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1.
Doping of ZnO nanoparticles (NPs) is being used to increase their commercialization in the optical and semiconductor fields. This paper addresses whether doping with Al alters how ZnO NPs at nonlethal levels modifies the metabolism of soil-borne pseudomonads which are beneficial in performing bioremediation or promoting plant growth. The differences in X-ray diffraction (XRD) patterns, observed between commercial ZnO and Al-doped ZnO NPs indicated the aluminum was present as Al NPs. Both particles aggregated in the bacterial growth medium and formed colloids of different surface charges. They had similar effects on bacterial metabolism: rapid, dose-dependent loss in light output indicative of temporary toxicity in a biosensor constructed in Pseudomonas putida KT2440; increased production of a fluorescent pyoverdine-type siderophore, and decreased levels of indole acetic acid and phenazines in Pseudomonas chlororaphis O6. Solubilization of Zn and Al from the NPs contributed to these responses to different extents. These findings indicate that Al-doping of the ZnO NPs did not reduce the ability of the NPs to alter bacterial metabolism in ways that could influence performance of the pseudomonads in their soil environment.  相似文献   

2.
O-acetyltransferase (SAT) is a key enzyme converting serine into O-acetylserine in the synthesis of sulphur-containing amino acids. To characterize the function of FgSAT in Fusarium graminearum, three deletion mutants of FgSAT (ΔFgSAT-1, -2 and -18) were obtained using a gene replacement strategy. The three mutants did not show recognizable phenotypic changes on potato dextrose agar medium, but exhibited a very weak growth on fructose gelatin agar (FGA) medium containing SO4 2? as sole sulfur source. Supplementation of O-acetylserine, cysteine, or methionine, but not serine, rescued the defect of mycelial growth in FgSAT deletion mutants, indicating that FgSAT is involved in conversion of serine into O-acetylserine. The three mutants had a decrease in conidiation in mung bean liquid, but not in carboxymethyl cellulose. Virulence, deoxynivalenol production and fungicide sensitivity assays found that the three mutants showed no significant difference from wild-type progenitor PH-1. Real-time PCR assays detected an increase in expression levels of FgOAHS, FgCBS and FgCGL genes involved in the alternative pathway in FgSAT deletion mutants, suggesting that the alternative pathway in F. graminearum is present and can operate. Addition of homoserine, the upstream substrate of the alternative pathway, also restored the normal mycelial growth of FgSAT deletion mutants on FGA, indicating that the alternative pathway in F. graminearum might be positively regulated by homoserine.  相似文献   

3.
【背景】由禾谷镰刀菌(Fusarium graminearum)引起的小麦赤霉病严重威胁我国的小麦生产。【目的】筛选对禾谷镰刀菌具有拮抗能力的链霉菌菌株,为生防菌剂开发提供理论基础。【方法】利用平板对峙法筛选对禾谷镰刀菌具有拮抗能力的链霉菌;通过形态特征、生理生化特征和16S rRNA基因序列分析对其进行鉴定;通过病原菌菌丝生长、孢子产生及萌发抑制试验分析其发酵液的抑菌活性;利用人工接种试验测定该菌株发酵液的防病效果。【结果】筛选到一株对禾谷镰刀菌具有较强拮抗活性的链霉菌21-1,抑菌率为59.5%。依据形态特征、生理生化特性和16S rRNA基因序列分析,将该菌株鉴定为黄三素链霉菌(Streptomycesflavotricini)。菌株21-1发酵液能够抑制禾谷镰刀菌的菌丝生长、孢子产生及萌发过程,而且可以降低禾谷镰刀菌菌丝中可溶性蛋白质的含量,并增加丙二醛的含量。菌株21-1可以产生蛋白酶及纤维素酶。菌株21-1菌液10倍稀释液对小麦赤霉病的防效最佳,为70.1%。此外,菌株21-1发酵液对其他8种植物病原菌均有较好的抑制作用。【结论】菌株21-1对禾谷镰刀菌有较好的抑菌活性,具...  相似文献   

