纳豆激酶的克隆及在大肠杆菌中的表达

该文采用PCR方法扩增获得了纳豆激酶基因(pro-NK),通过酶切与酶连反应使其与原核表达载体Pet32a相连,构建重组质粒Pet32a-pro-NK,先转入到大肠杆菌DH5α中进行筛选与验证,再将阳性克隆子转化到宿主菌BL21(DE3)中,在IPTG诱导下进行纳豆激酶蛋白的表达研究。SDS-PAGE电泳分析结果表明,纳豆激酶蛋白在BL21(DE3)中获得高效表达。     

Dynamics of shiga-toxin producing Escherichia coli (STEC) and their virulence factors in cattle

Starting at birth, twenty Holstein calves were housed individually, in groups of five and finally in one large freestall while fecal samples were collected weekly for 25 weeks. From each sample, twenty isolates of Escherichia coli were screened for 6 virulence markers including shiga-toxin 1, 2, intimin, enterohemolysin, the fimbrial antigen efa1 and the adhesin saa. Dynamic models of transmission of E. coli were used to model the transmission of different virulotypes between calves and the loss of the same virulotypes from the calves. It was found that, once E. coli encoding shiga-toxins in combination with enterohemolysin were transmitted and established in a calf, they tended to be eliminated less efficiently compared to E. coli without this combination of virulence markers. It was concluded that the presence of certain combinations of virulence markers coincided with persistence of E. coli in the bovine gastrointestinal tract. In addition, the combinations of stx with either eae or ehxA in E. coli have a greater impact on the loss rates than on the transmission rates.     

Automatic image analysis and spot classification for detection of pathogenic Escherichia coli on glass slide DNA microarrays

A computer algorithm was created to analyze and quantify scanned images from DNA microarray slides developed for detecting pathogenic Escherichia coli isolates recovered from agricultural food products. The algorithm computed centroid locations for signal and background pixel intensities in RGB space and defined a plane perpendicular to the line connecting the centroids as a decision boundary. The algorithm was tested on 1534 potential spot locations which were visually classified depending on the strength of the signal. Three other standard measures of SNR (SSR, SBR, and SSDR) were also performed for each potential spot location. The number of errors as compared to visual classifications was computed for each of the four measures. SSR and SSDR, which depend on pixel intensity standard deviations, performed poorly with high false positive results, while the current algorithm and SBR, which were independent of standard deviations, performed much better. Overall error rates were 1.4% for the reported algorithm, 2.0% for SBR, 14.2% for SSDR, and 16.8% for SSR.     

茶氨酸生物合成基因工程菌的质粒稳定性研究

研究了茶氨酸生物合成基因工程菌重组质粒pET32a-GGT的稳定性。结果表明,该基因工程菌在连续传代100代后,质粒的目的基因片断没有缺失,具有结构稳定性;但在无抗生素选择压力下,连续传代20代后开始出现质粒丢失的细胞,连续传代100代后18%的细胞含有正常质粒,因此,表现出一定的分裂不稳定性。该基因工程菌在优化培养基和优化条件下的整个发酵过程中,始终表现出良好的结构和分裂稳定性,γ-谷氨酰转肽酶的活性为4.64U/ml,催化合成茶氨酸的产量为35.18g/L。     

L-茶氨酸对产肠毒素大肠杆菌引起的免疫应激小鼠肠道的保护作用研究

以SPF级Balb/c雌性小鼠为实验动物,对其适应性饲养3 d后连续30 d灌喂不同剂量L-茶氨酸,然后腹腔注射产肠毒素大肠杆菌E44813诱导免疫应激,5 h后取样,分析研究了L-茶氨酸对小鼠体重,回肠组织谷胱甘肽过氧化物酶(Glutathione peroxidase,GSH-Px)、过氧化氢酶(Homogenate catalase,CAT)与诱导型一氧化氮合成酶(Inducible nitric oxide synthase,i NOS)活性,丙二醛(Malondialdehyde,MDA)含量、空肠组织病理学变化,以及血清肿瘤坏死因子α(Tumor necrosis factor-α,TNF-α)、细胞间粘附分子1(Intercellular cell adhesion molecule-1,ICAM-1)和白介素1β(Interleukin-1β,IL~(-1)β)表达量的影响,以探明L-茶氨酸对产肠毒素大肠杆菌免疫应激小鼠肠道的保护作用。结果表明,各剂量L-茶氨酸均能显著增加小鼠体重,可减轻产肠毒素大肠杆菌E44813引起的肠道组织病变程度,升高回肠组织GSH-Px和CAT酶活性,降低MDA含量和i NOS酶活性,在不同程度上抑制血清TNF-α、IL~(-1)β和ICAM-1的表达量。说明L-茶氨酸可通过抑制炎性细胞因子表达水平、降低脂质过氧化程度和提高抗氧化能力来维护肠道组织形态与结构的完整性,并达到保护肠道的作用。     

