鹿蹄草素对金黄色葡萄球菌的抑制作用及其机理研究

对鹿蹄草素作用下的金黄色葡萄球菌生长曲线、膜通透性和结构进行了研究,探讨鹿蹄草素抑菌和杀菌机理。鹿蹄草素能够有效抑制金黄色葡萄球菌的生长,其最小抑菌质量浓度为0.16mg/mL;鹿蹄草素对金黄色葡萄球菌具有较强的杀菌作用,最小杀菌质量浓度为0.2mg/mL。鹿蹄草素作用于金黄色葡萄球菌后,细胞膜通透性与空白对照组相比显著提高。扫描电镜的结果表明,鹿蹄草素作用后菌体细胞结构被破坏,细胞壁呈溶解状,菌体细胞间相互粘结,细胞与细胞间的界限变得模糊。试验结果表明,鹿蹄草素的抑菌性和杀菌功能与其对金黄色葡萄球菌细胞膜和细胞壁结构的破坏直接相关。     

鹿蹄草素对金黄色葡萄球菌和绿脓杆菌的抑制效果观察

对鹿蹄草素作用下金黄色葡萄球菌和绿脓杆菌生长曲线、膜通透性和扫描电镜下形态进行研究,初步探讨了鹿蹄草素抑菌和杀菌机理.结果表明:鹿蹄草素能有效抑制金黄色葡萄球菌和绿脓杆菌的生长,抑制作用随着药物浓度增加而增加,且对金黄色葡萄球菌具有杀灭作用.鹿蹄草素作用细菌后,金黄色葡萄球菌细胞膜通透性与空白对照组相比显著提高,绿脓杆菌无明显变化.扫描电镜结果表明,鹿蹄草素作用后金黄色葡萄球菌菌体细胞结构被明显破坏,细胞壁呈溶解状,菌体细胞间相互粘结,细胞间界限变模糊;绿脓杆菌菌体细胞间界限变模糊,但并未对菌体细胞壁和细胞膜造成破坏.结果分析认为,鹿蹄草素对金黄色葡萄球菌的抑制和杀灭与菌体细胞膜和细胞壁结构被破坏直接相关,而鹿蹄草素对绿脓杆菌的抑制与菌体细胞膜和细胞壁无关.     

鹿蹄草素对苹果轮纹病菌的抑制作用及其超微结构的研究

为探讨鹿蹄草素对苹果轮纹病菌的抑制活性及作用机理,采用倍比稀释法测定鹿蹄草素最小抑菌浓度(MIC)和最小杀菌浓度(MBC),扫描和透射电镜观察鹿蹄草素对苹果轮纹病菌超微结构的影响.结果表明,鹿蹄草素对苹果轮纹病菌具有较强的抑菌活性,其最小抑菌质量浓度为0.078 mg/mL,最小杀菌质量浓度为0.156mg/mL.用扫描电镜观察,菌丝扭曲变形,菌丝体之间相互粘连,细胞壁破裂,表面出现絮状凝集物,部分菌丝断裂、消融、干瘪、空腔.用透射电镜观察,细胞壁明显变薄,胞内空腔增多,细胞内部组成紊乱,原生质大量外泄,细胞结构遭到严重破坏,最终菌体崩解死亡.     

鹿蹄草素对链格孢病菌的抑制作用研究

采用牛津杯法,研究了鹿蹄草素对链格孢病菌的抑制作用.通过单因子-正交实验方法,分别考察了不同浓度、不同溶剂和不同pH 3个因素对鹿蹄草素抑制链格孢病菌效果的影响.实验结果表明,最佳抑菌条件为:鹿蹄草素浓度:5mg/mL,pH:7～8;溶剂:60%乙醇.     

