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1.
Active defense mechanisms of plants against pathogens often include a rapid plant cell death known as the hypersensitive cell death (HCD). Hypersensitive response-assisting protein (HRAP) isolated from sweet pepper intensifies the harpinPss-mediated HCD. Here we demonstrate that constitutive expression of the hrap gene in Arabidopsis results in an enhanced disease resistance towards soft rot pathogen, E. carotovora subsp. carotovora. This resistance was due to the induction of HCD since different HCD markers viz. Athsr3, Athsr4, ion leakage, H2O2 and protein kinase were induced. One of the elicitor harpin proteins, HrpN, from Erwinia carotovora subsp. carotovora was able to induce a stronger HCD in hrap-Arabidopsis than non-transgenic controls. To elucidate the role of HrpN, we used E. carotovora subsp. carotovora defective in HrpN production. The hrpN mutant did not induce disease resistance or HCD markers in hrap-Arabidopsis. These results imply that the disease resistance of hrap-Arabidopsis against a virulent pathogen is harpin dependent.  相似文献   

2.
Summary The suicide vector pJB4JI was used to generate a range of Tn5-induced mutants of Erwinia carotovora subsp. carotovora (Ecc). One mutant, HC500, was a cysteine auxotroph which had a non-pectolytic, non-cellulolytic, non-proteolytic phenotype when grown under sulphate-limitation. The cysteine lesion of HC500 was shown to be analogous to the cysB mutation of Escherichia coli. The Ecc-cysB + gene product was identified as a protein of Mr 36000.  相似文献   

3.
Bactenecin7, a cationic antibacterial peptide, contains a repeating region of Xaa-Pro-Arg-Pro (Xaa = hydrophobic residues). A series of peptides, Xaa-Pro-Arg-Pro (Xaa = D-Ala, D-Leu, D-Val, D-Phe and D-Lys) were synthesized to investigate the effect of change of N-terminal configuration on antimicrobial activity. The conformationalpreferences of these peptides in water and TFE were examined by circular dichroism. All the synthetic peptides with D-amino acid substitution at N-terminal showed potent antifungal activity against Aspergillus niger, Aspergillus flavus and Fusarium moniliforme at the concentration level of 8–10 g ml-1. But the same tetrapeptides were unable to kill or suppress the growth of gram-negativeand gram-positive bacteria such as Escherichia coli HB101, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus even at the concentration level of 400 g ml-1. The present study reveals that the change of configuration at the N-terminal of tetrapeptide has negative impact on antibacterial activity but enhanced antifungal activity.  相似文献   

4.
Calcium is essential for the growth of rhizobia and the formation of nitrogen-fixing root-nodules on legumes, but its precise role in these processes remains unknown. We have found that Rhizobium fredii USDA208 accumulates a major 38 kDa protein when grown in media supplemented with 0.3–2 mM CaCl2. We have purified this protein and raised polyclonal antibodies against it. The protein initially is synthesized as a 40 kDa precursor which subsequently undergoes calcium-dependent processing to give rise to the mature polypeptide. Subcellular and immunocytochemical localization studies indicate that the 38 kDa protein accumulates preferentially in the periplasmic space. Its N-terminal sequence, AETIKIGVAGPMTG, shows significant homology to the N-termini of amino acid binding proteins from the periplasm, including leucine-, isoleucine-, and valine-specific binding proteins of Pseudomonas aeruginosa and Escherichia coli and a leucine-specific binding protein of E. coli. The R. fredii protein does not, however, bind [3H]-leucine. The 38 kDa protein is encoded by the bacterial chromosome. It is absent in several rhizobia other than R. fredii, but antigenically related polypeptides are present in Escherichia coli and Erwinia carotovora subsp. carotovora.  相似文献   

5.
HP (2-20) (AKKVFKRLEKLFSKIQNDK-NH2) is an antibacterial 19-mer peptide derived from the N-terminal region of Helicobacter pylori ribosomal protein L1 (RPL1). Several truncated peptides were synthesized to investigate the effects of the N- or C-terminal regions of HP (2-20) on antimicrobial activity. The antimicrobial activity of the peptides was measured by their growth inhibitory effect upon Pseudomonas aeruginosa, Salmonella typhimurium, Saccharomyces cerevisae, Trichosporon beigelii and Candida albicans. Antimicrobial activity required a full length N-terminus. None of the peptides exhibited hemolytic activity against human erythrocyte cells. The membrane-disrupting activity of these peptides, using liposomes and 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe, confirmed that the full N-terminal region of HP (2-20) is a prerequisite for antibiotic activity and that this region may facilitate penetration of the cell membrane. Circular dichroism indicated that the -helical structure of the peptides important for antimicrobial activity.  相似文献   

