pea lectin. substitution of asn125 for asp in the monosaccharide-binding site eliminates mannose/glucose-binding activity. | as part of a strategy to determine the precise role of pea (pisum sativum) lectin, psl, in nodulation of pea by rhizobium leguminosarum, mutations were introduced into the genetic determinant for pea lectin by site-directed mutagenesis using pcr. introduction of a specific mutation, n125d, into a central area of the sugar-binding site resulted in complete loss of binding of psl to dextran as well as of mannose/glucose-sensitive haemagglutination activity. as a control, substitution of an adjacen ... | 1992 | 1463840 |
| multiple copies of virg enhance the transient transformation of celery, carrot and rice tissues by agrobacterium tumefaciens. | in an effort to improve the t-dna-mediated transformation frequency of economically important crops, we investigated the possible enhancement effect of multiple copies of virg genes contained in agrobacterium tumefaciens strains upon the transient transformation of celery, carrot and rice tissues. four days after a. tumefaciens infection, we performed histochemical beta-glucuronidase (gus) assays to determine the frequency of transient transformation of calli from celery and carrot, and explants ... | 1992 | 1463842 |
| nucleosomal structure and histone h1 subfractional composition of pea (pisum sativum) root nodules, radicles and callus chromatin. | higher-order packaging of dna in chromatin structures could be an essential step in the complex chain of events leading to activation/repression of eukaryotic gene expression. with the goal to investigate this aspect of transcriptional regulation of plant genes involved in symbiotic interactions between legumes and rhizobia we analyze here the molecular parameters of chromatin structure in functioning root nodules, callus and radicles of pea. morphological intactness and the typical nucleosomal ... | 1992 | 1463843 |
| new plant binary vectors with selectable markers located proximal to the left t-dna border. | five new binary vectors have been constructed which have the following features: (1) different plant selectable markers including neomycin phosphotransferase (nptii), hygromycin phosphotransferase (hpt), dihydrofolate reductase (dhfr), phosphinothricin acetyl transferase (bar), and bleomycin resistance (ble); (2) selectable markers are located near the t-dna left border and; (3) selectable marker and beta-glucuronidase (uida) reporter genes are divergently organized for efficient expression, and ... | 1992 | 1463855 |
| a versatile binary vector system with a t-dna organisational structure conducive to efficient integration of cloned dna into the plant genome. | a versatile gene expression cartridge and binary vector system was constructed for use in agrobacterium-mediated plant transformation. the expression cartridge of the primary cloning vector, part7, comprises of cauliflower mosaic virus cabb b-ji isolate 35s promoter, a multiple cloning site and the transcriptional termination region of the octopine synthase gene. the entire cartridge can be removed from part7 as a not i fragment and introduced directly into the binary vector, part27, recombinant ... | 1992 | 1463857 |
| organization and functional analysis of three t-dnas from the vitopine ti plasmid ptis4. | the vitopine ti plasmid ptis4 of agrobacterium vitis has an unusual t-dna organization. the ptis4 oncogenes, localized by screening selected ptis4 clones for growth-inducing activity, are localized on three t-dnas, whereas in all other characterized ti plasmids one or two t-dnas are found. the nucleotide sequences and predicted amino acid sequences of the ptis4 oncogenes set them apart from the corresponding genes from other ti or ri plasmids. the oncogenes induce the same type of reaction on va ... | 1992 | 1465104 |
| effect of t-dna configuration on transgene expression. | t-dna vectors were constructed which carry a beta-glucuronidase (gusa) gene fused to the promoter of the nopaline synthase (nos) gene and the 3' end of the octopine synthase (ocs) gene. this reporter gene was cloned at different locations and orientations towards the right t-dna border. for each construct, between 30 and 60 stably transformed calli were analysed for beta-glucuronidase activity. depending on the t-dna configuration, distinct populations of gusa-expressing calli were obtained. pla ... | 1992 | 1465111 |
