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Updated: Jun 13, 2025

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
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The double-edged role of FASII regulator FabT in Streptococcus pyogenes infection

Clara Lambert1,2, Marine Gaillard1, Paprapach Wongdontree3

  • 1Université Paris Cité, Institut Cochin, INSERM, U1016, CNRS, UMR8104, Paris, France.

Nature Communications
|October 4, 2024
PubMed

Insights

Streptococcus pyogenes FabT repressor controls fatty acid synthesis (FASII). FabT defects reduce virulence but mutants emerge, thriving in lipid-rich environments while failing in host tissues due to energy dissipation.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • The type II fatty acid synthesis pathway (FASII) in Streptococcus pyogenes is regulated by the FabT repressor.
  • FabT repressor binds to acyl-Acyl carrier protein to control FASII.
  • FabT defects have been linked to reduced virulence in animal models, yet spontaneous fabT mutants emerge during infection.

Purpose of the Study:

  • To investigate the conditions and mechanisms governing FabT activity and fabT mutant emergence.
  • To resolve the paradox between FabT's role in virulence and the in vivo emergence of fabT mutants.
  • To understand the implications of FabT defects on bacterial survival in different environments.

Main Methods:

  • Characterization of fabT mutant phenotypes under varying growth conditions.
  • Analysis of energy dissipation and metabolic consumption in fabT mutants.
  • Assessment of bacterial membrane composition and fatty acid incorporation.

Main Results:

  • FabT defects cause energy dissipation, limiting growth on human tissue products and explaining the need for FabT during infection.
  • fabT mutants exhibit enhanced growth in saturated fatty acid-rich environments.
  • Continued FASII activity in fabT mutants hinders saturated fatty acid incorporation in lipid-rich biotopes.

Conclusions:

  • FabT is essential for virulence by preventing energy dissipation in nutrient-limited host environments.
  • Emergence of fabT mutants is favored in lipid-rich biotopes due to altered fatty acid metabolism.
  • FabT defects create a trade-off: improved survival in lipid-rich niches but a genetic disadvantage for infection.

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