ppGpp controls cell size in Erwinia amylovora. (A) Epifluorescence microscopy images of E. amylovora WT and relA, spoT, and relA/spoT (ppGpp0) mutant strains constitutively expressing GFP and grown in LB medium or HMM for 4 h. Magnification, ×200. (B) Distributions of sizes and average cell lengths of WT and relA, spoT, and relA/spoT (ppGpp0) mutant strains constitutively expressing GFP and grown in LB medium or HMM. The experiments were repeated at least two times with similar results.