Staphylococcus aureus mutants with increased lysostaphin resistance

Area of Science:

• Microbiology
• Biochemistry

Background:

• Lysostaphin, an enzyme secreted by Staphylococcus simulans, targets Staphylococcus aureus cell walls by cleaving pentaglycine cross bridges.
• Studying lysostaphin-resistant mutants has previously illuminated bacterial cell wall assembly pathways.

Purpose of the Study:

• To discover novel genes involved in Staphylococcus aureus cell wall envelope biosynthesis.
• To identify genetic factors contributing to lysostaphin resistance in S. aureus.

Main Methods:

• Screening a collection of S. aureus strain Newman transposon mutants for resistance to lysostaphin.
• Characterizing the cell wall properties and antibiotic resistance of identified mutants.

Main Results:

• Transposon insertion in SAV2335 (named lyrA) conferred high lysostaphin resistance without gross alterations to peptidoglycan cross bridges.
• Unlike femAB mutants, lyrA inactivation did not decrease beta-lactam resistance in methicillin-resistant S. aureus.
• Lysostaphin binding to lyrA mutant cell walls was similar to wild-type, suggesting resistance is due to altered envelope properties.

Conclusions:

• The novel gene lyrA plays a role in Staphylococcus aureus cell wall properties influencing lysostaphin resistance.
• Altered cell wall envelope properties, potentially including modified cross bridges, contribute to lysostaphin resistance in lyrA mutants.
• Other identified resistance mechanisms involved genes in GTP pyrophosphokinase and purine biosynthesis pathways.