A systems approach to understanding beta lactam antibiotic mechanism of action

About This Grant

SUMMARY The b-lactam antibiotics (penicillin and related compounds) are among the strongest weapons in our antimicrobial arsenal, due to their ability to effectively induce lysis and thus death in many bacterial species. Despite their importance and concomitant decades of intense research efforts, we do not understand how exactly these drugs kill bacteria, though some clues exist. b-lactams inhibit penicillin-binding proteins (PBPs), the principal cell wall synthases. PBP inhibition leads to cell wall degradation, likely via the poorly-understood dysregulated action of so-called “autolysins”, a diverse group of endogenous cell wall cleavage enzymes. Research efforts into the molecular details of b-lactam induced cell wall breakdown have traditionally been stymied by the absence of appropriate tools to quantitatively and qualitatively analyze cell wall breakdown products consisting of peptidoglycan (PG) fragments, and by the dynamic situation of analyzing a cell during the process of its lysis. Here, we propose to use a novel PG architecture analysis pipeline to assess cell wall turnover in a high-throughput fashion. We have also established new bacterial model systems that recapitulate b-lactam- induced cell wall degradation while retaining structural integrity, solving the complication of using lysing cells for PG architecture analysis. Using these tools, we will comprehensively interrogate downstream consequences of b-lactam exposure, determine the contributions of specific autolysins to the cell wall turnover process and map out new pathways and environmental conditions that modulate b-lactam mechanism of action. At the end of the project, we will generate a model that functionally integrates environmental cues, intrinsic metabolic functions and autolytic potential to finally fully understand b-lactam mechanism of action. Such an understanding will fuel the development of novel antibiotic adjuvants that optimize the effectiveness of b-lactams by exploiting key pathways that determine b-lactam-induced structural integrity failure.