Beyond dueling: roles of the type VI secretion system in microbiome modulation, pathogenesis and stress resistance

Abstract

Bacteria inhabit diverse and dynamic environments, where nutrients may be limited and toxic chemicals can be prevalent. To adapt to these stressful conditions, bacteria have evolved specialized protein secretion systems, such as the type VI secretion system (T6SS) to facilitate their survival. As a molecular syringe, the T6SS expels various effectors into neighboring bacterial cells, eukaryotic cells, or the extracellular environment. These effectors improve the competitive fitness and environmental adaption of bacterial cells. Although primarily recognized as antibacterial weapons, recent studies have demonstrated that T6SSs have functions beyond interspecies competition. Here, we summarize recent research on the role of T6SSs in microbiome modulation, pathogenesis, and stress resistance.

Pseudomonas aeruginosa H3-T6SS Combats H2O2 Stress by Diminishing the Amount of Intracellular Unincorporated Iron in a Dps-Dependent Manner and Inhibiting the Synthesis of PQS

“…The role of T6SS in bacterial antagonism has been extensively explored in various environments [ 25 , 53 , 54 , 55 ]. However, recent data suggest that this system also plays an important role in combating oxidative stress [ 18 , 20 , 21 , 56 ].…”

The role of the type VI secretion system in the stress resistance of plant-associated bacteria

“…The T6SS system was first discovered and studied in the plant-associated bacterium Rhizobium leguminosarum that affects pea nodulation and nitrogen fixation (Bladergroen et al 2003 ). However, with the deepening of research, the T6SS has been demonstrated to have diverse functions (Lin et al 2021 ), including anti-bacterial (Trunk et al 2018 ) and anti-host activities (Coulthurst. 2019 ), mediating the uptake of metal ions (Lin et al 2017 ; Han et al 2019 ), resistance to environmental stress (Si et al 2017a ; Wan et al 2017 ), inhibition of bacterial infection in the host (Bendor et al 2015 ), and regulating the formation of bacterial biofilms (Lin et al 2015 ; Chen et al 2020 ).…”

A review on mechanisms and prospects of endophytic bacteria in biocontrol of plant pathogenic fungi and their plant growth-promoting activities

“…is important for its biocontrol activity. The T6SS is a syringe-like structure resembling a phage tail capable of secreting effector proteins into targeted prokaryotic and eukaryotic cells [ 144 , 145 ]. This system has been recognized as a powerful antifungal weapon, and fungal-specific effector proteins, Tfe1 and Tfe2, have been identified.…”