Effects of oxacillin and tetracycline on autolysis, autolysin processing and atl transcription in Staphylococcus aureus

Autolysins are peptidoglycan hydrolases involved in cell growth and cell lysis. Atl is an important autolysin of Staphylococcus aureus and is essential for penicillin-induced autolysis. The objective of our study was to examine the effect of oxacillin, chloramphenicol and tetracycline on autolysis, peptidoglycan hydrolase profiles and transcription of atl encoding the major S. aureus autolysin on cells grown in the presence of minimum inhibitory concentrations of the antibiotics. Growth of methicillin-susceptible strains in the presence of oxacillin led to increased autolysis, a loss of low molecular weight and a gain of high molecular weight peptidoglycan hydrolase bands suggesting altered proteolytic processing of peptidoglycan hydrolases, and a decrease in atl transcription. In contrast, growth in the presence of tetracycline led to a decrease in autolysis, an increase in atl transcription, and a drastic decrease in the protein concentration of freeze–thaw extracts obtained for peptidoglycan hydrolase analysis. Growth of methicillin-resistant strains in the presence of oxacillin had only moderate effects on autolysis and peptidoglycan hydrolase profiles.