Molecular Cell Article Distinct Single-Cell Morphological Dynamics under Beta-Lactam Antibiotics Zhizhong Yao,1,3 Daniel Kahne,1,4,* and Roy Kishony2,3,* 1Department of Chemistry and Chemical Biology 2School of Engineering and Applied Sciences Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA 3Department of Systems Biology 4Department of Biological Chemistry and Molecular Pharmacology Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA *Correspondence:
[email protected] (D.K.),
[email protected] (R.K.) http://dx.doi.org/10.1016/j.molcel.2012.09.016 SUMMARY in cell division, elongation, and shape maintenance (Spratt, 1975). It has been proposed that inhibition of crosslink forma- The bacterial cell wall is conserved in prokaryotes, tion by beta-lactams combined with misregulated cell-wall stabilizing cells against osmotic stress. Beta- degradation by PG hydrolases results in the accumulation of lactams inhibit cell-wall synthesis and induce lysis PG defects, which ultimately leads to cell lysis (Chung et al., through a bulge-mediated mechanism; however, 2009). little is known about the formation dynamics and The physical process of PG defect formation and subsequent stability of these bulges. To capture processes of lysis is poorly understood. Previous literature suggested a bulge-mediated process (Chung et al., 2009; Huang et al., different timescales, we developed an imaging 2008), and the reported rates of lysis have been loosely charac- platform combining automated image analysis with terized as slow and fast (de Pedro et al., 2002). However, in the live-cell microscopy at high time resolution. Beta- absence of systematic characterization of bulge-formation lactam killing of Escherichia coli cells proceeded dynamics and their variability across individual cells, it is unclear through four stages: elongation, bulge formation, whether lysis occurs uniformly within isogenic cell populations, bulge stagnation, and lysis.