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Rat/MgrA, a regulator of autolysis, is a regulator of virulence genes in Staphylococcus aureus

Susham Ingavale1, Willem van Wamel, Thanh T Luong

  • 1Department of Microbiology, Dartmouth Medical School, Hanover, NH 03755, USA.

Infection and Immunity
|February 26, 2005
PubMed

Insights

The mgrA gene regulates Staphylococcus aureus virulence factors alpha-hemolysin and protein A. MgrA controls these genes through both the agr system-dependent and -independent pathways.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • The Staphylococcus aureus mgrA gene regulates autolysis and virulence gene expression.
  • Previous studies indicated mgrA influences RNAIII of agr, hla, sarS, and spa expression.

Purpose of the Study:

  • To elucidate the regulatory mechanisms of mgrA on Staphylococcus aureus virulence genes hla and spa.
  • To define the interaction of mgrA with other regulatory elements like agr, sarS, and sarT.

Main Methods:

  • Northern analysis
  • Transcription fusion assays
  • Analysis of double mutants (sarT mgrA)

Main Results:

  • MgrA inactivation downregulated RNAIII of agr and hla, and upregulated sarS and spa.
  • MgrA regulates hla and spa independently of SarA and SarT.
  • MgrA exhibits dual regulation of hla and spa: one dependent on agr, and another independent pathway where MgrA directly binds hla and sarS promoters.

Conclusions:

  • MgrA is a key regulator in the Staphylococcus aureus virulence network.
  • MgrA controls alpha-hemolysin and protein A expression via both agr-dependent and -independent mechanisms.
  • MgrA directly interacts with hla and sarS promoters in an agr-independent manner.

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