| diurnal rhythms in calcium and phosphate metabolism in rodents and their relations to lighting and feeding schedules. | diurnal fluctuations in serum ca, inorganic phosphorus, mg, and alkaline phosphatase activity and their relations to lighting and feeding schedules were investigated in nocturnal rats and diurnal asiatic chipmunks. the following results were obtained: all parameters in the animals fed ad libitum and adapted to a regulated light-dark cycle (with light from 7.00 to 19.00 h) showed diurnal rhythms; under the same experimental condition, the patterns of the rhythms in the nocturnal rat and the diurn ... | 1985 | 4040208 |
| [immunological study of anti-cancer effects of human alpha interferon for advanced renal cell carcinoma]. | | 1985 | 4079199 |
| [development of polyribosomes during maturation of reticulocytes in vivo]. | | 1970 | 4098024 |
| studies on the therapeutic use of mercurascan (msc). part 2: antiarrhythmogenic and haemodynamic effect of msc in experimental myocardial ischaemia. | | 1974 | 4140846 |
| analgesia produced by clonidine in mice and rats. | | 1974 | 4152777 |
| hidden antigenic determinant in secretory immunoglobulin a. | | 1968 | 4176458 |
| the vaccination of man and other animals against rabies. | | 1973 | 4207636 |
| [stabilization of n-antigens of enteroviruses]. | | 1970 | 4322838 |
| isolation of heart-resistant clostridium perfringens from healthy cattle. | | 1972 | 4333445 |
| [electrophysiologic, histochemical and immunologic correlates in the central mechanism of audiogenic epilepsy]. | | 1972 | 4336346 |
| effects of photooxidation of histidine-38 on the acetylphosphatase activity of glyceraldehyde-3-phosphate dehydrogenase. | | 1973 | 4345586 |
| suppression of herpes simplex virus infection by phosphonoacetic acid. | disodium phosphonoacetate when administered orally or topically to mice experimentally infected with herpes simplex virus was able to significantly reduce the mortality associated with the agent. in addition, this compound was able to reduce herpesvirus lesions on the corneas of infected rabbits. | 1973 | 4356456 |
| [muscarinic receptors of the superior cervical lymph node of the cat]. | | 1966 | 4386667 |
| effects of steroid and nonsteroid metabolites on enzyme conformation and pyridoxal phosphate binding. | | 1969 | 4391266 |
| a hydrogen-bond network at the active site of subtilisin bpn'. | | 1970 | 4399039 |
| effect of prostaglandin f2alpha on the luteal phase of the cycle in nonpregnant women. | 11 healthy nonpregnant female volunteers were treated with (pgf) prostaglandin f2alpha as the tham salt in aqueous solution administratered intravaginally. (hcg) human chorionic gonadotropins was also administered to 9 of these women prior to or following the pg therapy to simulate secreting the phoblast. it was considered that luteolysis occurred if serum progestin declined to preovulatory levels, if there was no increase of serum progestin levels following hcg, and if there was shortening of ... | 1974 | 4429112 |
| [specificity of antibodies in experimental trichinosis of the rat]. | | 1974 | 4455270 |
| "uterine" and "luteal" effects of prostaglandins (pg) in rats and guinea pigs as potential abortifacient mechanisms. | | 1973 | 4542124 |
| cyclizing compounds. 3. local anesthetic action of n-(omega-haloalkyl)-n-methylaminoaceto-2,6-xylidides. | | 1973 | 4542166 |
| antibody-dependent lymphocyte-mediated cytotoxicity in man: no requirement for lymphocytes with membrane-bound immunoglobulin. | | 1973 | 4542262 |
| [response of the recipient's tissue bed and features of reparative osteogenesis in retransplantation of bone tissue]. | | 1972 | 4553209 |
| biochemical aspects of some pig muscle disorders. | | 1972 | 4553607 |
| phases of the inflammatory response to subcutaneous implantation of a cotton pellet and their modification by certain anti-inflammatory agents. | | 1972 | 4562620 |
| bilateral tubal pregnancy with an unusual complication. | | 1973 | 4570658 |
| the mechanism of action of beta-galactosidase. effect of aglycone nature and -deuterium substitution on the hydrolysis of aryl galactosides. | 1. steady-state kinetic parameters for the beta-galactosidase-catalysed hydrolysis of 13 aryl beta-d-galactopyranosides show no simple dependence on aglycone acidity. 2. alpha-deuterium kinetic isotope effects (k(h)/k(d)) for seven of these substrates, measured under steady-state conditions with [s]>>k(m), vary from 1.00 for poor substrates to 1.25 for hydrolysis of the galactosyl-enzyme. 3. methanolysis of the galactosyl-enzyme in 1.5m-methanol increases k(h)/k(d) for degalactosylation, but lea ... | 1973 | 4578762 |
| biogenesis of mitochondria. xxv. studies on the mitochondrial genomes of petite mutants of yeast using ethidium bromide as a probe. | | 1973 | 4583801 |
| sensitivity of klebsiella, enterobacter, and escherichia coli to cephalothin. | | 1969 | 4885058 |
| significance of achromobacter nematophilus poinar and thomas (achromobacteraceae: eubacteriales) in the development of the nematode, dd-136 (neoaplectana sp. steinernematidae). | | 1966 | 4960247 |
| ultrastructure of achromobacter nematophilus poinar et thomas bacteria. | | 1972 | 5052048 |
| relationship of rumen volatile fatty acids to type of grain,sorghum grain processing method and feedlot performance. | | 1972 | 5055758 |
| antimicrobial activity and biosynthesis of indole antibiotics produced by xenorhabdus nematophilus. | we have investigated the mechanism of action and physiology of production of the indole derivative antibiotics produced by the nematode-associated, entomopathogenic bacterium xenorhabdus nematophilus. maximum antibiotic concentration was reached during the late stationary phase of growth, and the antibiotic yield was appreciably enhanced by supplementation with tryptophan. antibiotic biosynthesis apparently involved the removal of the side-chain carboxyl (c-1) carbon of tryptophan. the c-3 methy ... | 1993 | 7510325 |
| purification and characterization of xenorhabdicin, a phage tail-like bacteriocin, from the lysogenic strain f1 of xenorhabdus nematophilus. | xenorhabdicin, the phage tail-like bacteriocins of xenorhabdus nematophilus, and phage head particles, elements produced together after mitomycin induction in x. nematophilus lysogenic strain f1 cultures, were separated by deae chromatography, examined by transmission electron microscopy, and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. electrophoresis of xenorhabdicin showed two major subunits of 43 and 20 kda corresponding to the sheath and the inner core, respec ... | 1995 | 7646048 |
