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1.
Capillary gas chromatography with flame ionization detection (GC-FID) was used to determine the cellular fatty acid (CFA) profiles of 134 Enterobacter sakazakii strains, and these were compared to the CFA profiles of other closely related Enterobacter and Citrobacter species. For GC-FID analysis, whole cell fatty acid methyl esters (FAMEs) from cells cultured on brain heart infusion (BHI) agar at 37 degrees C for 24 h were obtained by saponification, methylation, and extraction into hexane/methyl tert-butyl ether. A database for E. sakazakii was prepared using fatty acid profiles from the 134 strains. Major fatty acids of E. sakazakii strains evaluated in this study were straight-chain 12:0, 14:0, and 16:0, unsaturated 18:1 omega7c, and 17:0 omegacyclo 7-8. Principal component analysis (PCA) based on CFA profiles for E. sakazakii strains shows separation of E. sakazakii subgroups A and B. The CFA profiles for E. sakazakii and Enterobacter cloacae show that there are several fatty acids, 14:0, 17:0 omegacyclo 7-8, 18:1 omega7c, and summed 16:1 omega6c/16:1 omega7c, that differ significantly between these two species. A PCA model based on CFA profiles for E. sakazakii strains clearly shows separation of E. sakazakii from closely related Enterobacter and Citrobacter species. Analysis of FAMEs from E. sakazakii strains grown on BHI agar by a rapid GC-FID method can provide a sensitive procedure for the identification of this organism, and this analytical method provides a confirmatory procedure for the differentiation of E. sakazakii strains from closely related Enterobacter and Citrobacter species.  相似文献   

2.
双效菌素(zwittermicin A,ZwA)是一种广谱、新型的抗生素,对很多植物病原菌具有抑制作用;酰基高丝氨酸内酯酶(AHL)通过降解植物病原菌群体感应(quorum-sensing)系统的信号分子,减弱致病基因的表达从而达到抗病的效果。结合这两种物质的不同抗病机理,将来自苏云金芽胞杆菌(Bacillus thuringiensis)中的AHL基因导入到蜡状芽胞杆菌(B.cereus)中,得到相应的重组菌株。实验表明,AHL基因在重组菌中可正常表达,并且不影响受体菌ZwA的表达和产量;感病实验证明,同时表达ZwA和AHL的重组菌对于胡萝卜软腐欧文氏菌(Erwinia carotovora)感染马铃薯(Solanum tuberosum)所引起的病害的抗病效果比单独含产ZwA或AHL的蜡状芽胞杆菌的抗病效果有明显增强。说明结合ZwA和AHL的不同抗病机理来提高抗病效果是可行的。  相似文献   

3.
利用自主分离的芽孢杆菌菌株TS01和15种芽孢杆菌(地衣芽孢杆菌,枯草芽孢杆菌,短小芽孢杆菌,巨大芽孢杆菌,凝结芽孢杆菌,蜡状芽孢杆菌,迟缓芽孢杆菌,苏云金芽孢杆菌,嗜热脂肪芽孢杆菌,解淀粉芽孢杆菌,环状芽孢杆菌,球形芽孢杆菌,侧孢短芽孢杆菌,多粘类芽孢杆菌,泛酸枝芽孢杆菌)模式菌种进行ARDRA分析。采用16S rDNA通用引物16S-27和16S-1525进行PCR扩增,16S rDNA扩增片段经六种限制性酶（Alu I、Taq I、Mse I、Bst UI、Hha I和Tsp509 I）酶切电泳,获得了TS01菌株的特征性ARDRA指纹图谱。ARDRA图谱通过GelcomparⅡ软件进行聚类分析(UPGMA),结果表明菌株TS01和地衣芽孢杆菌处于同一分支,亲缘关系最近。ARDRA分析鉴定结果与实验室前期菌株TS01形态、生化鉴定和16S rDNA序列分析结果一致,TS01是一株地衣芽孢杆菌菌株,从而证明ARDRA技术在菌种水平上对芽孢杆菌TS01进行鉴别具有可靠性。  相似文献   

4.
The use of the lipid globule stain to aid in differentiating the Bacillus cereus group (i.e., B. cereus, B. cereus var. mycoides, and B. thuringiensis) from other Bacillus species was investigated. Smears from colonies grown on suitable agar were made on precleaned slides, stained, and examined microscopically for characteristic deep blue lipid globules. The study included a total of 649 cultures of Bacillus species plus 143 incompletely characterized Bacillus isolates from food. Only B. cereus, B. cereus var. mycoides, B. thuringiensis, B. megaterium, and B. sphaericus were consistently positive for lipid globules, although at times, a few cells of B. aneurinolyticus and B. thiaminolyticus were also positive. The lipid globule stain procedure is of value in differentiating Bacillus species, especially when performed by an experienced analyst and used in conjunction with tests for cell and spore morphology.  相似文献   

