| molecular basis of the interaction of salmonella with the intestinal mucosa. | salmonella is one of the most extensively characterized bacterial pathogens and is a leading cause of bacterial gastroenteritis. despite this, we are only just beginning to understand at a molecular level how salmonella interacts with its mammalian hosts to cause disease. studies during the past decade on the genetic basis of virulence of salmonella have significantly advanced our understanding of the molecular basis of the host-pathogen interaction, yet many questions remain. in this review, we ... | 1999 | 10398673 |
| a vibrio cholerae lysr homolog, aphb, cooperates with apha at the tcpph promoter to activate expression of the toxr virulence cascade. | we describe here a new member of the lysr family of transcriptional regulators, aphb, which is required for activation of the vibrio cholerae toxr virulence cascade. aphb activates the transcription of the tcpph operon in response to environmental stimuli, and this process requires cooperation with a second protein, apha. the expression of neither apha or aphb is strongly regulated by environmental stimuli, raising the possibility that the activities of the proteins themselves may be influenced ... | 1999 | 10400582 |
| a rna polymerase with transcriptional activity at 0 degrees c from the antarctic bacterium pseudomonas syringae. | a dna-dependent rna polymerase was purified from the antarctic psychrotrophic bacterium pseudomonas syringae. the rna polymerase showed a typical eubacterial subunit composition with beta, beta', alpha2 and sigma subunits. the subunits cross-reacted with antibodies raised against holoenzyme and the individual subunits of the rna polymerase of escherichia coli. however, the enzyme was considered unique, since unlike the rna polymerase of mesophilic e. coli it exhibited significant and consistent ... | 1999 | 10405167 |
| gut colonization by an ice nucleation active bacterium, erwinia (pantoea) ananas reduces the cold hardiness of mulberry pyralid larvae. | to evaluate the suitability of using ice nucleation active (ina) bacteria for the biological control of insect pests, the supercooling point (scp) of larvae of mulberry pyralid, glyphodes duplicalis, and silkworm, bombyx mori, ingesting ina strains of erwinia (pantoea) ananas and pseudomonas syringae was determined. mean scp of the guts of silkworm larvae ingesting ina strains of e. ananas ranged from -2.5 to -2.8 degrees c, being 5 degrees c higher than that in control treatments. similarly, me ... | 1999 | 10413571 |
| isolation of additional bacteriophages with genomes of segmented double-stranded rna. | eight different bacteriophages were isolated from leaves of pisum sativum, phaseolus vulgaris, lycopersicon esculentum, daucus carota sativum, raphanus sativum, and ocimum basilicum. all contain three segments of double-stranded rna and have genomic-segment sizes that are similar but not identical to those of previously described bacteriophage phi6. all appear to have lipid-containing membranes. the base sequences of some of the viruses are very similar but not identical to those of phi6. three ... | 1999 | 10419946 |
| structure of the o-polysaccharide of the lipopolysaccharide of pseudomonas syringae pv. garcae icmp 8047. | the composition and structure of the o-polysaccharide of the lipopolysaccharide of pseudomonas syringae pathovar garcae icmp 8047 were studied using methylation analyses, smith degradation, and 1h- and 13c-nmr spectroscopy, including two-dimensional correlation spectroscopy (cosy), total correlation spectroscopy (tocsy), nuclear overhauser effect spectroscopy (noesy), and h-detected 1h,13c heteronuclear multiple-quantum coherence (hmqc) experiments. the polysaccharide was found to contain l-rham ... | 1999 | 10424899 |
| genetic structure of natural populations of escherichia coli in wild hosts on different continents. | current knowledge of genotypic and phenotypic diversity in the species escherichia coli is based almost entirely on strains recovered from humans or zoo animals. in this study, we analyzed a collection of 202 strains obtained from 81 mammalian species representing 39 families and 14 orders in australia and the americas, as well as several reference strains; we also included a strain from a reptile and 10 from different families of birds collected in mexico. the strains were characterized genotyp ... | 1999 | 10427022 |
| the xanthomonas hrp type iii system secretes proteins from plant and mammalian bacterial pathogens. | studies of essential pathogenicity determinants in gram-negative bacteria have revealed the conservation of type iii protein secretion systems that allow delivery of virulence factors into host cells from plant and animal pathogens. ten of 21 hrp proteins of the plant pathogen xanthomonas campestris pv. vesicatoria have been suggested to be part of a type iii machinery. here, we report the hrp-dependent secretion of two avirulence proteins, avrbs3 and avrrxv, by x. campestris pv. vesicatoria str ... | 1999 | 10430949 |
| a bean cdna expressed during a hypersensitive reaction encodes a putative calcium-binding protein. | the hypersensitive reaction (hr) is an inducible plant response that is associated with disease resistance. it is characterized by rapid, localized cell death at the site of infection and is believed to inhibit the spread of invading pathogens. we have isolated a cdna clone, designated hra32 (for hypersensitive reaction associated), corresponding to an rna transcript that accumulates in bean during an hr. the predicted protein product of the hra32 cdna is an approximately 17 kda protein of 161 a ... | 1999 | 10432637 |
| rapid transcript accumulation of pathogenesis-related genes during an incompatible interaction in bacterial speck disease-resistant tomato plants. | in the yeast two-hybrid system, the pto kinase interacts with three putative transcription factors pti4, pti5 and pti6. the pti4/5/6 proteins contain a dna binding domain that recognizes and binds a dna sequence (5'-agccgcc3'; the 'pr box') present in the promoter region of a large number of genes encoding 'pathogenesis-related' (pr) proteins. we have now investigated the pathogen-induced expression of pr box-containing genes in tomato. we isolated a tomato osmotin gene that contains two pr boxe ... | 1999 | 10437829 |
| influence of a putative ecf sigma factor on expression of the major outer membrane protein, oprf, in pseudomonas aeruginosa and pseudomonas fluorescens. | the gene encoding oprf, a major outer membrane protein in pseudomonas species (formerly known as type 1 pseudomonads), was thought to be constitutively transcribed from a single sigma 70 promoter immediately upstream of the gene. we now report the identification of a novel putative ecf (extracytoplasmic function) sigma factor gene, sigx, located immediately upstream of oprf in both pseudomonas aeruginosa pao1 and pseudomonas fluorescens oe 28.3 and show that disruption of this gene significantly ... | 1999 | 10438740 |
| the avr (effector) proteins hrma (hoppsya) and avrpto are secreted in culture from pseudomonas syringae pathovars via the hrp (type iii) protein secretion system in a temperature- and ph-sensitive manner. | we present here data showing that the avr proteins hrma and avrpto are secreted in culture via the native hrp pathways from pseudomonas syringae pathovars that produce these proteins. moreover, their secretion is strongly affected by the temperature and ph of the culture medium. both hrma and avrpto were secreted at their highest amounts when the temperature was between 18 and 22 degrees c and when the culture medium was ph 6.0. in contrast, temperature did not affect the secretion of hrpz. ph d ... | 1999 | 10438746 |
| disruption of narg, the gene encoding the catalytic subunit of respiratory nitrate reductase, also affects nitrite respiration in pseudomonas fluorescens yt101. | the pseudomonas fluorescens yt101 gene narg, which encodes the catalytic alpha subunit of the respiratory nitrate reductase, was disrupted by insertion of a gentamicin resistance cassette. in the nar(-) mutants, nitrate reductase activity was not detectable under all the conditions tested, suggesting that p. fluorescens yt101 contains only one membrane-bound nitrate reductase and no periplasmic nitrate reductase. whereas n(2)o respiration was not affected, anaerobic growth with no(2) as the sole ... | 1999 | 10438786 |