| characterization and environmental regulation of outer membrane proteins in xenorhabdus nematophilus. | we have examined the production of the outer membrane proteins of the primary and secondary forms of xenorhabdus nematophilus during exponential- and stationary-phase growth at different temperatures. the most highly expressed outer membrane protein of x. nematophilus was opnp. the amino acid composition of opnp was very similar to those of the porin proteins ompf and ompc of escherichia coli. n-terminal amino acid sequence analysis revealed that residues 1 to 27 of the mature opnp shared 70 and ... | 1995 | 7887602 |
| interaction of mutants of xenorhabdus nematophilus (enterobacteriaceae) with antibacterial systems of galleria mellonella larvae (insecta: pyralidae). | xenorhabdus nematophilus mutants that took longer to kill insects than did the wild type were used to determine the relationship of the physicochemical properties and outer membrane composition to bacterial interaction with the antibacterial systems of galleria mellonella larvae and to bacterial virulence. insect serum slowed the growth of the wild-type and mutant bacteria. this was attributed to increased spheroplast formation for the mutants. spheroplast formation was associated with an increa ... | 1994 | 8012904 |
| molecular analysis of the two-component genes, ompr and envz, in the symbiotic bacterium xenorhabdus nematophilus. | in escherichia coli the histidine kinase sensor protein, envz, undergoes autophosphorylation and subsequently phosphorylates the regulatory protein, ompr. modulation of the levels of ompr-phosphate controls the differential expression of ompf and ompc. while the phosphotransfer reaction between envz and ompr has been extensively studied, the domains involved in the sensing function of envz are not well understood. we have used a comparative approach to study the sensing function of envz. during ... | 1995 | 8801419 |
| functional and regulatory analysis of the ompf-like porin, opnp, of the symbiotic bacterium xenorhabdus nematophilus. | the function and novel regulation of opnp of the symbiotic/pathogenic bacterium, xenorhabdus nematophilus was studied. in vitro pore-function analysis of purified opnp indicated that the single-channel-conductance values were similar to that measured for the porin protein, ompf, of esherichia coli. nucleotide sequence analysis revealed that the mature opnp protein contained 348 amino acid residues and shared 55% amino acid sequence identity with ompf. similar to ompf, opnp mapped between asns an ... | 1995 | 8817498 |
| chitinase activity of xenorhabdus and photorhabdus species, bacterial associates of entomopathogenic nematodes. | xenorhabdus nematophilus (three strains), xenorhabdus bovienii (one strain), and photorhabdus luminescens (one strain) showed both exo- and endochitinase activity using p-nitrophenyl-n-acetyl-beta-d-glucosaminide and p-nitrophenyl-beta-d-n,n',n'-triacetylchitotriose, respectively, as substrates. one to three bands were detected on page gel with glycol chitin after electrophoresis. variation in exo- and endochitinase activity among different species and strains was detected with the strongest act ... | 1996 | 8858906 |
| phylogenetic relationships of entomopathogenic nematophilic bacteria: xenorhabdus spp. and photorhabdus sp. | phylogenetic relationships of xenorhabdus spp. and photorhabdus sp. were investigated on the basis of 16s rrna gene sequences. xenorhabdus spp. and photorhabdus sp. were grouped together with proteus vulgaris and arsenophonus nasoniae. this group was distant from other members of the family enterobacteriaceae. xenorhabdus japonicus, previously proposed as a new species, was nearly located to xenorhabdus nematophilus. signature nucleotides of x. japonicus were identified that distinguish it other ... | 1996 | 8914266 |
| cloning and nucleotide sequence of a flagellin encoding genetic locus from xenorhabdus nematophilus: phase variation leads to differential transcription of two flagellar genes (flicd). | the insect-pathogenic bacterium xenorhabdus undergoes spontaneous phase variation involving a large number of phenotypes. our previous study indicated that phase i variants were motile, whereas phase ii variants of x. nematophilus f1 were nonflagellated cells which did not synthesize flagellin [givaudan a., baghdiguian, s., lanois, a. and boemare, n. (1995) appl. environ. microbiol. 61, 1408-1413]. in order to approach the study of the flagellar switching, a locus containing two orfs from x. nem ... | 1996 | 8996114 |
| role of the histidine kinase, envz, in the production of outer membrane proteins in the symbiotic-pathogenic bacterium xenorhabdus nematophilus. | we show that inactivation of envz, the gene encoding the histidine kinase sensor protein, envz, of xenorhabdus nematophilus, affected the production of several outer membrane proteins (opns). x. nematophilus produced five major opns during exponential growth. insertional inactivation of envz led to a decrease in the production of opnp, the ompf-like pore-forming protein which constitutes approximately 50% of the total outer membrane protein in x. nematophilus. opna production was also reduced, w ... | 1997 | 9055414 |
| a homoserine lactone autoinducer regulates virulence of an insect-pathogenic bacterium, xenorhabdus nematophilus (enterobacteriaceae). | n-beta-hydroxybutanoyl homoserine lactone (hbhl), the autoinducer of the luminescent system of vibrio harveyi, has been identified as the first small compound to restore virulence to avirulent mutants of xenorhabdus nematophilus. hbhl stimulated the level of lipase activity excreted by avirulent x. nematophilus and lowered the phenoloxidase activity in the hemolymph of insects infected with x. nematophilus, parameters that are both associated with insect pathogenesis. moreover, mortality of the ... | 1997 | 9286978 |