4.
Antifungal activities of zinc oxide nanoparticles (ZnO NPs) and their mode of action against two postharvest pathogenic fungi (Botrytis cinerea and Penicillium expansum) were investigated in this study. ZnO NPs with sizes of 70 ± 15 nm and concentrations of 0, 3, 6 and 12 mmol l−1 were used. Traditional microbiological plating, scanning electron microscopy (SEM), and Raman spectroscopy were used to study antifungal activities of ZnO NPs and to characterize the changes in morphology and cellular compositions of fungal hyphae treated with ZnO NPs. Results show that ZnO NPs at concentrations greater than 3 mmol l−1 can significantly inhibit the growth of B. cinerea and P. expansum. P. expansum was more sensitive to the treatment with ZnO NPs than B. cinerea. SEM images and Raman spectra indicate two different antifungal activities of ZnO NPs against B. cinerea and P. expansum. ZnO NPs inhibited the growth of B. cinerea by affecting cellular functions, which caused deformation in fungal hyphae. In comparison, ZnO NPs prevented the development of conidiophores and conidia of P. expansum, which eventually led to the death of fungal hyphae. These results suggest that ZnO NPs could be used as an effective fungicide in agricultural and food safety applications.  相似文献   

5.
In the present work, a bionanocomposite for plant crop protection was prepared by non-toxic biocompatible & biodegradable nanomaterials (Cellulose & TiO2) to utilize its synergistic effects against antimicrobial pathogens. The commercially available microcrystalline cellulose has been reduced to a nanometric scale regime using acid hydrolysis, while the standard TiO2 nano-powder of particle size ~20 nm has been used to prepare their nanocomposite (NC). The antibacterial studies via agar well diffusion method demonstrated that after 72 h of incubation, parent nanomaterials Ncell and TiO2 were not showing any activity against phytopathogens X. campestris pv. campestris, and Clavibacter while the nanocomposite's NC's were still effective depicting both bacteriostatic and bactericidal actions. However, the bacterial growth of biocontrol P. fluorescence was not affected by Ncell, TiO2 NPs and NC after 72 h of incubation. The antifungal testing results via poison food agar assay method suggest that the nanocomposite, along with Ncell and TiO2 NPs, exhibited strong inhibition of fungal growth of Phytophthora Spp at 0.125 mg/ml concentration while for F. graminearum, similar effect was observed at 0.25 mg/ml concentration. The nanocomposite has proved its potential by exhibiting longer & stronger synergistic effects against plant pathogens as a good antimicrobial agent for protection of agricultural crops.  相似文献   

6.
Fusarium graminearum is associated with the cereal damping-off complex which reduces germination, seedling stand and yield. Fifty-two bacterial strains and six Trichoderma spp. isolated from the wheat rhizosphere were evaluated for biocontrol of seedling blight of wheat caused by F. graminearum. Their potential as biocontrol agents was tested in vitro and in the greenhouse. Isolates varied in their ability to inhibit the mycelial growth of F. graminearum in agar plate bioassays by 0–79%. This parameter was not related with biocontrol efficacy of in vivo assays. In greenhouse trials, all isolates were initially evaluated for reducing disease on wheat cultivars Klein Centauro (moderately resistant to F. graminearum) and Pro INTA Oasis (susceptible) planted in sterilized soil artificially infested with the pathogen. Among the 25 bacteria and six fungal isolates that exhibited a pronounced suppressive effect, the most efficient 10 for both cultivars were further assayed on eight cultivars (Buck Candil, Buck Catriel, Buck Chambergo, Buck Poncho, Buck Topacio, Klein Cacique, Klein Centauro and Pro INTA Oasis) potted in cultivated–inoculated soil. Three weeks after sowing, plant stand, percentage of diseased emerging seedlings, plant height and dry weight were evaluated. Among the antagonists only Stenotrophomonas maltophilia was significantly better than the control for the average of the eight cultivars for plant stand, height and dry weight. Stenotrophomonas maltophilia also caused a non-significant decrease in the percentage of diseased plants. Three strains of Bacillus cereus and one isolate of Trichoderma harzianum gave also a good control in some cultivars. The ability of these isolates to affect the infection of wheat seedlings by F. graminearum may be of potential value in field trials.  相似文献   