| leucine aminopeptidase rnas, proteins, and activities increase in response to water deficit, salinity, and the wound signals systemin, methyl jasmonate, and abscisic acid | lapa rnas, proteins, and activities increased in response to systemin, methyl jasmonate, abscisic acid (aba), ethylene, water deficit, and salinity in tomato (lycopersicon esculentum). salicylic acid inhibited wound-induced increases of lapa rnas. experiments using the aba-deficient flacca mutant indicated that aba was essential for wound and systemin induction of lapa, and aba and systemin acted synergistically to induce lapa gene expression. in contrast, pin2 (proteinase inhibitor 2) was not d ... | 1999 | 10444081 |
| early events in the signal pathway for the oxidative burst in soybean cells exposed to avirulent pseudomonas syringae pv glycinea | soybean (glycine max) cv williams 82 suspension cultures exhibit an oxidative burst approximately 3 h after challenge with pseudomonas syringae pv glycinea (psg) harboring the avra (avirulence) gene. pretreatment with the tyrosine (tyr) kinase inhibitor herbimycin a or the serine/threonine kinase inhibitor k252a abolished the burst and subsequent induction of glutathione s-transferase. however, imposition of a 45-min rest period between pathogen challenge and subsequent addition of the kinase in ... | 1999 | 10444097 |
| involvement of the exopolysaccharide alginate in the virulence and epiphytic fitness of pseudomonas syringae pv. syringae. | alginate, a co-polymer of o-acetylated beta-1,4-linked d-mannuronic acid and l-guluronic acid, has been reported to function in the virulence of pseudomonas syringae, although genetic studies to test this hypothesis have not been undertaken previously. in the present study, we used a genetic approach to evaluate the role of alginate in the pathogenicity of p. syringae pv. syringae 3525, which causes bacterial brown spot on beans. alginate biosynthesis in strain 3525 was disrupted by recombining ... | 1999 | 10447881 |
| salicylic acid induction-deficient mutants of arabidopsis express pr-2 and pr-5 and accumulate high levels of camalexin after pathogen inoculation. | in arabidopsis, systemic acquired resistance against pathogens has been associated with the accumulation of salicylic acid (sa) and the expression of the pathogenesis-related proteins pr-1, pr-2, and pr-5. we report here the isolation of two nonallelic mutants impaired in the pathway leading to sa biosynthesis. these sa induction-deficient (sid) mutants do not accumulate sa after pathogen inoculation and are more susceptible to both virulent and avirulent forms of pseudomonas syringae and perono ... | 1999 | 10449575 |
| role of the hrp type iii protein secretion system in growth of pseudomonas syringae pv. syringae b728a on host plants in the field. | hrp genes are reportedly required for pathogenicity in pseudomonas syringae pv. syringae (pss) and other phytopathogenic bacterial species. a subset of these genes encodes a type iii secretion system through which virulence factors are thought to be delivered to plant cells. in this study, we sought to better understand the role that hrp genes play in interactions of pss with its host as they occur naturally under field conditions. population sizes of hrp mutants with defects in genes that encod ... | 1999 | 10449783 |
| a simplified subtractive hybridization protocol used to isolate dna sequences specific to xylella fastidiosa. | a simplified protocol of subtractive hybridization based on the technique of l. m. kunkel, a. p. monaco, w. middlesworth, h. d. ochs & s. a. latt (1985, proc natl acad sci usa, 82, 4778-4782) was used to obtain dna sequences specific to xylella fastidiosa isolated from diseased citrus plants. as a driver, dna extracted from bacteria showing different degrees of relatedness was used: xy. fastidiosa 788 isolated from another host (plum), xanthomonas campestris pv. campestris and burkholderia gladi ... | 1999 | 10463163 |
| amplified fragment length polymorphism fingerprinting of pseudomonas strains from a poultry processing plant. | molecular typing has been used previously to identify and trace dissemination of pathogenic and spoilage bacteria associated with food processing. amplified fragment length polymorphism (aflp) is a novel dna fingerprinting technique which is considered highly reproducible and has high discriminatory power. this technique was used to fingerprint 88 pseudomonas fluorescens and pseudomonas putida strains that were previously isolated from plate counts of carcasses at six processing stages and vario ... | 1999 | 10473382 |
| microbial proline 4-hydroxylase screening and gene cloning. | microbial proline 4-hydroxylases, which hydroxylate free l-proline to trans-4-hydroxy-l-proline, were screened in order to establish an industrial system for biotransformation of l-proline to trans-4-hydroxy-l-proline. enzyme activities were detected in eight strains, including strains of dactylosporangium spp. and amycolatopsis spp. the dactylosporangium sp. strain rh1 enzyme was partially purified 3,300-fold and was estimated to be a monomer polypeptide with an apparent molecular mass of 31 kd ... | 1999 | 10473412 |
| identification of the pseudomonas stutzeri ox1 toluene-o-xylene monooxygenase regulatory gene (tour) and of its cognate promoter. | toluene-o-xylene monooxygenase is an enzymatic complex, encoded by the touabcdef genes, responsible for the early stages of toluene and o-xylene degradation in pseudomonas stutzeri ox1. in order to identify the loci involved in the transcriptional regulation of the tou gene cluster, deletion analysis and complementation studies were carried out with pseudomonas putida paw340 as a heterologous host harboring pfb1112, a plasmid that allowed regulated expression, inducible by toluene and o-xylene a ... | 1999 | 10473416 |
| development and application of pathovar-specific monoclonal antibodies that recognize the lipopolysaccharide o antigen and the type iv fimbriae of xanthomonas hyacinthi. | the objective of this study was to develop a specific immunological diagnostic assay for yellow disease in hyacinths, using monoclonal antibodies (mabs). mice were immunized with a crude cell wall preparation (shear fraction) from xanthomonas hyacinthi and with purified type iv fimbriae. hybridomas were screened for a positive reaction with x. hyacinthi cells or fimbriae and for a negative reaction with x. translucens pv. graminis or erwinia carotovora subsp. carotovora. nine mabs recognized fim ... | 1999 | 10473431 |
| systemic resistance in arabidopsis induced by rhizobacteria requires ethylene-dependent signaling at the site of application. | root colonization of arabidopsis thaliana by the nonpathogenic, rhizosphere-colonizing, biocontrol bacterium pseudomonas fluorescens wcs417r has been shown to elicit induced systemic resistance (isr) against pseudomonas syringae pv. tomato (pst). the isr response differs from the pathogen-inducible systemic acquired resistance (sar) response in that isr is independent of salicylic acid and not associated with pathogenesis-related proteins. several ethylene-response mutants were tested and showed ... | 1999 | 10475689 |
| deficiency in phytoalexin production causes enhanced susceptibility of arabidopsis thaliana to the fungus alternaria brassicicola. | the phytoalexin-deficient arabidopsis mutant pad3-1, which is affected in the production of the indole-type phytoalexin camalexin, has previously been shown not to display altered susceptibility to either the bacterium pseudomonas syringae (glazebrook & ausubel 1994; proc. natl. acad. sci. usa, 91: 8955-8959) or the biotrophic fungi peronospora parasitica (glazebrook et al. 1997; genetics, 146: 381-392) and erysiphe orontii (reuber et al. 1998; plant j. 16: 473-485). we now show that this mutant ... | 1999 | 10476063 |
