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1.
Cyclic hydroxamic acids present in some species of Gramineae have been reported to be important in resistance of these plants to fungi and insects. Since the nonglucosylated forms of these acids are unstable in aqueous solution, in vitro methods for the measurement of their antibiotic properties have been difficult. Kinetics of the decomposition of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA), the major hydroxamate in corn (Zea mays L.) extracts, were studied in buffered aqueous solutions from pH 5 to 7.5 at temperatures from 20 to 80 C. Kinetics were apparently first order under all conditions tested; energies of activation (24 to 28 kcal/mol) were nearly pH-independent. DIMBOA decomposed rapidly (half-life = 5.3 hours at 28 C, pH 6.75) relative to the time required for many procedures which have been used to demonstrate the biological activity of DIMBOA. The rate of disappearance of inhibitory activity of DIMBOA toward Erwinia carotovora was indistinguishable from the rate of decomposition of DIMBOA. Contrary to reports, yields of 6-methoxy-2-benzoxazolinone (MBOA) were not quantitative. Gas-liquid chromatography analytical procedures were developed for quantitation of trimethylsilyl and acetyl derivatives of MBOA. As measured by ultraviolet spectroscopy and/or gas-liquid chromatography, conversion of DIMBOA to MBOA ranged from 40 to 75% of theoretical in aqueous buffers, bacterial growth medium, and ethyl acetate extracts of corn tissue resuspended in buffer. Yields varied with temperature, pH, and constituents in the medium.  相似文献   

2.
The ability of endophytic bacteria to influence Erwinia carotovora var. atroseptica (Eca) growth and disease development was examined in potatoes. Bacterial populations isolated from within the tubers of five potato (Solanum tuberosum L.) cultivars (Kennebec, Butte, Green Mountain, Russet Burbank and Sebago) showed antibiosis toward Eca in an in vitro assay. Sebago was host to the highest percentage of bacterial isolates inhibiting Eca growth in vitro (49.5%), followed by Green Mountain (33.3%), Kennebec (29.3%), Russet Burbank (12.9%) and Butte (1.8%). Of these, Curtobacterium luteum was the most common species. Few endophytic bacteria from Butte were inhibitory to Erwinia; all were from Pantoea agglomerans. Significantly higher populations of Erwinia-inhibiting bacteria were recovered from Kennebec (1.89 × 106 cfu fresh weight tuber tissue) as compared to the other cultivars; the lowest populations were recovered from Butte (0.01 × 106 cfu per g fresh weight tuber tissue). Published levels of cultivar disease resistance to blackleg did not correspond to actual bacterial soft rot development (induced by Eca) in an in vivo (tuber) assay. However, bacterial soft rot development was negatively correlated with the density of tuber populations of endophytic bacteria found able to inhibit Eca growth in vitro (R=−0.879, p=0.05).  相似文献   

3.
Factors affecting the inhibitory activity of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) against Erwinia carotovora, a nonpathogen of Zea mays L., and against a maize pathovar of Erwinia chrysanthemi (ECZ) were examined. Most experiments were performed with DIMBOA dissolved in a bacterial growth medium containing 10 g/liter of sucrose, inorganic salts, and 1 g/liter of casamino acids at pH 6.75. When temperature and pH were held constant, inhibition of E. carotovora varied linearly with the logarithm of the initial cell population. By altering temperatures, assays with constant pH and initial cell populations were performed under conditions of varying DIMBOA stability. When E. carotovora was grown at 24, 28, 32, and 36 C in the presence of 0.1 to 0.5 mm DIMBOA, the inhibition of bacterial growth was maintained long after DIMBOA had decomposed in the medium to levels which, if added initially, would not have been inhibitory. When assays were performed at pH 5.5, the pH of aqueous maize extracts, E. carotovora was more inhibited than at pH 6.75; however, ECZ was substantially less inhibited at the lower pH.  相似文献   