5.
蜡样芽孢杆菌905（Bacillus cereus 905）是从小麦体内分离获得的一株植物有益内生细菌。为从氧自由基毒性角度分析该细菌在植物体内的定殖机制,本研究利用PCR方法得到了B. cereus 905的CuZn-SOD基因全长（sodC）。该基因由537 bp组成,编码179个氨基酸残基。构建表达载体pET-22b-sodC,转化Escherichia coli BL21(DE3),IPTG诱导表达结果表明：该基因表达出的蛋白表现出SOD功能,化学抑制法验证其为CuZn-SOD。  相似文献   

6.
The antimicrobial effect of linolenic acid with or without monoglyceride (glycerol laurate or glycerol myristate) against six food-borne microorganisms was determined in broth medium. Minimum inhibitory concentration of linolenic acid on Bacillus cereus and Staphylococcus aureus was 20 and 50 ppm, respectively. The growth of B. cereus treated with linolenic acid at 10 ppm with 10 ppm monoglyceride was more inhibitory than that of linolenic acid alone, and the viable cell population was reduced 2-4 log cycles compared to that of the control. When linolenic acid was added at that level, the adenosine triphosphate (ATP) concentration of extracellular fluid was drastically increased compared with that of the control, and the combined effect with monoglyceride was higher than that with linolenic acid alone. However, the intracellular ATP concentration decreased compared with that of the control. From these results, we concluded that linolenic acid has a strong antimicrobial activity against B. cereus and S. aureus, and that linolenic acid combined with monoglyceride showed stronger antimicrobial activity than using linolenic acid alone.  相似文献   

7.
Capillary gas chromatography (GC) with flame ionization detection was used to determine the cellular fatty acid profiles of various food-borne microbial pathogens and to compare the fatty acid profiles of spores and vegetative cells of the same endospore-forming bacilli. Fifteen bacteria, representing eight genera (Staphylococcus, Listeria, Bacillus, Yersinia, Salmonella, Shigella, Escherichia, and Vibrio) and 11 species were used to compare the extracted fatty acid methyl esters (FAMEs). Endospore-forming bacilli were processed to obtain pure spores and whole cell FAMEs for GC analysis. A data set for each bacterial agent was prepared using fatty acid profiles from five replicates prepared on different days. The results showed that these fatty acid intensity profiles were unique for each of the 11 species and that they could be used as a fingerprint for the organisms. The cellular fatty acid profiles for Bacillus anthracis and Bacillus cereus show that there are two branched chain fatty acids, iso 17:1 omega10c and 17:1 anteiso, which are unique in these species. Iso 17:1 omega10c is present in B. cereus vegetative cells and spores but is not observed in B. anthracis. The 17:1 anteiso fatty acid is present in B. anthracis cells but not in B. cereus cells. Fatty acids 16:0 2OH and 17:0 iso 3OH are present in B. anthracis and B. cereus spores but not in the vegetative cells. In summary, analysis of FAMEs from bacteria and spores can provide a sensitive procedure for the identification of food-borne pathogens.  相似文献   

8.
Bacillus thuringiensis is indistinguishable from Bacillus cereus except for the production of insecticidal crystal proteins (ICPs). B. thuringiensis strains may show enterotoxin profiles and toxin levels similar to those of B. cereus strains isolated from food-poisoning cases. It is important for the food industry and farmers to consider that with the application of B. thuringiensis strains to crops, their spores may be introduced into the human food chain. In this study, 59 B. thuringiensis strains were assayed for their hemolysin BL (HBL) using a BCET-RPLA kit and their cytotoxicity to Chinese hamster ovary (CHO) cells. The enterotoxin titer was as high as that of B. cereus diarrheal-type strain ATCC 49064. In an attempt to obtain a food safety strain for bioinsecticide use, in this study, a 3.5-kb cry1Ac DNA fragment was amplified with PCR from the total DNA of B. thuringiensis subsp. kurstaki CCRC 11502 and cloned into the Bacillus expression vector pHY300PLK. The alpha-amylase promoter, amyE, was then introduced into the promoter region and, afterward, the recombinant plasmid pHYe1Ac35 was introduced into a non-enterotoxigenic and non-cytotoxic B. thuringiensis subsp. kurstaki Tt14 strain. The transformant, without any detectable enterotoxigenicity or cytotoxicity, produced Cry1Ac toxin properly, and its insecticidal activity against Trichoplusia ni larvae was found to be satisfactory.  相似文献   