| genetics of o-antigen biosynthesis in pseudomonas aeruginosa. | pathogenic bacteria produce an elaborate assortment of extracellular and cell-associated bacterial products that enable colonization and establishment of infection within a host. lipopolysaccharide (lps) molecules are cell surface factors that are typically known for their protective role against serum-mediated lysis and their endotoxic properties. the most heterogeneous portion of lps is the o antigen or o polysaccharide, and it is this region which confers serum resistance to the organism. pse ... | 1999 | 10477307 |
| dnak and the heat stress response of pseudomonas syringae pv. glycinea. | the dnak gene from pseudomonas syringae pv. glycinea pg4180 was cloned and sequenced. the dnak coding region was 1,917 bp and contained a putative sigma 32 heat shock promoter 86 bp upstream of the translational start site. grpe, another heat shock gene, was found immediately upstream of the putative dnak promoter. the predicted amino acid sequence of dnak showed relatedness to the atpase and substrate binding domains commonly found in heat shock proteins, as well as the highly conserved signatu ... | 1999 | 10478477 |
| determining chemotactic responses by two subsurface microaerophiles using a simplified capillary assay method. | a simplified capillary chemotaxis assay utilizing a hypodermic needle, syringe, and disposable pipette tip was developed to measure bacterial tactic responses. the method was applied to two strains of subsurface microaerophilic bacteria. this method was more convenient than the adler method and required less practice. isolate vt10 was a strain of pseudomonas syringae, which was isolated from the shallow subsurface. it was chemotactically attracted toward dextrose, glycerol, and phenol, which cou ... | 1999 | 10480269 |
| trac of incn plasmid pkm101 associates with membranes and extracellular high-molecular-weight structures in escherichia coli. | conjugative transfer of incn plasmid pkm101 is mediated by the trai-traii region-encoded transfer machinery components. similar to the case for the related agrobacterium tumefaciens t-complex transfer apparatus, this machinery is needed for assembly of pili to initiate cell-to-cell contact preceding dna transfer. biochemical and cell biological experiments presented here show extracellular localization of trac, as suggested by extracellular complementation of trac-deficient bacteria by helper ce ... | 1999 | 10482495 |
| pathways of assimilative sulfur metabolism in pseudomonas putida. | cysteine and methionine biosynthesis was studied in pseudomonas putida s-313 and pseudomonas aeruginosa pao1. both these organisms used direct sulfhydrylation of o-succinylhomoserine for the synthesis of methionine but also contained substantial levels of o-acetylserine sulfhydrylase (cysteine synthase) activity. the enzymes of the transsulfuration pathway (cystathionine gamma-synthase and cystathionine beta-lyase) were expressed at low levels in both pseudomonads but were strongly upregulated d ... | 1999 | 10482527 |
| hydrogen peroxide from the oxidative burst is neither necessary nor sufficient for hypersensitive cell death induction, phenylalanine ammonia lyase stimulation, salicylic acid accumulation, or scopoletin consumption in cultured tobacco cells treated with elicitin. | h(2)o(2) from the oxidative burst, cell death, and defense responses such as the production of phenylalanine ammonia lyase (pal), salicylic acid (sa), and scopoletin were analyzed in cultured tobacco (nicotiana tabacum) cells treated with three proteinaceous elicitors: two elicitins (alpha-megaspermin and beta-megaspermin) and one glycoprotein. these three proteins have been isolated from phytophthora megasperma h20 and have been previously shown to be equally efficient in inducing a hypersensit ... | 1999 | 10482671 |
| the generation of active oxygen species differs in tobacco and grapevine mesophyll protoplasts. | our previous results have shown that oxidative stress may reduce the regeneration potential of protoplasts, but only protoplasts that are able to supply extracellularly h(2)o(2) can actually divide (c.i. siminis, a.k. kanellis, k.a. roubelakis-angelakis [1993] physiol plant 87: 263-270; c.i. siminis, a.k. kanellis, k.a. roubelakis-angelakis [1994] plant physiol 1105: 1375-1383; a. de marco, k.a. roubelakis-angelakis [1996a] plant physiol 110: 137-145; a. de marco, k.a. roubelakis-angelakis [1996 ... | 1999 | 10482675 |
| identification of a pathogenicity island, which contains genes for virulence and avirulence, on a large native plasmid in the bean pathogen pseudomonas syringae pathovar phaseolicola. | the 154-kb plasmid was cured from race 7 strain 1449b of the phytopathogen pseudomonas syringae pv. phaseolicola (pph). cured strains lost virulence toward bean, causing the hypersensitive reaction in previously susceptible cultivars. restoration of virulence was achieved by complementation with cosmid clones spanning a 30-kb region of the plasmid that contained previously identified avirulence (avr) genes avrd, avrpphc, and avrpphf. single transposon insertions at multiple sites (including one ... | 1999 | 10485919 |
| the gain-of-function arabidopsis acd6 mutant reveals novel regulation and function of the salicylic acid signaling pathway in controlling cell death, defenses, and cell growth. | we isolated a dominant gain-of-function arabidopsis mutant, accelerated cell death 6 (acd6), with elevated defenses, patches of dead and enlarged cells, reduced stature, and increased resistance to pseudomonas syringae. the acd6-conferred phenotypes are suppressed by removing a key signaling molecule, salicylic acid (sa), by using the nahg transgene, which encodes sa hydroxylase. this suppression includes phenotypes that are not induced by application of sa to wild-type plants, indicating that s ... | 1999 | 10488236 |
| a new peroxidase cdna from white clover: its characterization and expression in root tissue challenged with homologous rhizobia, heterologous rhizobia, or pseudomonas syringae. | temporal reverse transcription-polymerase chain reaction (rt-pcr) expression analyses were performed on trprx2, a new white clover peroxidase, with roots challenged with homologous rhizobia, heterologous rhizobia, and a pathogen, pseudomonas syringae. low levels of trprx2 expression were evident in all rhizobial treatments but in p.syringae-treated clover background expression was dramatically reduced within 1 h and was undetectable in treatments inoculated for more than 3 h. spraying 4 mm salic ... | 1999 | 10494634 |
| genomic subtractive hybridization and selective capture of transcribed sequences identify a novel salmonella typhimurium fimbrial operon and putative transcriptional regulator that are absent from the salmonella typhi genome. | salmonella typhi, the etiologic agent of typhoid fever, is adapted to the human host and unable to infect nonprimate species. the genetic basis for host specificity in s. typhi is unknown. the avirulence of s. typhi in animal hosts may result from a lack of genes present in the broad-host-range pathogen salmonella typhimurium. genomic subtractive hybridization was successfully employed to isolate s. typhimurium genomic sequences which are absent from the s. typhi genome. these genomic subtracted ... | 1999 | 10496884 |
| differential transcription of the tcpph operon confers biotype-specific control of the vibrio cholerae toxr virulence regulon. | epidemic strains of vibrio cholerae o1 are divided into two biotypes, classical and el tor. in both biotypes, regulation of virulence gene expression depends on a cascade in which toxr activates expression of toxt, and toxt activates expression of cholera toxin and other virulence genes. in the classical biotype, maximal expression of this toxr regulon in vitro occurs at 30 degrees c at ph 6.5 (toxr-inducing conditions), whereas in the el tor biotype, production of these virulence genes only occ ... | 1999 | 10496885 |
