沙门菌致病岛2 Ⅲ型分泌系统研究进展

沙门菌(Salmonella)是革兰氏阴性的兼性胞内菌,可引起其广泛宿主的一系列疾病,严重时可导致全身性感染,威胁生命安全。沙门菌致病岛2(SPI2)是与沙门菌全身性感染密切相关的重要毒力基因簇,其编码的Ⅲ型分泌系统2(T3SS2)在沙门菌侵入宿主细胞后开始组装合成,经该装置分泌的多种效应蛋白对沙门菌在宿主细胞内的生存和增殖起着重要作用。近些年来,与沙门菌T3SS2相关的研究一直都是病原微生物领域关注的焦点之一。本文简要综述了SPI2的基因特征、SPI2基因表达的调控、T3SS2的结构和组成、T3SS2的效应蛋白及与T3SS2相关的疫苗研究等方面的主要研究进展。     

沙门氏菌毒力岛及其Ⅲ型分泌系统

沙门氏菌含两个编码三型分泌系统的毒力岛(SPIs),每个毒力岛编码一个Ⅲ型分泌系统.SPI1与细菌的侵袭性有关,而SPI2与系统感染和沙门氏菌在真核细胞中的聚集有关.本文对SPI1和SPI2的分子结构、Ⅲ型分泌系统的功能、基因表达的调节及SPI1和SPI2的进化进行了综述.     

沙门氏茵毒力岛及其Ⅲ型分泌系统

沙门氏菌含两个编码三型分泌系统的毒力岛(SPIs),每个毒力岛编码一个Ⅲ型分泌系统。SPI1与细菌的侵袭性有关,而SPI2与系统感染和沙门氏菌在真核细胞中的聚集有关。本对SPIl和SPI2的分子结构、Ⅲ型分泌系统的功能、基因表达的调节及SPIl和SPI2的进化进行了综述。     

病原性细菌的Ⅲ型分泌系统,毒力岛和基因组学

近几年来在细菌学领域出现了几个新的概念：Ⅲ型分泌系统（ｔｙｐｅⅢｓｅｃｒｅｔｉｏｎｓｙｓｔｅｍ）毒力岛（又称致病性岛）和基因组学（ｇｅｎｏｍｉｃｓ）。这些概念这些出现反映了医学细菌学研究的最新趋势,对今后的研究工作具有重要的指导意义,本文分别对此三者的含义,特点以及当前的研究情况作了一介绍。     

肠出血性大肠杆菌Ⅲ型分泌系统效应因子与宿主细胞相互作用研究进展

肠出血性大肠杆菌(Enterohemorrhagic Escherichia coli,EHEC)通过其Ⅲ型分泌系统将效应因子注入到宿主细胞内,破坏宿主细胞内的多种信号通路从而有利于细菌的感染及定植。近年来对于EHEC Ⅲ型分泌系统效应因子与宿主细胞相互作用研究成为EHEC致病机制研究新的热点,研究表明,除了经典的效应因子外,一些新发现的效应因子在细菌的致病过程中也发挥着重要作用,有些效应因子能够抑制宿主细胞内正常的信号通路,有些效应因子还具有抑制细胞凋亡,干扰炎症信号通路和抑制吞噬的作用。这些发现揭示了EHEC效应因子具有多种功能,它们通过与宿主细胞间的相互作用,在细菌的感染过程中发挥着重要作用。     