| metabolic engineering of medicinal plants: transgenic atropa belladonna with an improved alkaloid composition. | the tropane alkaloid scopolamine is a medicinally important anticholinergic drug present in several solanaceous plants. hyoscyamine 6 beta-hydroxylase (ec 1.14.11.11) catalyzes the oxidative reactions in the biosynthetic pathway leading from hyoscyamine to scopolamine. we introduced the hydroxylase gene from hyoscyamus niger under the control of the cauliflower mosaic virus 35s promoter into hyoscyamine-rich atropa belladonna by the use of an agrobacterium-mediated transformation system. a trans ... | 1992 | 1465402 |
| a nuclear localization signal and the c-terminal omega sequence in the agrobacterium tumefaciens vird2 endonuclease are important for tumor formation. | the t-dna portion of the agrobacterium tumefaciens tumor-inducing (ti) plasmid integrates into plant nuclear dna. direct repeats define the t-dna ends; transfer begins when the vird2 endonuclease produces a site-specific nick in the right-hand border repeat and attaches to the 5' end of the nicked strand. subsequent events generate linear single-stranded vird2-bound dna molecules that include the entire t-dna (t-strands). vird2 protein contains a nuclear localization signal (nls) near the c term ... | 1992 | 1465407 |
| arabidopsis and nicotiana anthocyanin production activated by maize regulators r and c1. | anthocyanin pathway-specific transcriptional activators r and c1 from the monocot maize were expressed in two dicots, arabidopsis thaliana and nicotiana tabacum. expression of r caused augmented anthocyanin pigmentation in both plant species and augmented trichome (hair) production in arabidopsis. alone, c1 had no effect. hybrid transgenic arabidopsis expressing both c1 and r produced anthocyanins in root, petal, and stamen tissues that normally never express anthrocyanins. when r was expressed ... | 1992 | 1465611 |
| two g-box-related sequences confer different expression patterns in transgenic tobacco. | we have analyzed the expression patterns conferred by two g-box-related motifs, a perfect palindromic sequence (pa, 5'-gccacgtggc-3') and motif i (iwt, 5'-gtacgtggcg-3'), in transgenic tobacco plants. a mutant version of motif i, imu, was used as a negative control. pa is present in the promoters of several different genes, whereas iwt is a conserved sequence found in abscisic acid-inducible promoters. previously we have demonstrated that pa and iwt, but not imu, can bind to the tobacco transcri ... | 1992 | 1467649 |
| nucleotide sequence and organization of an h2-uptake gene cluster from rhizobium leguminosarum bv. viciae containing a rubredoxin-like gene and four additional open reading frames. | the nucleotide sequence of a 3.2 kb region following the hydrogenase structural operon (hupslcdef) in the h2-uptake gene cluster from rhizobium leguminosarum by viciae strain 128c53 has been determined. five closely linked genes encoding products of 16.3 (hupg), 30.5 (huph), 8.0 (hupi), 18.4 (hupj) and 38.7 (hupk) kda were identified 166 bp downstream from hupf. transposon insertions into hupg, huph, hupj and hupk suppress the h2-oxidizing capability of the wild-type strain. the amino acid seque ... | 1992 | 1469733 |
| sequential expression of two late nodulin genes in the infected cells of alfalfa root nodules. | the nms-22 and leghemoglobin (lb) genes are expressed exclusively in the infected cells of alfalfa root nodules. expression of these two late nodulin genes originated at distinct cellular boundaries within the symbiotic region of the nodule. the nms-22 gene was expressed in all infected cells, including those just adjacent to the meristematic region. lb gene expression was induced in older infected cells and was most prominent in the mature region of the nodule. despite this temporal separation ... | 1992 | 1472719 |
| homology of rhizobium meliloti nodc to polysaccharide polymerizing enzymes. | rhizobium bacteria form nitrogen-fixing nodules on legume roots. as part of the nodulation process, they secrete nod factors that are beta-1,4-linked oligomers of n-acetylglucosamine. these factors depend on nodulation (nod) genes, but most aspects of factor synthesis are not yet known. we show here that one gene, nodc, shows striking similarity to genes encoding proteins known to be involved in polysaccharide synthesis in yeast and bacteria, specifically chitin and cellulose synthases, as well ... | 1992 | 1472720 |