7.
Zinc Oxide Nanoparticles (ZnO NPs) have attracted increasing concerns because of their widespread use and toxic potential. In this study, Zn accumulations in different tissues (gills, liver, muscle, and gut) of goldfish (Carassius auratus) after exposure to ZnO NPs were studied in comparison with bulk ZnO and Zn2+. And the technique of subcellular partitioning was firstly used on the liver of goldfish to study the hepatic accumulation of ZnO NPs. The results showed that at sublethal Zn concentration (2 mg/L), bioaccumulation in goldfish was tissue-specific and dependent on the exposure materials. Compared with Zn2+, the particles of bulk ZnO and the ZnO NPs appeared to aggregate in the environmentally contacted tissues (gills and gut), rather than transport to the internal tissues (liver and muscle). The subcellular distributions of liver differed for the three exposure treatments. After ZnO NPs exposure, Zn percentage in metal-rich granule (MRG) increased significantly, and after Zn2+ exposure, it increased significantly in the organelles. Metallothionein-like proteins (MTLP) were the main target for Zn2+, while MRG played dominant role for ZnO NPs. The different results of subcellular distributions revealed that metal detoxification mechanisms of liver for ZnO NPs, bulk ZnO, and Zn2+ were different. Overall, subcellular partitioning provided an interesting start to better understanding of the toxicity of nano- and conventional materials.  相似文献   

8.
王丽华  王发园  景新新  李帅  刘雪琴 《生态学报》2015,35(15):5254-5261
纳米氧化锌是应用最广的人工纳米颗粒(nanoparticles,NPs)之一,具有一定生物毒性。丛枝菌根(arbuscular mycorrhizal,AM)真菌能与陆地上80%以上的高等植物形成丛枝菌根共生体,并能改善宿主植物矿质营养,提高其抗逆性。然而纳米ZnO与丛枝菌根的关系尚不清楚。通过温室沙培盆栽试验,研究了施加不同水平纳米ZnO(0、500、1000、2000、3000 mg/kg)和接种AM真菌Acaulospora mellea对大豆生长及营养状况的影响。结果表明,3000 mg/kg的纳米ZnO显著抑制大豆植株生长,表现出植物毒性,在其他水平时没有显著影响。纳米ZnO在施加水平500、1000 mg/kg时没有抑制AM真菌对大豆根系的侵染,但是高施加水平(2000 mg/kg)时对AM真菌产生毒害,几乎完全抑制大豆根系菌根侵染。接种AM真菌仅在500 mg/kg纳米ZnO时显著促进大豆生长,增加大豆植株对P、K、N的吸收,降低根系Zn含量。纳米ZnO可能会持续释放锌离子,并抑制大豆根系对矿质营养元素的吸收,从而产生生物毒性,而AM真菌与大豆根系的共生可起到有益作用。  相似文献   

9.
Biological control of plant diseases with antagonistic bacteria is a promising alternative to conventional chemical control strategies. In vitro screening for inhibition of mycelial growth of phytopathogenic fungi by bacterial isolates is the first step in selecting putative bacterial biocontrol agents. Dual culture plate assay is the most common method involved in this first-line selection process. However, it needs independent agar plates to test antagonism by a specific bacterial isolate against each of the fungal phytopathogen. Two modified in vitro antagonism tests are proposed here. Antagonistic activity of a putative biocontrol bacterial strain against four different fungal phytopathogens could be assessed in a single agar plate simultaneously. A comparison of the new methods with conventional dual culture plate assay was also done. The proposed methods are easy to perform and results of antagonism are obtained rapidly. Results of fungal inhibition were qualitatively comparable with that generated through dual culture plate assay. Quantity of resources such as agar medium and plates required for the modified antagonistic assays is several folds less than that required for dual culture plate assay.  相似文献   