没食子酸的体外抑菌作用研究

研究了没食子酸对常见食源性致病菌和腐败菌的抑菌作用.采用液体二倍稀释法和牛津杯法测定了没食子酸的最小抑菌浓度及抑菌活性;采用酶标仪测定了细菌生长曲线的变化;采用扫描电镜观察了单增李斯特菌的形态变化.结果表明,没食子酸对单增李斯特菌、大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌、蜡状芽孢杆菌、巨大芽孢杆菌最小抑菌浓度分别为0.125、0.25、2、4、4、4mg/mL,抑菌圈分别为24.03±0.17、20.67±0.28、17.17±0.64、14.43±0.10、14.77±0.04、(15.07±0.03) mm;对生长曲线均有影响,并使单增李斯特菌的菌体从中间处凹陷,大部分出现破损,具有明显的细胞原生质泄漏现象.     

鹿蹄草等中草药对水果褐腐病菌（Monilinia．fracticola）的抑制作用

筛选出鹿蹄草、厚朴、虎杖等7种中草药，探讨其单剂及复配组合对水果褐腐病菌的抑制作用。方法：（1）各中草药水煎浸提，生长速率法测定各药液对褐腐病菌生长抑制率的大小；（2）等倍稀释法测定对褐腐病菌抑制作用较好的几种中草药复配组合的最小抑菌浓度（MIC）和最小杀菌浓度（MBC）；（3）扫描电镜观察增效组合MIC和MBC作用下褐腐病菌的菌丝形态。结果：（1）各单剂及复配组合对褐腐病菌均有不同程度的抑制作用，复配组合中，以11号（鹿蹄草＋厚朴＋大黄）、14号（鹿蹄草＋高良姜＋虎杖）、21号（鹿蹄草＋虎杖＋大黄）组合效果最好，10mg／ml浓度的抑制率分别达到89．77％、B5．50％和85．02％；（2）三种组合的MIC分别是1．25、2．5、1．25mg／ml；MBC分别是2．5、5．0、5．0mg／ml；（3）电镜观察发现，增效中草药组合11号MIC和MBC作用下，褐腐病菌菌丝数量减少，出现断裂，且部分消融。     

鹿蹄草提取物抑菌活性的研究

本文以鹿蹄草为研究对象,利用制得的鹿蹄草提取物对多种食品中常见的微生物进行抑菌活性试验,结果表明:鹿蹄草提取物抑菌作用因菌种不同而最低抑菌浓度有所不同,金黄色葡萄球菌为5%,大肠杆菌为10%,绿脓杆菌20%,根霉10%,青霉20%;同时,其抑菌活性随着浓度的增加而增强;鹿蹄草提取物具有一定的耐热性,但不是很稳定;鹿蹄草...     

金针菇多糖抑菌作用的研究

采用纸片扩散法研究金针菇多糖对8种细菌和真菌的抑菌效果,测试了金针菇多糖对细菌、真菌的抑菌圈大小、最小抑菌浓度。结果表明:金针菇多糖对真菌的抑制作用强于对细菌的抑制作用。最小抑菌浓度MIC在31 g/L~500 g/L之间。同时金针菇多糖对食品防腐具有一定的作用。     

茶树精油对灰葡萄胞霉生理功能的干扰研究

为探寻新型生物防治方法,揭示茶树精油(TTO)对果蔬采后病原真菌灰葡萄孢霉(Botrytis Cinerea)的抑菌作用机理,以液体培养后收集的B.Cinerea菌丝体为研究对象,进行2倍MIC(最小抑菌浓度)的TTO处理,采用荧光显微镜(FEM)、扫描电镜(SEM)和透射电镜(TEM)研究了处理对细胞膜通透性、菌体形态和超微结构的影响,以及处理过程中菌丝体内活性氧(ROS)积累及相关抗氧化酶类和物质的变化。结果表明:TTO处理后菌丝荧光强度增强,说明其细胞膜通透性明显上升,细胞膜完整性受到破坏;同时菌丝发生严重的皱缩、干瘪,胞浆消化呈碎渣样;TTO导致了菌丝内过氧化氢(H2O2)的大量积累,诱导提高了超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸-谷胱甘肽(As A-GSH)循环的活性,说明TTO是通过提高B.Cinerea细胞膜通透性、破坏菌体结构和诱导ROS爆发来发挥抑菌作用。     