| nematophin, a novel antimicrobial substance produced by xenorhabdus nematophilus (enterobactereaceae). | a new antibiotic, nematophin, was isolated from strain bc1 of xenorhabdus nematophilus and detected in all strains of x. nematophilus studied. its structure is fully established as 3-indoleethyl (3'-methyl-2'-oxo)pentanamide by extensive spectroscopic study. the production of nematophin is affected by the strain type and culture conditions. the compound shows strong in vitro bioactivity against a series of fungal and bacterial species. | 1997 | 9304787 |
| isolation and entomotoxic properties of the xenorhabdus nematophilus f1 lecithinase. | xenorhabdus spp. and photorhabdus spp., entomopathogenic bacteria symbiotically associated with nematodes of the families steinernematidae and heterorhabditidae, respectively, were shown to produce different lipases when they were grown on suitable nutrient agar. substrate specificity studies showed that photorhabdus spp. exhibited a broad lipase activity, while most of the xenorhabdus spp. secreted a specific lecithinase. xenorhabdus spp. occur spontaneously in two variants, phase i and phase i ... | 1998 | 9647801 |
| photorhabdus toxins: novel biological insecticides. | following concerns over the potential for insect resistance to insecticidal bacillus thuringiensis toxins expressed in transgenic plants, there has been recent interest in novel biological insecticides. over the past year there has been considerable progress in the cloning of several alternative toxin genes from the bacteria photorhabdus luminescens and xenorhabdus nematophilus. these genes encode large insecticidal toxin complexes with little homology to other known toxins. | 1999 | 10383860 |
| flhdc, the flagellar master operon of xenorhabdus nematophilus: requirement for motility, lipolysis, extracellular hemolysis, and full virulence in insects. | xenorhabdus is a major insect pathogen symbiotically associated with nematodes of the family steinernematidae. this motile bacterium displays swarming behavior on suitable media, but a spontaneous loss of motility is observed as part of a phenomenon designated phase variation which involves the loss of stationary-phase products active as antibiotics and potential virulence factors. to investigate the role of one of the transcriptional activators of flagellar genes, flhdc, in motility and virulen ... | 2000 | 10613869 |
| pathogenicity caused by high virulent and low virulent strains of steinernema carpocapsae to galleria mellonella. | steinernema carpocapsae is an entomopathogenic nematode associated with a symbiotic bacterium, xenorhabdus nematophilus. both components of the complex participate in a pathogenic process in insects. this has raised two questions: how much does each one participate, and what mechanisms are involved? in this paper we compare the virulence of two strains of s. carpocapsae: a high virulent strain (breton) and a low virulent strain (az27), both of which are free of symbiotic bacteria. breton and az2 ... | 2000 | 10631057 |
| pathogenicity, development, and reproduction of heterorhabditis bacteriophora and steinernema carpocapsae under axenic in vivo conditions. | galleria mellonella larvae cultured axenically were treated with axenic dauer juveniles of heterorhabditis bacteriophora and steinernema carpocapsae. after 3 days s. carpocapsae had killed all insects, with 9.4 +/- 4.3 nematodes per larva. h. bacteriophora were unable to kill g. mellonella, although 13.3 +/- 6.4 nematodes per galleria were found in the hemocoel. invading nematodes of both strains recovered from the dauer stage. h. bacteriophora developed into hermaphrodites with eggs and j1 in t ... | 2000 | 10631058 |
| interaction of hemocytes and prophenoloxidase system of fifth instar nymphs of acheta domesticus with bacteria. | the hemocytes to which bacteria adhere were defined and the contribution of the prophenoloxidase system of fifth instar nymphs of acheta domesticus to adhesion were examined. the physicochemical parameters affecting hemocyte and phenoloxidase activity were determined. both plasmatocytes and granular cells responded to bacteria, the latter cells entrapping the microorganisms on filopodial extensions. the optimum ph for hemocyte adhesion to glass slides was 6.5, the granular cells being the most s ... | 2000 | 10736521 |
| inactivation of a novel gene produces a phenotypic variant cell and affects the symbiotic behavior of xenorhabdus nematophilus. | xenorhabdus nematophilus is an insect pathogen that lives in a symbiotic association with a specific entomopathogenic nematode. during prolonged culturing, variant cells arise that are deficient in numerous properties. to understand the genetic mechanism underlying variant cell formation, a transposon mutagenesis approach was taken. three phenotypically similar variant strains of x. nematophilus, each of which contained a single transposon insertion, were isolated. the insertions occurred at dif ... | 2000 | 10742251 |
| eicosanoids rescue spodoptera exigua infected with xenorhabdus nematophilus, the symbiotic bacteria to the entomopathogenic nematode steinernema carpocapsae. | xenorhabdus nematophilus is a pathogenic bacterium causing insect haemolymph septicemia, which leads to host insect death. to address the fundamental mechanisms underlying this haemolymph septicemia, or the immunodepressive response of the host insects following bacterial infection, we tested a hypothesis that the insect immune-mediating eicosanoid pathway is blocked by inhibitory action of the bacterium. haemocoelic injection of the bacteria into the fifth instar larvae of spodoptera exigua red ... | 2000 | 10891575 |
| novel insecticidal toxins from nematode-symbiotic bacteria. | the current strategy of using transgenic crops expressing insecticidal protein toxins is placing increasing emphasis on the discovery of novel toxins, beyond those already derived from the bacterium bacillus thuringiensis. here we review the cloning of four insecticidal toxin complex (tc) encoding genes from a different bacterium photorhabdus luminescens and of similar gene sequences from xenorhabdus nematophilus. both these bacteria occupy the gut of entomopathogenic nematodes and are released ... | 2000 | 10892346 |