6.
Lectins I and II isolated from the nitrogen-fixing soil bacterium Paenibacillus polymyxa 1460 were found to be able to suppress the growth of Rhizobium leguminosarum 252 and Bacillus subtilis 36 at nearly all the concentrations tested (from 1 to 10 g/ml). Lectin I was also inhibitory to Azospirillum brasilense 245 and Erwinia carotovora subsp. citrulis 603, while lectin II exerted bactericidal activity against Xanthomonas campestris B-610 and B-611 and A. brasilense 245. The bacillar lectins incubated with Rhizobiumand Azospirillum cells caused leakage of low-molecular-weight substances from the cells, presumably resulting from impairment of the membrane barrier function. We believe that one of the possible mechanisms of the bacterial growth inhibition by lectins is mediated by the lectin-specific receptors occurring on the bacterial membrane, whose interaction with the lectin molecules induces conformational alterations in the membrane and concurrent malfunction of the metabolism of bacterial cells.  相似文献   

7.
Tachyplesin I is a 2.3 kDa antimicrobial peptide isolated from Southeast Asian horseshoe crabs. Bacterial suspensions containing 1×106 colony-forming units/ml of six isolates of pectolytic Erwinia spp., the causal pathogens of potato soft rot and blackleg, were killed in vitro by 1.4 to 11.1 g/ml of tachyplesin I. In an attempt to enhance resistance to Erwinia spp., each of the potato cultivars Bintje, Karnico and Kondor were transformed with two gene constructs encoding different precursor tachyplesin I proteins under the control of a cauliflower mosaic virus 35S promotor. Northern and western blot analysis showed that the tachyplesin I gene was expressed in transgenic plants. Small tubers of 17 transgenic clones were screened twice for soft rot resistance to Erwinia carotovora ssp. atroseptica. Under aerobic or anaerobic conditions, transgenic clones showed slightly less rot than control tubers.Abbreviations AP acidic carboxyl terminal polypeptide - Eca Erwinia carotovora ssp. atroseptica - Ecc E. carotovora ssp. carotovora - Ech E. chrysanthemi - IF intercellular fluid - SP signal peptide - TPNI (tpnI) tachyplesin I  相似文献   

8.
Tip-over disease has become a serious threat to banana plantations in the past decade. The disease is reported to be caused by Erwinia carotovorasubsp. carotovora and Erwinia chrysanthemi. We compared nine Erwinia strains of diseased banana plants from different agroclimatic zones of Karnataka and Andhra Pradesh, Southern India by conventional means. On the basis of morphological, cultural, physiological and biochemical characteristics and pathogenicity tests, the seven isolates I1 to I6 and I8 showed similarities to Erwinia carotovorasubsp. carotovora. Isolate I9 from Andhra Pradesh expressed characteristics similar to that of Erwinia chrysanthemi and was identified as Erwinia chrysanthemi. The isolate I7 which showed wider variation, neither confirmed to the characteristics of Erwinia carotovorasubsp. carotovora nor with that of Erwinia chrysanthemi, and possessed characteristics in between the two species. Further we studied the host range of the bacterium causing tip-over disease of banana.  相似文献   

9.
As the occurrence of Candida species infections increases, so does resistance against commonly-used antifungal agents. It is therefore necessary to look for new antifungal drugs. This study investigated the antifungal activity of recently isolated, synthesized and characterized antimicrobial α-helical amphipathic peptides (12–18 amino acids long) from the venom of hymenoptera (melectin, lasioglossins I, II, and III, halictines I and II) as well as a whole series of synthetic analogs. The minimal inhibitory concentrations (MICs) against different Candida species (C. albicans, C. krusei, C. glabrata, C. tropicalis and C. parapsilosis) of the natural peptides amounted to 4–20 μM (7–40 mg/l). The most active were the synthetic analog all-D-lasioglossin III and lasioglossin III analog KNWKK-Aib-LGK-Aib-IK-Aib-VK-NH2. As shown using a) colony forming unit determination on agar plates, b) the efflux of the dye from rhodamine 6B-loaded cells, c) propidium iodide and DAPI staining, and d) fluorescently labeled antimicrobial peptide (5(6)-carboxyfluorescein lasioglossin-III), the killing of fungi by the peptides studied occurs within minutes and might be accompanied by a disturbance of all membrane barriers. The peptides represent a promising lead for the development of new, effective antifungal drugs.  相似文献   

