Liaw Janie, Hong Geunhye, Davies Cadi, Elmi Abdi, Sima Filip, Stratakos Alexandros, Stef Lavinia, Pet Ioan, Hachani Abderrahman, Corcionivoschi Nicolae, Wren Brendan W, Gundogdu Ozan, Dorrell Nick
Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom.
Bacteriology Branch, Veterinary Sciences Division, Agri-Food and Biosciences Institute, Belfast, United Kingdom.
Front Microbiol. 2019 Dec 17;10:2864. doi: 10.3389/fmicb.2019.02864. eCollection 2019.
The role of the Type VI secretion system (T6SS) in is poorly understood despite an increasing prevalence of the T6SS in recent isolates in humans and chickens. The T6SS is a contractile secretion machinery capable of delivering effectors that can play a role in host colonization and niche establishment. During host colonization, is exposed to oxidative stress in the host gastrointestinal tract, and in other bacteria the T6SS has been linked with the oxidative stress response. In this study, comparisons of whole genome sequences of a novel human isolate 488 with previously sequenced strains revealed a single highly conserved T6SS cluster shared between strains isolated from humans and chickens. The presence of a functional T6SS in the 488 wild-type strain is indicated by expression of T6SS genes and secretion of the effector TssD. Increased expression of oxidative stress response genes , , and , and increased oxidative stress resistance in 488 wild-type strain suggest T6SS is associated with oxidative stress response. The role of the T6SS in interactions with host cells is explored using and models, and the presence of the T6SS is shown to increase cytotoxicity in the infection model. In biologically relevant models, the T6SS enhances interactions with and invasion of chicken primary intestinal cells and enhances the ability of to colonize chickens. This study demonstrates that the T6SS provides defense against oxidative stress and enhances host colonization, and highlights the importance of the T6SS during survival of T6SS-positive strains.
尽管在人类和鸡的近期分离株中VI型分泌系统（T6SS）的流行率不断上升，但其作用仍知之甚少。T6SS是一种可收缩的分泌机制，能够传递在宿主定殖和生态位建立中发挥作用的效应蛋白。在宿主定殖过程中，其暴露于宿主胃肠道的氧化应激中，并且在其他细菌中，T6SS已与氧化应激反应相关联。在本研究中，将新型人类分离株488的全基因组序列与先前测序的菌株进行比较，发现从人类和鸡分离的菌株之间共享一个高度保守的T6SS簇。488野生型菌株中功能性T6SS的存在通过T6SS基因的表达和效应蛋白TssD的分泌来表明。488野生型菌株中氧化应激反应基因、和的表达增加以及氧化应激抗性增加表明T6SS与氧化应激反应相关。使用和模型探索了T6SS在与宿主细胞相互作用中的作用，并且在感染模型中显示T6SS的存在会增加细胞毒性。在生物学相关模型中，T6SS增强了与鸡原代肠细胞的相互作用和侵袭，并增强了在鸡体内定殖的能力。本研究表明，T6SS提供了对氧化应激的防御并增强了宿主定殖，并突出了T6SS在T6SS阳性菌株生存期间的重要性。