| a new broad-spectrum protease inhibitor from the entomopathogenic bacterium photorhabdus luminescens. | a new protease inhibitor was purified to apparent homogeneity from a culture medium of photorhabdus luminescens by ammonium sulfate precipitation and preparative isoelectric focusing followed by affinity chromatography. ph. luminescens, a bacterium symbiotically associated with the insect-parasitic nematode heterorhabditis bacteriophora, exists in two morphologically distinguishable phases (primary and secondary). it appears that only the secondary-phase bacterium produces this protease inhibito ... | 2000 | 11101672 |
| interaction of xenorhabdus nematophilus (enterobacteriaceae) with the antimicrobial defenses of the house cricket, acheta domesticus. | fifth instar acheta domesticus nymphs exhibited a decline in total hemocyte counts during the first hour of exposure to dead xenorhabdus nematophilus; the bacterial level in the hemolymph also declined during this time. thereafter bacterial numbers in the hemolymph increased as the level of damaged hemocytes increased. the bacteria lowered phenoloxidase activity in vivo by initially reducing the number of hemocytes containing prophenoloxidase and later by inhibiting enzyme activation. preincubat ... | 2000 | 11112374 |
| sequence analysis of insecticidal genes from xenorhabdus nematophilus pmfi296. | three strains of xenorhabdus nematophilus showed insecticidal activity when fed to pieris brassicae (cabbage white butterfly) larvae. from one of these strains (x. nematophilus pmfi296) a cosmid genome library was prepared in escherichia coli and screened for oral insecticidal activity. two overlapping cosmid clones were shown to encode insecticidal proteins, which had activity when expressed in e. coli (50% lethal concentration [lc(50)] of 2 to 6 microg of total protein/g of diet). the complete ... | 2001 | 11319082 |
| two distinct hemolytic activities in xenorhabdus nematophila are active against immunocompetent insect cells. | xenorhabdus spp. and photorhabdus spp. are major insect bacterial pathogens symbiotically associated with nematodes. these bacteria are transported by their nematode hosts into the hemocoel of the insect prey, where they proliferate within hemolymph. in this work we report that wild strains belonging to different species of both genera are able to produce hemolysin activity on blood agar plates. using a hemocyte monolayer bioassay, cytolytic activity against immunocompetent cells from the hemoly ... | 2001 | 11375158 |
| the effect of temperature on the fatty acids and isozymes of a psychrotrophic and two mesophilic species of xenorhabdus, a bacterial symbiont of entomopathogenic nematodes. | in the first part of this study, generation times relative to temperature, together with cardinal and conceptual temperatures, were determined for four strains of xenorhabdus bacteria that represented three geographically distinct species. the data showed that the nf strain of xenorhabdus bovienii, like the umeå strain of the same species, is psychrotrophic, while xenorhabdus sp. tx strain resembles xenorhabdus nematophila all strain in being mesophilic. in the second part, the capacity of these ... | 2001 | 11400727 |
| xenorhabdus nematophilus as a model for host-bacterium interactions: rpos is necessary for mutualism with nematodes. | xenorhabdus nematophilus, a gram-negative bacterium, is a mutualist of steinernema carpocapsae nematodes and a pathogen of larval-stage insects. we use this organism as a model of host-microbe interactions to identify the functions bacteria require for mutualism, pathogenesis, or both. in many gram-negative bacteria, the transcription factor sigma(s) controls regulons that can mediate stress resistance, survival, or host interactions. therefore, we examined the role of sigma(s) in the ability of ... | 2001 | 11466270 |
| purification and characterization of an extracellular protease from xenorhabdus nematophila involved in insect immunosuppression. | xenorhabdus nematophila, a bacterium pathogenic for insects associated with the nematode steinernema carpocapsae, releases high quantities of proteases, which may participate in the virulence against insects. zymogram assays and cross-reactions of antibodies suggested that two distinct proteases were present. the major one, protease ii, was purified and shown to have a molecular mass of 60 kda and an estimated isoelectric point of 8.5. protease ii digested the chromogenic substrate n-tosyl-gly-p ... | 2002 | 11872480 |
| identification of xenorhabdus nematophila genes required for mutualistic colonization of steinernema carpocapsae nematodes. | one stage in the symbiotic interaction between the bacterium xenorhabdus nematophila and its nematode host, steinernema carpocapsae, involves the species-specific colonization of the nematode intestinal vesicle by the bacterium. to characterize the bacterial molecular determinants that are essential for vesicle colonization, we adapted and applied a signature-tagged mutagenesis (stm) screen to this system. we identified 15 out of 3000 transposon mutants of x. nematophila with at least a 15-fold ... | 2002 | 12207701 |
| xenorhabdus nematophila (enterobacteriacea) secretes a cation-selective calcium-independent porin which causes vacuolation of the rough endoplasmic reticulum and cell lysis. | xenorhabdus nematophila and photorhabdus luminescens are two related enterobacteriaceae studied for their use in biological control and for synthesis of original virulence factors and new kinds of antibiotics. x. nematophila broth growth exhibits different cytotoxic activities on insect (spodoptera littoralis, lepidoptera) immunocytes (hemocytes). here we report the purification of the flhdc-dependent cytotoxin, a 10,790-da peptide we have called alpha-xenorhabdolysin (alpha x). we show that pla ... | 2003 | 12441337 |
| characterization of the pleiotropic phenotype of an ompr strain of xenorhabdus nematophila. | xenorhabdus nematophila is an insect pathogen that forms a symbiotic association with the nematode, steinernema carpocapsae. xenorhabdus is carried into the insect host by the nematode, is released into the hemolymph and participates in killing the insect. the bacteria grow to high concentrations supporting the development of the nematode in the hemolymph. ompr is a global regulatory protein involved in the regulation of porin genes, motility, acid tolerance and virulence in several enteric bact ... | 2002 | 12448704 |
