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Type 6 secretion system-mediated immunity to type 4 secretion system-mediated gene transfer

Brian T Ho1, Marek Basler, John J Mekalanos

  • 1Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA.

Science (New York, N.Y.)
|October 12, 2013
PubMed

Insights

Pseudomonas aeruginosa mounts a lethal type VI secretion system (T6SS) attack against donor cells. This response, triggered by mating pair formation (Mpf) systems, may prevent the acquisition of foreign DNA.

Area of Science:

  • Microbiology
  • Bacterial genetics
  • Cellular communication

Background:

  • Gram-negative bacteria utilize the type VI secretion system (T6SS) for interbacterial antagonism.
  • The Pseudomonas aeruginosa H1-locus T6SS is known to activate in response to external T6SS attacks.

Purpose of the Study:

  • To investigate the triggers for Pseudomonas aeruginosa's H1-locus T6SS counterattack.
  • To determine if the mating pair formation (Mpf) system of conjugative plasmids induces T6SS activity.

Main Methods:

  • Genetic disruption of Mpf system components in plasmid RP4.
  • Assessing T6SS activity in Pseudomonas aeruginosa recipient cells.
  • Induction of T6SS by polymyxin B.

Main Results:

  • The Pseudomonas aeruginosa T6SS counterattack is induced by the Mpf system of IncPα conjugative plasmid RP4.
  • T6SS induction requires Mpf structural genes, not DNA transfer components.
  • Membrane-perturbing agents like polymyxin B also induce T6SS activity.

Conclusions:

  • Conjugative plasmids can trigger "donor-directed T6SS attacks" in recipient bacteria.
  • This T6SS response is linked to membrane perturbation sites caused by Mpf.
  • The T6SS may function to block the uptake of foreign DNA during conjugation.

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