磺胺类化合物对大肠杆菌突变QSAR预测模型初探

抗生素被广泛应用于医疗、农业和畜牧业等领域,但是长期滥用会促进细菌的突变作用。本文以大肠杆菌(E.coli)为受试生物,测定了10种磺胺类抗生素(SAs)单一暴露时对E.coli的突变效应,采用物化参数Ebinding(抗生素与其靶蛋白的相互作用能力)与突变效应参数lgRC0-2(最高可观测突变促进效应浓度)或lgRCmax(突变促进率最大值对应的浓度),建立了突变效应的QSAR模型,并采用雷达图进行验证。结果表明,lgRC0-2与Ebinding模型和lgRCmax与Ebinding、DMG(偶极矩)模型的拟合系数R2分别是0.888、0.873,即lgRC0-2或lgRCmax与Ebinding相关性均较好,可能由于磺胺类化合物(SAs)会作用于叶酸合成通路,影响嘌呤、嘧啶碱基的合成,从而对E.coli的突变具有促进效应,且雷达图验证表明,上述2个模型均具有良好的内部预测能力。本研究有望为抗生素使用带来的生态风险评价以及药物设计提供相关指导。     

大肠杆菌总DNA快速提取方法的比较研究

从动物粪便中分离大肠埃希氏杆菌（Escherichia coli）,利用五种不同方法提取大肠埃希氏杆菌的基因组DNA .通过定性、定量分析加以比较 ,确定一套经济、有效的适用于提取大肠埃希氏杆菌基因组DNA的方法--液氮法.以该方法提取的DNA为模板,通过扩增核糖体基因区间序列（16s-23s基因间隔区）可以应用于海水中粪便污染源示踪研究.     

Method to Partition Between Attached and Unattached E. coli in Runoff From Agricultural Lands1

Abstract: Remediation of waters impaired by bacterial indicators is usually dictated by total maximum daily load plans, which are heavily dependent on fate and transport modeling of bacterial indicators. Nonpoint source pollution models are most frequently used to assess bacterial transport to surface waters and most models typically simulate bacterial transport as a dissolved pollutant. Previous studies have found that cells preferentially attach to sediments; however, a variety of techniques have been used to assess attachment including filtration, fractional filtration, and centrifugation. In addition, a variety of chemical and physical dispersion techniques are used to release attached and bioflocculated cells from particulates. Here we developed and validated an easy‐to‐replicate laboratory procedure for separation of unattached from attached E. coli which will also identify particle sizes to which E. coli preferentially attach. Physical and chemical dispersion techniques were evaluated and a combined hand shaker treatment for 10 min followed by dilutions in 1,000 mg/l of Tween 85 significantly increased total E. coli concentrations by 31% when compared with a control. In order to separate unattached from attached fractions, two commonly used techniques, fractional filtration, and centrifugation were combined. The filtration and centrifugation treatments did not reduce E. coli concentrations when compared with a control (p > 0.05), indicating that damage was not inflicted upon the E. coli cells during the separation procedure.     

Photocatalytic bacterial inactivation by polyoxometalates

The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO₂ photocatalyst. Aqueous suspensions of the microorganisms (10⁷–10⁸ cfu ml⁻¹) and POM (or TiO₂) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO₂-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, and H₄SiW₁₂O₄₀) tested in this study, the inactivation of E. coli was fastest with H₄SiW₁₂O₄₀ while that of B. subtilis was the most efficient with H₃PW₁₂O₄₀. Although the biocidal action of TiO₂ photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO₂-PCI. While TiO₂ caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO₂-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology.     

载银活性碳纤维对大肠杆菌吸附作用的研究

以大肠杆菌（Ｅｓｃｈｅｒｉｃｈｉａｃｏｌｉ）为对象，通过细菌吸附实验研究了载银活性碳纤维（ＡＣＦ（Ａｇ））对大肠杆菌的吸附特性．借助扫描电子显微镜（ＳＥＭ）进行细菌分布形态的观察和细菌数量的计算．结果表明，大肠杆菌易分布于ＡＣＦ（Ａｇ）表面的沟槽处；ＡＣＦ（Ａｇ）吸附的细菌数量随银含量、比表面积的增加而增大．此外，细菌吸附量还与ＡＣＦ（Ａｇ）表面银颗粒的大小有关．对吸附细菌的动力学亦进行了研究．     