大肠杆菌三型分泌系统2转录调节子EtrA对禽致病性大肠杆菌致病性的影响

【背景】禽致病性大肠杆菌(avian pathogenic Escherichia coli,APEC)是禽类主要病原菌之一,大肠杆菌三型分泌系统2 (Escherichia coli type III secretion system 2,ETT2)可通过转录调节子调控其致病性,但在APEC中转录调节子EtrA对其致病性的影响目前尚不清楚。【目的】研究ETT2中转录调节子EtrA对APEC致病性的影响。【方法】利用Red同源重组技术构建ETT2-etrA基因缺失株及回复株。比较生长性能、生物被膜形成、运动性及对血清敏感性的差异,基于RNA-Seq测序及Real-timePCR技术比较野生株和缺失株中与生物被膜形成、运动性以及毒力因子相关基因的转录水平。【结果】与野生株相比,缺失株及回复株生长特性无显著变化(P0.05),但APEC40-ΔetrA生物被膜形成能力和对血清敏感性明显增强(P0.001),运动性较野生株明显下降(P0.01),回复株的表型有所回复。转录组学筛选出7个毒力差异基因,生物被膜形成相关基因显著上调,参与影响细菌运动性的基因显著下调。qRT-PCR验证与转录组学结果一致。【结论】etrA缺失可以显著影响APEC的生物被膜形成、运动性及对血清的敏感性,这可为进一步探讨ETT2对APEC的致病作用提供参考。     

肠出血性大肠杆菌Ⅲ型分泌系统及其转位效应器蛋白质

肠出血性大肠杆菌(enterohemorrhagic Escherichia coli,EHEC)0157:H7是一种重要的肠道病原微生物,感染后可引发多种疾病,严重者可导致死亡.EHEC O157:H7通过Ⅲ型分泌系统(TTSS)将其转位效应器蛋白质转位至宿主细胞,经一系列的信号传导过程介导与宿主细胞的"黏附与擦拭"(attaching and effacing,A/E)损伤.对EHEC0157:H7 Ⅲ型分泌系统及其转位效应器蛋白质进行研究,可使我们进一步认识EHEC以及引起A/E损伤的病原菌的致病机理,丰富有关Ⅲ型分泌系统和致病岛的知识.     

青枯菌Rsc1285参与III型分泌系统及致病力的调控

摘要:【目的】研究青枯菌Rsc1285参与调控其III型分泌系统(Type III secretion system,T3SS)及致病力的途径。【方法】通过基因敲除、基因互补等研究Rsc1285对T3SS基因表达和致病力的影响。【结果】青枯菌rsc1285基因缺失突变体对寄主西红柿植株的致病力明显减弱,其hrpB、T3SS等基因表达水平较野生型明显降低,但hrpG、prhG的表达不受影响。【结论】青枯菌通过一个全新的途径利用Rsc1285调控hrpB及T3SS的转录表达并决定其致病力。     

细菌Ⅲ型分泌系统

1 .细菌分泌机制概述致病细菌和宿主细胞相互作用的特点是将致病因子定位到细菌表面或分泌到胞外。虽然其分泌的细菌蛋白质数量和种类都很多且具有范围很广的作用 (包括蛋白质水解、溶血、细胞毒性、蛋白质的磷酸化和去磷酸化 ) ,但是只存在几种途径把这些蛋白质从细菌的细胞质运输到胞外。在革兰氏阴性细菌中已发现四种蛋白质分泌途径 ,称为Ｉ、ＩＩ、ＩＩＩ、ＩＶ型分泌机制。另外 ,第五种大分子分泌途径和质粒的接合转移有关。根癌农杆菌Ｔ ＤＮＡ的转移 ,百日咳杆菌毒素的分泌 ,称之为Ｖ型分泌 ,这方面的研究很少[1] 。ＩＩ型和ＩＶ型是…     

细菌的Ⅲ型和Ⅳ型分泌系统

细菌拥有很多分泌系统,通过这些系统,许多分泌性蛋白和外露蛋白被输送到菌体细胞外,与宿主细胞发生相互作用而发挥其毒性。革兰阴性菌拥有5型蛋白分泌系统,其中Ⅲ型和Ⅳ型分泌系统与细菌的致病性密切相关,正日益受到各方学者的关注。本文对细菌Ⅲ型和Ⅳ型分泌系统的组成、结构和功能等进行概述。     

Identification of a type III secretion system in uropathogenic Escherichia coli

To determine virulence-related genes in uropathogenic Escherichia coli (UPEC) showing invasiveness to T-24 bladder cancer cells, genomic subtractive hybridization was performed between a highly invasive and a less invasive strain. Forty-nine DNA fragments were isolated from the invasive strain. One of them showed homology with Salmonella invA gene. By chromosomal walking of the strain, a type III secretion system that has been described in E. coli O157:H7 was identified on the genome of the invasive strains. Three strains out of 100 UPEC isolates had a type III secretion system inserted at 64 min of the chromosome, corresponding to E. coli K-12 MG1655. This finding suggested that the type III secretion system could play a part in uropathogenicity of UPEC.     

