Staphylococcus aureus hyaluronidase is a CodY-regulated virulence factor

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Staphylococcus aureus is a major Gram-positive pathogen causing various infections.
• Invasive strains utilize secreted factors like hemolysins, immunomodulators, and exoenzymes for virulence.
• Hyaluronidase (HysA) is a secreted enzyme that degrades hyaluronic acid, a key component of connective tissue.

Purpose of the Study:

• To investigate the regulatory mechanisms controlling hyaluronidase (HysA) expression in S. aureus.
• To determine the role of HysA as a virulence factor in S. aureus pathogenesis.
• To elucidate the specific regulators involved in HysA production and activity.

Main Methods:

• Utilized the Nebraska Transposon Mutant Library (NTML) to identify genetic insertions affecting HysA activity.
• Analyzed the impact of global regulators (SigB, SarA, CodY) on HysA levels.
• Constructed and tested a ΔhysA mutant in a murine model of pulmonary infection.
• Investigated CodY binding to the hysA promoter region.

Main Results:

• Insertions in sigB, SarA, and CodY genes significantly increased extracellular HysA activity.
• CodY was identified as a direct repressor of hysA expression, with repression dependent on branched-chain amino acid availability.
• Mutation of the CodY binding box abolished HysA repression.
• A ΔhysA mutant exhibited significant attenuation in a neutropenic murine model of pulmonary infection, showing reduced bacterial burden and lung pathology.

Conclusions:

• Staphylococcus aureus hyaluronidase (HysA) is a virulence factor contributing to S. aureus pathogenesis.
• HysA expression is directly repressed by the global regulator CodY.
• Understanding HysA regulation provides insights into S. aureus infection mechanisms.