细菌SOD对微生物紫外光辐射损伤的恢复作用

将培养至对数中期的大肠杆菌、钝齿棒杆菌和啤酒酵母等３种微生物的细胞适度稀释液，分别涂布于培养皿上使受紫外光照射，在细胞受辐射后死亡率大于９０％时停止照射，立即加入一定剂量的细菌超氧化物岐化酶（ＳＯＤ），以观察ＳＯＤ对微生物活力的恢复效应．结果表明，ＳＯＤ可使受辐照的细胞存活率显著提高，且量效关系明显，而照前添加ＳＯＤ则无上述效应．检测表明，紫外光照射可引发细菌的超弱发光，且该种超弱发光可因氧气的充入而瞬间增强，鲁米诺也能增强这种超弱发光，加入甘露醇对发光无影响．当紫外光照射后加入ＳＯＤ能使发光强度大为减弱，表明此种超弱发光与的活动有关，并对ＳＯＤ拮抗紫外线杀菌的机理作了讨论．     

高选择性基因工程菌E.coli SE5000生物富集水体中的镍离子

利用基因工程菌E．coli SE5000对水体中的镍离子进行富集研究．菌体细胞对Ni^2 的富集速率很快,富集过程满足Langmuir等温线模型．经基因改造的基因工程菌不仅最大镍富集容量与原始宿主菌相比增加了4倍多,而且对pH值的变化呈现出更强的适应性．对离子强度及其它共存重金属离子的影响的实验结果表明：Na^ ,Ca^2 ,Cd^2 ,Pb^2 的影响较小,但Mg^2 ,Hg^2 ,Cr^3 和Cu^2 所引起的负面效应较大．金属螯合剂EDTA的存在对基因工程菌的富集行为影响很大．     

远程氧等离子体灭活大肠杆菌的研究

研究放电等离子体灭活大肠杆菌的效果。采用远程氧等离子体反应器,分别考察探究放电功率、处理时间、氧气流量、远程距离及有机污染物对灭菌效果的影响,并观察灭菌前后大肠杆菌的显微结构。结果表明在100W,60s,40cm3/min条件下,远程氧等离子体的杀菌效果值在距放电区0、20、40cm处分别为3.42、3.38和3.32。有机物浓度升高,灭菌效果急剧下降。结论为氧等离子体在距放电区040cm内均能有效灭活大肠杆菌,但有机污染物影响较大。氧等离子体场中高能粒子的刻蚀作用是导致细菌死亡的主要原因。     

Sterilization of Escherichia coli cells by the application of pulsed magnetic field

The inactivation of microorganisms by pulsed magnetic field was studied. It was improved that the application of electromagnetic pulses evidently causes a lethal effect on E. coil cells suspended in phosphate buffer solution Na2HPO4/NaH2 PO4 (0.334/0.867mmol/L). Experimental results indicated that the survivability( N/N0 ; where N0 and N are the number of cells survived per milliliter before and after electromagnetic pulses application, respectively) of E. coil decreased with magnetic field intensity B and treatment time t. It was also found that the medium temperatures, the frequencies of pulse f, and the initial bacterial cell concentrations have determinate influences in destruction of E. coil cells by the application of magnetic pulses. The application of an magnetic intensity B = 160 mT at pulses frequency f= 62 kHz and treatment time t = 16 h result in a considerable destruction levels of E. coil cells ( N/N0=10^-4). Possible mechanisms involved in sterilization of the magnetic field treatment were discussed. In order to shorten the treatment time, many groups of parallel inductive coil were used. The practicability test showed that the treatment time was shortened to 4 h with the application of three groups of parallel coil when the survivability of E. coli cells was less than 0.01%; and the power consumption was about 0.2 kWh/m^3 .     

群体感应抑制剂与磺胺甲恶唑、盐酸强力霉素对大肠杆菌的联合毒性及其机制初探

群体感应抑制剂(QSIs)具有不产生抗药性的特点,从而被作为抗生素的可能替代品,具有广阔的应用前景,因此其存在着与传统抗生素环境联合暴露的可能,但是目前尚缺乏相关联合效应的研究。本文以大肠杆菌(Escherichia coli)为受试生物,测定了7种QSIs(DL-焦谷氨酸、N-乙烯基吡咯烷酮、呋喃酮乙酸酯、2-甲基四氢呋喃-3-酮、3,4-二溴-2(5H)-呋喃酮、(R)-3-吡咯烷醇、D-脯氨醇)分别与磺胺甲恶唑(SMX)和盐酸强力霉素(DH)的二元联合毒性,并初步探讨了它们的联合作用机制。结果表明,前5种QSIs作用于AI-2类信号分子介导的群体感应系统,与AI-2类信号分子竞争结合LsrB蛋白,此通路与SMX、DH的作用通路互不影响,因此联合效应为相加;后2种QSIs作用于AI-1类信号分子介导的群体感应系统,与AI-1类信号分子竞争结合SdiA蛋白,而SMX、DH的作用可能刺激SdiA蛋白的表达,从而需要消耗更多的QSIs与SdiA结合,因而联合效应为拮抗。本实验研究可为传统抗生素与QSIs联合暴露的生态风险评价提供一定理论基础。