Fig. 3.

Inhibition of peptidoglycan insertion decouples surface growth from biomass growth. (A) and (B) Single-cell time lapse of filamenting cells (bAB56) grown in S7₅₀+GlcCaa medium and treated with vancomycin (50 μg/ml), which was added on top of the agarose pad at time = 0. Relative increase (left) and rates (middle-bottom) of volume, surface, and dry mass. After 20 min, a fraction of cells starts to shrink in surface area (middle-top) and lose part of their mass (see also Figure S3C). Right: relative change of dry-mass density, surface-to-mass ratio, and width (solid lines + shadings = average ± 2*SE). (B) Relative increase of volume, surface, and dry mass for a representative single cell. (C) Kymographs of MreB-GFP rotation in bYS19 cells during 30 s movie before and 7 min after vancomycin addition (as in A) along the lines indicated in MreB-GFP snapshots (top). (D) Comparison of surface expansion rate (yellow; as in A) and relative MreB activity (total length of MreB tracks divided by projected cell area and movie duration; green line + shading = average ± SE) of vancomycin-treated cells to that of nonperturbed cells. (E) Residual surface expansion after MreB motion was arrested by Van (vancomycin 50 μg/ml), DCS (D-cycloserine 10 mM), PenG (Penicillin G 0.5 mg/ml), and Bac (Bacitracin 0.5 mg/ml). Experiments were performed in the same way as (A) and (C) (yellow dots = single-cell values; white circles = median; and gray rectangles = interquartile range). (F) Single-cell time lapse of filamenting cells (bAB56) treated with chloramphenicol (100 μg/ml). Otherwise the same as in A. (G) Comparison of surface expansion rate (yellow: as in F) and relative MreB activity (green line + shading = average ± SE) of chloramphenicol-treated cells to that of nonperturbed cells.