Priming and polymerization of a bacterial contractile tail structure

Area of Science:

• Microbiology
• Molecular Biology
• Structural Biology

Background:

• Type VI secretion systems (TSS) are essential for bacterial interactions, utilizing contractile tails for delivering effectors.
• The structure of the TSS contractile sheath is known, but the mechanisms controlling its polymerization and coordination with the inner tube are unclear.

Purpose of the Study:

• To investigate the role of the TssA complex in the assembly of the type VI secretion system contractile tail.
• To elucidate the mechanism by which TssA initiates and coordinates the biogenesis of the inner tube and outer sheath.

Main Methods:

• Fluorescence microscopy in enteroaggregative Escherichia coli.
• Biochemical analysis of TssA complex interactions with tail components.

Main Results:

• The TssA dodecameric complex interacts with both inner tube and outer sheath components.
• TssA binds to the membrane core complex and initiates tail polymerization.
• TssA localizes to the tip of the growing tail, incorporating new subunits.

Conclusions:

• TssA acts as a crucial initiator and coordinator of type VI secretion system contractile tail assembly.
• TssA primes and regulates the biogenesis of both the inner tube and outer sheath.
• Understanding TssA function provides insights into bacterial virulence and inter-bacterial competition mechanisms.