T6SS Mediated Stress Responses for Bacterial Environmental Survival and Host Adaptation

Kai-Wei Yu,Yang Fu,Peng Xue,Liang Yang

doi:10.3390/ijms22020478

Abstract

The bacterial type VI secretion system (T6SS) is a protein secretion apparatus widely distributed in Gram-negative bacterial species. Many bacterial pathogens employ T6SS to compete with the host and to coordinate the invasion process. The T6SS apparatus consists of a membrane complex and an inner tail tube-like structure that is surrounded by a contractile sheath and capped with a spike complex. A series of antibacterial or antieukaryotic effectors is delivered by the puncturing device consisting of a Hcp tube decorated by the VgrG/PAAR complex into the target following the contraction of the TssB/C sheath, which often leads to damage and death of the competitor and/or host cells. As a tool for protein secretion and interspecies interactions, T6SS can be triggered by many different mechanisms to respond to various physiological conditions. This review summarizes our current knowledge of T6SS in coordinating bacterial stress responses against the unfavorable environmental and host conditions.

Highlights

Bacteria can use secretion systems to transport individual proteins, as well as DNA–protein and protein–protein complexes into adjacent cells or the external medium
The T6SS effector EvpP inhibits the recruitment of neutrophils to promote E. piscicida proliferation and infection [99]
Current studies show that bacteria can take up metal ions through

Summary

Introduction

Bacteria can use secretion systems to transport individual proteins, as well as DNA–. It has been revealed that T6SS is involved in the process of oxidative stress response in bacterial pathogens, such as Vibrio anguillarum [39], Burkholderia thailandensis [40], Enterohemorrhagic E. coli [41], and Yersinia pseudotuberculosis [42] Metal ions, such as zinc (Zn2+ ) and manganese (Mn2+ ), can be used as structural components or cofactors of antioxidant enzymes [35]. HmuR, was lower than the wild-type strain and the mutant accumulated higher level of intracellular ROS than the wild-type strain [48] This group demonstrated that T6SS effector TseZ interacts with HmuR (the outer membrane heme transporter) and further showed that the HmuRSTUV system is involved in the acquisition of Zn2+ under oxidative stress conditions [48]. Compared with the wild-type strain, the survival rate of B. thailandensis T6SS clpV4 mutant strains under oxidative stress was decreased significantly in manganese-rich environment [40].

Adaptation to Changes in Temperature and pH

Interspecies and Intraspecies Competition

Involvement of T6SS in the Regulation of Host Immune Signaling Pathways

Conclusions

Methods