陕西省常见食源性致病菌耐药性研究进展

近年来食品安全问题层出不穷,而食源性致病菌则是引起食品安全问题的主要因素之一,严重危害了人类的健康.引发食源性疾病的常见致病菌主要有大肠杆菌、沙门氏菌、金黄色葡萄球菌、单核细胞增生李斯特菌等.研究表明,在过去的几十年里,由于在医疗、养殖业等领域中过度使用抗生素,造成细菌耐药现象日趋严重,这更加重了食源性致病菌的潜在危险...     

Carbon Metabolism of a Soilborne Mn(II)-Oxidizing Escherichia coli Isolate Implicated as a Pronounced Modulator of Bacterial Mn Oxidation

Mn(II)-oxidizing microorganisms are generally considered the primary driving forces in the biological formation of Mn oxides. However, the mechanistic elucidation of the actuation and regulation of Mn oxidation in soilborne bacteria remains elusive. Here, we performed joint multiple gene-knockout analyses and comparative morphological and physiological determinations to characterize the influence of carbon metabolism on the Mn oxide deposit amount (MnODA) and the Mn oxide formation of a soilborne bacterium, Escherichia coli MB266. Different carbon source substances exhibited significantly varied effects on the MnODA of MB266. A total of 16 carbon metabolism-related genes with significant variant expression levels under Mn supplementation conditions were knocked out in the MB266 genome accordingly, but only little effect on the MnODA of each mutant strain was accounted for. However, a simultaneous four-gene-knockout mutant (namely, MB801) showed an overall remarkable MnODA reduction and an initially delayed Mn oxide formation compared with the wild-type MB266. The assays using scanning/transmission electron microscopy verified that MB801 exhibited not only a delayed Mn-oxide aggregate processing, but also relatively smaller microspherical agglomerations, and presented flocculent deposit Mn oxides compared with normal fibrous and crystalline Mn oxides formed by MB266. Moreover, the Mn oxide aggregate formation was highly related to the intracellular ROS level. Thus, this study demonstrates that carbon metabolism acts as a pronounced modulator of MnODA in MB266, which will provide new insights into the occurrence of Mn oxidation and Mn oxide formation by soilborne bacteria in habitats where Mn(II) naturally occurs.     

生物负载微孔渗水型混凝土对土壤中残留毒死蜱的去除试验

为了解决农村农药面源污染问题,利用小流量渗透法将毒死蜱降解菌负载在微孔渗水型混凝土上,研究不同降雨强度下不同孔隙率混凝土对毒死蜱的降解截留效果.结果表明:对于3种不同透水系数的微孔混凝土,微孔渗水型混凝土负载生物量和生物活性随孔隙率增大呈先升高后降低趋势;对于两种不同的降雨强度,毒死蜱降解率最优的都是孔隙率为48.1％...     

硫酸盐还原菌对低碳钢的腐蚀

本文用失重法测定半连续、不连续培养的硫酸盐还原菌对低碳钢的腐蚀速度,采用线性极化技术测定活性生长的硫酸盐还原菌中低碳钢的线性极化阻力(同时测定自腐蚀电位、菌数、硫化物浓度)随时间的变化,并测量不同电位变化区间的阴阳极恒电位极化曲线。结果表明:在一定Fe2 浓度的硫酸盐还原菌培养基中,硫酸盐还原菌对钢的腐蚀速度与菌的生长时期有密切关系。在活性生长的硫酸盐还原菌系统中一直发生强烈的阴极去极化腐蚀。     

细胞周期同步化方法在细菌细胞周期研究中的应用

细胞群体在恒定条件的培养过程中是一个混合的群体,由处于细胞周期不同时期的细胞组成.对细胞周期特定时期的研究需要使细胞群体的生长同步化,即使用细胞周期同步化方法,通过物理或化学的方法将混合群体中特定时期的细胞分离出来或将整个群体阻断在细胞周期的某个阶段.经过同步化的细胞群体在后续培养的过程中可以在一段时间内同步地进行生长...     