| the rhizobium, bradyrhizobium, and azorhizobium nodc proteins are homologous to yeast chitin synthases. | the nodabc genes of rhizobia are essential for the synthesis of lipo-oligosaccharidic (n-acylated chitin oligomers) nodulation signals. nodc gene products from rhizobium, bradyrhizobium, and azorhizobium exhibit extensive homology with chitin synthases, suggesting that the nodc proteins are involved in the synthesis of the chitin oligomer backbone by catalyzing the beta-1,4-linkage between n-acetyl-d-glucosamine residues. | 1992 | 1472721 |
| a new method for the analysis of amide-linked hydroxy fatty acids in lipid-as from gram-negative bacteria. | lipid-a represents the ubiquitous, covalently bound hydrophobic component of bacterial lipopolysaccharides (endotoxins). lipid-as isolated and characterized from rhizobial species have large variations in their backbone sugars, as well as in their hydroxy fatty acid substituents. the sugar backbones consist of either glucosamine and galacturonic acid or glucosamine and 2,3-diaminoglucose. the published procedures for characterizing amide-linked fatty acids do not release all these fatty acids, h ... | 1992 | 1472760 |
| tandem dctd-binding sites of the rhizobium meliloti dcta upstream activating sequence are essential for optimal function despite a 50- to 100-fold difference in affinity for dctd. | the rhizobium meliloti genes dctb and dctd positively regulate the expression of dcta, which encodes a c4-dicarboxylate transport protein. here we characterize an element (uas) located upstream of dcta that has tandem binding sites for the dctd gene product (dctd). at relatively low concentrations of active dctd, the element activated dcta transcription, but at relatively high concentrations of dctd it was inhibitory. the uas failed to function when placed further upstream of dcta. both dctd-bin ... | 1992 | 1474893 |
| broad-host-range rhizobium species strain ngr234 secretes a family of carbamoylated, and fucosylated, nodulation signals that are o-acetylated or sulphated. | rhizobium species strain ngr234 is the most promiscuous known rhizobium. in addition to the non-legume parasponia andersonii, it nodulates at least 70 genera of legumes. here we show that the nodulation genes of this bacterium determine the production of a large family of nod-factors which are n-acylated chitin pentamers carrying a variety of substituents. the terminal non-reducing glucosamine is n-acylated with vaccenic or palmitic acids, is n-methylated, and carries varying numbers of carbamoy ... | 1992 | 1474899 |
| evaluation of acidic heteropolysaccharide structures in rhizobium leguminosarum biovars altered in nodulation genes and host range. | 1h-nmr spectroscopy showed that the extracellular heterpolysaccharides (eps) from derivatives of rhizobium leguminosarum bv. trifolii anu843 altered in psym nod composition or function (transposon insertions, deletion of psym, induction by flavone, and introduction of cloned psym nod regions from anu843 and r. l. bv. viciae 248 on recombinant plasmids into the psym-cured background of anu843) differed only in 3-hydroxybutyrate stoichiometry per octaglycosyl unit. this change in eps was likely to ... | 1992 | 1477403 |
| characterisation of rhizobium isolates by amplification of dna polymorphisms using random primers. | the use of single random primers, selected in the absence of target sequence information, has been shown to be effective in producing dna amplifications that provide fingerprints which are unique to individual organisms. dna amplification by random priming was applied to the dna from isolates of rhizobium leguminosarum biovar trifolii. amplification products were produced using a number of primers, and the resulting fingerprints allowed strain differentiation. however, the effectiveness of prime ... | 1992 | 1477784 |
| organization of non-vertebrate globin genes. | the organization of non-vertebrate globin genes exhibits substantially more variability than the three-exon, two-intron structure of the vertebrate globin genes. (1) the structures of genes of the single-domain globin chains of the annelid lumbricus and the mollusc anadara, and the globin gene coding for the two-domain chains of the clam barbatia, are similar to the vertebrate plan. (2) genes for single-domain chains exist in bacteria and protozoa. although the globin gene is highly expressed in ... | 1992 | 1478060 |
