Acinetobacter baumannii utilizes a type VI secretion system for bacterial competition

PLoS One. 2013;8(3):e59388. doi: 10.1371/journal.pone.0059388. Epub 2013 Mar 19.


Type VI secretion systems (T6SS) are a class of macromolecular secretion machines that are utilized by a number of bacteria for inter-bacterial competition or to elicit responses in eukaryotic cells. Acinetobacter baumannii is an opportunistic pathogen that causes severe infections in humans. These infections, including pneumonia and bacteremia, are important, as they are often associated with hospitals and medical-settings where they disproportionally affect critically ill patients like those residing in intensive care units. While it is known that A. baumannii genomes carry genes whose predicted products have homology with T6SS-associated gene products from other bacteria, and secretion of a major T6SS structural protein Hcp has been demonstrated, no additional work on an A. baumannii T6SS has been reported. Herein, we demonstrated that A. baumannii strain M2 secretes Hcp and this secretion was dependent upon TssB, an ortholog of a bacteriophage contractile sheath protein, confirming that strain M2 produces a functional T6SS. Additionally, we demonstrated that the ability of strain M2 to out-compete Escherichia coli was reliant upon the products of tssB and hcp. Collectively, our data have provided the first evidence demonstrating function in inter-bacterial competition, for a T6SS produced by A. baumannii.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter baumannii / genetics
  • Acinetobacter baumannii / physiology*
  • Bacterial Secretion Systems / genetics
  • Bacterial Secretion Systems / physiology*
  • Blotting, Western
  • Computational Biology / methods
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli
  • Genetic Complementation Test
  • Hemolysin Proteins / metabolism
  • Microbial Interactions / physiology*
  • Plasmids / genetics
  • Statistics, Nonparametric


  • Bacterial Secretion Systems
  • Hemolysin Proteins

Grant support

This research was supported by discretionary funds to RSM from The Research Institute at Nationwide Children's Hospital. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.