| expression of the soxr gene of pseudomonas aeruginosa is inducible during infection of burn wounds in mice and is required to cause efficient bacteremia. | burn wounds are prone to infection by pseudomonas aeruginosa, which is an opportunistic pathogen causing various human diseases. during infection, the bacterium senses environmental changes and regulates the expression of genes appropriate for survival. a purine-auxotrophic mutant of p. aeruginosa was unable to replicate efficiently on burn wounds, suggesting that burn wounds are purine-deficient environments. an in vivo expression technology based on purek gene expression was applied to the bur ... | 1999 | 10496912 |
| antifungal activities of antineoplastic agents: saccharomyces cerevisiae as a model system to study drug action. | recent evolutionary studies reveal that microorganisms including yeasts and fungi are more closely related to mammals than was previously appreciated. possibly as a consequence, many natural-product toxins that have antimicrobial activity are also toxic to mammalian cells. while this makes it difficult to discover antifungal agents without toxic side effects, it also has enabled detailed studies of drug action in simple genetic model systems. we review here studies on the antifungal actions of a ... | 1999 | 10515904 |
| cloning and sequence analysis of two pseudomonas flavoprotein xenobiotic reductases. | the genes encoding flavin mononucleotide-containing oxidoreductases, designated xenobiotic reductases, from pseudomonas putida ii-b and p. fluorescens i-c that removed nitrite from nitroglycerin (ng) by cleavage of the nitroester bond were cloned, sequenced, and characterized. the p. putida gene, xena, encodes a 39,702-da monomeric, nad(p)h-dependent flavoprotein that removes either the terminal or central nitro groups from ng and that reduces 2-cyclohexen-1-one but did not readily reduce 2,4,6- ... | 1999 | 10515912 |
| identification of a locus in arabidopsis controlling both the expression of rhizobacteria-mediated induced systemic resistance (isr) and basal resistance against pseudomonas syringae pv. tomato. | selected nonpathogenic rhizobacteria with biological disease control activity are able to elicit an induced systemic resistance (isr) response that is phenotypically similar to pathogen-induced systemic acquired resistance (sar). ten ecotypes of arabidopsis thaliana were screened for their potential to express rhizobacteria-mediated isr and pathogen-induced sar against the leaf pathogen pseudomonas syringae pv. tomato dc3000 (pst). all ecotypes expressed sar. however, of the 10 ecotypes tested, ... | 1999 | 10517031 |
| the transcriptional activator corr is involved in biosynthesis of the phytotoxin coronatine and binds to the cmaabt promoter region in a temperature-dependent manner. | a modified two-component regulatory system consisting of the histidine protein kinase cors and two highly homologous response regulators, corr and corp, controls biosynthesis of the polyketide phytotoxin coronatine (cor) by pseudomonas syringae pv. glycinea pg4180 in a temperature-dependent manner. cor synthesis is maximal at 18 degrees c but does not occur at 28 degrees c. fusions of corr and corp to the maltose-binding protein (mbp) were overproduced in escherichia coli and p. syringae pg4180, ... | 1999 | 10517320 |
| pathogen-induced map kinases in tobacco. | the activation of two tobacco map kinases, sipk and wipk, by a variety of pathogen-associated stimuli and other stresses have been analyzed (table 1). sipk was activated by sa, a cwd carbohydrate elicitor and two elicitins from phytophthora spp, bacterial harpin, tmv, and avr9 from cladosporium fulvum. in addition to these pathogen-associated stimuli, wounding also activated sipk, suggesting that this enzyme is involved in multiple signal transduction pathways. in all cases tested, sipk activati ... | 2000 | 10533199 |
| reciprocal secretion of proteins by the bacterial type iii machines of plant and animal pathogens suggests universal recognition of mrna targeting signals. | bacterial pathogens of both animals and plants use type iii secretion machines to inject virulence proteins into host cells. although many components of the secretion machinery are conserved among different bacterial species, the substrates for their type iii pathways are not. the yersinia type iii machinery recognizes some secretion substrates via a signal that is encoded within the first 15 codons of yop mrna. these signals can be altered by frameshift mutations without affecting secretion of ... | 1999 | 10536009 |
| stable packaging of phage prd1 dna requires adsorption protein p2, which binds to the incp plasmid-encoded conjugative transfer complex. | the double-stranded dna bacteriophage prd1 uses an incp plasmid-encoded conjugal transfer complex as a receptor. plasmid functions in the prd1 life cycle are restricted to phage adsorption and dna entry. a single phage structural protein, p2, located at the fivefold capsid vertices, is responsible for prd1 attachment to its host. the purified recombinant adsorption protein was judged to be monomeric by gel filtration, rate zonal centrifugation, analytical ultracentrifugation, and chemical cross- ... | 1999 | 10542170 |
| role of crotonyl coenzyme a reductase in determining the ratio of polyketides monensin a and monensin b produced by streptomyces cinnamonensis. | the ccr gene, encoding crotonyl coenzyme a (coa) reductase (ccr), was cloned from streptomyces cinnamonensis c730.1 and shown to encode a protein with 90% amino acid sequence identity to the ccrs of streptomyces collinus and streptomyces coelicolor. a ccr-disrupted mutant, s. cinnamonensis l1, was constructed by inserting the hyg resistance gene into a unique bglii site within the ccr coding region. by use of the erme* promoter, the s. collinus ccr gene was expressed from plasmids in s. cinnamon ... | 1999 | 10542184 |
| distribution of tetracycline resistance genes and transposons among phylloplane bacteria in michigan apple orchards. | the extent and nature of tetracycline resistance in bacterial populations of two apple orchards with no or a limited history of oxytetracycline usage were assessed. tetracycline-resistant (tc(r)) bacteria were mostly gram negative and represented from 0 to 47% of the total bacterial population on blossoms and leaves (versus 26 to 84% for streptomycin-resistant bacteria). a total of 87 isolates were screened for the presence of specific tc(r) determinants. tc(r) was determined to be due to the pr ... | 1999 | 10543801 |
| characterization of plasmids encoding the phytotoxin coronatine in pseudomonas syringae. | coronatine (cor) is a nonhost-specific phytotoxin that substantially contributes to the virulence of several pathovars (pvs.) of pseudomonas syringae. the cor gene cluster in p. syringae is generally plasmid-encoded in pvs. atropurpurea, glycinea, morsprunorum, and tomato but chromosomally encoded in pv. maculicola. in the present study, we investigated whether the cor plasmids in four pathovars shared other traits including self-transmissibility, conserved oriv/par loci, and insertion sequences ... | 1999 | 10545263 |
| a novel virus-host cell membrane interaction. membrane voltage-dependent endocytic-like entry of bacteriophage straight phi6 nucleocapsid. | studies on the virus-cell interactions have proven valuable in elucidating vital cellular processes. interestingly, certain virus-host membrane interactions found in eukaryotic systems seem also to operate in prokaryotes (bamford, d.h., m. romantschuk, and p. j. somerharju, 1987. embo (eur. mol. biol. organ.) j. 6:1467-1473; romantschuk, m., v.m. olkkonen, and d.h. bamford. 1988. embo (eur. mol. biol. organ.) j. 7:1821-1829). straight phi6 is an enveloped double-stranded rna virus infecting a gr ... | 1999 | 10545509 |