高转化大豆异黄酮乳酸菌的筛选及在豆乳中的发酵特性

为提高大豆异黄酮生物活性及利用度,该研究以含七叶苷和柠檬酸铁的特殊培养基,从实验室保藏的人源乳酸菌中筛出产β-葡萄糖苷酶目标菌株,并采用高效液相色谱法测定其发酵豆乳转化大豆异黄酮的能力,分析持水力、产酸速率和发酵末活菌数.结果显示,从140株乳酸菌中筛出的12株目标菌株,菌株58和菌株m91发酵豆乳产大豆异黄酮苷元能力...     

发酵香肠发酵过程中菌落总数数学模型的建立

用SAS9．0中的响应曲面试验设计,研究了盐浓度、水分活度、发酵温度、发酵时间和糖浓度等环境因子对发酵香肠发酵过程中细菌总数变化的影响,建立科学的数学模型,此数学模型能够表达发酵香肠发酵过程中细菌总数的变化趋势。用建立的数学模型对发酵过程中的微生物进行了预测,结果可靠。细菌总数与实验测定数据进行比较,平均误差范围是-10．20％～8．43％。此数学模型为发酵香肠发酵过程的控制,提高发酵肉制品的安全性,缩短生产周期提供了依据,也是微生物预报的重要基础。     

利用发光菌测量汽油发动机润滑油生物毒性的试验研究

利用发光菌作为受试物种,参照美国材料与试验学会ASTMD6081和国标GB/T15441进行汽油机润滑油生物毒性的试验研究。介绍了试验所用器材、润滑油水溶性馏分（WSF）和可容纳水馏分（WAF）的制备过程及生物毒性试验方法,对我国目前使用的3种典型的汽油机水冷润滑油进行了发光菌毒性实际检测,试验研究表明,利用发光菌作为汽油机润滑油急性生物毒性检测具有一定的科学性和先进性。试验中发光菌与毒液的接触时间为15-20s,制备WAF过程中转速为1200r/min搅拌时间6h条件下,分别测得3种润滑油WSF的毒性半致死量LD50,参照我国“急性毒性（LD50）剂量分级”3种润滑油相当于大鼠口服半致死量的无毒级别,相当于人的致死量低毒级别。     

钼掺杂铜硅钙石的制备及其抗菌性能和细胞相容性研究

含铜生物材料在高浓度铜离子释放时对细菌有优异的抑制作用,但同时具有细胞毒性;而在低浓度铜离子释放时虽然具有良好的细胞相容性,但其抗菌性能低.因此,开发一种含铜生物材料,使其能够在高浓度铜离子释放情况下同时具有优异抗菌性能和良好细胞相容性,具有重要意义.本研究利用钼和铜之间的拮抗作用原理,采用溶胶-凝胶法制备了钼掺杂铜硅...     

Cloning and Characterization of a Thermostable Endolysin of Bacteriophage TP-84 as a Potential Disinfectant and Biofilm-Removing Biological Agent

The obligatory step in the life cycle of a lytic bacteriophage is the release of its progeny particles from infected bacterial cells. The main barrier to overcome is the cell wall, composed of crosslinked peptidoglycan, which counteracts the pressure prevailing in the cytoplasm and protects the cell against osmotic lysis and mechanical damage. Bacteriophages have developed two strategies leading to the release of progeny particles: the inhibition of peptidoglycan synthesis and enzymatic cleavage by a bacteriophage-coded endolysin. In this study, we cloned and investigated the TP84_28 endolysin of the bacteriophage TP-84, which infects thermophilic Geobacillus stearothermophilus, determined the enzymatic characteristics, and initially evaluated the endolysin application as a non-invasive agent for disinfecting surfaces, including those exposed to high temperatures. Both the native and recombinant TP84_28 endolysins, obtained through the Escherichia coli T7-lac expression system, are highly thermostable and retain trace activity after incubation at 100 °C for 30 min. The proteins exhibit strong bacterial wall digestion activity up to 77.6 °C, decreasing to marginal activity at ambient temperatures. We assayed the lysis of various types of bacteria using TP84_28 endolysins: Gram-positive, Gram-negative, encapsulated, and pathogenic. Significant lytic activity was observed on the thermophilic and mesophilic Gram-positive bacteria and, to a lesser extent, on the thermophilic and mesophilic Gram-negative bacteria. The thermostable TP84_28 endolysin seems to be a promising mild agent for disinfecting surfaces exposed to high temperatures.