10.
Eight peptides with differential growth–inhibitory activity against the gram-positive bacterium Staphylococcus aureus, the gram-negative bacterium Escherichia coli and the yeast, Candida albicans were isolated from an extract of the skin of the North American pig frog Rana grylio. The primary structures of these antimicrobial peptides were different from previously characterized antimicrobial peptides from Ranid frogs but on the basis of sequence similarities, the peptides may be classified as belonged to four previously characterized peptide families: the ranatuerin-1, ranatuerin-2 and ranalexin families, first identified in the North American bullfrog, Rana catesbeiana, and the temporin family first identified in the European common frog Rana temporaria. Peptides belonging to the brevinin-1, brevinin-2, esculentin-1, and esculentin-2 families, previously isolated from the skins of other species of Ranid frogs, were not identified in the extracts. The ranatuerin-1 and ranalexin peptides showed broadest spectrum of antimicrobial activity whereas the temporins were active only against S. aureus. Synthetic replicates of temporin-1Gb (SILPTIVSFLSKFL.NH2) and temporin-1Gd (FILPLIASFLSKFL.NH2) produced concentration-dependent relaxation of preconstricted vascular rings from the rat thoracic aorta (EC50=2.4±0.1 μM for temporin-1Gb and 2.3±0.2 μM for temporin-1Gd). The antimicrobial peptides that were isolated in extracts of the skin R. grylio were present in the same molecular forms in electrically-stimulated skin secretions of the animal demonstrating that the peptides are stored in the granular glands of the skin in their fully processed forms.  相似文献   

11.
Summary The fungus Aspergillus terreus Thorn var. terreus isolated from an Ecuador soil sample was cultured in liquid and solid media and yielded three main metabolites identified as terreic acid (1), butyrolactone I (2) and lovastatin (3). The natural products as well as three synthetic butyrolactone I derivatives were assessed for antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi as well as for seed germination and seedling growth. Furthermore, the compounds were assessed as inhibitors towards the enzymes acetylcholinesterase, β-glucosidase, and β-glucuronidase. Terreic acid, butyrolactone I, butyrolactone 4′,4′′-diacetate (2.1), and 3′-(3-methylbutyl)-butyrolactone II (2.2) were active towards the phytopathogenic bacteria Erwinia carotovora with IC50 of 5 and 4–18 μg/ml, respectively. Under the same experimental conditions, the IC50 of streptomycin was 1.9 μg/ml. 3′-(3-Methylbutyl)-butyrolactone II was moderately active against Pseudomonas syringae and Botrytis cinerea with IC50 of 21μg/ml and MIC of 15.6 μg/ml, respectively. Butyrolactone I also inhibited germination of the dicot Lactuca sativa with an IC50 of 5 × 10−5 M. The IC50 of reference herbicide acetochlor was 1 × 10−5 M. The effect of 2.2 and 2.3, known as butyrolactone III on Panicum millaceum germination and growth was stronger than that of 2 and 2.1. Reduction of the double bond in the isoprenyl side chain of butyrolactone I increased the antibacterial effect against E. carotovora as well as acetylation. To our best knowledge, this is the first report on the antibacterial effect of butyrolactone derivatives towards Erwinia carotovora and the phytopathogenic fungus Botrytis cinerea. The butyrolactone I derivative 2.2 presented a moderate inhibitory effect against the enzyme acetylcholinesterase with an IC50 of 47 μg/ml. Under the same experimental conditions, the reference inhibitor galanthamine had an IC50 of 3 μg/ml.  相似文献   

12.
Aneurinibacillus: sp. YR247 was newly isolated from the deep-sea sediment inside the Calyptogena community at a depth of 1171 m in Sagami Bay. The strain exhibited antifungal activity against the filamentous fungus Aspergillus brasiliensis NBRC9455. A crude extract prepared from the YR247 cells by ethanol extraction exhibited broad antimicrobial activities. The antifungal compound is stable at 4–70?°C and pH 2.0–12.0. After treatment with proteinase K, the antifungal activity was not detected, indicating that the antifungal compound of strain YR247 is a peptidic compound. Electrospray ionization mass spectrometry of the purified antifungal compound indicated that the peptidic compound has an average molecular weight of 1167.9. The molecular weight of the antifungal compound from strain YR247 is different from those of antimicrobial peptides produced by the related Aneurinibacillus and Bacillus bacteria. The antifungal peptidic compound from the deep-sea bacterium Aneurinibacillus sp. YR247 may be useful as a biocontrol agent.  相似文献   