Acidic pH is required for the functional assembly of the type III secretion system encoded by Salmonella pathogenicity island 2

Salmonella enterica employs two type III secretion systems (T3SS) for interactions with host cells during pathogenesis. The T3SS encoded by Salmonella pathogenicity island 2 (SPI2) is required for the intracellular replication of Salmonella and the survival inside phagocytes. During growth in vitro, acidic pH is a signal that promotes secretion of proteins by this T3SS. We analyzed protein levels and subcellular localization of various T3SS subunits under in vitro conditions at acidic or neutral pH, inducing or ablating secretion, respectively. Growth at acidic pH resulted in higher levels of SsaC, a protein forming the outer membrane secretin, without increasing expression of the operon containing ssaC. Acidic pH also induced oligomerization of SsaC subunits, a prerequisite for a functional secretin pore. It has previously been described that environmental stimuli resembling the intraphagosomal habitat of Salmonella control the expression of SPI2 genes. Here we propose that such stimuli also modulate the assembly of a functional T3SS that is capable of translocation of effector proteins into the host cell.     

VI型分泌系统核心组分VgrG的致病功能

正VI型分泌系统(Type VI secretion system,T6SS)是一种接触依赖性分泌系统,能够将效应因子分泌至细菌胞外,具有多种不同功能,包括增强致病菌毒力、抗细菌毒力、增加机会致病菌的菌间竞争力。T6SS存在于超过四分之一的革兰阴性菌中[1-2]。禽致病性大肠杆菌(Avian Pathogenic Escherichia coli,APEC)可引起鸡、鸭及其他禽类的肠道外疾病,严重制约养禽业的健康发展,同时对食品安全构成威胁。APEC中存     

Type III secretion of EspB in enterohemorrhagic Escherichia coli O157:H7

EspB of enterohemorrhagic Escherichia coli O157:H7 is one of the type III proteins, categorized as translocators, that are secreted in abundance. To define the secretion determinants, different fragments of EspB were fused in recombinant proteins and the proteins secreted into media analyzed by Western blot. The results indicated that the C-terminal 30 residues of EspB were dispensable for secretion whereas the N-terminal first 117 residues played a major role. However, this N-terminal segment alone was not sufficient to confer the secretion. To acquire basic activity, the EspB fusion protein had to contain the N-terminal segment and another segment consisting of either residues 118–190 or residues 191–282. It is possible that the N-terminal region may act as the primary component of the secretion signal while other determinants help to maintain a conformation of EspB favorable for secretion. However, alternative mechanisms cannot be completely excluded. Not withstanding this, the signal for the type III secretion of EspB is apparently distinct from those previously described for the secretion of effector proteins such as Yops in Yersinia.     

Functional analysis of the type III secretion system in enteropathogenic Escherichia coli O157:H45

A mass outbreak of Escherichia coli O157:H45 was first reported in Japan in 1998. This pathogen was classified as an enteropathogenic E. coli (EPEC) O157 because it was characterized by the Shiga toxin gene (stx)-negative and bundle-forming pilus (bfp) gene-positive genotypes. In this study, we investigated the type III secretion system in EPEC O157. Although no type III secreted proteins, Esps (E. colisecreted proteins), in EPEC O157:H45 were detectable in culture supernatant, secreted proteins were induced by the introduction of an EPEC plasmid-encoded regulator, per. In further contrast to EHEC O157:H7, EPEC O157:H45 triggered the accumulation of tyrosine phosphorylated proteins beneath the adherent bacteria. These results suggest that regulation of the type III secretion apparatus and host signal transduction events between E. coli O157:H45 and O157:H7 are completely different.     