| lsd1 regulates salicylic acid induction of copper zinc superoxide dismutase in arabidopsis thaliana. | we characterized the accumulation patterns of arabidopsis thaliana proteins, two cuznsods, fesod, mnsod, pr1, pr5, and gst1, in response to various pathogen-associated treatments. these treatments included inoculation with virulent and avirulent pseudomonas syringae strains, spontaneous lesion formation in the lsd1 mutant, and treatment with the salicylic acid (sa) analogs ina (2,6-dichloroisonicotinic acid) and bth (benzothiadiazole). the pr1, pr5, and gst1 proteins were inducible by all treatm ... | 1999 | 10550898 |
| phylogenetic analysis of pseudomonas syringae pathovars suggests the horizontal gene transfer of argk and the evolutionary stability of hrp gene cluster. | pseudomonas syringae are differentiated into approximately 50 pathovars with different plant pathogenicities and host specificities. to understand its pathogenicity differentiation and the evolutionary mechanisms of pathogenicity-related genes, phylogenetic analyses were conducted using 56 strains belonging to 19 pathovars. gyrb and rpod were adopted as the index genes to determine the course of bacterial genome evolution, and hrpl and hrps were selected as the representatives of the pathogenici ... | 1999 | 10552044 |
| assembly dynamics of the nucleocapsid shell subunit (p8) of bacteriophage phi6. | phi6 is an enveloped dsrna bacteriophage of pseudomonas syringae. the viral envelope encloses a nucleocapsid, consisting of an rna-dependent rna polymerase complex within an icosahedral shell assembled from approximately 800 copies of a 16 kda subunit (protein p8, encoded by viral gene 8). during infection, the nucleocapsid penetrates the host plasma membrane and enters the cytosol, whereupon the p8 shell disassembles and the polymerase complex is activated. to understand the molecular mechanism ... | 1999 | 10555985 |
| arabidopsis thaliana pad4 encodes a lipase-like gene that is important for salicylic acid signaling. | the arabidopsis pad4 gene previously was found to be required for expression of multiple defense responses including camalexin synthesis and pr-1 gene expression in response to infection by the bacterial pathogen pseudomonas syringae pv. maculicola. this report describes the isolation of pad4. the predicted pad4 protein sequence displays similarity to triacyl glycerol lipases and other esterases. the pad4 transcript was found to accumulate after p. syringae infection or treatment with salicylic ... | 1999 | 10557364 |
| immunochemical characterization and taxonomic evaluation of the o polysaccharides of the lipopolysaccharides of pseudomonas syringae serogroup o1 strains. | the o polysaccharide (ops) of the lipopolysaccharide (lps) of pseudomonas syringae pv. atrofaciens imv 7836 and some other strains that are classified in serogroup o1 was shown to be a novel linear alpha-d-rhamnan with the tetrasaccharide o repeat -->3)-alpha-d-rhap-(1-->3)-alpha-d-rhap-(1-->2)-alpha-d-r hap-(1-->2)- alpha-d-rhap-(1--> (chemotype 1a). the same alpha-d-rhamnan serves as the backbone in branched opss with lateral (alpha1-->3)-linked d-rhap, (beta1-->4)-linked d-glcpnac, and (alpha ... | 1999 | 10559159 |
| a novel lipolytic enzyme located in the outer membrane of pseudomonas aeruginosa. | a lipase-negative deletion mutant of pseudomonas aeruginosa pao1 still showed extracellular lipolytic activity toward short-chain p-nitrophenylesters. by screening a genomic dna library of p. aeruginosa pao1, an esterase gene, esta, was identified, cloned, and sequenced, revealing an open reading frame of 1,941 bp. the product of esta is a 69.5-kda protein, which is probably processed by removal of an n-terminal signal peptide to yield a 67-kda mature protein. a molecular mass of 66 kda was dete ... | 1999 | 10559163 |
| mutational analysis of the pseudomonas syringae pv. tomato hrpa gene encoding hrp pilus subunit. | plant pathogenic pseudomonas syringae strains harbour a type iii secretion pathway suggested to be involved in the delivery of effector proteins from the bacteria into plant cells. during plant interaction, the bacteria apparently produce surface appendages, termed hrp pili, that are indispensable for the secretion process. we have created an insertion mutation library, as well as deletion mutations to hrpa, the structural gene encoding hrp pilin. analysis of the mutants revealed gene regions im ... | 1999 | 10564513 |
| global gaca-steered control of cyanide and exoprotease production in pseudomonas fluorescens involves specific ribosome binding sites. | the conserved two-component regulatory system gacs/gaca determines the expression of extracellular products and virulence factors in a variety of gram-negative bacteria. in the biocontrol strain cha0 of pseudomonas fluorescens, the response regulator gaca is essential for the synthesis of extracellular protease (apra) and secondary metabolites including hydrogen cyanide. gaca was found to exert its control on the hydrogen cyanide biosynthetic genes (hcnabc) and on the apra gene indirectly via a ... | 1999 | 10570200 |
| transgenic tobacco plants with reduced capability to detoxify reactive oxygen intermediates are hyperresponsive to pathogen infection. | reactive oxygen intermediates (roi) play a critical role in the defense of plants against invading pathogens. produced during the "oxidative burst," they are thought to activate programmed cell death (pcd) and induce antimicrobial defenses such as pathogenesis-related proteins. it was shown recently that during the interaction of plants with pathogens, the expression of roi-detoxifying enzymes such as ascorbate peroxidase (apx) and catalase (cat) is suppressed. it was suggested that this suppres ... | 1999 | 10570216 |
| a novel myb oncogene homologue in arabidopsis thaliana related to hypersensitive cell death. | a novel myb oncogene homologue (atmyb30) has been isolated by differential screening of a cdna library prepared from xanthomonas campestris pv. campestris (x. campestris)-inoculated arabidopsis thaliana cells cultured in the presence of cycloheximide. atmyb30 is a single-copy gene, and the encoded protein contains a myb domain highly homologous to other plant and animal myb proteins. analyses of transcript levels in a. thaliana plants, or in cultured a. thaliana cells infected with either virule ... | 1999 | 10571865 |
| harpin induces disease resistance in arabidopsis through the systemic acquired resistance pathway mediated by salicylic acid and the nim1 gene. | harpin, the product of the hrpn gene of erwinia amylovora, elicits the hypersensitive response and disease resistance in many plants. harpin and known inducers of systemic acquired resistance (sar) were tested on five genotypes of arabidopsis thaliana to assess the role of sar in harpin-induced resistance. in wild-type plants, harpin elicited systemic resistance to peronospora parasitica and pseudomonas syringae pv. tomato, accompanied by induction of the sar genes pr-1 and pr-2. however, in exp ... | 1999 | 10571880 |
| the arabidopsis rps4 bacterial-resistance gene is a member of the tir-nbs-lrr family of disease-resistance genes. | plant-disease resistance (r) genes mediate the specific recognition of invading pathogens carrying cognate avirulence (avr) determinants. rps4 is a disease-resistance locus on chromosome 5 of arabidopsis thaliana specifying resistance to strains of pseudomonas syringae pv. tomato expressing avrrps4. we have isolated the rps4 gene using a map-based cloning approach. rps4 encodes a predicted protein of 1217 amino acids that contains an n-terminus with homology to the intracellular domains of the d ... | 1999 | 10571887 |
| algt (sigma22) controls alginate production and tolerance to environmental stress in pseudomonas syringae. | pseudomonas aeruginosa and the phytopathogen p. syringae produce the exopolysaccharide alginate, which is a copolymer of d-mannuronic and l-guluronic acids. one of the key regulatory genes controlling alginate biosynthesis in p. aeruginosa is algt, which encodes the alternate sigma factor, sigma(22). in the present study, the algt gene product from p. syringae pv. syringae showed 90% amino acid identity with its p. aeruginosa counterpart, and sequence analysis of the region flanking algt in p. s ... | 1999 | 10572118 |
