Demonstration of the role of cell wall homeostasis in Staphylococcus aureus growth and the action of bactericidal antibiotics

Abstract

Bacterial cell wall peptidoglycan is essential, maintaining both cellular integrity and morphology, in the face of internal turgor pressure. Peptidoglycan synthesis is important, as it is targeted by cell wall antibiotics, including methicillin and vancomycin. Here, we have used the major human pathogen Staphylococcus aureus to elucidate both the cell wall dynamic processes essential for growth (life) and the bactericidal effects of cell wall antibiotics (death) based on the principle of coordinated peptidoglycan synthesis and hydrolysis. The death of S. aureus due to depletion of the essential, two-component and positive regulatory system for peptidoglycan hydrolase activity (WalKR) is prevented by addition of otherwise bactericidal cell wall antibiotics, resulting in stasis. In contrast, cell wall antibiotics kill via the activity of peptidoglycan hydrolases in the absence of concomitant synthesis. Both methicillin and vancomycin treatment lead to the appearance of perforating holes throughout the cell wall due to peptidoglycan hydrolases. Methicillin alone also results in plasmolysis and misshapen septa with the involvement of the major peptidoglycan hydrolase Atl, a process that is inhibited by vancomycin. The bactericidal effect of vancomycin involves the peptidoglycan hydrolase SagB. In the presence of cell wall antibiotics, the inhibition of peptidoglycan hydrolase activity using the inhibitor complestatin results in reduced killing, while, conversely, the deregulation of hydrolase activity via loss of wall teichoic acids increases the death rate. For S. aureus, the independent regulation of cell wall synthesis and hydrolysis can lead to cell growth, death, or stasis, with implications for the development of new control regimes for this important pathogen.

Penicillin-Binding Protein 1 (PBP1) of Staphylococcus aureus Has Multiple Essential Functions in Cell Division

“…This phenotype is mirrored by the mode of action of β-lactam antibiotics, which bind to and inhibit the TP activity of PBPs ( 7 ). We have recently described the morphological effects of methicillin and oxacillin on S. aureus , which result in cell swelling and cessation of septal and peripheral cell wall synthesis ( 31 ). Our results suggest that PBP1 TP activity has a role in septal plate formation, and without this, the septum is misshapen.…”

Targeting the Achilles’ Heel of Multidrug-Resistant Staphylococcus aureus by the Endocannabinoid Anandamide

“…CidA acts antagonistically with LrgA by promoting autolysis and eDNA release [ 85 , 86 ]. Simultaneous, AEA induced a 3-fold increase of the small non-coding sprX that positively regulates the expression of the autolysin regulator WalR, which, in turn, modulates the expression of the autolysins isaA and lytM [ 87 , 116 , 117 ]. SprX has been shown to sensitize MRSA to antibiotics by negatively regulating the translation of the transcription factor spoVG , which is a master regulator of capsule production, virulence, and cell-wall metabolism, and required for methicillin and glycopeptide resistance [ 118 , 119 , 120 ].…”

WhyD tailors surface polymers to prevent premature bacteriolysis and direct cell elongation in Streptococcus pneumoniae

“…Given their potential to induce cell wall damage, it has long been appreciated that bacteria must employ robust mechanisms to prevent aberrant PG cleavage and lysis by autolysins. Notably, β-lactams and related antibiotics have long been known to kill bacteria by corrupting the activity of PG hydrolases to damage the cell wall and cause catastrophic lysis ( Cho et al, 2014 ; Salamaga et al, 2021 ; Tomasz and Waks, 1975 ; Tomasz et al, 1970 ). Despite the relevance of this phenomenon for antibiotic development, surprisingly little is known about the regulatory mechanisms governing when and where autolysins are activated during normal growth and how antibiotics disrupt these processes to induce lysis.…”