4.
Antibacterial and antifungal activities of aqueous, ethanol and ethyl acetate extract of Torilis anthriscus (L.) Gmel. (Apiaceae) were tested in vitro against ten species of bacteria and five of fungi. Antimicrobial properties were determined by disk diffusion and broth tube dilution method. In the minimum inhibitory concentrations (MICs), the ethanol extract showed the highest activity, followed by the ethyl acetate extract and the aqueous extract against bacterial species, while the extracts were inactive against the tested fungi species. The most active extract was chosen to examine the effects of its combinations with commercial antibiotics by checkerboard method. The obtained results showed that the interactions between ethanol extract/streptomycin and ethanol extract/chloramphenicol were additive and indifferent against the tested human-pathogenic bacteria. Synergism and antagonism were not observed.  相似文献   

5.
The soft rot Enterobacteriaceae (SRE) Pectobacterium and Dickeya species (formerly classified as pectinolytic Erwinia spp.) cause important diseases on potato and other arable and horticultural crops. They may affect the growing potato plant causing blackleg and are responsible for tuber soft rot in storage thereby reducing yield and quality. Efficient and cost‐effective detection and identification methods are essential to investigate the ecology and pathogenesis of the SRE as well as in seed certification programmes. The aim of this review was to collect all existing information on methods available for SRE detection. The review reports on the sampling and preparation of plant material for testing and on over thirty methods to detect, identify and differentiate the soft rot and blackleg causing bacteria to species and subspecies level. These include methods based on biochemical characters, serology, molecular techniques which rely on DNA sequence amplification as well as several less‐investigated ones.  相似文献   

6.
In the present study, in vitro anticariogenic potential of ethyl acetate, hexane and methanol and aqueous extracts of plant leaves of Eucalyptus globules Labill. were evaluated by using four cariogenic bacteria, Lactobacillus acidophilus, Lactobacillus casei, Staphylococcus aureus and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The ethyl acetate extracted fraction of plant leaves showed good inhibitory effects against all selected bacteria. In Eucalyptus globules, hexane and ethyl acetate extracts found highly effective against, Lactobacillus acidophilus with MIC value of 0.031 and 0.062 mg/mL, respectively. Qualitative phytochemical investigation of above extracts showed the presence of alkaloids, phenolic compounds, steroids, cardiac glycosides and terpenes. Based on the MIC value and bioautography, ethyl acetate of plant leaf was selected for further study. Further investigation on the structure elucidation of the bioactive compound using IR, GC-MS and NMR techniques revealed the presence of alpha-farnesene, a sesquiterpene. Eucalyptus globules plant leaf extracts have great potential as anticariogenic agents that may be useful in the treatment of oral disease.  相似文献   

7.
Aspergillus microcysticus Sappa TÜ 502 produces a formerly unknown antibiotic named asposterol. Extractions of culture filtrates from fermentations with ethyl acetate and subsequent column chromatography of the extracts on silica gel using benzene/ethyl acetate for the elution yielded up to 35 mg/l of practically pure preparations of the antibiotic. Asposterol is lipophilic and instable. The elemental composition was determined as C24H33NO4, molecular weight 399. The antibiotic exists in two isomeric forms. A steran skeleton is attributed to the compound. There is no evidence for other similarities with known steroid antibiotics. Asposterol inhibits both bacteria and fungi. The minimal inhibitory concentrations are 0.3 μg/ml for Bacillus subtilis and 1.2 μg/ml for Schizosaccharomyces pombe. The inhibitory effect of asposterol is compensated by α-tocopherol. It is assumed that the cytoplasmic membrane is the site of the primary antibiotic action. Linolenic acid, undecylenic acid and other unsaturated fatty acids show similarities with respect to the type of their antimicrobial effects.  相似文献   