| biosynthetic origin of syringomycin and syringopeptin 22, toxic secondary metabolites of the phytopathogenic bacterium pseudomonas syringae pv. syringae. | the biosynthesis of syringomycin (sr) and syringopeptin 22 (sp22), bioactive lipodepsipeptides of the phytopathogenic bacterium pseudomonas syringae pv. syringae, was studied by feeding (14)c-labeled precursors to chloramphenicol-containing bacterial suspensions. the preferential sites of incorporation were determined by comparing the specific activities of the intact radiolabeled metabolites and their single structural elements, obtained by hydrolytic degradation followed by derivatization and ... | 1999 | 10580109 |
| utilization of heterologous siderophores enhances levels of iron available to pseudomonas putida in the rhizosphere. | pseudomonas spp. have the capacity to utilize siderophores produced by diverse species of bacteria and fungi, and the present study was initiated to determine if siderophores produced by rhizosphere microorganisms enhance the levels of iron available to a strain of pseudomonas putida in this natural habitat. we used a previously described transcriptional fusion (pvd-inaz) between an iron-regulated promoter (pvd) and the ice nucleation reporter gene (inaz) to detect alterations in iron availabili ... | 1999 | 10583989 |
| requirement for phosphoglucose isomerase of xanthomonas campestris in pathogenesis of citrus canker. | a mutant (xt906) of xanthomonas campestris pv. citri, the causal agent of citrus canker, was induced by insertion of the transposon tn5tac1 and isolated. this mutant did not grow or elicit canker disease in citrus leaves but was still able to induce a hypersensitive response in a nonhost plant (the common bean). the mutant was also unable to grow on minimal medium containing fructose or glycerol as the sole carbon source. a 2.5-kb fragment of wild-type dna that complemented the mutant phenotype ... | 1999 | 10584018 |
| arabidopsis pad3, a gene required for camalexin biosynthesis, encodes a putative cytochrome p450 monooxygenase. | phytoalexins are low molecular weight antimicrobial compounds that are synthesized in response to pathogen attack. the phytoalexin camalexin, an indole derivative, is produced by arabidopsis in response to infection with the bacterial pathogen pseudomonas syringae. the phytoalexin deficient 3 (pad3) mutation, which causes a defect in camalexin production, has no effect on resistance to p. syringae but compromises resistance to the fungal pathogen alternaria brassicicola. we have now isolated pad ... | 1999 | 10590168 |
| harpin induces mitogen-activated protein kinase activity during defence responses in arabidopsis thaliana suspension cultures. | elicitation of arabidopsis thaliana (l.) heynh. suspension cultures with the bacterial protein harpin (from pseudomonas syringae pv. syringae) induced the activation of two kinases of 39 and 44 kda, as demonstrated by in-gel kinase assays using myelin basic protein (mbp) as a substrate. both these kinases appeared to be tyrosine-phosphorylated upon activation, as demonstrated by treatment with tyrosine phosphatase and immunoprecipitation using an anti-phosphotyrosine monoclonal antibody. an inhi ... | 1999 | 10592037 |
| requirement of functional ethylene-insensitive 2 gene for efficient resistance of arabidopsis to infection by botrytis cinerea. | inoculation of wild-type arabidopsis plants with the fungus alternaria brassicicola results in systemic induction of genes encoding a plant defensin (pdf1.2), a basic chitinase (pr-3), and an acidic hevein-like protein (pr-4). pathogen-induced induction of these three genes is almost completely abolished in the ethylene-insensitive arabidopsis mutant ein2-1. this indicates that a functional ethylene signal transduction component (ein2) is required in this response. the ein2-1 mutants were found ... | 1999 | 10594097 |
| n-acylethanolamines in signal transduction of elicitor perception. attenuation of alkalinization response and activation of defense gene expression | in a recent study of n-acylphosphatidylethanolamine (nape) metabolism in elicitor-treated tobacco (nicotiana tabacum l.) cells, we identified a rapid release and accumulation of medium-chain n-acylethanolamines (naes) (e.g. n-myristoylethanolamine or nae 14:0) and a compensatory decrease in cellular nape (k.d. chapman, s. tripathy, b. venables, a.d. desouza [1998] plant physiol 116: 1163-1168). in the present study, we extend this observation and report a 10- to 50-fold increase in nae 14:0 cont ... | 1999 | 10594117 |
| vir proteins stabilize virb5 and mediate its association with the t pilus of agrobacterium tumefaciens. | three virb proteins (virb1*, virb2, and virb5) have been implicated as putative components of the t pilus from agrobacterium tumefaciens, which likely mediates binding to plant cells followed by transfer of genetic material. recently, virb2 was indeed shown to be its major component (e.-m. lai and c. i. kado, j. bacteriol. 180:2711-2717, 1998). here, the influence of other vir proteins on the stability and cellular localization of virb1*, virb2, and virb5 was analyzed. solubility of virb1* and m ... | 1999 | 10601205 |
| citrate synthase mutants of sinorhizobium meliloti are ineffective and have altered cell surface polysaccharides. | the glta gene, encoding sinorhizobium meliloti 104a14 citrate synthase, was isolated by complementing an escherichia coli glta mutant. the s. meliloti glta gene was mutated by inserting a kanamycin resistance gene and then using homologous recombination to replace the wild-type glta with the glta::kan allele. the resulting strain, csdx1, was a glutamate auxotroph, and enzyme assays confirmed the absence of a requirement for glutamate. csdx1 did not grow on succinate, malate, aspartate, pyruvate, ... | 1999 | 10601220 |
| biological control of postharvest decays of apple can prevent growth of escherichia coli o157:h7 in apple wounds. | fresh cells of the antagonist pseudomonas syringae at 2.4 x 10(8) cfu/ml inoculated into wounds of 'golden delicious' apple prevented escherichia coli o157:h7 (concentrations ranging from 2.4 x 10(5) to 2.4 x 10(7) cfu/ml) from growing in the wounds. this occurred when the two microorganisms were co-inoculated or inoculation with e. coli o157:h7 was conducted 1 or 2 days after inoculation with the antagonist. in similar tests, application of the commercial formulation of this antagonist prevente ... | 1999 | 10606139 |
| pseudomonas syringae pv tomato induces the expression of tomato erebp-like genes pti4 and pti5 independent of ethylene, salicylate and jasmonate | the tomato genes pti4 and pti5 encode ethylene-responsive element binding protein-like transcription factors that bind to the gcc box, a conserved cis-element in many defense-related genes. the pti proteins have previously been shown to interact with the tomato disease resistance protein pto. here we report that the expression of both pti4 and pti5 are induced by a virulent strain of pseudomonas syringae pv tomato. the expression of pti5 is further enhanced by the interaction of the pto gene in ... | 1999 | 10607299 |
| rhizobacteria-mediated induced systemic resistance (isr) in arabidopsis is not associated with a direct effect on expression of known defense-related genes but stimulates the expression of the jasmonate-inducible gene atvsp upon challenge. | selected strains of nonpathogenic rhizobacteria from the genus pseudomonas are capable of eliciting broad-spectrum induced systemic resistance (isr) in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (sar). in arabidopsis, the isr pathway functions independently of salicylic acid (sa) but requires responsiveness to jasmonate and ethylene. here, we demonstrate that known defense-related genes, i.e. the sa-responsive genes pr-1, pr-2, and pr-5, the ethylene-i ... | 1999 | 10608663 |
