Type VI secretion system: secretion by a contractile nanomachine

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Type VI secretion systems (T6SS) are conserved across diverse Gram-negative bacteria.
• T6SS components share evolutionary links with contractile nanomachines like phages and pyocins.
• T6SS function is crucial for bacterial interactions, pathogenicity, and inter-bacterial competition.

Purpose of the Study:

• To review the current understanding of the T6SS mechanism of action.
• To elucidate the dynamic assembly and energy transduction processes of T6SS.
• To highlight the role of TSS effectors in bacterial virulence and competition.

Main Methods:

• Literature review of T6SS research.
• Analysis of structural and functional data of T6SS components.
• Integration of live-cell imaging studies on T6SS dynamics.

Main Results:

• T6SS assembly involves a membrane complex, baseplate, inner tube, and contractile sheath.
• Sheath contraction provides energy for effector delivery into target cells (bacterial and eukaryotic).
• Effector loading, sheath subunit recycling, and precise subcellular localization are key features.

Conclusions:

• T6SS represents a potent cell-to-cell weapon in bacteria.
• Understanding T6SS mechanism is vital for deciphering bacterial pathogenesis and inter-species competition.
• The dynamic and regulated nature of T6SS assembly underscores its evolutionary significance.