Penicillin-induced changes in the cell wall composition of Staphylococcus aureus before the onset of bacteriolysis

Abstract

To analyze if chemical cell wall alterations contribute to penicillin-induced bacteriolysis, changes in the amount, stability, and chemical composition of staphylococcal cell walls were investigated. All analyses were performed before onset of bacteriolysis i.e. during the first 60 min following addition of different penicillin G doses. Only a slight reduction of the amount of cell wall material incorporated after penicillin addition at the optimal lytic concentration was observed as compared to control cells. However, the presence of higher penicillin G concentrations reduced the incorporation of wall material progressively without bacteriolysis. Losses of wall material during isolation of dodecylsulfate insoluble cell walls were monitored to assess the stability of the wall material following penicillin addition. Wall material grown at the lytic penicillin concentration was least stable but about 30% of the newly incorporated wall material withstood even the harsh conditions of mechanical breakage and dodecylsulfate treatment. Dodecylsulfate insoluble cell walls were used for chemical analyses. While peptidoglycan chain length was unaffected in the presence of penicillin, other wall parameters were considerably altered: peptide cross-linking was reduced in the wall material synthesized after addition of penicillin; reductions from approx. 85% in controls to about 60% were similar for lytic and also for very high penicillin concentrations leading to nonlytic death. O-acetylation was also reduced after treatment with penicillin; this effect paralleled the occurrence of subsequent bacteriolysis at different drug concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

femA, which encodes a factor essential for expression of methicillin resistance, affects glycine content of peptidoglycan in methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains

“…It is noteworthy that no significant error arises from part of the wall label being held back in the cytoplasm, since fractionation of the labeled cells by the method of Park and Hancock (24) regularly showed that only less than 5% of the wall label resides in the cytoplasm from which it is lost to the growth medium at a rate of about 5% per generation time (36; see also references 5 and 29). Furthermore, boiling of the cells with 5% SDS did not solubilize any significant amount of the label, an observation that is in agreement with earlier results (29). Therefore, the release rate of the specific cell wall marker of [14C]N-acetylglucosamine from growing cells was measured in strains SG511, BB270, Col, and their femA mutants BB742, BB308, and BB403, respectively, to determine if inactivatingfemA had an effect on cell wall turnover.…”

Peptidoglycan structure of Lactobacillus casei, a species highly resistant to glycopeptide antibiotics

“…This is in agreement with the results of previous studies in which exposure to concentrations of ␤-lactams below the MICs decreased O-acetylation of peptidoglycan in Neisseria gonorrhoeae, Proteus mirabilis, and Staphylococcus aureus (13,24,28). In conclusion, the results indicate that in L. casei ATCC 393, which is naturally resistant to glycopeptides, the tetralactate precursor is readily exported by the lipid transporter and, similarly to what was found in E. faecium expressing vancomycin resistance, well processed to be integrated in the peptidoglycan (8).…”

Abnormal Peptidoglycan Produced in a Methicillin-Resistant Strain of Staphylococcus aureus Grown in the Presence of Methicillin: Functional Role for Penicillin-Binding Protein 2A in Cell Wall Synthesis

“…The fact that the concentration of this particular group of muropeptides remained unchanged in cells grown with or without antibiotic suggests that these compounds may have some special, essential function in the cell walls. Our findings confirm and extend the findings of earlier studies (5,6). Most recently, Snowden and Perkins (7) used a gel filtration technique to demonstrate changes in peptidoglycan composition when methicillin-susceptible staphylococci were grown in the presence of sub-MICs of various beta-lactam antibiotics.…”