Rot repression of enterotoxin B expression in Staphylococcus aureus

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• The accessory gene regulator (Agr) system is a key quorum-sensing mechanism in Staphylococcus aureus.
• Agr regulates virulence factor expression, including upregulation of exoproteins like enterotoxin B (seb).
• Understanding Agr's regulatory targets and pathways is crucial for controlling S. aureus infections.

Purpose of the Study:

• To elucidate the regulatory mechanism by which the Agr system controls the transcription of the enterotoxin B (seb) gene.
• To identify specific cis-acting elements and trans-acting factors involved in Agr-mediated seb regulation.

Main Methods:

• Deletion analyses of the seb promoter region.
• Construction of hybrid promoters using the staphylococcal lac operon promoter.
• Reporter gene assays using chloramphenicol acetyltransferase (CAT) with seb promoter fusions.
• Introduction of constructs into S. aureus mutants deficient in Agr or Sar family regulators.

Main Results:

• Agr-mediated upregulation of the seb promoter was confirmed.
• Agr control of seb transcription was found to be dependent on the presence of a functional Rot protein.
• The Rot protein was demonstrated to bind directly to the seb promoter region.
• The Agr system's effect on seb transcription involves the inactivation of Rot repressor activity.

Conclusions:

• The Agr system regulates enterotoxin B expression by repressing the Rot repressor.
• This Agr-mediated inactivation of Rot leads to increased seb transcription during the post-exponential growth phase.
• The findings provide a detailed molecular mechanism for Agr control of a key S. aureus virulence factor.