| cloning of chlorophyllase, the key enzyme in chlorophyll degradation: finding of a lipase motif and the induction by methyl jasmonate. | chlorophyllase (chlase) is the first enzyme involved in chlorophyll (chl) degradation and catalyzes the hydrolysis of ester bond to yield chlorophyllide and phytol. in the present study, we isolated the chlase cdna. we synthesized degenerate oligo dna probes based on the internal amino acid sequences of purified chlase from chenopodium album, screened the c. album cdna library, and cloned a cdna (caclh, c. album chlorophyll-chlorophyllido hydrolase). the deduced amino acid sequence (347 aa resid ... | 1999 | 10611389 |
| the virr response regulator from clostridium perfringens binds independently to two imperfect direct repeats located upstream of the pfoa promoter. | regulation of toxin production in the gram-positive anaerobe clostridium perfringens occurs at the level of transcription and involves a two-component signal transduction system. the sensor histidine kinase is encoded by the virs gene, while its cognate response regulator is encoded by the virr gene. we have constructed a virr expression plasmid in escherichia coli and purified the resultant his-tagged virr protein. gel mobility shift assays demonstrated that virr binds to the region upstream of ... | 2000 | 10613863 |
| production and comparison of peptide siderophores from strains of distantly related pathovars of pseudomonas syringae and pseudomonas viridiflava lmg 2352. | the production of peptide siderophores and the variation in siderophore production among strains of pseudomonas syringae and pseudomonas viridiflava were investigated. an antibiose test was used to select a free amino acid-containing agar medium favorable for production of fluorescent siderophores by two p. syringae strains. a culture technique in which both liquid and solid asparagine-containing culture media were used proved to be reproducible and highly effective for inducing production of si ... | 2000 | 10618243 |
| role of leaf surface sugars in colonization of plants by bacterial epiphytes. | the relationship between nutrients leached onto the leaf surface and the colonization of plants by bacteria was studied by measuring both the abundance of simple sugars and the growth of pseudomonas fluorescens on individual bean leaves. data obtained in this study indicate that the population size of epiphytic bacteria on plants under environmentally favorable conditions is limited by the abundance of carbon sources on the leaf surface. sugars were depleted during the course of bacterial coloni ... | 2000 | 10618250 |
| the pspa protein of escherichia coli is a negative regulator of sigma(54)-dependent transcription. | in eubacteria, expression of genes transcribed by an rna polymerase holoenzyme containing the alternate sigma factor sigma(54) is positively regulated by proteins belonging to the family of enhancer-binding proteins (ebps). these proteins bind to upstream activation sequences and are required for the initiation of transcription at the sigma(54)-dependent promoters. they are typically inactive until modified in their n-terminal regulatory domain either by specific phosphorylation or by the bindin ... | 2000 | 10629175 |
| helicobacter pylori uptake and efflux: basis for intrinsic susceptibility to antibiotics in vitro. | we previously demonstrated (m. m. exner, p. doig, t. j. trust, and r. e. w. hancock, infect. immun. 63:1567-1572, 1995) that helicobacter pylori has at least one nonspecific porin, hope, which has a low abundance in the outer membrane but forms large channels. h. pylori is relatively susceptible to most antimicrobial agents but less susceptible to the polycationic antibiotic polymyxin b. we demonstrate here that h. pylori is able to take up higher basal levels of the hydrophobic fluorescent prob ... | 2000 | 10639345 |
| isolation of neisseria gonorrhoeae mutants that show enhanced trafficking across polarized t84 epithelial monolayers. | initiation of a gonococcal infection involves attachment of neisseria gonorrhoeae to the plasma membrane of an epithelial cell in the mucosal epithelium and its internalization, transepithelial trafficking, and exocytosis from the basal membrane. piliation and expression of certain opa proteins and the immunoglobulin a1 protease influence the transcytosis process. we are interested in identifying other genetic determinants of n. gonorrhoeae that play a role in transcellular trafficking. using po ... | 2000 | 10639460 |
| crc is involved in catabolite repression control of the bkd operons of pseudomonas putida and pseudomonas aeruginosa. | crc (catabolite repression control) protein of pseudomonas aeruginosa has shown to be involved in carbon regulation of several pathways. in this study, the role of crc in catabolite repression control has been studied in pseudomonas putida. the bkd operons of p. putida and p. aeruginosa encode the inducible multienzyme complex branched-chain keto acid dehydrogenase, which is regulated in both species by catabolite repression. we report here that this effect is mediated in both species by crc. a ... | 2000 | 10648542 |
| bacterial cell surface display of an enzyme library for selective screening of improved cellulase variants. | the bacterial surface display method was used to selectively screen for improved variants of carboxymethyl cellulase (cmcase). a library of mutated cmcase genes generated by dna shuffling was fused to the ice nucleation protein (inp) gene so that the resulting fusion proteins would be displayed on the bacterial cell surface. some cells displaying mutant proteins grew more rapidly on carboxymethyl cellulose plates than controls, forming heterogeneous colonies. in contrast, cells displaying the no ... | 2000 | 10653752 |
| pathovars of pseudomonas syringae causing bacterial brown spot and halo blight in phaseolus vulgaris l. are distinguishable by ribotyping. | ribotyping was evaluated as a method to differentiate between pseudomonas syringae pv. phaseolicola and pv. syringae strains causing bacterial brown spot and halo blight diseases in phaseolus vulgaris l. ribotyping, with restriction enzymes bgli and sali and using the escherichia coli rrnb operon as the probe, differentiated 11 and 14 ribotypes, respectively, and a combination of data from both procedures yielded 19 combined ribotypes. cluster analysis of the combined ribotypes differentiated th ... | 2000 | 10653764 |
| cloning and expression in escherichia coli of 2-hydroxypropylphosphonic acid epoxidase from the fosfomycin-producing organism, pseudomonas syringae pb-5123. | the fosfomycin resistance gene, fosc, has been cloned from the fosfomycin-producing organism, pseudomonas syringae pb-5123. sequence analysis upstream of this gene found a new orf showing significant homology to 2-hydroxypropylphosphonic acid epoxidase from fosfomycin-producing streptomyces wedmorensis. the purified recombinant protein of this orf converted 2-hydroxypropylphosphonic acid to fosfomycin. this result clearly showed the orf to encode 2-hydroxypropylphosphonic acid epoxidase in pb-51 ... | 1999 | 10664856 |
| cell surface display of hepatitis b virus surface antigen by using pseudomonas syringae ice nucleation protein. | a new system designed for cell surface display of recombinant proteins on escherichia coli was evaluated for expression of eukaryotic viral antigens. the major surface antigen of hepatitis b virus (hbsag) was fused to the ice nucleation protein (inp), an outer membrane protein of pseudomonas syringae. western blotting, immunofluorescence microscopy, whole-cell elisa, and ice nucleation activity assay confirmed expression of recombinant proteins on the surface of escherichia coli. this study indi ... | 1999 | 10664968 |
| effects of calcium and calcium chelators on growth and morphology of escherichia coli l-form nc-7. | growth of a wall-less, l-form of escherichia coli specifically requires calcium, and in its absence, cells ceased dividing, became spherical, swelled, developed large vacuoles, and eventually lysed. the key cell division protein, ftsz, was present in the l-form at a concentration five times less than that in the parental strain. one interpretation of these results is that the l-form possesses an enzoskeleton partly regulated by calcium. | 2000 | 10671467 |
