Using genotype-to-phenotype analyses to identify the genetic determinants of gastroenteritis caused by the food-borne pathogen Campylobacter jejuni.

空肠弯曲杆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禽业的食品安全至关重要。空肠弯曲菌的三个主要毒力决定因素是荚膜、脂寡糖和鞭毛。这些结构对弯曲杆菌的生存和定植很重要。因此，免疫系统的逃避是至关重要的，因为这些结构具有潜在的免疫优势表位，否则将导致空肠弯曲菌的早期识别和随后的清除。免疫逃避的一个机制是用各种糖分子(多糖)修饰蛋白质结构。空肠弯曲菌鞭毛蛋白TLR-5识别的保守表位已在空肠弯曲菌中丢失。这个表位的丢失使其他细菌，如沙门氏菌，变得不能移动。然而，通过TLR-5表位突变而引入鞭毛的结构不稳定性已被鞭毛亚基外部结构域的糖基化所补偿(Kreutzberger等人，2020年)。这突显了葡聚糖在弯曲杆菌生存和免疫逃避中的作用程度。此外，由于基因含量、等位基因变异和阶段变异的不同，这些多糖在不同菌株之间具有很高的可变性。相变是一种可逆的机制，它导致与同聚体区域相关的偶发基因座基因表达的开/关切换。这导致了不同的表型，通过不同的基因表达，无论它们是开/关，以及表达了什么结合。在我们的实验室中，研究表明，与重组FlaA蛋白相比，糖基化FlaA攻击的禽类出现了延迟的抗体反应。因此，我们的研究旨在进一步研究引入表型变异的遗传因素对弯曲杆菌病和弯曲杆菌生存的贡献。

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.The three major virulence determinants of C. jejuni are capsule, lipooligosaccharide and flagella. These structures are important for survival and colonisation of Campylobacter. Consequently, evasion of the immune system is paramount as these structures possess potential immunodominant epitopes that would otherwise result in early recognition of C. jejuni and its subsequent clearance.One mechanism of immune evasion is the decoration of protein structures with a variety of sugar molecules (glycans). A conserved epitope recognised by TLR-5 on the flagellin protein has been lost in C. jejuni. Loss of this epitope renders other bacteria, such as Salmonella, non-motile. However, the structural instability introduced into the flagella through mutations in the TLR-5 epitope has been compensated for by glycosylation of outer domains of the flagellin subunits (Kreutzberger et al., 2020). This highlights the degree to which glycans can play in the survival and immune evasion of Campylobacter. Further, these glycans are highly variable between strains due to differences in gene content, allelic variation and phase variation. Phase variation is a reversible mechanism that leads to ON/OFF switching of gene expression for contingency loci associated with homopolymeric tracts. This leads to different phenotypes through varied expression of genes, whether they are ON/OFF, and what combination is expressed. In our lab, it was shown that a delayed antibody response was observed in birds challenged with glycosylated FlaA when compared to recombinant FlaA protein. Therefore, our research aims to further investigate the contribution of genetic elements that introduce phenotypic variation towards Campylobacteriosis and the survival of Campylobacter.