8.
Acanthamoeba spp. commonly cause Acanthamoeba keratitis which is typically associated with the wear of contact lenses. Therefore, finding an economic, efficient, and safe therapy of natural origin is of outmost importance. This study examined the in vitro lethal potential of ethyl acetate and methanol extracts of Helianthemum lippii (L.) (sun roses) against Acanthamoeba castellanii cysts isolated from patients with amoebic keratitis. Both extracts proved to be potent as regard to their lethal effects on A. castellanii cysts with comparable results to chlorhexidine. The ethyl acetate was more promising with cumulative lethality. It showed a highly significant lethal percentage along the duration of treatment. The analysis of the more potent ethyl acetate extract revealed the presence of 2.96 mg/100 g of total phenolics, 0.289 mg/100 ml of total flavonoids and 37 mg/100 mg of total tannins which highlighted their phytomedicinal role.  相似文献   

9.
Antimicrobial activities of rhizome extracts of Cyperus rotundus were investigated on selected plant pathogenic bacteria and fungi. Ethyl acetate and hexane extracts showed antibacterial activity against three isolates of Clavibacter michiganensis subsp. michiganensis at concentrations of 900 and 1000 μg/ml. However, Gram-negative bacterial pathogens of tomato; Pseudomonas syringae pv. tomato and Ralstonia solanacearum were not inhibited from the extracts. Ethyl acetate extracts at 100 μg/ml inhibited mycelial growth and spore germination of the two strawberry isolates of Botrytis cinerea; however, no significant inhibition was found in tomato fungal pathogen, Fusarium oxysporum f. sp. radicis lycopersici. Minimum inhibitory concentrations were determined as 0.0625 and 0.125 mg/ml against C. michiganensis subsp. michiganensis for ethyl acetate and hexane extracts of rhizomes, respectively. This study shows the potentials of extracts of C. rotundus rhizomes as antimicrobial agents that are effective against the tested plant pathogenic bacteria and fungi.  相似文献   

10.
Terminalia chebula Retz. is a northern Indian plant species known for its anti-inflammatory and antimicrobial properties. T. chebula fruit powder was extracted with solvents of varying polarity and screened for bacterial growth inhibition by disc diffusion assay. The minimum inhibitory concentration (MIC) was quantified by both liquid dilution and disc diffusion techniques. To screen for combinatorial effects, the T. chebula fruit extracts were combined with a range of conventional antibiotics and tested against each bacteria using a liquid dilution assay. Where synergy was detected, the optimal ratios were determined using isobologram analysis. Toxicity was examined using Artemia nauplii and HDF bioassays. T. chebula fruit methanolic, aqueous and ethyl acetate extracts displayed strong antimicrobial activity against the bacterial triggers of all autoimmune inflammatory diseases except K. pneumoniae, for which only moderate inhibition was observed. Indeed, MIC values as low as 195 μg/mL were measured for the aqueous extract against a resistant strain of P. aeruginosa. Of further note, both the aqueous and ethyl acetate extracts interacted synergistically in combination with tetracycline against K. pneumoniae (Σ FIC 0.38 and 0.25 respectively). All extracts were nontoxic in the Artemia and HDF toxicity assays, further indicating their potential for medicinal use.  相似文献   

11.
The number of microorganisms of major metabolic groups and the rates of sulfate reduction and methanogenesis processes in the formation waters of the high-temperature horizons of Dagang oil field have been determined. Using cultural methods, it was shown that the microbial community contained aerobic bacteria oxidizing crude oil, anaerobic fermentative bacteria, sulfate-reducing bacteria, and methanogens. Using cultural methods, the possibility of methane production from a mixture of hydrogen and carbon dioxide (H2 + CO2) and from acetate was established, and this result was confirmed by radioisotope methods involving NaH14CO3 and 14CH3COONa. Analysis of enrichment cultures 16S rDNA of methanogens demonstrated that these microorganisms belong to Methanothermobacter sp. (M. thermautotrophicus), which consumes hydrogen and carbon dioxide as basic substrates. The genes of acetate-utilizing bacteria were not revealed. Phylotypes of the representatives of Thermococcus spp. were found among archaeal 16S rDNA. 16S rRNA genes of bacterial clones belong to the orders Thermoanaerobacteriales (Thermoanaerobacter, Thermovenabulum, Thermacetogenium, and Coprothermobacter spp.), Thermotogales, Nitrospirales (Thermodesulfovibrio sp.) and Planctomycetales. 16S rDNA of a bacterium capable of oxidizing acetate in the course of syntrophic growth with H2-utilizing methanogens was found in high-temperature petroleum reservoirs for the first time. These results provide further insight into the composition of microbial communities of high-temperature petroleum reservoirs, indicating that syntrophic processes play an important part in acetate degradation accompanied by methane production.  相似文献   