| expression and localization of nitrilase during symptom development of the clubroot disease in arabidopsis. | the expression of nitrilase in arabidopsis during the development of the clubroot disease caused by the obligate biotroph plasmodiophora brassicae was investigated. a time course study showed that only during the exponential growth phase of the clubs was nitrilase prominently enhanced in infected roots compared with controls. nit1 and nit2 are the nitrilase isoforms predominantly expressed in clubroot tissue, as shown by investigating promoter-beta-glucuronidase fusions of each. two peaks of bet ... | 2000 | 10677430 |
| isolation and characterization of powdery mildew-resistant arabidopsis mutants. | a compatible interaction between a plant and a pathogen is the result of a complex interplay between many factors of both plant and pathogen origin. our objective was to identify host factors involved in this interaction. these factors may include susceptibility factors required for pathogen growth, factors manipulated by the pathogen to inactivate or avoid host defenses, or negative regulators of defense responses. to this end, we identified 20 recessive arabidopsis mutants that do not support ... | 2000 | 10677553 |
| characterization of the foma and fomb gene products from streptomyces wedmorensis, which confer fosfomycin resistance on escherichia coli. | together, the foma and fomb genes in the fosfomycin biosynthetic gene cluster of streptomyces wedmorensis confer high-level fosfomycin resistance on escherichia coli. to elucidate their functions, the foma and fomb genes were overexpressed in e. coli and the gene products were characterized. the recombinant foma protein converted fosfomycin to fosfomycin monophosphate, which was inactive on e. coli, in the presence of a magnesium ion and atp. on the other hand, the recombinant fomb protein did n ... | 2000 | 10681332 |
| arabidopsis cytochrome p450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis. | plants synthesize numerous secondary metabolites that are used as developmental signals or as defense against pathogens. tryptophan (trp)-derived secondary metabolites include camalexin, indole glucosinolates, and indole-3-acetic acid (iaa); however, the steps in their synthesis from trp or its precursors remain unclear. we have identified two arabidopsis cytochrome p450s (cyp79b2 and cyp79b3) that can convert trp to indole-3-acetaldoxime (iaox), a precursor to iaa and indole glucosinolates. | 2000 | 10681464 |
| the gene coding for the hrp pilus structural protein is required for type iii secretion of hrp and avr proteins in pseudomonas syringae pv. tomato. | bacterial surface appendages called pili often are associated with dna and/or protein transfer between cells. the exact function of pili in the transfer process is not understood and is a matter of considerable debate. the hrp pilus is assembled by the hrp type iii protein secretion system of pseudomonas syringae pv. tomato (pst) strain dc3000. in this study, we show that the hrpa gene, which encodes the major subunit of the hrp pilus, is required for secretion of putative virulence proteins, su ... | 2000 | 10681465 |
| molecular cloning of a defense-response-related cytochrome p450 gene from tobacco. | plant defenses against pathogen attack involve a series of inducible responses that contribute to resistance. tobacco leaves injected with hwc (hyphal wall components prepared from phytophthora infestans) elicitor showed typical defense responses, including the induction of localized necrosis and the accumulation of pathogenesis-related proteins. in order to elucidate the molecular mechanisms by which plant defense systems are activated, we screened tobacco plants for genes differentially expres ... | 1999 | 10682345 |
| functional analysis of pvds, an iron starvation sigma factor of pseudomonas aeruginosa. | in pseudomonas aeruginosa, iron modulates gene expression through a cascade of negative and positive regulatory proteins. the master regulator fur is involved in iron-dependent repression of several genes. one of these genes, pvds, was predicted to encode a putative sigma factor responsible for the transcription of a subset of genes of the fur regulon. pvds appears to belong to a structurally and functionally distinct subgroup of the extracytoplasmic function family of alternative sigma factors. ... | 2000 | 10692351 |
| identification of genes in the rosr regulon of rhizobium etli. | rosr is a determinant of nodulation competitiveness and cell surface characteristics of rhizobium etli and has sequence similarity to a family of transcriptional repressors. to understand how rosr affects these phenotypes, we mutagenized a rosr mutant derivative of r. etli strain ce3 with a mini-tn5 that contains a promoterless gusa gene at one end, which acts as a transcriptional reporter. using a mass-mating technique, we introduced rosr into each mutant in trans and screened for mutants that ... | 2000 | 10692377 |
| the right end of the vir region of an octopine-type ti plasmid contains four new members of the vir regulon that are not essential for pathogenesis. | we sequenced the vird-vire, vire-virf, and virf-t-dna intergenic regions of an octopine ti plasmid. four newly described genes were induced by the vir gene inducer acetosyringone, two of which are conserved in the nopaline-type ti plasmid ptic58. one gene resembles a family of phosphatase genes. each of these genes is dispensable for tumorigenesis. | 2000 | 10692388 |
| frequency and biodiversity of 2,4-diacetylphloroglucinol-producing bacteria isolated from the maize rhizosphere at different stages of plant growth. | a pseudomonas 2,4-diacetylphloroglucinol (dapg)-producing population that occurred naturally on the roots, in rhizosphere soil of zea mays and in the nonrhizosphere soil was investigated in order to assess the microbial diversity at five stages of plant growth. a total of 1,716 isolates were obtained, and 188 of these isolates were able to produce dapg. dapg producers were isolated at each stage of plant growth, indicating that the maize rhizosphere is colonized by natural dapg producers through ... | 2000 | 10698757 |
| characterization and determination of origin of lactic acid bacteria from a sorghum-based fermented weaning food by analysis of soluble proteins and amplified fragment length polymorphism fingerprinting. | the group that includes the lactic acid bacteria is one of the most diverse groups of bacteria known, and these organisms have been characterized extensively by using different techniques. in this study, 180 lactic acid bacterial strains isolated from sorghum powder (44 strains) and from corresponding fermented (93 strains) and cooked fermented (43 strains) porridge samples that were prepared in 15 households were characterized by using biochemical and physiological methods, as well as by analyz ... | 2000 | 10698775 |
| survival and epiphytic fitness of a nonpathogenic mutant of xanthomonas campestris pv. glycines. | xanthomonas campestris pv. glycines is the causal agent of bacterial pustule disease of soybeans. the objective of this work was to construct a nonpathogenic mutant derived from the pathogenic wild-type strain yr32 and to evaluate its effectiveness in preventing growth of its parent on the soybean phyllosphere. a mini-tn5-derived transposon was used to generate nonpathogenic mutants. southern hybridization and pulsed-field gel electrophoresis confirmed the presence of a single transposon in each ... | 2000 | 10698789 |
| identification of arabidopsis mutants exhibiting an altered hypersensitive response in gene-for-gene disease resistance. | a mutational study was carried out to isolate arabidopsis thaliana plants that exhibit full or partial disruption of the rps2-mediated hypersensitive response (hr) to pseudomonas syringae that express avrrpt2. five classes of mutants were identified including mutations at rps2, dnd mutations causing a "defense, no death" loss-of-hr phenotype, a lesion-mimic mutant that also exhibited an hr- phenotype, and a number of intermediate or partial-loss-of-hr mutants. surprisingly, many of these mutants ... | 2000 | 10707353 |