13.
The emergence, in recent years, of microbial resistance to commonly used antibiotics has aroused a search for new naturally occurring bactericidal and fungicidal agents that may have clinical utility. In the present study, three new antimicrobial peptides were purified from the electrical-stimulated skin secretion of the South American frog Leptodactylus ocellatus by reversed-phase chromatographic procedures. Ocellatin 1 (1GVVDILKGAGKDLLAHLVG ISEKV25-CONH2), ocellatin 2 (1GVVDILKGAGKDLLAHLVGKISEKV25-CONH2) and ocellatin 3 (1GVLDILKNAAKNILAHAAEQI21-CONH2) are structurally related peptides. These peptides present hemolytic activity against human erythrocytes and are also active against Escherichia coli. Ocellatins exhibit significant sequence similarity to other amphibian antimicrobial peptides, mainly to brevinin 2ED from Rana esculenta.  相似文献   

14.
Genetic engineering to date has not been used to introduce disease resistance genes into the orchid gene pool. The ferredoxin-like protein gene originally isolated from sweet pepper is thought to function as a natural defense against infection due to its antimicrobial properties. Hence it was reasoned that introduction of this gene might produce Oncidium plants resistant to Erwinia carotovora, the causal agent for the soft rot disease. An expression vector containing sweet pepper ferredoxin-like protein (pflp) cDNA, hph and gusA coding sequence was successfully transformed into protocorm-like bodies (PLBs) of Oncidium orchid, using Agrobacterium tumefaciens strain EHA105. A total of 17 independent transgenic orchid lines was obtained, out of which six transgenic lines (-glucuronidase (GUS) positive) were randomly selected and confirmed by Southern, northern and western blot analyses. A bioassay was conducted on the transgenic lines. Transgenic plants showed enhanced resistance to E. carotovora, even when the entire plant was challenged with the pathogen. Our results suggest that pflp may be an extremely useful gene for genetic engineering strategies in orchids to confer resistance against soft rot disease.  相似文献   

15.
Lactic acid bacteria isolated from Boza, a cereal-fermented beverage from Belogratchik, Bulgaria, were screened for the production of bacteriocins. With the first screening, 13 of the 52 isolates inhibited the growth of Listeria innocua and Lactobacillus plantarum. The cell-free supernatant of one of these strains, classified as Leuconostoc mesenteroides subsp. dextranicum ST99, inhibited the growth of Bacillus subtilis, Enterococcus faecalis, several Lactobacillus spp., Lactococcus lactis subsp. cremoris, Listeria innocua, Listeria monocytogenes, Pediococcus pentosaceus, Staphylococcus aureus and Streptococcus thermophilus. Clostridium spp., Carnobacterium spp., L. mesenteroides and Gram-negative bacteria were not inhibited. Maximum antimicrobial activity, i.e. 6,400 arbitrary units (AU)/ml, was recorded in MRS broth after 24 h at 30°C. Incubation in the presence of protease IV and pronase E resulted in loss of antimicrobial activity, confirming that growth inhibition was caused by a bacteriocin, designated here as mesentericin ST99. No loss in activity was recorded after treatment with -amylase, SDS, Tween 20, Tween 80, urea, Triton X-100, N-laurylsarcosin, EDTA and phenylmethylsulfonylfluoride. Mesentericin ST99 remained active after 30 min at 121°C and after 2 h of incubation at pH 2 to 12. Metabolically active cells of L. innocua treated with mesentericin ST99 did not undergo lysis. Mesentericin ST99 did not adhere to the cell surface of strain ST99. Precipitation with ammonium sulfate (70% saturation), followed by Sep-Pack C18 chromatography and reverse-phase HPLC on a C18 Nucleosil column yielded one antimicrobial peptide.  相似文献   