12.
Orthosiphon stamineus (Java tea) has been widely used as traditional herb and several bioactive compounds against animal cells have been isolated. However, no bioactive compound against plants has been reported. Therefore, we investigated possible allelopathic properties and substances in O. stamineus. Aqueous methanol extracts of O. stamineus inhibited root and hypocotyl growth of cress (Lepidium sativum) and lettuce (Lactuca sativa) seedlings. Increasing the extract concentration increased the inhibition, which suggests that O. stamineus may have allelopathic properties. When the extract was divided into an ethyl acetate and an aqueous fraction, the ethyl acetate fraction showed the stronger inhibitory effect. Thus, the ethyl acetate phase was further purified, and the main allelopathic substance was isolated and identified as 13-epi-orthosiphol N, a novel compound, by spectral data. 13-epi-Orthosiphol N inhibited root and hypocotyl growth of cress and lettuce at concentrations greater than 10 μmol/L. The concentrations required for 50% inhibition ranged from 41 to 102 μmol/L. These results suggest that 13-epi-orthosiphol N may be an allelochemical and main contributor to the growth inhibitory effect of O. stamineus and may have potential as a template for the development of new plant control substances.  相似文献   

13.
《农业工程》2019,39(5):398-405
This study carried out to identify certain microbial allelochemicals with antifungal activity of some rhziobacterial isolates against Bipolaris sorokiniana fungi. The fungicidal activity of isolated microbe metabolites was compared based on inhibition % of fungal growth. Results showed that ethyl acetate crude extracts with two concentrations (500 and 1000 ppm) of Pseudomonas geniculata (SC) and Bacillus cereus (S4) were the most efficient isolates recorded inhibition % 33.62 and 52.59% followed by S4 (Bacillus cereus (ATCC 14579) which achieved inhibition % 33.62 and 46.55% at the same concentrations, respectively. After 4 days.The constituents analyzed by LC-MS/MS and FTIR of the ethyl acetate extracts of the Pseudomonas geniculata ATCC19374 were afforded aminobutyric acid, 1,4-benzoquinone, coumaric acid, sinapic acid, tryptophan amino acid, Succinic acid and ferulic acid. While, the secondary metabolites of (Bacillus cereus ATCC 14579 extract were aminobutyric acid, 1,4-benzoquinone, coumaric acids, sinapic acid, ferulic acid and benzoic acid. Results indicated that the isolates of Pseudomonas geniculata ATCC19374 and Bacillus cereus ATCC 14579 could be use as a good element in plant root rot pathogen Bipolaris sorokiniana management.  相似文献   