10.
The capacity of cell-free extracts of 2·5-day-old castor bean seedlings for synthesis of casbene from mevalonic acid were compared for seedings which had been germinated under sterile conditions and seedlings which were intentionally exposed to fungal cultures. Extracts from seedlings exposed to cultures of Rhizopus stolonifer, Aspergillus niger or Fusarium moniliforme produced much higher levels of casbene than extracts from sterile controls; the initial rates of casbene synthesis were 20–40 times higher in the extracts of seedlings that had been exposed to fungus. Although some variation in the capacity for synthesis of other diterpene hydrocarbons from mevalonic acid was seen in the two types of extracts, no consistent or striking stimulation in the synthesis of any of these was noted under these conditions of exposure of the seedlings to fungi. The potato-dectrose agar used as a fungal growth medium did not itself evoke the increase in casbene synthesis. Intact mycelia and cell-free extracts of mycelia of Rhizopus stolonifer gave no indication of diterpene biosynthesis from mevalonic acid. Purified casbene at concentrations of 10 μg ml−1 or greater retarded the development of A. niger on potato-dextrose medium. Casbene was also found to inhibit the endogenous and gibberellic acid-stimulated growth of leaf sheaths of the dwarf-5 mutant of Zea mays and of the growth of the K-12 strain of Escherichia coli on glucose-minerals medium. It is suggested that casbene may serve the castor bean plant as a phytoalexin.  相似文献   

11.
12.
We evaluated the effects of zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles (NPs) preilluminated with ultraviolet light on Escherichia coli and Bacillus subtilis. The experiments were conducted using three different types of light: visible, Ultraviolet A (UVA, 315–400 nm), and Ultraviolet B (UVB, 280–315 nm). The bacteria were exposed to NPs, either as liquid suspensions for growth inhibition assays or on agar plates for colony forming unit (CFU) assays. We found that the ZnO NPs were more toxic when preilluminated with UVA or UVB light than with visible light in both growth inhibition and CFU assays. TiO2 NPs were not toxic to the bacteria under UVA or UVB preillumination conditions. The photo-dissolution of ZnO NPs increased with UV preillumination, which could explain the observed toxicity of ZnO NPs. We detected oxidative stress elicited by photoactive nanoparticles by measuring superoxide dismutase activity. The results of this study show that the toxicity of photoactive nanoparticles can be increased by UV preillumination by dissolution of toxic ions, which suggests the potential for preillumination-dependent toxicity of nanoparticles on soil environments in low light or darkness.  相似文献   

13.
In this research, the in vitro antimicrobial effect of zinc oxide (ZnO), copper oxide (CuO) and iron oxide (Fe2O3) nanoparticles (NPs)—with average sizes of 20, 46 and 30 nm, respectively—on the root rot disease caused by the fungus Fusarium oxysporum and on blight disease caused by the fungus Alternaria solani were studied. Also, bacterial diseases caused by Clavibacter michiganensis and Pseudomonas syringae that infects a wide range of plant species were assessed. Different concentrations of NPs (0, 100, 250, 500, 700 and 1,000 mg/L) were prepared on PDA agar or King's B medium in a complete randomized design with four replicates. According to the results, ZnO NPs exhibited an outstanding inhibitory effect against fungi and bacteria strains. The above results were associated with the smaller particle size. Fungi strains showed a differential sensitivity depending on the kind of NPs used. A. solani showed the highest sensitivity to ZnO NPs at 1,000 mg/L (99%), followed by CuO NPs at the same dose (95%). Fe2O3 NPs at all evaluated doses had no inhibitory effects on the mycelia growth of this strain, although F. oxysporum revealed greater effectiveness of the CuO NPs (96%) compared with ZnO NPs since it only inhibited 91% of the mycelial growth. The antibacterial activity was studied through optical density. C. michiganensis was found to be more sensitive to ZnO NPs because a lesser dose (700 mg/L) was required to reduce the bacterial growth (90%); in comparison, P. syringae required a dose of 1,000 mg/L to inhibit its growth (67%). CuO NPs displayed the smallest growth inhibition against the bacteria strains analysed. The antimicrobial effect of the metallic NPs that were assayed increased with higher doses.  相似文献   