3种姜科植物提取物的体外抗菌活性

采用试管倍比稀释法研究3种姜科植物(砂仁、草豆蔻和高良姜)乙醇提取物对5种鸡、猪致病菌的体外抗菌活性。结果表明,3种姜科植物提取物对5种致病菌均有较好的抑制作用,对鸡和猪大肠杆菌、鸡和猪金黄色葡萄球菌、鸡沙门氏菌最低杀菌浓度(MBC)分别为125、15.6、62.5 mg/mL。说明3种姜科植物乙醇提取物对鸡、猪5种常见致病菌均具有较好的体外抗菌效果,其中对金黄色葡萄球菌的体外抑杀效果优于大肠杆菌和沙门氏菌。     

Effects of Using Rice Bran and Cottonseed Meal as Organic Fertilizers on Water Quality,Plankton, and Growth and Yield of Striped Bass,Morone saxatilis,Fingerlings in Ponds

Several significant differences in water quality, primary production, production of plankton, or yield of striped bass, "Morone saxatilis," fingerlings were found between ponds fertilized with either rice bran and inorganic fertilizer or those ferilized with cottonseed meal and inorganic fertilizer. Ponds fertilized with rice bran had the lowest ammonia concentrations and Secchi disc readings and the highest concentrations of cladocerans and crustracean zooplankton. At harvest, after 82 days of culture, striped bass fingerlings from ponds fertilized with rice bran were significantly larger than were those from ponds fertilized with cottonseed meal. Numbers of fingerlins produced per hectare did not differ by treatment but ferilizer cost were US$94.78/ha less for ponds fertilized with rice bran.     

泰安及周边地区禽大肠杆菌分离鉴定及耐药分析

对泰安及周边地区鸡大肠杆菌病的流行情况和致病性大肠杆菌的耐药性状况进行了比较系统的调查分析：对25株鸡源性大肠杆菌进行了分离纯化、生化试验,同时对所分离的菌株进行了耐药性测定及β内酰胺药物耐药基因TEM的检测等研究。结果表明：大肠杆菌对多种抗生素均产生了耐药性,对β－内酰胺类药物的耐药性也相当严重,对在药敏试验中检测出对头孢菌素类药物不敏感的菌株进行TEM基因检测,发现这些菌株均含有耐β-内酰胺酶耐药基因,与Genebank上登录的其他耐β-内酰胺酶耐药基因序列的同源性达到97％以上,仅存在个别的碱基突变。通过研究以期探明地区鸡源性大肠杆菌病的流行情况和细菌的耐药现状．从而为有效控制鸡大肠杆菌病的发生流行提供可靠的理论依据,以便制订出较为科学合理的预防和治疗措施,以提高养殖效益。     

禽致病性大肠杆菌实验感染模型研究进展

禽致病性大肠杆菌（avian pathogenic Escherichia coli,APEC）是导致不同日龄禽类局部和全身感染的重要病原菌,也是人肠外致病性大肠杆菌（extraintestinal pathogenic Escherichia coli,ExPEC）毒力基因的重要储存宿主或来源。为深入理解APEC的感染过程、致病机理、宿主免疫应答及遗传抵抗机制、评估药物和疫苗防治效果,研究者通过不同途径建立了多种评估APEC毒力的实验感染模型。根据所涉及的系统不同可分为呼吸系统、脉管系统、肌肉系统、皮肤系统、生殖系统、消化系统及鸡胚系统等。此外,尚有小鼠与大鼠感染试验及组织培养细胞和外植块感染试验等。作者重点介绍了不同APEC实验感染模型的建立、致病机制、宿主应答及应用。