16.
Wu G  Ding J  Li H  Li L  Zhao R  Shen Z  Fan X  Xi T 《Current microbiology》2008,57(6):552-557
This study analyzes the in vitro effects of cations and pH on antimicrobial activity of thanatin and s-thanatin against Escherichia coli ATCC25922 and B. subtilis ATCC21332. Thanatin and s-thanatin were synthesized by the solid-phase method using a model 432A synthesizer. The bacterial strains tested included two antibiotic-susceptible strains of Escherichia coli ATCC25922 and B. subtilis ATCC21332. Susceptibility determinations were carried out either in a variety of cation concentrations or in pH conditions from pH 5 to pH 8. NaCl or KCl was added to the media to final concentrations of 0, 10, 50, 100, 200, and 500 mM, whereas CaCl2 and MgCl2 were added to the media to final concentrations of 0, 1, 2, 5, 10, and 20 mM. The antimicrobial activity of thanatin and s-thanatin against Escherichia coli ATCC25922 and B. subtilis ATCC21332 decreased, as indicated by the increasing minimal inhibitory concentrations (MICs) of both peptides with increasing concentrations of Na+/K+/Ca2+/Mg2+. Both peptides lost their activities at 500 mM Na+/K+ but retained them at 20 mM Ca2+/Mg2+. Both peptides have MICs that are not significantly different at a variety of pH levels, with the antimicrobial activity slightly higher in neutral or slightly basic media than under acidic conditions. The antimicrobial peptides thanatin and s-thanatin, which have an anti-parallel β-sheet constrained by disulfide bonds, were salt sensitive against both Gram-positive and Gram-negative pathogens in vitro. Determining the reason why the thanatins are salt sensitive would be useful to provide an understanding of how thanatin and s-thanatin kill bacteria. Futher investigation of the antimicrobial properties of these peptides is warranted. G. Wu and J. Ding contributed equally to this article.  相似文献   

17.
The essential oil of Satureja montana L. had a broad-spectrum of antimicrobial activity against 46 species of yeasts. This high and diffused activity could be used to control potential pathogenic and spoilage yeasts. The assay of MIC toward some pathogenic and spoilage yeasts showed a range values from 0.10 to 0.25 l ml–1. The MIC and growth rate reduction assay were effective tests for quantitative evaluation of antimicrobial activity.  相似文献   

18.
Bacteriocins are antimicrobial peptides synthesized and secreted by bacteria and could potentially be used as natural food preservatives. Here, we report the production of bacteriocin-like inhibitor substances (Bt-BLIS) by five Mexican strains of Bacillus thuringiensis. Bacillus thuringiensis subsp. morrisoni (LBIT 269), B. thuringiensis subsp. kurstaki (LBIT 287), B. thuringiensis subsp kenyae (LBIT 404), B. thuringiensis subsp. entomocidus (LBIT 420) and B. thuringiensis subsp. tolworthi (LBIT 524) produced proteinaceous Bt-BLIS with high levels of activity against Bacillus cereus and other gram-positive bacteria. Although none was active against the gram-negative bacteria, Escherichia coli, Shigella species and Pseudomonas aeruginosa, the five Bt-BLIS demonstrated antimicrobial activity against Vibrio cholerae, the etiologic agent of cholera. Biochemical and biophysical studies demonstrated that the five Bt-BLIS could be categorized into two groups, those produced by LBIT 269 and 287 (Group A) and LBIT 404, 420, 524 (Group B), based on relative time of peptide synthesis, distinctive bacterial target specificity and stability in a wide range of temperatures and pH. Because of their stability and bactericidal activities against B. cereus and V. cholerae agents of emetic, diarrheal and lethal syndromes in humans, these Bt-BLIS could potentially be used as biodegradable preservatives in the food industry.  相似文献   

19.
Changes in properties of phytopathogenic bacteria effected by plasmid pRD1   总被引:2,自引:0,他引:2  
Transfer of plasmid pRD1 from Escherichia coli K12J62-1 to phytopathogenic bacteria, Agrobacterium tumefaciens, Xanthomonas beticola and Erwinia carotovora subsp. carotovora caused changes in conjugant properties not determined by the plasmid and the emergence of the properties not present in the parent strains. Clones have been obtained with intermediate properties between donor and recipient, including those with altered or lost virulence. In transconjugants of A. tumefaciens virulence increased. In transconjugants of X. beticola and E. carotovora subsp. carotovora highly virulent as well as avirulent forms have been observed. The loss of virulence in X. beticola correlated with the Nif* phenotype. Plasmid pRD1 also affected the biochemical properties of the new hosts.  相似文献   

20.
Larvae of the insect Galleria mellonella were employed to assess the in vivo antifungal efficacy of ([Ag2(mal)(phen)3]), AgNO3 and 1,10-phenanthroline. Larvae pre-inoculated with these compounds were protected from a subsequent lethal infection by the yeast Candida albicans while larvae inoculated 1 and 4 h post-infection showed significantly increased survival (P < 0.01) compared to control larvae. Administration of these compounds resulted in an increase over 48 h in the density of insect haemocytes (immune cells) but there was no widespread activation of genes for antimicrobial peptides. This work demonstrates that G. mellonella larvae may be employed to ascertain the antifungal efficacy of silver(I) compounds and offers a rapid and effective means of assessing the in vivo activity of inorganic antimicrobial compounds.  相似文献   

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