| response of ants to a deterrent factor(s) produced by the symbiotic bacteria of entomopathogenic nematodes. | the production of an ant-deterrent factor(s) (adf) by xenorhabdus nematophila and photorhabdus luminescens, the symbiotic bacteria of the nematodes steinernema carpocapsae and heterorhabditis bacteriophora, respectively, was examined. in addition to an in vivo assay in which bacteria were tested for their ability to produce adf within insect cadavers (m.e. baur, h. k. kaya, and d. r. strong, biol. control 12:231-236, 1998), an in vitro microtiter dish assay was developed to monitor adf activity ... | 2002 | 12450845 |
| n-phenethyl-2-phenylacetamide isolated from xenorhabdus nematophilus induces apoptosis through caspase activation and calpain-mediated bax cleavage in u937 cells. | the present study was designed to assess the mechanism of n-phenethyl-2-phenylacetamide (nppa), one of three new compounds isolated from xenorhabdus nematophilus, on the induction of apoptosis in u937 cells. nppa displayed strong inhibitory effects on cell proliferation and viability of u937 cells and induced apoptosis. investigation of the mechanism of nppa-induced apoptosis revealed that treatment with nppa produced morphological features of apoptosis and dna fragmentation. this was associated ... | 2003 | 12469198 |
| generation and properties of a luminescent insect pathogen xenorhabdus nematophilus (enterobacteriaceae). | studies on the interaction of the insect pathogenic bacterium, xenorhabdus nematophilus (enterobacteriaceae), with its nematode and insect hosts would be greatly assisted if a luminescent phenotype were generated that would allow the detection of viable bacteria in vivo without the necessity for disruption of the cellular interactions. the plasmid, pmgm221, containing the luminescence gene (luxcdabe) of vibrio harveyi was introduced into different strains (dd136 and 19061) and phases (one and tw ... | 1998 | 12501420 |
| the bacterium xenorhabdus nematophilus depresses nodulation reactions to infection by inhibiting eicosanoid biosynthesis in tobacco hornworms, manduca sexta. | the bacterium, xenorhabdus nematophilus, is a virulent insect pathogen. we tested the hypothesis that this bacterium impairs insect cellular immune defense reactions by inhibiting biosynthesis of eicosanoids involved in mediating cellular defense reactions. fifth instar tobacco hornworms, manduca sexta, produced melanized nodules in reaction to challenge with living and heat-killed x. nematophilus. however, the nodulation reactions were much attenuated in insects challenged with living bacteria ... | 2003 | 12529862 |
| holin locus characterisation from lysogenic xenorhabdus nematophila and its involvement in escherichia coli shea haemolytic phenotype. | lysogeny has previously been described in the entomopathogenic bacteria of the genus xenorhabdus. screening of a x. nematophila prophage dna library on blood agar resulted in the identification of a 5.7-kb locus that caused a haemolytic phenotype when cloned in escherichia coli, but not in the e. coli shea null mutant, lacking the shea cryptic haemolysin. this locus exhibited similarity to lysis genes from lambdoid phages. in particular, it encoded a functional holin able to complement a lambda ... | 2003 | 12583905 |
| insecticidal activity associated with the outer membrane vesicles of xenorhabdus nematophilus. | xenorhabdus nematophilus secretes a large number of proteins into the culture supernatant as soluble proteins and also as large molecular complexes associated with the outer membrane. transmission electron micrographs of x. nematophilus cells showed that there was blebbing of the outer membrane from the surface of the bacterium. the naturally secreted outer membrane vesicles (omvs) were purified from the culture supernatant of x. nematophilus and analyzed. electron microscopy revealed a vesicula ... | 2003 | 12676679 |
| early colonization events in the mutualistic association between steinernema carpocapsae nematodes and xenorhabdus nematophila bacteria. | the bacterium xenorhabdus nematophila is a mutualist of the entomopathogenic nematode steinernema carpocapsae. during its life cycle, the bacterium exists both separately from the nematode and as an intestinal resident of a nonfeeding nematode form, the infective juvenile (ij). the progression of x. nematophila from an ex vivo existence to a specific and persistent colonization of ijs is a model to understand the mechanisms mediating the initiation and maintenance of benign host-microbe interact ... | 2003 | 12730175 |
| insect immunity-effects of factors produced by a nematobacterial complex on immunocompetent cells(1). | during in vitro incubations, the nematobacterial complex steinernema carpocapsae-xenorhabdus nematophilus produces different factors having toxic activities in vitro towards haemocytes, the insect cells responsible for cellular immune defense reactions. among others, two effects were evident on haemocyte monolayers; one of them was a cytotoxic activity while the other was an unsticking effect. the factors responsible for cytotoxic activity and unsticking effect, were separated from each other by ... | 1999 | 12770353 |
| haemolymph proteins of larvae of galleria mellonella detoxify endotoxins of the insect pathogenic bacteria xenorhabdus nematophilus (enterobacteriaceae). | haemolymph of non-vaccinated galleria mellonella larvae contains two proteins, lbp-1 (17.2kda) and lbp-2 (26.0kda) that:bond to the surfaces of the insect pathogenic bacteria, xenorhabdus nematophilus;prevented lipid a-binding dye attaching to the lipid a of x. nematophilus endotoxin; andreduced endotoxin activity on the haemocytes.protein lbp-1 also blocked the inhibition of prophenoloxidase activation by the endotoxins. it is proposed that proteins lbp-1 and lbp-2 are part of the containment r ... | 1997 | 12770474 |
| xenorhabdus nematophila requires an intact iscrsua-hscba-fdx operon to colonize steinernema carpocapsae nematodes. | an insertion between isca and hscb of the xenorhabdus nematophila iscrsua-hscba-fdx locus, predicted to encode fe-s assembly machinery, prevented colonization of steinernema carpocapsae nematodes. the insertion disrupted cotranscription of isca and hscb, but did not reduce hscba expression, suggesting that x. nematophila requires coordinated expression of the isc-hsc-fdx locus for colonization. | 2003 | 12775707 |
