Figure 1. YFP-EndA clusters in competent pneumococci.
(A) YFP-EndA distribution in cells 10 min after addition (or not - noncompetent) of CSP with or without R304 DNA. Top: overlay of phase-contrast images and YFP-EndA. Bottom: deconvolved fluorescent images (Materials and Methods) of YFP-EndA. Scale bars: 1 µM. (B) EndA clusters in a subset of the population. Data are mean ± s.d. of 4 fields of hundreds cells from 3 independent experiments (2,563 competent and 2,823 noncompetent cells analyzed). (C) Distribution of foci along longitudinal axis in cells without constriction. Focus (n = 146) position is given in relative coordinates from 0 (pole) to 0.5 (midcell). P, pole; M, midcell. (D) Transformation proficiency (open diamonds), fraction of cells containing foci and focus position (histograms). Transformation proficiency was assayed by selecting for SmR transformants as described in Materials and Methods. Color code (see inset cell diagram): red, midcell foci; white, intermediate position foci; orange, septal foci (S, septum); green, polar foci. (E) Fluorescence time-lapse microscopy of 6 competent YFP-EndA cells. Representative cells were extracted from a field containing 25 cells, all of which exhibited an EndA focus at some stage during the 25 minutes following CSP addition. Cells with foci are framed by blue squares.