Activity, delivery, and diversity of Type VI secretion effectors

Mol Microbiol. 2021 Mar;115(3):383-394. doi: 10.1111/mmi.14648. Epub 2020 Dec 7.


The bacterial type VI secretion system (T6SS) system is a contractile secretion apparatus that delivers proteins to neighboring bacterial or eukaryotic cells. Antibacterial effectors are mostly toxins that inhibit the growth of other species and help to dominate the niche. A broad variety of these toxins cause cell lysis of the prey cell by disrupting the cell envelope. Other effectors are delivered into the cytoplasm where they affect DNA integrity, cell division or exhaust energy resources. The modular nature of T6SS machinery allows different means of recruitment of toxic effectors to secreted inner tube and spike components that act as carriers. Toxic effectors can be translationally fused to the secreted components or interact with them through specialized structural domains. These interactions can also be assisted by dedicated chaperone proteins. Moreover, conserved sequence motifs in effector-associated domains are subject to genetic rearrangements and therefore engage in the diversification of the arsenal of toxic effectors. This review discusses the diversity of T6SS secreted toxins and presents current knowledge about their loading on the T6SS machinery.

Keywords: T6SS; bacterial competition; bacterial toxins; effectors; protein secretion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Anti-Bacterial Agents / metabolism
  • Bacterial Proteins / physiology*
  • Bacterial Toxins / metabolism
  • Bacterial Toxins / pharmacology
  • Conserved Sequence
  • Cytoplasm / drug effects
  • Microbial Interactions
  • Molecular Chaperones / physiology*
  • Periplasm / drug effects
  • Protein Domains
  • Type VI Secretion Systems / physiology*


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Bacterial Toxins
  • Molecular Chaperones
  • Type VI Secretion Systems