14.
The aim of this study was to evaluate diffusion and dilution methods for determining the antibacterial activity of plant extracts and their mixtures. Several methods for measurement of the minimal inhibitory concentration (MIC) of a plant extract are available, but there is no standard procedure as there is for antibiotics. We tested different plant extracts, their mixtures and phenolic acids on selected gram-positive (Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes) and gram-negative bacteria (Escherichia coli O157:H7, Salmonella Infantis, Campylobacter jejuni, Campylobacter coli) with the disk diffusion, agar dilution, broth microdilution and macrodilution methods. The disk diffusion method was appropriate only as a preliminary screening test prior to quantitative MIC determination with dilution methods. A comparison of the results for MIC obtained by agar dilution and broth microdilution was possible only for gram-positive bacteria, and indicated the latter as the most accurate way of assessing the antimicrobial effect. The microdilution method with TTC (2,3,5-triphenyl tetrazolium chloride) or INT (2-p-iodophenyl-3-p-nitrophenyl-5-phenyl tetrazolium chloride) to indicate the viability of aerobic bacteria was found to be the best alternative approach, while only ATP determination was appropriate for microaerophilic Campylobacter spp. Using survival curves the kinetics of bacterial inactivation on plant extract exposure was followed for 24 h and in this way the MIC values determined by the microdilution method were confirmed as the concentrations of extracts that inhibited bacterial growth. We suggest evaluation of the antibacterial activity of plant extracts using the broth microdilution method as a fast screening method for MIC determination and the macrodilution method at selected MIC values to confirm bacterial inactivation. Campylobacter spp. showed a similar sensitivity to plant extracts as the tested gram-positive bacteria, but S. Infantis and E. coli O157:H7 were more resistant.  相似文献   

15.
Baker’s yeast suspensions having bacterial populations of 106 and 108 CFU/ml were subjected to autolysis processes designed to obtain yeast extracts (YE). The bacterial contaminants added to the yeast cell suspensions were produced with spent broths obtained from a commercial yeast production plant and contained 59% cocci (Leuconostoc, Aerococcus, Lactococcus) as well as 41% bacilli (Bacillus). Autolyses were conducted at four different pH levels (4.0, 5.5, 7.0, and 8.5) and with two autolysis-promoting agents (ethyl acetate and chitosan). Processing parameters were more important than the initial bacterial population in the development of contaminating bacteria during manufacture of YE. Drops in the viable bacterial population after a 24-h autolysis were observed when pH was adjusted to 4.0 or when ethyl acetate was added. A significant interaction was found between the effects of pH and autolysis promoters on the bacterial population in YE, indicating that the activity of ethyl acetate, as opposed to that of chitosan, was not influenced by pH.  相似文献   

16.
The growth inhibitory effect of cucumber (Cucumis sativus L.) plants after crop harvested was investigated. Aqueous methanol extracts of the cucumber plants inhibited the growth of roots and shoots of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), ryegrass (Lolium multiflorum L.), timothy (Pheleum pratense L.), crabgrass (Digitaria sanguinalis L.), Echinochloa crus-galli (L.) Beauv and Echinochloa colonum (L.) Link, and increasing the extract concentration increased the inhibition. These results suggest that cucumber plants may possess allelopathic activity. The aqueous methanol extract of cucumber plants was divided into ethyl acetate and aqueous fractions, and the growth inhibitory activity of ethyl acetate fraction was greater than that of aqueous fraction. Thus, ethyl acetate fraction was further purified and a main allopathically active substance in the fraction was isolated and determined as (S)-2-benzoyloxy-3-phenyl-1-propanol by spectral data. This substance inhibited root and shoot growth of cress seedlings at concentrations greater than 10 μM, and the concentration required for 50% inhibition of root and shoot growth was 21 and 23 μM, respectively. These results suggest that (S)-2-benzoyloxy-3-phenyl-1-propanol may contribute to the growth inhibitory effect of cucumber plants and may play an important role in cucumber allelopathy. Thus, cucumber plants may be potentially useful for weed management in a field setting. An erratum to this article can be found at  相似文献   