| interactions of insecticidal toxin gene products from xenorhabdus nematophilus pmfi296. | four genes on a genomic fragment from xenorhabdus nematophilus pmfi296 were shown to be involved in insecticidal activity towards three commercially important insect species. each gene was expressed individually and in combinations in escherichia coli, and the insecticidal activity of the lysates was determined. the combined four genes (xpta1, xpta2, xptb1, and xptc1), in e. coli, showed activity towards pieris brassicae, pieris rapae, and heliothis virescens. the genes xpta1, xptb1, and xptc1 w ... | 2003 | 12788735 |
| lysozyme of the beet armyworm, spodoptera exigua: activity induction and cdna structure. | lysozyme of the beet armyworm, spodoptera exigua, was characterized in its up-regulation pattern, and its cdna was cloned by rt-pcr using degenerate primers designed from some conserved amino acid regions shared with related lepidopteran species. lysozyme activity of the non-immunized s. exigua had developmental variation, with the highest level in the fifth instar larvae. the basal level of the lysozyme activity was significantly enhanced by the injection of laminarin or lipopolysaccharide (lps ... | 2003 | 12831771 |
| inactivation of ompr promotes precocious swarming and flhdc expression in xenorhabdus nematophila. | the response regulator ompr is involved in numerous adaptive responses to environmental challenges. the role that ompr plays in swarming behavior and swarm-cell differentiation in the symbiotic-pathogenic bacterium xenorhabdus nematophila was examined in this study. swarming began 4 h sooner in an ompr mutant strain than in wild-type cells. precocious swarming was correlated with elevated expression of flic, early flagellation, and cell elongation. the level of flhdc mrna was elevated during the ... | 2003 | 12923104 |
| xenorhabdus nematophilus inhibits p-bromophenacyl bromide (bpb)-sensitive pla2 of spodoptera exigua. | xenorhabdus nematophilus is a gram-negative symbiotic bacterium of the entomopathogenic nematode, steinernema carpocapsae. the bacteria delivered into the insect hemocoel by the nematodes cause immunodepression of the target insects to protect host nematodes and themselves from the cellular immune reaction. previous reports suggest that the immunodepression is caused by inhibition of the eicosanoid pathway that is known to be critically important to mediate cellular immunity. this study focused ... | 2003 | 14571507 |
| a novel secreted protein toxin from the insect pathogenic bacterium xenorhabdus nematophila. | the bacterium xenorhabdus nematophila is an insect pathogen that produces several proteins that enable it to kill insects. screening of a cosmid library constructed from x. nematophila strain a24 identified a gene that encoded a novel protein that was toxic to insects. the 42-kda protein encoded by the toxin gene was expressed and purified from a recombinant system, and was shown to kill the larvae of insects such as galleria mellonella and helicoverpa armigera when injected at doses of around 3 ... | 2004 | 14707137 |
| characterization of a cytotoxic pilin subunit of xenorhabdus nematophila. | xenorhabdus nematophila is an insect pathogenic bacterium, known to produce protein toxins that kill the larval host. we have described a cytotoxic pilin subunit of x. nematophila, which is expressed on the cell surface and also secreted in the extracellular medium associated with outer membrane vesicles. a 17kda pilin subunit was isolated and purified from x. nematophila cell surface. the protein showed cytotoxicity to larval hemocytes of helicoverpa armigera in an in vitro assay, causing agglu ... | 2004 | 14751223 |
| bacterial insecticidal toxins. | over the years it has been important for humans to control the populations of harmful insects and insecticides have been used for this purpose in agricultural and horticultural sectors. synthetic insecticides, owing to their various side effects, have been widely replaced by biological insecticides. in this review we attempt to describe three bacterial species that are known to produce insecticidal toxins of tremendous biotechnological, agricultural, and economic importance. bacillus thuringiens ... | 2004 | 15116762 |
| unique organization and regulation of the mrx fimbrial operon in xenorhabdus nematophila. | xenorhabdus nematophila, a gram-negative bacterium belonging to the proteus clade of the family enterobacteriaceae, forms a mutualistic association with the soil nematode steinernema carpocapsae. the nematode invades insects and releases xenorhabdus into the haemolymph, where it participates in insect killing. to begin to understand the role of fimbriae in the unique life cycle of xenorhabdus, the organization and expression of the mrx fimbrial operon was analysed. the mrx operon contained only ... | 2004 | 15133105 |
| an entomopathogenic bacterium, xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, spodoptera exigua. | an entomopathogenic bacterium, xenorhabdus nematophila, is known to depress hemocyte nodule formation of target insects by inhibiting eicosanoid biosynthesis. this study analyzed the inhibitory effect of x. nematophila on the humoral immunity of the target insects and tested its association with the host eicosanoid pathway. plasma collected from the fifth instar larvae of spodoptera exigua, when they were injected with x. nematophila, did not show antibacterial activity against escherichia coli ... | 2004 | 15183278 |
| cloning and heterologous expression of a novel insecticidal gene (tccc1) from xenorhabdus nematophilus strain. | we have identified and cloned a novel toxin gene (tccc1/xptb1) from xenorhabdus nematophilus strain isolated from korea-specific entomophagous nematode steinernema glaseri mk. the dna sequence of cloned toxin gene (3048 bp) has an open reading frame encoding 1016 amino acids with a predicted molecular mass of 111058 da. the toxin sequence shares 50-96% identical amino acid residues with the previously reported tccc1 cloned from x. nematophilus, photorhabdus luminescens w14 p. luminescens tto1, a ... | 2004 | 15194482 |