The type III secretion system is involved in Escherichia coli K1 interactions with Acanthamoeba

The type III secretion system among Gram-negative bacteria is known to deliver effectors into host cell to interfere with host cellular processes. The type III secretion system in Yersina, Pseudomonas and Enterohemorrhagic Escherichia coli have been well documented to be involved in the bacterial pathogenicity. The existence of type III secretion system has been demonstrated in neuropathogenic E. coli K1 strains. Here, it is observed that the deletion mutant of type III secretion system in E. coli strain EC10 exhibited defects in the invasion and intracellular survival in Acanthamoeba castellanii (a keratitis isolate) compared to its parent strain. Next, it was determined whether type III secretion system plays a role in E. coli K1 survival inside Acanthamoeba during the encystment process. Using encystment assays, our findings revealed that the type III secretion system-deletion mutant exhibited significantly reduced survival inside Acanthamoeba cysts compared with its parent strain, EC10 (P < 0.01). This is the first demonstration that the type III secretion system plays an important role in E. coli interactions with Acanthamoeba. A complete understanding of how amoebae harbor bacterial pathogens will help design strategies against E. coli transmission to the susceptible hosts.     

断奶仔猪源大肠杆菌LEE及HPI毒力岛的检测

应用Duplex_PCR方法,对240株断奶仔猪源大肠杆菌分离株的LEE毒力岛的eaeA基因和耶尔森菌强毒力岛核心区的irp2基因进行了检测,并对HPI毒力岛的fyuA基因及其在大肠杆菌染色体中的插入位置进行了分析,以及随机选取部分PCR产物进行了克隆和序列分析。结果表明:其中29株(12.08%)为LEE HPI ,39株(16.25%)为LEE ,11株(4.58%)为HPI ;另外还发现:不同病例来源的分离株之间,两种毒力岛的携带率不同;在断奶仔猪腹泻源分离株中,29株(20.71%)为LEE HPI ,22株(15.71%)为LEE ,9株(6.43%)为HPI ;断奶仔猪水肿病源分离株中,仅5株(6.58%)为LEE ,2株(2.63%)为HPI ,未发现LEE HPI 菌株;断奶仔猪水肿病并发腹泻源分离株中,仅12株(50%)为LEE ,未发现HPI 及LEE HPI 菌株。本实验克隆的eaeA(425bp)与已发表序列完全一致,irp2(280bp)f、yuA(948bp)、asn_tRNA_intB(1391bp)均与已发表的序列高度同源,同源性分别在98.2%、98.3%、95.8%以上;40株LEE HPI 或HPI 分离株中,29株(72.5%)为fyuA ,且其HPI毒力岛位于大肠杆菌染色体asn_tRNA位点。     

Enzymatic characterization of the enteropathogenic Escherichia coli type III secretion ATPase EscN

Type III secretion is a transport mechanism by which bacteria secrete proteins across their cell envelope. This protein export pathway is used by two different bacterial nanomachines: the flagellum and the injectisome. An indispensable component of these secretion systems is an ATPase similar to the F₁-ATPase β subunit. Here we characterize EscN, an enteropathogenic Escherichia coli type III ATPase. A recombinant version of EscN, which was fully functional in complementation tests, was purified to homogeneity. Our results demonstrate that EscN is a Mg²⁺-dependent ATPase (k_cat 0.35 s⁻¹). We also define optimal conditions for the hydrolysis reaction. EscN displays protein concentration-dependent activity, suggesting that the specific activity changes with the oligomeric state of the protein. The presence of active oligomers was revealed by size exclusion chromatography and native gel electrophoresis.     

A comparison of enteropathogenic and enterohaemorrhagic Escherichia coli pathogenesis

This review covers enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC) infections, focusing on differences in their virulence factors and regulation. While Shiga-toxin expression from integrated bacteriophages sets EHEC apart from EPEC, EHEC infections often originate from asymptomatic carriage in ruminants whereas human EPEC are considered to be overt pathogens and more host-restricted. In part, these differences reflect variation in adhesin repertoire, type III-secreted effectors and the way in which these factors are regulated.