Fig. 3

Overexpression of the pptE and pdhR ORFs cause E. coli filamentation independent of recA (SOS response). The pptE and pdhR ORFs from UTI89 were cloned into pBAD24, transformed into BW25113, and BW25113 (ΔrecA), and cultures induced with 0.2% L-arabinose in M9 medium. Fixed cells were analysed by microscopy (a) and Coulter cytometry to obtain cell volume distributions (b). c Fixed cells were stained using the Hoechst 33342 (DNA) and FM4–64 (membrane) and imaged by fluorescence microscopy. An overlay of the Hoechst and FM4–64 channels is also shown, indicating the obvious anti-correlation between the two stains, suggesting a possible physical exclusion of these features