| bacterial formyl peptides affect the innate cellular antimicrobial responses of larval galleria mellonella (insecta: lepidoptera). | the non-self cellular (hemocytic) responses of galleria mellonella larvae, including the attachment to slides and the removal of the bacteria xenorhabdus nematophila and bacillus subtilis from the hemolymph, were affected by n-formyl peptides. both n-formyl methionyl-leucyl-phenylalanine (fmlf) and the ester derivative decreased hemocyte adhesion in vitro, and both elevated hemocyte counts and suppressed the removal of both x. nematophila and b. subtilis from the hemolymph in vivo. the amide der ... | 2004 | 15213752 |
| silkworm (bombyx mori) hemocytes do not produce reactive oxygen metabolites as a part of defense mechanisms. | to investigate whether hemocytes of bombyx mori (lepidoptera) larvae produce reactive oxygen species (ros) as part of the oxidative killing of invading pathogens, the production of ros was measured as a luminol- and lucigenin-enhanced chemiluminescence of unstimulated or stimulated (zymosan particles, phorbol myristate acetate, calcium ionophore, rice starch or xenorhabdus nematophila) hemolymph. no detectable ros production was found. the spontaneous and activated ros production measured with h ... | 2004 | 15259774 |
| an entomopathogenic bacterium, xenorhabdus nematophila, inhibits hemocytic phospholipase a2 (pla2) in tobacco hornworms manduca sexta. | the entomopathogenic bacterium, xenorhabdus nematophila, induces immunodepression in target insects and finally leads to lethal septicemia of the infected hosts. a hypothesis has been raised that the bacteria inhibit eicosanoid-biosynthesis pathway to interrupt immune signaling of the infected hosts. here, we show direct evidence that x. nematophila inhibits the activity of phospholipase a2 (pla2), the initial step in the eicosanoid-biosynthesis pathway. inhibition of pla2 was dependent on both ... | 2004 | 15261769 |
| the bacterium xenorhabdus nematophila inhibits phospholipases a2 from insect, prokaryote, and vertebrate sources. | the bacterium, xenorhabdus nematophila, is a virulent insect pathogen. part of its pathogenicity is due to impairing cellular immunity by blocking biosynthesis of eicosanoids, the major recognized signal transduction system in insect cellular immunity. x. nematophila inhibits the first step in eicosanoid biosynthesis, phospholipase a(2) (pla(2)). here we report that the bacterium inhibits pla(2) from two insect immune tissues, hemocytes and fat body, as well as pla(2)s selected to represent a wi ... | 2004 | 15278222 |
| when mutualists are pathogens: an experimental study of the symbioses between steinernema (entomopathogenic nematodes) and xenorhabdus (bacteria). | in this paper, we investigate the level of specialization of the symbiotic association between an entomopathogenic nematode (steinernema carpocapsae) and its mutualistic native bacterium (xenorhabdus nematophila). we made experimental combinations on an insect host where nematodes were associated with non-native symbionts belonging to the same species as the native symbiont, to the same genus or even to a different genus of bacteria. all non-native strains are mutualistically associated with con ... | 2004 | 15312071 |
| identification and functional characterization of a xenorhabdus nematophila oligopeptide permease. | the bacterium xenorhabdus nematophila is a mutualist of steinernema carpocapsae nematodes and a pathogen of insects. presently, it is not known what nutrients the bacterium uses to thrive in these host environments. in other symbiotic bacteria, oligopeptide permeases have been shown to be important in host interactions, and we therefore sought to determine if oligopeptide uptake is essential for growth or symbiotic functions of x. nematophila in laboratory or host environments. we identified an ... | 2004 | 15345451 |
| microbial control of diamondback moth, plutella xylostella l. (lepidoptera: yponomeutidae) using bacteria (xenorhabdus nematophila) and its metabolites from the entomopathogenic nematode steinernema carpocapsae. | cells and cell-free solutions of the culture filtrate of the bacterial symbiont, xenorhabdus nematophila taken from the entomopathogenic nematode steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth plutella xylostella. their application on leaves of chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. cell-free solutions containing metabolites were also proved as effective as bacterial cells ... | 2004 | 15362188 |
| insecticidal pilin subunit from the insect pathogen xenorhabdus nematophila. | xenorhabdus nematophila is an insect pathogen and produces protein toxins which kill the larval host. previously, we characterized an orally toxic, large, outer membrane-associated protein complex from the culture medium of x. nematophila. here, we describe the cloning, expression, and characterization of a 17-kda pilin subunit of x. nematophila isolated from that protein complex. the gene was amplified by pcr, cloned, and expressed in escherichia coli. the recombinant protein was refolded in vi ... | 2004 | 15375127 |
| characterization of a lipoprotein, nilc, required by xenorhabdus nematophila for mutualism with its nematode host. | xenorhabdus nematophila is a gamma-proteobacterial mutualist of an insect-pathogenic nematode, steinernema carpocapsae. x. nematophila requires nilc, a gene predicted to encode an outer membrane lipoprotein of unknown function, for colonization of its nematode host. characterization of nilc, described here, demonstrated it is a 28 kda lipoprotein directed to the periplasm by an n-terminal signal sequence. lipidation and processing of nilc occurs by a mechanism that is conserved in proteobacteria ... | 2004 | 15469517 |
| identification of an antibacterial compound, benzylideneacetone, from xenorhabdus nematophila against major plant-pathogenic bacteria. | an entomopathogenic bacterium, xenorhabdus nematophila, is known to have potent antibiotic activities to maintain monoxenic condition in its insect host for effective pathogenesis and ultimately for optimal development of its nematode symbiont, steinernema carpocapsae. in this study we assess its antibacterial activity against plant-pathogenic bacteria and identify its unknown antibiotics. the bacterial culture broth had significant antibacterial activity that increased with development of the b ... | 2004 | 15476972 |