| molecular mechanisms of attachment of rhizobium bacteria to plant roots. | attachment of bacteria to plant cells is one of the earliest steps in many plant-bacterium interactions. this review covers the current knowledge on one of the best-studied examples of bacterium-plant attachment, namely the molecular mechanism by which rhizobium bacteria adhere to plant roots. despite differences in several studies with regard to growth conditions of bacteria and plants and to methods used for measuring attachment, an overall consensus can be drawn from the available data. rhizo ... | 1992 | 1479881 |
| the bar gene as selectable and screenable marker in plant engineering. | | 1992 | 1479912 |
| thaumatin ii: a sweet marker gene for use in plants. | | 1992 | 1479913 |
| morphology of phages of a general salmonella typing set. | the typing set includes 27 tailed phages belonging to three families, the myoviridae (contractile tails, 4 phages), siphoviridae (long, non-contractile tails, 21 phages) and podoviridae (short tails, 2 phages). heads are isometric or elongated. the phages fall into 10 morphological groups, seven of which correspond to known enterobacterial phage species (jersey, n4, t5, t7, zg/3a, chi, 16-19) and one to a rhizobium phage species (cm1). t5-type and t7-type phages are for the first time reported i ... | 1992 | 1480822 |
| differential expression of nods accounts for the varied abilities of rhizobium fredii usda257 and rhizobium sp. strain ngr234 to nodulate leucaena spp. | transfer of a cosmid containing nodsu from rhizobium sp. ngr234 to rhizobium fredii usda257 expands the host range for nodulation to include the perennial tropical legumes, leucaena leucocephala and leucaena diversifolia. complementation experiments with a series of subclones established that nods and its associated nod-box promoter from ngr234 are sufficient to confer this extended host-range phenotype to l. leucocephala. strain usda257 contains its own copy of nodsu, including upstream nod-box ... | 1992 | 1484488 |
| the rhizobium leguminosarum fnrn protein is functionally similar to escherichia coli fnr and promotes heterologous oxygen-dependent activation of transcription. | an open reading frame from rhizobium leguminosarum bv. viciae strain vf39, previously identified and found to be similar to escherichia coli fnr and rhizobium meliloti fixk (orf240, thereafter called fnrn), was further analysed. analysis of the expression of an fnrn-lacz transcriptional fusion revealed that fnrn is preferentially expressed under oxygen limitation. using r. meliloti fixn-lacz fusions it was shown that the fnrn gene product only mediates transcriptional activation under microaerob ... | 1992 | 1484491 |
| characterization of a cell-free translation system from agrobacterium tumefaciens. | | 1992 | 1486984 |
| some ecological and physiological studies on bacteria isolated from salt-affected soils of egypt. | members of bacillaceae, rhizobiaceae, actinomycetes and others were isolated from cultivated and non-cultivated saline soils. the high population of bacteria and actinomycetes were almost coincided with the relatively high levels of organic matter whatever the degree of soil salinity. bacillus stearothermophilus and b. subtilis were more frequently isolated than other bacillus species. most of rhizobium isolates were salt tolerant being able to grow in media containing 3% and 6% nacl. the abilit ... | 1992 | 1487820 |
| design of a novel system for the construction of vectors for agrobacterium-mediated plant transformation. | the loxp-cre site-specific recombination system of phage p1 was used to develop a novel strategy to construct cointegrate vectors for agrobacterium-mediated plant transformation. a pti disarmed helper plasmid (pal1166) was constructed by replacing the oncogenic t-dna by a loxp sequence and a spectinomycin resistance marker in the octopine-type ptib6 plasmid. the cre gene was cloned into an unstable incp plasmid. a third plasmid, which did not replicate in agrobacterium and contained another loxp ... | 1992 | 1494341 |
