Distinct Single-Cell Morphological Dynamics under Beta-Lactam Antibiotics

SummaryThe bacterial cell wall is conserved in prokaryotes, stabilizing cells against osmotic stress. Beta-lactams inhibit cell-wall synthesis and induce lysis through a bulge-mediated mechanism; however, little is known about the formation dynamics and stability of these bulges. To capture processes of different timescales, we developed an imaging platform combining automated image analysis with live-cell microscopy at high time resolution. Beta-lactam killing of Escherichia coli cells proceeded through four stages: elongation, bulge formation, bulge stagnation, and lysis. Both the cell wall and outer membrane (OM) affect the observed dynamics; damaging the cell wall with different beta-lactams and compromising OM integrity cause different modes and rates of lysis. Our results show that the bulge-formation dynamics are determined by how the cell wall is perturbed. The OM plays an independent role in stabilizing the bulge once it is formed. The stabilized bulge delays lysis and allows recovery upon drug removal.

Graphical AbstractFigure optionsDownload high-quality image (396 K)Download as PowerPoint slideHighlights
► Live-cell microscopy is used to monitor single-cell shape dynamics
► Beta-lactam-induced lysis proceeds through four distinct physical stages
► Dynamics of bulge formation and its stability vary for different beta-lactams
► Cells with stabilized bulges revert to rod shape upon drug removal