香兰素抑菌作用的研究

用平板稀释法测定香兰素对细菌及真菌的抑菌作用。结果表明,香兰素具有较强的抑菌作用。对大肠杆菌的最低抑菌浓度(MIC)为0.235%,对金黄色葡萄球菌的最低抑菌浓度为0.294%,对酵母菌的最低抑菌浓度为0.118%,对黑曲霉的最低抑菌浓度为0.059%。     

多粘菌素B抑制丝状真菌的定量测定方法研究

为规范抗菌肽抑制丝状真菌的活力评价方法,采用多粘菌素B为抗菌肽研究对象,以黑曲霉(Aspergillus niger ATCC 16404)和产黄青霉(Pencillinm chrysogenum ATCC 10106)为指示菌,选用察氏培养基(20 mL培养基/90 mm平板)比较孢子萌发抑制法和菌丝生长抑制法,获得适合丝状真菌的测定方法,并进一步研究该方法的最适测定条件。结果表明,菌丝生长抑制法更适用于多粘菌素B抑制2株丝状真菌的定量检测。其中多粘菌素B抑制Aspergillus niger ATCC 16404的最适条件:指示菌培养48 h,接种菌饼直径(8.00±0.02) mm,在此条件下,测得多粘菌素B的EC₅₀为0.68 mg/mL;多粘菌素B抑制Pencillinm chrysogenum ATCC 10106的适宜条件:指示菌培养72 h,接种菌饼直径(5.80±0.02) mm,此时多粘菌素B的EC₅₀为0.45 mg/mL。本研究建立的抗菌肽抑制丝状真菌的活力测定方法具有普遍适用性,可为抗菌肽活性测定方法的规范及评价标准的建立奠定基础。     

In vitro inhibition of postharvest pathogens of fruit and control of gray mold of strawberry and green mold of citrus by aureobasidin A

Aureobasidin A (AbA), an antifungal cyclic depsipeptide antibiotic produced by Aureobasidium pullulans R106, has previously been shown to be effective against a wide range of fungi and protozoa. Here we report the inhibitory effects of AbA on spore germination, germ tuber elongation and hyphal growth of five pathogenic fungi including Penicillium digitatum, P. italicum, P. expansum, Botrytis cinerea and Monilinia fructicola, which are major pathogens causing postharvest diseases of a variety of fruits. AbA inhibited five pathogenic fungi by reducing conidial germination rates, delaying conidial germination initiation, restricting elongation of germ tuber and mycelium, as well as inducing abnormal alternations of morphology of germ tubes and hyphae of these fungi. The sensitivity of these fungi to AbA was pathogen species-dependent. P. digitatum was the most sensitive and M. fructicola the least. Importantly, AbA at 50 microg/ml was effective in controlling the citrus green mold and in reducing the strawberry gray mold incidence and severity, caused by P. digitatum and B. cinerea, respectively, after artificial inoculation. AbA and/or its analogs, therefore, hold promise as relatively safe and promising fungicide candidates to control postharvest decays of fruits, because AbA targets the inositol phosphorylceramide (IPC) synthase, an enzyme essential for fungi but absent from mammals.     

Antifungal Activity of Sodium Silicate on Fusarium sulphureum and Its Effect on Dry Rot of Potato Tubers

ABSTRACT:  The antifungal activity of sodium silicate on Fusarium sulphureum and its inhibitory effect on dry rot of potato tubers were investigated. Sodium silicate strongly inhibited spore germination and mycelial growth. Morphological changes in sodium silicate-treated hyphae such as mycelium sparsity and asymmetry, hyphal swelling, curling, and cupped shape were observed by scanning electron microscopy. Ultrastructural alterations were also observed using transmission electron microscopy, including thickening of the hyphal cell walls, cell distortion, cavity, or electron-dense material in hyphal cells. Daughter hyphae and new daughter hyphae inside of the collapsed hyphal cells were often detected in the cytoplasm of sodium silicate-treated hyphae, although the septa of treated hyphae remained uniform. In vivo testing showed that sodium silicate at 100 and 200 mM effectively controlled dry rot of tubers that were challenged by inoculation with a F. sulphureum spore suspension. These findings suggest that sodium silicate has direct fungitoxic activity against the pathogen.     