17.
Lactobacilli have been shown to inhibit in vitro growth of many pathogens and have been used as probiotics to treat a broad range of gastrointestinal and/or vaginal disorders. We sought to determine the in vitro inhibitory potential of lactobacilli of vaginal origin to some bacteria associated with bacterial vaginosis (BV), to characterize the inhibitory substances produced by these lactobacilli and to assess H2O2 production. Vaginal specimens were obtained by swabbing the lateral vaginal walls from 107 women two months following BV treatment. One hundred and fifty eight Lactobacillus spp. were isolated in 82 of the 107 women. Lactobacillus jensenii was the predominant strain isolated among these women (29/158; 18.4%). Among 158 culture supernatants tested for antibacterial activity against BV-associated bacteria, none inhibited the growth of Bacteroides fragilis while 23% (37/158), 28% (45/158) and 29% (46/158) inhibited the growth of Prevotella bivia, Gardnerella vaginalis and Mobiluncus spp. respectively. The lactobacilli produced supernatants with a pH range between 2.62 and 6.71; the highly acidic (pH 2–3.99) supernatants were more inhibitory to the indicator strains. There was significant reduction in the mean zones of inhibition following chemical and physical treatment of the supernatants (p = 0.0025). Acid, bacteriocins and H2O2 demonstrated potential for antagonism of the bacterial pathogens. These substances may augment each other rather that each working independently on the pathogens.  相似文献   

18.
The aim of this study was to assess the phytotoxic potential of Cleome arabica L, as well as to isolate the main bioactive compounds. Phytotoxicity was evaluated on germination and seedling growth of Lactuca sativa, Raphanus sativus, Peganum harmala and Silybum marianum, through testing aqueous and organic extracts of different C. arabica organs (roots, shoots, siliquae and seeds). Results showed that siliquae methanol extract caused the greatest negative effect on lettuce germination and growth. For the bioactive subfractions (petroleum ether, ethyl acetate and methanol–water), the ethyl acetate induced highly significant reduction, showing 100% inhibition of lettuce growth at 6 g/L. The bioactive ethyl acetate subfraction was chromatographed and subjected to NMR techniques. Based on bio-guided chromatographic fractionation, five bioactive allelochemical compounds were isolated from ethyl acetate extract of siliquae of C. arabica. The most inhibitory compound on lettuce seedling growth was elucidated as 11-α-acetylbrachy-carpone-22(23)-ene.  相似文献   

19.
Stenocarpella maydis causes a fungal dry-rot of maize ears and is associated with diplodiosis, a neuromycotoxicosis in cattle grazing harvested maize fields in southern Africa and Argentina. There have been no reports of Stenocarpella metabolites in maize crop residues. Chemical investigations of S. maydis-infected grain from ears exhibiting different levels of ear rot severity following a 2010 field outbreak of Stenocarpella ear rot in Illinois led to the detection of diplodiatoxin and chaetoglobosins M and O as major components in the ethyl acetate extracts by LC-MS. Following post-harvest moist incubation of the S. maydis-infected grain, the amounts of each compound increased (approx. tenfold) and chaetoglobosin K was detected as a dominant toxin. In separate 1H NMR-based analyses, the neurotoxin diplonine was detected as a minor component in methanol extracts of S. maydis-infected grain as well as cultures of S. maydis isolates from Midwest corn. Proline betaine (=stachydrine) and glycine betaine were also detected in these extracts as major components. This constitutes the first report of chaetoglobosin M, chaetoglobosin O, proline betaine, or glycine betaine from S. maydis, and the first record of diplodiatoxin, diplonine, proline betaine, glycine betaine, or chaetoglobosins M, O, or K being associated with a natural field outreak of S. maydis ear rot.  相似文献   

20.
In vitro antibacterial potential of the chloroform, ethyl acetate, hexane, methanol and aqueous extracts of Calotropis gigantia (L.) R. Br. was evaluated by using five cariogenic bacteria, Actinomyces viscosus, Lactobacillus acidophilus, Lactobacillus casei, Streptococcus mitis and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The chloroform extracted fraction of latex showed inhibitory effect against S. mutans and L. acidophilus with MIC value of 0.032 and 0.52 mg/mL, respectively. Qualitative investigation on structure elucidation of bioactive compound using IR, NMR and GC–MS techniques revealed the presence of methyl nonanoate, a saturated fatty acid.  相似文献   

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