Genetic analysis of type 5 capsular polysaccharide expression by Staphylococcus aureus

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Staphylococcus aureus frequently produces capsules, with type 5 capsular polysaccharide (CP5) found in about 25% of clinical isolates.
• Understanding the genetic basis of CP5 expression is vital for studying Staphylococcus aureus pathogenesis.

Purpose of the Study:

• To identify and characterize the genes responsible for type 5 capsular polysaccharide (CP5) expression in Staphylococcus aureus.
• To lay the groundwork for future identification of specific genes involved in CP5 biosynthesis.

Main Methods:

• Mutagenesis of Staphylococcus aureus strain Reynolds using Tn918 to generate capsule-deficient mutants.
• Cloning and characterization of DNA fragments flanking the transposon insertion site.
• Construction of a restriction map and screening of a cosmid library from the wild-type strain.
• Subcloning of DNA fragments into a shuttle vector for complementation studies.

Main Results:

• A 9.4-kb DNA fragment containing putative capsule genes was isolated.
• A 34-kb insert clone (pJCL19) was constructed and mapped.
• A central DNA fragment from pJCL19 specifically hybridized to DNA from capsular types 2, 4, and 5.
• A 6.2-kb fragment complemented CP5 expression in a capsule-negative mutant.

Conclusions:

• The identified DNA fragments are essential for CP5 expression in Staphylococcus aureus.
• These findings provide a critical foundation for the molecular identification of genes involved in CP5 biosynthesis.
• This research facilitates further investigation into the genetic regulation of capsular polysaccharide production.