江香薷活性成分香芹酚对指状青霉的抑菌作用

以指状青霉菌(Penicillium digitatum)为供试菌,研究江香薷活性成分香芹酚的抑菌活性及其抑菌机理。本文采用二倍稀释法测定其最小抑菌浓度(MIC)和最小杀菌浓度(MFC),以此评价香芹酚对指状青霉菌的抑菌效果;并通过研究香芹酚对指状青霉的菌丝形态变化、孢子萌发率、细胞膜渗透性和菌体内可溶性糖含量,阐述香芹酚对指状青霉菌的抑菌机理。结果表明:香芹酚对指状青霉菌的MIC、MFC分别为0.125 mg/mL和0.25 mg/mL;经不同浓度香芹酚处理后的指状青霉,菌丝形态发生明显改变,孢子萌发率显著降低,细胞膜渗透性增强,菌体内可溶性糖含量降低。说明香芹酚能有效抑制指状青霉菌的孢子萌发,破坏细胞膜结构完整性,内含物外渗,降低营养物质含量,影响病原菌正常生长发育,从而发挥抑菌效果。     

Control of Aspergillus flavus with essential oil and methanol extract of Satureja hortensis

The essential oil and methanol extract of Satureja hortensis were tested for antifungal activity against Aspergillus flavus in vitro on Petri plates and liquid culture, and under storage conditions. The oil showed strong antifungal activity based on the inhibition zone and minimal inhibitory concentration values against the pathogen on Petri plates assays. The very low concentrations of them also reduced wet and dry mycelium weight of pathogen fungus in liquid culture. When the oils at 25, 12.5 and 6.25 microl/mL concentrations were applied to lemon fruits before seven days of pathogen inoculation on storage conditions, the decay on fruits caused by the pathogen could be prevented completely. The results in this study showed that the essential oil of S. hortensis had strong antifungal activity against pathogen fungi tested. So, the essential oil of S. hortensis could be used for management of this pathogen as a potential source of sustainable eco-friendly botanical fungicides.     

鼠李糖脂对梨采后黑斑病的抑制机理

以梨果黑斑病菌 Alternaria alternate为研究对象，研究了鼠李糖脂（rhamnolipids，RLS）对抑制A. alternata的生长和控制黑斑病的作用，并进一步探讨了其抑菌作用机理。结果表明：RLS能显著抑制 A. alternata 的生长，且其抑制效果随质量浓度的增加而显著提高，其中30 mg/mL RLS处理的菌落培养7 d时直径仅为对照组的19.22%，且菌落呈白色、球状。同时，RLS处理能有效控制梨果黑斑病的扩展，其中50 mg/mL RLS处理的果实的病斑直径仅为对照的21.42%。进一步研究发现RLS处理严重破坏了A. alternata 细胞膜和线粒体的完整性，提高了膜电导率，促进了活性氧的产生与积累。超微观察发现RLS处理后A. alternata的菌丝形态、细胞结构均发生了明显改变。     

三种海藻内生真菌的分离及其抑菌活性研究

从烟台浅海处采集到的鼠尾藻、裙带菜、海带三种海藻表面消毒后用PDA培养基将内生真菌进行分离纯化,将纯化的内生真菌进行液体培养7d后离心,菌丝体烘干研磨后用无水乙醇提取,分别测定发酵液和菌丝体乙醇提取物对七种植物病原真菌的抑菌活性。结果表明:三种发酵液都至少对三种病原菌有大于50%的抑菌活性,裙带菜发酵液对六种病原菌都有大于50%的抑菌率,最高为78.8%,说明它们能产生广谱高效的胞外代谢产物;而菌丝体提取物的抑菌活性并不明显,说明三种海藻内生真菌产生的胞内代谢产物无明显的抑菌活性。     