14.
The volatile organic compounds (VOCs) produced by antagonistic microbes have great antifungal potential against soil-borne fungal pathogens. The VOCs produced by Paenibacillus polymyxa strain WR-2 in the presence of root exudates and organic fertilizer were identified and their effects on the growth and spore germination of Fusarium oxysporum f. sp. niveum were evaluated. The VOCs produced by WR-2 inhibited the growth of F. oxysporum by 38%, 36% and 40% in agar medium, sterilized soil and natural soil, respectively. This inhibitory effect was increased to 60%, 58% and 64% with the addition of organic fertilizer in agar medium, sterilized soil and natural soil, respectively. The addition of root exudates did not affect the production of antifungal VOCs by WR-2. The VOCs produced by WR-2 completely inhibited the germination of F. oxysporum spores. Out of 42 identified VOCs, seven VOCs; benzothiazole, benzaldehyde, undecanal, dodecanal, hexadecanal, 2-tridecanone and phenol were found to inhibit the growth of F. oxysporum. The results of these experiments suggest another significance of using organic fertilizer as a carrier material with the biocontrol agents to control soil-borne fungal pathogens.  相似文献   

15.
《Biological Control》2010,52(3):370-376
Fusarium head blight (FHB) caused by Gibberella zeae (anamorph = Fusarium graminearum) is a devastating disease that causes extensive yield and quality losses to wheat in humid and semi-humid regions of the world. Biological control has been demonstrated to be effective under laboratory conditions but a few biocontrol products have been effective under field conditions. The improvement in the physiological quality of biocontrol agents may improve survival under field conditions, and therefore, enhance biocontrol activity. Bacillus subtilis RC 218 and Brevibacillus sp. RC 263 were isolated from wheat anthers and showed significant effect on control of FHB under greenhouse assays. This study showed the effect of water availability measured as water activity (aW) using a growth medium modified with NaCl, glycerol and glucose on: (i) osmotic stress tolerance, (ii) viability in modified liquid medium, (iii) quantitative intracellular accumulation of betaine and ectoine and (iv) the biocontrol efficacy of the physiologically improved agents. Viability of B. subtilis RC 218 in NaCl modified media was similar to the control. Brevibacillus sp. RC 263 showed a limited adaptation to growth in osmotic stress. Betaine was detected in high levels in modified cells but ectoine accumulation was similar to the control cells. Biocontrol activity was studied in greenhouse assays on wheat inoculated at anthesis period with F. graminearum RC 276. Treatments with modified bacteria reduced disease severity from 60% for the control to below 20%. The physiological improvement of biocontrol agents could be an effective strategy to enhance stress tolerance and biocontrol activity under fluctuating environmental conditions.  相似文献   

16.
Fusarium head blight, which is primarily caused by Fusarium graminearum, is a devastating disease in the barley field. A real-time PCR protocol was developed to evaluate the growth of this pathogen in the host plant tissues. All four strains harbored the gene encoding ATP-BINDING CASSETTE TRANSPORTER (FgABC; FGSG_00541) as a single copy within their genomes. Our Southern blot result was identical with the genomic data for F. graminearum strain PH-1. Based on the crossing point (CP) values obtained in our TaqMan real-time PCR analysis, two standard curves describing the relationship among the CP value, FgABC copy number, and amount of fungal DNA were constructed. Chronological enumeration of fungal growth was coincided with the symptom development.  相似文献   

17.
The dramatic increase in the usage of nanoparticles (NPs) in a variety of applications extensively expanded the possibility regarding the release of NPs into our ecosystem. Pomegranate is a tropical and subtropical countries’ shrub, as offers food supplement and more pharmaceutical and medicinal applications. Here, we investigated the effects concerning different concentrations regarding each of ZnO NPs and its bulk on growth, uptake of Zn, potassium (K), phosphorus (P), proline, ascorbic acid, total phenolic compounds, total antioxidant, localization of Zn in callus cells by transmission electron microscope (TEM) and changes in macromolecules by Fourier transform infrared spectroscopy (FT-IR) in pomegranate (Punica granatum cv. Hegazy) callus. Growth parameters in callus exposure to high concentrations of ZnO (50–200 µg mL?1) were reduced. Different concentrations of ZnO NPs and bulk did not affect the content of K and P. In comparison according to control, uptake of Zn was increased in pomegranate callus exposed to both ZnO NPs and its bulk. Moreover, TEM images showed small cells with the tortuous cell wall, disintegrated cytoplasmic content and Zn deposition in the cell walls at low concentration of ZnO NPs. However, the high concentration of ZnO NPs showed a further Zn influx in the cytoplasm and attachment to the tonoplast. The FT-IR analysis confirmed variations in the peaks corresponding to the most macromolecules, phenolic compounds, lipids, proteins, carbohydrates, cellulose, and hemicellulose. From these results, we could consider the toxicity effects concerning ZnO NPs and its bulk.  相似文献   

