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A Visual Assay to Monitor T6SS-mediated Bacterial Competition
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A Visual Assay to Monitor T6SS-mediated Bacterial Competition

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PAAR-Rhs proteins harbor various C-terminal toxins to diversify the antibacterial pathways of type VI secretion

Jiale Ma1,2, Min Sun1,2, Wenyang Dong1,2

  • 1College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.

Environmental Microbiology
|November 22, 2016
PubMed

Insights

Researchers discovered novel Rhs proteins with Metallopeptidase-4 domains (Rhs-CTs) that use the type VI secretion system (T6SS) for bacterial competition in Escherichia coli, revealing diverse antibacterial mechanisms.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • The type VI secretion system (T6SS) mediates contact-dependent bacterial killing for niche competition.
  • Rhs proteins, characterized by variable C-terminal toxin domains, are implicated in inhibiting or killing neighboring cells.

Purpose of the Study:

  • To identify and characterize novel Rhs proteins with antibacterial activity mediated by T6SS in Escherichia coli.
  • To investigate the mechanisms and diversity of Rhs-CT effector delivery and function.

Main Methods:

  • Domain-architecture analysis for Rhs-CT effector retrieval.
  • Screening of Rhs-CTs in E. coli, including Rhs-CT1 (Metallopeptidase-4) and Rhs-CT3 (Restriction endonuclease-3).
  • Experimental validation of effector delivery and interbacterial antagonism, including analysis of vgrG and eagR/DUF1795 roles, and characterization of neighborless Rhs-CTs (Rhs-Nb).

Main Results:

  • A novel Rhs-CT1 with a Metallopeptidase-4 domain exhibiting antibacterial effects via T6SS was identified in E. coli.
  • Rhs-CT3, possessing a Restriction endonuclease-3 domain, also mediated interbacterial antagonism.
  • The vgrG and eagR/DUF1795 genes were found to be essential for Rhs-CT delivery, with eagR potentially acting as a T6SS chaperone.
  • Neighborless Rhs-CTs (Rhs-Nb) were identified as a distinct family, with Rhs-Nb-CT5 mediating antagonism via the Hcp2B-VgrG2 module.
  • A broad classification of toxin/immunity pairs into eight clans suggests extensive diversification of T6SS antibacterial pathways by Rhs-CTs.

Conclusions:

  • Rhs-CTs represent a significant source of functional diversity for T6SS-mediated antibacterial strategies across various bacterial species.
  • The study highlights the intricate mechanisms of Rhs-CT delivery and function, expanding our understanding of bacterial warfare and T6SS evolution.

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