Table_8_Bioinformatic Analysis of the Campylobacter jejuni Type VI Secretion System and Effector Prediction.XLSX

The Type VI Secretion System (T6SS) has important roles relating to bacterial antagonism, subversion of host cells, and niche colonisation. Campylobacter jejuni is one of the leading bacterial causes of human gastroenteritis worldwide and is a commensal coloniser of birds. Although recently discovered, the T6SS biological functions and identities of its effectors are still poorly defined in C. jejuni. Here, we perform a comprehensive bioinformatic analysis of the C. jejuni T6SS by investigating the prevalence and genetic architecture of the T6SS in 513 publicly available genomes using C. jejuni 488 strain as reference. A unique and conserved T6SS cluster associated with the Campylobacter jejuni Integrated Element 3 (CJIE3) was identified in the genomes of 117 strains. Analyses of the T6SS-positive 488 strain against the T6SS-negative C. jejuni RM1221 strain and the T6SS-positive plasmid pCJDM202 carried by C. jejuni WP2-202 strain defined the “T6SS-containing CJIE3” as a pathogenicity island, thus renamed as Campylobacter jejuni Pathogenicity Island-1 (CJPI-1). Analysis of CJPI-1 revealed two canonical VgrG homologues, CJ488_0978 and CJ488_0998, harbouring distinct C-termini in a genetically variable region downstream of the T6SS operon. CJPI-1 was also found to carry a putative DinJ-YafQ Type II toxin-antitoxin (TA) module, conserved across pCJDM202 and the genomic island CJIE3, as well as several open reading frames functionally predicted to encode for nucleases, lipases, and peptidoglycan hydrolases. This comprehensive in silico study provides a framework for experimental characterisation of T6SS-related effectors and TA modules in C. jejuni.

VI型分泌系统（Type VI Secretion System, T6SS）在细菌拮抗、宿主细胞劫持以及生态位定殖过程中发挥关键作用。空肠弯曲菌（Campylobacter jejuni）是全球范围内引发人类胃肠炎的主要病原菌之一，同时也是鸟类的共生定殖菌。尽管该系统近年才被发现，但空肠弯曲菌中T6SS的生物学功能及其效应因子的身份仍未得到明确界定。本研究以空肠弯曲菌488菌株为参照，对513个公开可用的基因组序列中的T6SS流行率与遗传结构展开全面的生物信息学分析。在117株菌株的基因组中，鉴定出一种与空肠弯曲菌整合元件3（Campylobacter jejuni Integrated Element 3, CJIE3）相关的独特且保守的T6SS基因簇。通过对比携带T6SS的488菌株、不携带T6SS的空肠弯曲菌RM1221菌株，以及空肠弯曲菌WP2-202菌株所携带的T6SS阳性质粒pCJDM202，本研究将“携带T6SS的CJIE3”界定为一种致病岛，并将其重新命名为空肠弯曲菌致病岛-1（Campylobacter jejuni Pathogenicity Island-1, CJPI-1）。对CJPI-1的分析显示，其包含两个经典的VgrG同源蛋白CJ488_0978与CJ488_0998，二者在T6SS操纵子下游的遗传变异区域中带有独特的C端结构域。研究还发现CJPI-1携带一个假定的DinJ-YafQ II型毒素-抗毒素（toxin-antitoxin, TA）模块，该模块在pCJDM202与基因组岛CJIE3中均保守存在，同时还包含多个经功能预测可编码核酸酶、脂肪酶以及肽聚糖水解酶的开放阅读框。这项全面的计算机模拟研究为空肠弯曲菌中T6SS相关效应因子与毒素-抗毒素模块的实验表征提供了系统性的研究框架。