18.
Improved Method for Detection of Vibrio parahaemolyticus in Seafood   总被引:2,自引:0,他引:2       下载免费PDF全文
We have developed a new, effective procedure for detecting Vibrio parahaemolyticus in seafoods using enrichment and plating onto a chromogenic agar medium. Samples were cultured in salt Trypticase soy broth, which is a nonselective medium, and then a portion of the culture was cultured with salt polymyxin broth, which is a selective medium for V. parahaemolyticus. This two-step enrichment was more effective than the one-step enrichment in salt polymyxin broth alone. The enrichment cultures were then plated onto a new chromogenic agar containing substrates for beta-galactosidase. The V. parahaemolyticus colonies developed a purple color on this growth medium that distinguished them from other related bacterial strains. V. parahaemolyticus was isolated more frequently from naturally contaminated seafood samples using the chromogenic agar than thiosulfate citrate bile salts sucrose agar medium, which is currently used for the isolation of V. parahaemolyticus. Our findings suggest that this new enrichment and isolation scheme is more sensitive and accurate for identifying V. parahaemolyticus in seafood samples than previously used methods.  相似文献   

19.
The effect of various agents on the activation of succinate dehydrogenase in cauliflower (Brassica oleracea) and mung bean (Phaseolus aureus) mitochondria and in sonicated particles has been investigated. Reduced coenzyme Q10, inosine diphosphate, inosine triphosphate, acid pH, and anions activate the enzyme in mitochondria from higher plants in the same manner as in mammalian preparations. Significant differences have been detected in the behavior of plant and animal preparations in the effects of ATP, ADP, NADH, NAD-linked substrates, and of 2, 4-dinitrophenol on the state of activation of the dehydrogenase. In mammalian mitochondria ATP activates, whereas ADP does not, and the ATP effect is shown only in intact mitochondria. In mung bean and cauliflower mitochondria, both ATP and ADP activate and the effect is also shown in sonicated and frozen-thawed preparations. In sonicated mung bean mitochondria NADH causes complete activation, as in mammalian submitochondrial particles, but in sonicated cauliflower mitochondria activation by NADH is incomplete, as is also true of intact, anaerobic cauliflower mitochondria. Moreover, neither NAD-linked substrates nor a combination of these with NADH can fully activate the enzyme in cauliflower mitochondria. In contrast to mammalian mitochondria, succinate dehydrogenase is not deactivated in cauliflower or mung beam mitochondria under the oxidized conditions brought about by uncoupling of oxidative phosphorylation by 2,4-dinitrophenol.  相似文献   

20.
The effects of 22 pesticides on the mycelial growth and pathogenicity of the biocontrol fungus ARFI8 to Heterodera glycines were tested in vitro. The chemicals were added to agar at 10, 100, and 1,000 ppm a.i.; a block of agar containing the fungus was added to each test concentration; and fungal growth was measured. Subsequently, a block of the fungus on the pesticide-containing agar was used to determine the ability of the fungus to parasitize eggs of H. glycines. Aldicarb, bentazone, and chlorothalonil had little or no effect on fungal growth, whereas benomyl and thiophanate methyl completely inhibited growth of the fungus at 10 ppm. The relative insensitivity of ARF18 to certain pesticides would permit selected use of those pesticides with ARF18 in an integrated control program if the effects on the fungus in the field are similar to results from petri dish studies.  相似文献   

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