共查询到20条相似文献,搜索用时 15 毫秒
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Marceau M 《Current issues in molecular biology》2005,7(2):151-177
In response to the ever-present need to adapt to environmental stress, bacteria have evolved complex (and often overlapping) regulatory networks that respond to various changes in growth conditions, including entry into the host. The expression of most bacterial virulence factors is regulated; thus the question of how bacteria orchestrate this process has become a recurrent research theme for every bacterial pathogen, and the three pathogenic Yersinia are no exception. The earliest studies of regulation in these species were prompted by the characterization of plasmid-encoded virulence determinants, and those conducted since have continued to focus on the principal aspects of virulence in these pathogens. Most Yersinia virulence factors are thermally regulated, and are active at either 28 degrees C (the optimal growth temperature) or 37 degrees C (the host temperature). However, regulation by this omnipresent thermal stimulus occurs through a wide variety of mechanisms, which generally act in conjunction with (or are modulated by) additional controls for other environmental cues such as pH, ion concentration, nutrient availability, osmolarity, oxygen tension and DNA damage. Yersinia's recent entry into the genome sequencing era has given scientists the opportunity to study these regulators on a genome-wide basis. This has prompted the first attempts to establish links between the presence or absence of regulatory elements and the three pathogenic species' respective lifestyles and degrees of virulence. 相似文献
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The histidines of the iron-uptake regulation protein, Fur 总被引:9,自引:0,他引:9
There are 12 histidine residues/molecule in the iron-uptake regulation protein (Fur). Here we examine their pH dependence using proton nuclear magnetic resonance spectroscopy. The histidines have widely spread acid dissociation constants but we can not offer a simple explantation for their complicated behaviour. 相似文献
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A cyanide-utilizing Yersinia species was isolated from the cyanide-bearing gold-plating industrial wastewater. Analysis of the fatty acid composition of the organism revealed that it contains large amounts of saturated fatty acids. The unsaturated hydroxy- and cyclopropyl-ring-bearing fatty acids are present in low concentrations. A comparison of the fatty acid composition with other Yersinia species shows that the genus Yersinia appears homogeneous, and that fatty-acid data of Yersiniae do not reflect the distance between Yersiniae species. 相似文献
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A hallmark of Yersinia type III machines is the presence of needles extending from the bacterial surface. Needles perform two functions, serving as the conduits for the transport of effectors into immune cells but also acting as a sensor. The polymerized needle protein, YscF, is thought to perceive threshold levels of environmental calcium ions to trigger secretion. yopR ( yscH ) is a gene downstream of yscEFG , encoding the chaperones and principal building blocks of the needle. Here we investigated the contribution of YopR towards type III secretion and pathogenesis. Yersinia pestis KIM D27 mutants lacking yopR were defective for virulence in a mouse model of septicemic plague. yopR variants of Yersinia enterocolitica W22703 displayed a reduced ability to inject effectors into macrophages and required lower calcium concentrations to activate type III secretion than wild-type yersiniae. Furthermore, yopR mutants failed to assemble YscF into needle complexes and instead secreted YscF into the medium. These results imply that YopR may be involved in controlling the secretion of YscF, thereby impacting the assembly of type III machines. An alternative possibility, which YopR participates directly in the polymerization of YscF, seems less likely as YopR is not associated with purified needles. 相似文献
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[目的]利用分子生物学实验研究鼠疫菌调控子OxyR对dps的转录调控机制.[方法]提取鼠疫菌野生株(WT)和oxyR突变株(ΔoxyR)的总RNA,采用引物延伸实验研究dps的转录起始位点,并根据产物的丰度判断OxyR对dps的调控关系.进一步采用实时定量RT-PCR的方法验证OxyR对dps的调控关系.PCR扩增dps的整个启动子区DNA序列,并纯化His-OxyR蛋白,通过凝胶阻滞实验(EMSA)验证OxyR对dps启动子区是否具有直接的相互作用.利用大肠杆菌OxyR识别基序,预测鼠疫菌OxyR对dps启动子区的结合位点,从而得出鼠疫菌OxyR对dps的转录调控机制.[结果]鼠疫菌dps有一个转录起始位点G(-40)(翻译起始位点为+1),其转录表达受OxyR的激活;体外实验及生物信息学预测结果表明OxyR能结合到dps启动子区-111到-78之间的碱基上.[结论]OxyR能直接结合到dps启动子区而激活其转录表达. 相似文献
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Alessandra Dalmasso Tiziana Civera Virginia Filipello Maria Teresa Bottero 《Molecular biology reports》2014,41(10):6329-6333
A multiplex primer-extension reaction (PER) assay, was specifically designed for the identification of ten Yersinia species. The assay, directed towards the tufA (elongation factor Tu) gene, was tested on a total of 42 samples representing Yersinia species and non-Yersinia species. The primers used in the preliminary PCR, designed in highly conserved regions upstream and downstream of the diagnosis sites, successfully amplified a 587 bp fragment. The diagnosis sites were simultaneously interrogated using a multiplex PER and the results were confirmed by fragment sequencing. The proposed test provides an appropriate tool to monitor the presence of Yersinia spp. in food samples and to evaluate the potential hazard for consumers. 相似文献
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Gene regulation of siderophore-mediated iron acquisition in Pseudomonas: not only the Fur repressor 总被引:2,自引:1,他引:1
Pseudomonads have several siderophore-mediated iron-acquisition systems. These can be classified into two groups: (i) the biosynthesis of a siderophore (iron-transport agent) followed by its uptake; and (ii) uptake of heterologous ferric-siderophores in which the siderophore is produced by other microbial species. The regulation of these mechanisms employs both positive and negative elements ensuring expression of the relevant genes only when they are absolutely required. Siderophore biosynthesis is induced in response to iron limitation. In contrast, activation of the heterologous transport systems is not only regulated by iron availability but also requires the presence of their cognate ferric-siderophores. The investigation of these regulation systems in three different Pseudomonas species gave similar results consisting of regulatory elements new to the field of iron regulation. These elements are superimposed upon the regulation by the Fur repressor, which in other bacteria directly regulate the expression of the iron-assimilation genes in response to iron availability. 相似文献
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The occurrence of Yersinia enterocolitica and related species (Y. intermedia, Y. frederiksenii, Y. kristensenii) in foods from France was investigated by using different enrichment procedures. Initially, seven procedures were evaluated with pork products. These methods included a cold preenrichment in yeast extract-rose bengal broth or in phosphate-sorbitol-bile medium, followed by selective enrichment either in Pastone-sucrose-Tris-azide broth, in modified Rappaport broth, or in bile-oxalate-sorbose broth, and then isolation onto Hektoen or cefsulodin-irgasan-novobiocin agar with or without KOH pretreatment. The best enrichment procedure in terms of percentage of positive samples obtained within the shortest time was the combination of phosphate-sorbitol-bile and bile-oxalate-sorbose with alkali treatment before isolation onto cefsulodin-irgasan-novobiocin agar. This system was then used to analyze foods other than pork. An average contamination rate of 33.5% was observed for 666 samples analyzed; pork products were by far the most contaminated, especially the so-called tartinette (96.8% of positive samples) which contained up to five different strains of Yersinia spp. Environmental serogroups of Y. enterocolitica O:5, O:39,41, O:6, and O:7,8 were predominant, but no isolate of either human pathogenic type (O:3 or O:9) was obtained. 相似文献
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