| evidence that the acidic polysaccharide secreted by agrobacterium radiobacter (atcc 53271) has a seventeen glycosyl-residue repeating unit. | the extracellular anionic polysaccharide produced by the bacterium agrobacterium radiobacter (atcc 53271) contains d-galactose, d-glucose, and pyruvic acid in the molar ratio 2:15:2. analysis of the methylated polysaccharide indicated the presence of terminal, non-reducing glucosyl, 3-, 4-, 6-, 2,4-, and 4,6-linked glucosyl residues, 3-linked 4,6-o-[(s)-1-carboxyethylidene]glucosyl residues, and 3-linked galactosyl residues. partial acid hydrolysis of the methylated polysaccharide, followed by r ... | 1992 | 1499017 |
| transconjugants of agrobacterium radiobacter harbouring sym genes of rhizobium galegae can form an effective symbiosis with medicago sativa. | it is known that the rhizobium galegae genomes contain megaplasmids. the suicide vector psup2111 with nifh gene of r. meliloti was introduced into the strains ciam 0703 and ciam 0711 of r. galegae inducing effective nodules on galega orientalis plants. the formation of self-transmissible megaplasmids was observed. the megaplasmid transfer into non-nodulating r. meliloti mutants resulted in partial complementation of the nodulation defect in recipient strains though only one transconjugant showed ... | 1992 | 1499987 |
| the t-dna-linked vird2 protein contains two distinct functional nuclear localization signals. | agrobacterium tumefaciens causes neoplastic growth in plants by transferring a piece of dna, called t-dna, into the nucleus of the plant cell. the virulence protein vird2 of a. tumefaciens is tightly linked to the t-dna and is thought to direct it to the plant genome. here we show that the vird2 protein contains two nuclear localization signals that are functional both in yeast and in plant cells. one signal is located in the n-terminal part of the protein and resembles a single-cluster-type nuc ... | 1992 | 1502156 |
| slow rehydration improves the recovery of dried bacterial populations. | slow rehydration of bacteria from dried inoculant formulations provided higher viable counts than did rapid rehydration. estimates were higher when clay and peat powder formulations of rhizobium meliloti, rhizobium leguminosarum biovar trifolii, and pseudomonas putida, with water activities between 0.280 and 0.650, were slowly rehydrated to water activities of approximately 0.992 before continuing the dilution plating sequence. rhizobium meliloti populations averaged 6.8 x 10(8) cfu/g and 1328 c ... | 1992 | 1504917 |
| synthesis of the ferredoxin-like protein fdxn from rhizobium meliloti bacteroids as a fusion protein in escherichia coli. | to analyze the overexpression of the rhizobium meliloti fdxn gene in escherichia coli, different translational and transcriptional fusions were constructed. the translational signals of r. meliloti fdxn were recognized in e. coli as demonstrated by the use of in-frame lac fusions. translational fusions consisting of the lacz or the lpp gene fused in frame to the 3' end of the entire fdxn gene were expressed at high levels in e. coli. in contrast, the wild-type r. meliloti fdxn protein without a ... | 1992 | 1504918 |
| similarities between legume-rhizobium communication and steroid-mediated intercellular communication in vertebrates. | regulation of the actions of flavonoids and nod factors in legume-rhizobia communication has several interesting similarities with that of steroid-mediated actions in vertebrates. oxidation or reduction of flavonoids and nod factors modifies their biological activity just as, for example, oxidation of an alcohol at c11 on hydrocortisone regulates its biological activity. second, some flavonoids are anti-inducers, functioning like steroid antagonists to negate the actions of inducer flavonoids. a ... | 1992 | 1504919 |
| overexpression of the dcta gene in rhizobium meliloti: effect on transport of c4 dicarboxylates and symbiotic nitrogen fixation. | symbiotic nitrogen fixation may be limited by the transport of c4 dicarboxylates into bacteroids in the nodule for use as a carbon and energy source. in an attempt to increase dicarboxylate transport, a plasmid was constructed in which the rhizobium meliloti structural transport gene dcta was fused to a tryptophan operon promoter from salmonella typhimurium, trppo. this resulted in a functional dcta gene that was no longer under the control of the dctbd regulatory genes, but the recombinant plas ... | 1992 | 1504920 |