Determining how phase variation contributes to host colonisation and extraintestinal spread of Campylobacter jejuni

空肠弯曲菌是欧洲食源性胃肠炎的主要病原体。受污染的鸡肉是感染的主要来源，因此控制这种病原体对家禽业的粮食安全至关重要。这种细菌有三个主要的毒力决定因素：荚膜，脂寡糖（LOS）和鞭毛。鞭毛介导这种细菌病原体的运动性，使其能够向营养物移动并远离破坏性物质。荚膜和LOS介导对免疫效应物的抵抗，影响粘附特性，并导致C.空肠感染所有三种成分都被各种糖分子（聚糖）修饰。由于基因含量和等位基因变异的差异，这些聚糖在菌株之间高度可变。由于高变序列引起的基因表达的高频可逆转换，这些聚糖中的许多在菌株内的结构和存在也不同，称为相位变异（PV）。作为最近BBSRC资助的项目赠款的一部分，发现相位可变基因在鸡的定殖和肠外传播过程中表现出方向性变化。样品来自两个大规模的鸡感染研究与四个C。空肠谱系、多个分离株和4个采样部位（盲肠内容物、回肠内容物、脾脏和肝脏）。仅详细检查了单基因表达状态，而多基因表达状态具有允许检测PV基因的共选择、瓶颈和肠外传播源（例如盲肠或回肠）的潜力。在这个项目中，假设相位变化有助于C的定植和肠外传播。鸡体内的空肠。该项目将检查组合PV表达状态变化的数据。将通过构建LOS、荚膜或外膜蛋白PV基因的突变体来评估特定PV基因的贡献，以将特定PV变化与特定类型的表型变异相关联。数学模型也将利用PV数据来检查定殖和肠外传播的动态。总的来说，这个项目将提供深入了解如何C。空肠在鸡体内定殖和传播，并确定可能阻止这种C.空肠胃肠道感染。

Campylobacter jejuni is the major causative agent of foodborne gastroenteritis across Europe. Contaminated chicken meat is the main source of infections and hence control of this pathogen is critical to food security in the poultry industry. This bacterial species has three major virulence determinants; capsule, lipooligosaccharide (LOS) and flagella. The flagella mediate motility of this bacterial pathogen enabling movement towards nutrients and away from damaging agents. The capsule and LOS mediate resistance to immune effectors, influence adhesive properties and contribute to autoimmune complications of C. jejuni infections. All three components are decorated with a variety of sugar molecules (glycans). These glycans are highly variable between strains due to differences in gene content and allelic variation. Many of these glycans also vary in structure and presence within strains due to high frequency, reversible switches in gene expression caused by hypermutable sequences and referred to as phase variation (PV). As part of a recent BBSRC-funded project grant, phase-variable genes were found to exhibit directional changes during colonisation of chickens and extraintestinal spread. Samples were derived from two large-scale chicken infection studies with four C. jejuni lineages, multiple isolates and four sample sites (caecal contents, ileal contents, spleen and liver). Only single-gene expression states have been examined in detail whereas multi-gene expression states have the potential to allow for detection of co-selection of PV genes, bottlenecks and sources of extraintestinal spread (e.g. caeca or ileum). In this project, it is hypothesised that phase variation contributes to colonisation and extraintestinal spread of C. jejuni within the chicken host. This project will examine data for combinatorial PV expression state changes. The contributions of specific PV genes will be assessed by constructing mutants in LOS, capsular or outer membrane protein PV genes to associate specific PV changes with specific types of phenotypic variation. Mathematical models will also utilise PV data to examine the dynamics of colonisation and extraintestinal spread. Overall this project will provide insights into how C. jejuni colonises and spreads within chicken and identify potential points of interference that could prevent this source of C. jejuni gastrointestinal infections.