Visualization of the Serratia Type VI Secretion System Reveals Unprovoked Attacks and Dynamic Assembly

Cell Rep. 2015 Sep 29;12(12):2131-42. doi: 10.1016/j.celrep.2015.08.053. Epub 2015 Sep 17.

Abstract

The Type VI secretion system (T6SS) is a bacterial nanomachine that fires toxic proteins into target cells. Deployment of the T6SS represents an efficient and widespread means by which bacteria attack competitors or interact with host organisms and may be triggered by contact from an attacking neighbor cell as a defensive strategy. Here, we use the opportunist pathogen Serratia marcescens and functional fluorescent fusions of key components of the T6SS to observe different subassemblies of the machinery simultaneously and on multiple timescales in vivo. We report that the localization and dynamic behavior of each of the components examined is distinct, revealing a multi-stage and dynamic assembly process for the T6SS machinery. We also show that the T6SS can assemble and fire without needing a cell contact trigger, defining an aggressive strategy that broadens target range and suggesting that activation of the T6SS is tailored to survival in specific niches.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Gene Expression Regulation, Bacterial*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Kinetics
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Microscopy, Fluorescence
  • Multigene Family
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Serratia marcescens / genetics*
  • Serratia marcescens / metabolism
  • Serratia marcescens / ultrastructure
  • Type VI Secretion Systems / genetics*
  • Type VI Secretion Systems / metabolism
  • Type VI Secretion Systems / ultrastructure

Substances

  • Bacterial Proteins
  • Luminescent Proteins
  • Recombinant Fusion Proteins
  • Type VI Secretion Systems
  • red fluorescent protein
  • Green Fluorescent Proteins