9.
蜡样芽孢杆菌是土壤中的优势菌,具有作为益生菌的潜在能力,同时它也是条件致病菌,能引起食物中毒等。蜡样芽孢杆菌的多种毒力因子受到多效性调控子（pleiotropic regulator,plcR）的调控,在其条件致病性作用中起着重要作用。真养产碱杆菌JMP34（Alcaligenes eutrophus）质粒上的2,4-二氯苯氧乙酸（2,4-dichlorophenoxyacetic acid,2,4-D）单加氧酶（tfdA）基因可以降解2,4-D。本研究利用同源重组技术使tfdA基因置换掉蜡样芽孢杆菌的plcR基因,构建了蜡样芽孢杆菌ATCC14579突变株B.cereus△plcRΩtf-dA,并对其毒性、一般生理生化特性进行分析。研究结果表明,突变株B.cereus△plcRΩtfdA的毒性显著减弱;生理生化实验结果显示突变株与野生株并没有明显区别,且突变株并没有表现出tfdA酶活性。所有的结果表明plcR控制着蜡样芽孢杆菌ATCC14579的致病性,同时剔除plcR并不破坏其酶系统。本研究为今后构建蜡样芽孢杆菌工程菌提供了新的思路和依据。  相似文献   

10.
A collaborative study was conducted in 15 laboratories to evaluate 2 different techniques for enumerating Bacillus cereus in foods. A direct plating technique using mannitol-egg yolk-poly-myxin agar and a most probable number (MPN) technique using trypticase-soy-polymyxin broth were compared for the enumeration of high and low populations of B. cereus in mashed potatoes. The collaborative results showed that the overall mean recovery obtained with the low population level was essentially the same by both techniques. However, the overall mean recovery was significantly higher by the direct plating technique at the high population level. A statistical evaluation of the data also showed that the direct plating technique had better repeatability and reproducibility than did the MPN technique at both the high and low population levels. These results suggest that the MPN technique is suitable for examining foods containing low populations of B. cereus, but that the direct plating technique is preferable for foods that contain a high population of this organism. The confirmatory technique used in the proposed method is reliable for presumptive identification of isolates as B. cereus. The method has been adopted as official first action.  相似文献   

11.
为比较蜡样芽孢杆菌及其生物被膜对环境压力的抗性,该文主要研究了4种有机酸（乙酸、柠檬酸、乳酸和苹果酸）和乙醇对蜡样芽孢杆菌及其生物被膜存活率的影响。结果表明：生物被膜态蜡样芽孢杆菌对乙酸的抗性高于浮游态菌。扫描电镜结果显示,经乙酸处理后,浮游态蜡样芽孢杆菌的细胞表面严重受损,而生物被膜态菌的表面形态未发生明显变化。在柠檬酸、乳酸、苹果酸和乙醇存在的条件下,生物被膜态蜡样芽孢杆菌比浮游态菌表现出更强的压力抗性,特别是在高浓度（有机酸16%～20%,乙醇50%～60%）的情况下,该现象尤为显著。因此,在食品工业中控制被膜态蜡样芽孢杆菌对预防和阻止食品腐败非常重要。该研究结果为实际生产中有效控制蜡样芽孢杆菌及其生物被膜的形成提供参考。  相似文献   

12.
Two strains of Pediococcus pentosaceus were isolated from refrigerated pork and found to produce antimicrobial substances that may inhibit foodborne pathogens and have potential as natural food preservatives. They were named P. pentosaceus L and S. The antimicrobial substances were purified to electrophoretical homogeneity by chloroform extraction and designated pentocins L and S with molecular masses (M) of 27 and 25 kDa, respectively. Both pentocins also had broad inhibition spectra and were thermostable. They inhibit the growth of tested spore-forming G+ and G- strains and the germination of Bacillus subtilis ATCC 10225, B. subtilis ATCC 10254, and Bacillus cereus ATCC 11778 spores. The inhibition activities decreased as the glucose in the medium decreased from 8.0 to 2.0%.  相似文献   

