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Gram-negative bacteria utilize sophisticated protein secretion systems to transport proteins across their double-membrane envelope into the extracellular environment or host cells. Based on their mechanism of action, these systems are classified into one-step and two-step pathways.One-Step Secretion Systems (Types I, III, IV, and VI)One-step secretion systems bypass the periplasm entirely, forming a continuous channel that spans both the inner and outer membranes:Type I Secretion System (T1SS):...
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A Visual Assay to Monitor T6SS-mediated Bacterial Competition
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Bacterial type VII secretion: An important player in host-microbe and microbe-microbe interactions.

Hiu-Ki R Tran1,2, Dirk W Grebenc1,2, Timothy A Klein1,2

  • 1Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.

Molecular Microbiology
|January 7, 2021
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Summary

Type VII secretion systems (T7SSs) are crucial for bacterial interactions. This review compares T7SSa and T7SSb pathways, revealing differences that explain their distinct roles in host-microbe and microbe-microbe relationships.

Keywords:
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Area of Science:

  • Microbiology
  • Bacterial protein secretion

Background:

  • Type VII secretion systems (T7SSs) are protein export machines in Gram-positive bacteria.
  • T7SSs are essential for Mycobacterium tuberculosis virulence but remain understudied in other bacteria.
  • A divergent subfamily, T7SSb, targets both eukaryotic and prokaryotic cells.

Purpose of the Study:

  • Compare the molecular architecture and substrates of T7SSa and T7SSb.
  • Elucidate the functional differences between these T7SS subfamilies.
  • Highlight the roles of T7SSb in host-microbe and microbe-microbe interactions.

Main Methods:

  • Comparative analysis of T7SSa and T7SSb systems.
  • Review of existing literature on T7SS molecular mechanisms and substrates.
  • Functional characterization of T7SSb pathways.

Main Results:

  • T7SSa and T7SSb exhibit distinct molecular architectures and substrate specificities.
  • T7SSb pathways are involved in both inter- and intra-species bacterial interactions.
  • Differences in T7SS structure correlate with their diverse biological functions.

Conclusions:

  • Understanding T7SS diversity is key to deciphering bacterial communication and pathogenesis.
  • T7SSb represents a significant, understudied pathway with broad biological relevance.
  • Further research into T7SSb mechanisms will uncover novel roles in microbial ecology.