白黄链霉菌TD-1产帕马霉素对黄曲霉2219等霉菌的抑制作用

为研究微生物及其次级代谢产物对黄曲霉2219等霉菌的抑制机理,以分离于土壤中的白黄链霉菌(Streptomyces alboflavus)TD-1为研究对象,利用薄层色谱、硅胶柱层析、高效液相色谱和液相-质谱联用技术对其代谢产生的活性物质——帕马霉素进行分离。利用扫描电子显微镜、荧光显微镜和高效液相色谱方法研究帕马霉素对黄曲霉2219等霉菌生长的抑制效果及抑制机理。结果表明,白黄链霉菌TD-1上清液和菌丝体中活性物质的分子式预测为C₃₅H₆₁NO₇,为帕马霉素及其同系物,相对分子质量为593、607、621、635、649。通过扫描电子显微镜观察帕马霉素处理后的霉菌细胞形态,其孢子和菌丝体会发生不同程度畸变。帕马霉素对桔青霉的最小抑菌浓度(minimal inhibitory concentration, MIC)为0.125mg/mL,对灰霉的MIC为0.500mg/mL,对黄曲霉2219、黑曲霉、哈茨木霉和米曲霉的 MIC 均为1.000mg/mL。帕马霉素对霉菌的作用靶点为其细胞膜的麦角甾醇,抑制机制是破坏细胞壁的完整性,改变细胞膜的通透性,影响线粒体的能量代谢,抑制菌丝细胞膜中麦角甾醇的生物合成。帕马霉素对黄曲霉2219产生黄曲霉毒素B₁的抑制率达到98.3%。因此,可利用白黄链霉菌 TD-1及其代谢产物帕马霉素对食品原料中的产毒真菌污染进行生物防治。     

Efficacy of bioactive compounds isolated from Albizia amara and Albizia saman as source of antifungal and antiaflatoxigenic agents

The antifungal and antiaflatoxigenic activities of budmunchiamine A (BUA) isolated from Albizia amara and pithecolobine (PI) isolated from Albizia saman were assessed. The present study reports the broad-spectrum and concentration-dependent antifungal activities of BUA and PI with zone of inhibitions and minimum inhibitory concentrations ranging from 6.8 to 19.6 mm and 0.015–0.5 mg/mL, respectively. Aspergillus flavus growth and its aflatoxin B₁ production were completely inhibited in vitro by BUA and PI at concentration of 1 mg/mL. BUA severely inhibited the growth of wide range of seed-borne fungi of maize including aflatoxigenic A. flavus with an increased seedling vigour index in vivo at a lower concentration (1.0 g/kg) than PI (2.0 g/kg). Enhanced seedling vigour was observed in BUA and PI treatments with no adverse effect on seed germination. The present findings indicate the possible use of BUA and PI as antifungal agents against post harvest fungal infestation of food commodities and mycotoxin contamination.     

Antifungal activity of sourdough fermented wheat germ used as an ingredient for bread making

This study aimed at investigating the antifungal activity of sourdough fermented (Lactobacillus plantarum LB1 and Lactobacillus rossiae LB5) wheat germ (SFWG). Preliminarily, methanol and water/salt-soluble extracts from SFWG were assayed by agar diffusion towards Penicillium roqueforti DPPMAF1. As shown by hyphal radial growth rate, the water/salt-soluble extract showed the inhibition of various fungi isolated from bakeries. The antifungal activity was attributed to a mixture of organic acids and peptides which were synthesized during fermentation. Formic (24.7 mM) acid showed the highest antifungal activity. Four peptides, having similarities with well known antifungal sequences, were identified and chemically synthesized. The minimal inhibitory concentration was 2.5–15.2 mg/ml. Slices of bread made by addition of 4% (wt/wt) of freeze dried SFWG were packed in polyethylene bags and stored at room temperature. Slices did not show contamination by fungi until at least 28 days of storage and behaved as the calcium propionate (0.3%, wt/wt).