13.
双效菌素(zwittermicin A,ZwA)是一种氨基多元醇类新型广谱抗生素,zmaR为其抗性基因。在苏云金芽胞杆菌(Bacillus thuringiensis)YBT-1520菌株ZwA合成基因簇末端存在一个类似ABC transporter的序列(命名为zwa-FEG)。将zwa-FEG基因在大肠杆菌(Escherichia coli)中表达,大肠杆菌能获得ZwA的抗性;将zwa-FEG转移到产ZwA的蜡状芽胞杆菌(Bacillus cereus)菌株UW85中,能使其ZwA产量显著提高。推测zwa-FEG是一种ZwA专一性的ABC transporter,它能将ZwA分泌到胞外,从而增强ZwA的合成和ZwA的抗性。  相似文献   

14.
双效菌素（Zwittermicin A,ZwA）是一种氨基多元醇类新型广谱抗生素,最初是从蜡状芽胞杆菌(Bacillus cereus) UW85中发现的,zmaR为它的抗性基因。在本实验室已测得的苏云金芽胞杆菌（Bacillus thuringiensis）YBT-1520菌株全基因组序列中有ZwA合成基因簇完整序列,分析发现在其末端存在一个类似ABC transporter的序列（命名为zwa-FEG）。将zwa-EFG在大肠杆菌（Escherichia coli）中表达,大肠杆菌能获得对ZwA的抗性;将zwa-EFG转移到产ZwA的菌株UW85中,能使其ZwA产量显著提高。推测zwa-EFG是一种ZwA专一性的ABC transporter,能将ZwA分泌到胞外,从而增强ZwA的合成和对ZwA的抗性。  相似文献   

15.
Cinnamomum burmannii Blume (cinnamon stick) from Indonesia is a little-investigated spice. In this study, the antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of cinnamon stick extract were evaluated against five common foodborne pathogenic bacteria (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella anatum). Cinnamon stick extract exhibited significant antibacterial properties. Major compounds in cinnamon stick were tentatively identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography (LC-MS) as a predominant volatile oil component ((E)-cinnamaldehyde) and several polyphenols (mainly proanthocyanidins and (epi)catechins). Both (E)-cinnamaldehyde and proanthocyanidins significantly contributed to the antibacterial properties. Additionally, scanning electron microscopy was used to observe morphological changes of bacteria treated with the crude extract of cinnamon stick and its major components. This study suggests that cinnamon stick and its bioactive components have potential for application as natural food preservatives.  相似文献   

16.
Field studies were conducted over three years on Podzol soils in Prince Edward Island (P.E.I.) on the effect of sulfur (S), calcium (Ca), and boron (B) fertilization on tissue nutrient concentration and potato yield. Leaf tissues were sampled at 10% bloom and again two weeks later for S, Ca, and B analysis. In the absence of S fertilization, S deficiency symptoms, as evidenced by lighter green foliage were found. The mean tuber yield response due to S addition was 1.1 (SE = 0.40) t/ha. Addition of S either as gypsum or magnesium sulfate was effective in overcoming the S deficiency symptoms and in increasing the S concentration in the leaves. Calcium and B additions did not affect the tuber yields. While Ca applications were ineffective in increasing the Ca concentration in the leaf tissue, B applications significantly increased the leaf tissue B concentration in both samplings. The interaction effects between S, Ca, and B were not significant on any of the components tested. Data indicated that 0.25 to 0.27 and 0.28 to 0.32% S in potato leaves were in the S deficiency and sufficiency range, respectively. This is the first documented case of S deficiency in the field in P.E.I. Potatoes and possibly other crops should be monitored for S‐deficiency symptoms and S levels in plant tissues should be recorded to detect any trends.  相似文献   

17.
The enantioselectivity of the generation of 3-mercaptohexanal and 3-mercaptohexanol, two potent sulfur-containing aroma compounds, by lipase-catalyzed hydrolysis of the corresponding 3-acetylthioesters was investigated. The stereochemical course of the kinetic resolutions was followed by capillary gas chromatography using modified cyclodextrins as chiral stationary phases. The enzyme preparations tested varied significantly in terms of activity and enantioselectivity (E). The highest E value (E = 36) was observed for the hydrolysis of 3-acetylthiohexanal catalyzed by lipase B from Candida antarctica resulting in (S)-configured thiol products. Immobilization of the enzyme (E = 85) and the use of tert-butyl alcohol as cosolvent (E = 49) improved the enantioselectivity. Modification of the acyl moiety of the substrate (3-benzoylthiohexanal) had no significant impact. The sulfur-containing compounds investigated possess attractive odor properties, and only one of the enantiomers exhibits the pleasant citrus type note.  相似文献   

