SdrX, a serine-aspartate repeat protein expressed by Staphylococcus capitis with collagen VI binding activity

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Staphylococcus capitis is a significant cause of infections in very-low-birth-weight infants.
• Coagulase-negative staphylococci, including S. capitis, pose a growing threat in healthcare settings.
• Identifying virulence factors is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the S. capitis genome for microbial surface components recognizing adhesive matrix molecules (MSCRAMM).
• To identify and characterize novel MSCRAMM proteins in S. capitis for potential therapeutic targeting.

Main Methods:

• Southern blot analysis was used to screen the S. capitis genome for MSCRAMM genes.
• Monospecific antisera, Western blot, and flow cytometry were employed to confirm SdrX surface expression.
• Recombinant SdrX protein and whole bacteria were used to assess collagen binding.

Main Results:

• A novel S. capitis gene, sdrX, encoding an Sdr family MSCRAMM protein, was identified.
• SdrX was confirmed to be expressed on the surface of S. capitis.
• SdrX demonstrated binding to human collagen type VI, both in its recombinant form and on the bacterial surface.

Conclusions:

• SdrX is the first identified collagen-binding Sdr protein and the first MSCRAMM identified in S. capitis.
• SdrX represents a potential therapeutic target for S. capitis infections, particularly in vulnerable infant populations.