假单胞菌ZS1糖基转移酶wbpXYZ的缺失对细胞壁结构及鼠李糖脂合成的影响

糖基供体通常以活性核糖的形式存在于细胞内,wbpX、wbpY以及wbpZ(糖基转移酶)等基因负责转运细胞内的活性糖基分子。糖基转移酶通过运送dTDP-鼠李糖(脂多糖合成前体之一)将鼠李糖基由细胞内转至胞外脂多糖O-抗原B-band部分。同时,参与鼠李糖脂合成的RhlB和RhlC(鼠李糖基转移酶)将dTDP-鼠李糖中的鼠李糖连接至3-羟基脂肪酸分别合成单、双鼠李糖脂。假单胞菌ZS1是本实验室在前期工作中从油污中分离出的1株高产鼠李糖脂菌株,本实验拟探究阻断脂多糖O-抗原B-band中鼠李糖基的添加对假单胞菌ZS1鼠李糖脂合成的影响。为此,构建了假单胞菌ZS1的wbpX、wbpY以及wbpZ 3个独立缺失突变菌株。结果表明,wbpX和wbpZ突变株的鼠李糖脂合成量均有增加,其中wbpZ的突变株合成量最高,较原菌株提高50%。SDS-PAGE分析结果表明,wbpZ缺失突变菌株的脂多糖O-抗原量显著降低;而wbpX和wbpY缺失突变菌株脂多糖含量变化不显著。

环介导等温扩增技术检测乳粉中肺炎克雷伯菌

以荚膜脂多糖(capsular polysaccharide,CPS)合成调控子resA为靶基因片段,设计了肺炎克雷伯菌特异性引物,建立了环介导恒温扩增技术(Loop-Mediated lsothermal Amplification,LAMP)检测方法.结果表明,3对LAMP引物对肺炎克雷伯菌不仅有菌种专一性,而且,具有相当高的灵敏度(2 CFU/100 g).因此,该方法有利于更快更准确的鉴定食品中肺炎克雷伯氏菌.

STUDIES ON THE SYNTHESES AND PROPERTIES OFSNAKE-CAGE TYPE CHELATE RESINS I System of Carboxymethyl-chitosan/B-62/Triethylenetetramine

Using carboxymethyl chitosan （CM-CTS） as snake resin, B-62 resin crosslinked by,triethylenetetramine （TETA） as cage resin, a series of novel snake-cage type resin weresynthesized. Such factors as the best synthetic conditions, the swelling and regenerationproperties, and the sorption capacities of the above mentioned resins for metal ions wereinvestigated. The experimental results show these resins have good swelling propertiesand mechanical stability and do not run off in organic and inorganic solvents. Thesorption capacities of them for Cu2+, Ni2+,Zn2+, and Pb2+ were 0.89, 0.54, 0.32, and0.22mmol/g, respectively.

ADSORPTION SELECTIVITY FOR Cu^(2+),Ni^(2+),Co^(2+)IONS USING CROSSLINKING CHITOSAN RESINS IMPRINTED BY METAL IONS

Metal ion-imprintedly crosslinked chitosan resin 1 and resin 2 were prepared by theuse of Cu2+ and Ni2+ as template ions and glutaraldehyde as crosslinking agent, respectively.Through investigation on the adsorption capacities and binding constants for Cu2+, Ni2+andCo2+ ions on chitosan resins, resin 1 and resin 2 exhibit the adsorption selectivity for themixture solution of 1:1 Cu2+ and Ni2+ ions. The adsorption selectivity of metal ion-imprintedresins for their template ions is much higher than that of uncrosslinked chitosan resin.

槲皮素对产肠毒素大肠杆菌转录组的影响

产肠毒素大肠杆菌(enterotoxigenic Escherichia coli,ETEC)是一种引起新生动物如仔猪、犊牛等腹泻的重要病原菌,严重影响动物健康,给养殖业造成重大经济损失。槲皮素是存在于多种中药、蔬菜和水果中的一种黄酮醇类化合物,具有抗炎、抗菌等作用。为了研究槲皮素对ETEC-O139转录组的影响,首先测定细菌的生长曲线以及槲皮素的最小抑菌浓度,之后利用RNA-seq进行测序分析,并通过qRT-PCR进行验证。结果显示,质量浓度为10,20 mg/L的槲皮素与细菌作用4 h后,ETEC-O139差异表达的基因主要与细菌趋化、运动、代谢过程、细胞膜以及膜上的受体蛋白等表型和通路有关。选择脂多糖生物合成的相关基因进行qRT-PCR验证,与测序结果一致。以上结果表明槲皮素能够在不抑制ETEC-O139的条件下,调控细菌的致病力和代谢过程,为寻找抗生素替代药物提供了新的研究思路。