18.
B atey , T. Soil Husbandry. A Practical Guide to the Use and Management of Soils. Soil & Land Use Consultants, Aberdeen, 1988. 157 pp. L16.50 (hardback), £10.50 (paperback).
D ixon , J. B. & W eeds , S. B. (eds) Minerals in Soil Environments .
H irekerur , L. R., S ehgal , J. L., P al , D. K. & D eshpande , S. B. (eds) Classification, Management and Use Potential of Swell-Shrink Soils.
J acobs , L. W. (ed.) Selenium in Agriculture and the Environment.
J ohnson , D. W. & V an H ook , R. I. (eds) Analysis of Biogeochemical Cycling Processes in Walker Branch Watershed.
K inloch , D. I., S hoji , S., B einroth , F. H. & E swaran , H. (eds) Proceedings of the Ninth International Soil Classification Workshop, Japan.
M c K yes , E. Agricultural Engineering Soil Mechanics.
P ereira , H. C. Policy and Practice in the Management of Tropical Watersheds.
R ocheleau , D., W eber , F. & F ield -J uma A. Agroforestry in Dryland Africa.
S awhney , B. L. & B rown , K. (eds) Reactions and Movement of Organic Chemicals in Soils.
S parks , D. L. Kinetics of Soil Chemical Processes.
S posito , G. The Chemistry of Soils.
S tewart , B. A. (ed.) Advances in Soil Science, Vol. 9.
S tewart , B. A. (ed.) Advances in Soil Science, Vol. 10.
W are , G. W. (ed.) Reviews of Environmental Contamination and Toxicology, Vol. 108.
B uckley , G. D. (ed.) Biological Habitat Reconstruction.
S haxson , T. F., H udson , N. W., S anders , D. W., R oose , E. & M oldenhauer , W. C. (eds) Land Husbandry: A Framework for Soil and Water Conservation.  相似文献   

19.
The high voltage electrophoresis bioautography method is applicable to meat, milk, and animal feeds. Meat is freeze-dried, powdered, and extracted with acetonitrile-water (9 + 1), and the extract is concentrated by evaporation at room temperature. Milk is examined directly or following acetonitrile-water extraction. Feed is extracted with acetonitrile-water. Samples or extracts are applied to preliminary assay plates of antibiotic medium No. 1 at pH 6 and 8, seeded with Micrococcus luteus (ATCC 9341), M. luteus DHSR (ATCC 9341A), Bacillus cereus (ATCC 11778), or B. cereus K250 TR (NCIB 11183), and nutrient agar at pH 7 seeded with B. subtilis BGA. Inactivation of penicillinase indicates beta-lactam antibiotics. Addition of trimethoprim increases sensitivity to sulfonamides. After 18-24 h incubation at 30 degrees C, plates yielding clear inhibition zones guide selection of conditions for subsequent electrophoresis bioautography. Extracts are applied (5-100 microL) to 10 mm diameter wells on electrophoresis plates 60 cm long and 40 cm wide, with a gel depth of 1.6 mm. The support medium is 1% agar and 1% agarose in Tris/succinic acid buffers pH 6 and pH 8. A potential of 1500 V is applied for 1.5 h at 15 degrees C. Following electrophoresis, the migrated antibiotics are visualized by over-layering with antibiotic medium No. 1, pH 6 or 8, seeded with M. luteus or B. cereus spore suspension; plates are incubated for 18-24 h at 30 degrees C. Identification is based on results of preliminary screening together with electrophoretic migration distances and inhibition zone appearances compared with standards.  相似文献   

20.
为了有效筛选出对作物青枯病具有防治效果的生防细菌,本研究采用群体感应淬灭基因aiiA的简并引物进行PCR扩增与室内盆栽防治效果测定相结合的方法进行生防细菌的筛选,并通过传统的细菌学鉴定方法和分子生物学手段明确其分类地位。结果表明,从253株生防菌株中获得了12株含有aiiA基因的生防菌株;进一步盆钵防效测定,获得了一株对烟草青枯病具有较好防治效果的生防菌株B15。该菌株接种处理后,烟草青枯病可推迟2 d 发生,在接种处理14 d后其对烟草青枯病防治效果为68.33%。B15菌株在NA平板培养基上菌落呈圆形、白色、表面有光泽且粗糙,菌体杆状,革兰氏染色阳性,耐盐性为7%;生理生化测定、16S rDNA和gyrB基因序列分析表明,菌株B15为蜡样芽胞杆菌(Bacillus cereus)。本研究获得的含有群体感应淬灭基因aiiA的蜡样芽胞杆菌B15菌株,为作物青枯病生物防治提供了新的生防菌株资源。  相似文献   

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