Unravelling the dynamic interactions between protective Esherichia coli and pathogenic Salmonella

背景技术背景：细菌感染是人类和农场动物发病和死亡的主要原因，福尔斯属于BBSRC的优先事项“生物科学促进可持续农业和食品”。益生菌大肠杆菌菌株Nissle 1917（EcN）通过尚未完全表征的机制提供对食源性病原体和传染性腹泻病的保护，并且福尔斯属于BBSRC“生物科学促进对健康的综合理解”的优先事项。假设：大肠杆菌Nissle和沙门氏菌之间的益生菌相互作用涉及细菌内细胞与细胞接触、原噬菌体编码因子和生化信号传导。研究报告：本研究旨在确定益生菌EcN与食源性病原体沙门氏菌（沙门氏菌）之间的相互作用，确定EcN介导沙门氏菌毒力和致病性降低的分子机制。我们已经开发了胃肠道相关的体外共培养条件，并产生了重要的初步数据。在EcN的存在下，主要沙门氏菌毒力因子的表达，例如沙门氏菌致病岛（SPI-1）3型分泌系统（T3 SS）和鞭毛，急剧减少，并且减少依赖于由EcN产生的大的、可扩散的耐热因子。EcN基因组还含有5-6个基因组区域，其在生物信息学上被鉴定为在其他大肠杆菌菌株中不存在的隐蔽原噬菌体，并且在与致病性大肠杆菌共培养中高度表达。我们将研究如何所有这些因素有助于益生菌的性质，EcN使用精细的培养，生化特性，转座子诱变，转录组学，和体内培养的组合。

BACKGROUND: Bacterial infections are a major cause of morbidity and mortality in humans and farm-animals and falls within the BBSRC priority of "Bioscience for sustainable agriculture and food". The probiotic Escherichia coli strain Nissle 1917 (EcN) provides protection against food-borne pathogens and infectious diarrheal diseases by mechanisms not yet fully characterized, and falls within the BBSRC priority of "Bioscience for an integrated understanding of health". HYPOTHESIS: The probiotic interactions between Escherichia coli Nissle and Salmonella involve intra-bacterial cell-to-cell contact, prophage encoded factors, and biochemical signalling. RESEARCH PLAN: This studentship aims to define the interactions between the probiotic EcN and the foodborne pathogen Salmonella Enteritidis (Salmonella), identifying the molecular mechanisms of EcN mediating reduced virulence and pathogenicity of Salmonella. We have developed gastrointestinal tract-relevant, in vitro co-culture conditions, and generated important preliminary data. In the presence of EcN, the expression of major Salmonella virulence factors, e.g. the Salmonella pathogenicity island (SPI-1) type 3 secretion system (T3SS) and flagella, is drastically reduced, and the reductions are dependent on a large, diffusible, heat-resistant factor generated by EcN. The EcN genome also harbors 5-6 genomic regions bioinformatically identified as cryptic prophages that are not present in other E.coli strains and are highly expressed in co-culture with pathogenic E.coli . We will investigate how all these factors contribute to the probiotic nature of EcN using a combination of refined culturing, biochemical characterisation, transposon mutagenesis, transcriptomics, and in vivo culture.