Size distribution of B. abortus carrying AidB-YFP, in the presence or absence of an alkylating agent (EMS). The bacterial lengths were grouped in classes of 0.25 μm, and the maximum value for each class is given on the × axis. (A) Size distribution of 276 bacteria (XDB1128 strain) with AidB-YFP either at the new pole (white), the new pole and the constriction site (dark grey), or the constriction site only (black). (B) Size distribution of B. abortus (XDB1128 strain) exposed to 0.4% of EMS for 4 h (light grey, n = 340) or the unexposed control (white, n = 218, bacteria without detectable constriction). (C) DIC and fluorescence pictures of the XDB1128 strain expressing aidB-yfp and pdhS-mCherry fusions, as described in figure 2. The bacteria in the lower panels have been exposed to 0.4% EMS for 4 h in rich (2YT) medium. On the top panels, control bacteria were incubated for 4 h in 2YT in the absence of EMS. Constriction sites are indicated by arrowheads. Each scale bar represents 2 μm.