| stages of infection during the tripartite interaction between xenorhabdus nematophila, its nematode vector, and insect hosts. | bacteria of the genus xenorhabdus are mutually associated with entomopathogenic nematodes of the genus steinernema and are pathogenic to a broad spectrum of insects. the nematodes act as vectors, transmitting the bacteria to insect larvae, which die within a few days of infection. we characterized the early stages of bacterial infection in the insects by constructing a constitutive green fluorescent protein (gfp)-labeled xenorhabdus nematophila strain. we injected the gfp-labeled bacteria into i ... | 2004 | 15528508 |
| monoxenic production of the entomopathogenic nematode steinernema carpocapsae using culture media containing agave juice (aguamiel) from mexican maguey-pulquero (agave spp). effects of the contents of nitrogen, carbohydrates and fat on infective juvenile production. | the production of infective juvenile stages (ij) of the entomopathogenic nematode steinernema carpocapsae in the presence of its symbiotic bacterium xenorhabdus nematophilus was carried out in orbitally agitated bottles. four complex culture media (m1-m4) were used, containing from 8% to 28% (by vol.) agave juice (aguamiel) from mexican maguey-pulquero (agave spp) as the main carbohydrate source. after 20 days of fermentation, a maximum viable ij concentration of 249,000 ij/ml and an initial nem ... | 2005 | 15650850 |
| expression and activity of a xenorhabdus nematophila haemolysin required for full virulence towards manduca sexta insects. | as an insect pathogen, the gamma-proteobacterium xenorhabdus nematophila likely possesses an arsenal of virulence factors, one of which is described in this work. we present evidence that the x . nematophilahaemolysin xhla is required for full virulence towards manduca sexta larvae. lrp (leucine-responsive regulatory protein), flhdc (regulator of flagella synthesis), and iron (ii) limitation positively influenced xhla transcript levels, suggesting xhla expression is linked with nutrient acquisit ... | 2005 | 15659065 |
| pathogenicity of bacterium, xenorhabdus nematophila isolated from entomopathogenic nematode (steinernema carpocapsae) and its secretion against galleria mellonella larvae. | the entomopathogenic bacterium, xenorhabdus nematophila was isolated from the hemolymph of galleria mellonella infected with steinernema carpocapsae. the bacterial cells and its metabolic secretions have been found lethal to the galleria larvae. toxic secretion in broth caused 95% mortality within 4 d of application whereas the bacterial cells caused 93% mortality after 6 d. when filter and sand substrates were compared, the later one was observed as appropriate. similarly, bacterial cells and s ... | 2005 | 15909327 |
| an encoded n-terminal extension results in low levels of heterologous protein production in escherichia coli. | the tdk gene (encoding deoxythymidine kinase) of the gamma-proteobacterium xenorhabdus nematophila has two potential translation start sites. the promoter-distal start site was predicted to be functional based on amino acid sequence alignment with closely related tdk proteins. however, to experimentally determine if either of the two possible start codons allows production of a functional tdk, we expressed the "long-form" (using the promoter-proximal start codon) and "short-form" (using the prom ... | 2005 | 16042769 |
| analysis of xenorhabdus nematophila metabolic mutants yields insight into stages of steinernema carpocapsae nematode intestinal colonization. | xenorhabdus nematophila colonizes the intestinal tract of infective-juvenile (ij) stage steinernema carpocapsae nematodes. during colonization, x. nematophila multiplies within the lumen of a discrete region of the ij intestine termed the vesicle. to begin to understand bacterial nutritional requirements during multiplication in the ij vesicle, we analysed the colonization behaviour of several x. nematophila metabolic mutants, including amino acid and vitamin auxotrophs. x. nematophila mutants d ... | 2005 | 16164547 |
| pyrimidine nucleoside salvage confers an advantage to xenorhabdus nematophila in its host interactions. | xenorhabdus nematophila is a mutualist of entomopathogenic nematodes and a pathogen of insects. to begin to examine the role of pyrimidine salvage in nutrient exchange between x. nematophila and its hosts, we identified and mutated an x. nematophila tdk homologue. x. nematophila tdk mutant strains had reduced virulence toward manduca sexta insects and a competitive defect for nematode colonization in plate-based assays. provision of a wild-type tdk allele in trans corrected the defects of the mu ... | 2005 | 16204546 |
| a secretory pla2 associated with tobacco hornworm hemocyte membrane preparations acts in cellular immune reactions. | we report on a secretory phospholipase a2 (spla2) associated with membrane-enriched fractions prepared from hemocytes of the tobacco hornworms, manduca sexta. virtually no pla2 activity was detected in serum of immunologically naive or bacterially challenged hornworms. pla2 activity was detected in cytosolic and membrane-enriched fractions prepared from hemocytes. pla2 activity in the cytosolic fraction (1.2 pmol/mg/h) was approximately 4-fold greater than in the membrane-enriched fraction. the ... | 2005 | 16235259 |
| effect of phenotypic variation in xenorhabdus nematophila on its mutualistic relationship with the entomopathogenic nematode steinernema carpocapsae. | the entomopathogenic nematode steinernema carpocapsae is mutualistically associated with the bacterium xenorhabdus nematophila. infective juveniles (ijs) transport x. nematophila cells that provide them with good conditions to reproduce within the insect. in the laboratory, long term stationary-phase culture conditions sometimes lead x. nematophila's variant 1 cells, which were previously isolated from the worms, to spontaneously and irreversibly change into a new phenotypic variant (variant 2). ... | 2005 | 16255827 |