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青枯雷尔氏菌胞外多糖合成缺失突变株构建及其生物学特性
编辑人员丨2023/8/6
[目的]由青枯雷尔氏菌(Ralstonia solanacearum)引起的植物青枯病是一种毁灭性土传病害.胞外多糖(extracellular polysaccharides,EPS)是青枯雷尔氏菌关键的致病因子之一.通过构建胞外多糖缺失突变株,研究胞外多糖在青枯病致病中的作用.[方法]从青枯雷尔氏菌FJAT-91的基因组中克隆出胞外多糖合成结构基因epsD同源臂,克隆至自杀性质粒pK18mobsacB,再将庆大霉素抗性基因(Gm)插入同源臂中间,获得重组质粒pK18-epsD.将重组质粒转化至青枯雷尔氏菌FJAT-91感受态细胞中,通过同源重组敲除epsD基因,获得EPS合成缺失的突变株FJAT-91ΔepsD.研究突变株与野生菌株在菌落形态、胞外多糖合成、运动能力、定殖能力的差异性.[结果]突变菌株FJAT-91ΔepsD与出发菌株FJAT-91相比:胞外多糖产量显著减少,生长较慢;泳动能力(swimming motility)和群集运动能力(swarming motility)显著降低;在番茄苗根部和茎部的定殖能力显著降低;弱化指数(AI)为0.905,鉴定为无致病力菌株.[结论]胞外多糖在青枯雷尔氏菌的致病中起着关键的作用,本课题研究成果为开发植物疫苗提供了优良的材料与研究基础.
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编辑人员丨2023/8/6
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Mesophasic Assembly of Inhibitory Postsynaptic Density
编辑人员丨2023/8/5
Neurotransmitter receptors are concentrated in a morpho-logical specialization of synapses known as the postsynap-tic density(PSD).A prominent PSD beneath the postsynaptic membrane in electron micrographs is a defining feature of excitatory synapses.Typically,the excitatory PSD(ePSD)has a disc-like shape 200-800 nm in diameter and 20-50 nm in thickness[1].In contrast,the inhibitory synapse only has thickened postsynaptic mem-branes in classical EM studies[2,3],thus whether inhibitory synapses contain PSD-like structures has been debated for decades.A few years ago,Bi and colleagues characterized the ultrastructure of excitatory and inhibitory synapses in cultured neurons by cryo-electron tomography(cryo-ET)and their high-resolution tomograms clearly showed electron-dense assemblies in both excitatory and inhibitory synapses[4].
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编辑人员丨2023/8/5
