Fig. 7.

A transiently “dead” microbe. Competent E. coli (NEB5α cells competent cells, cat # c2987, New England Biolabs, Ipswitch, MA, USA) were thawed on ice. For a control sample, 2 μL of cells was added to 98 μL LB culture medium, 100 μL propidium iodide added, and the mixture allowed to stain for 5 min at room temperature. The experimental E. coli NEB5α (25 μL) was added to an electroporation cuvette previously cooled to 5 °C and electroporated at 2500 V twice. The cells were then diluted in LB and stained as with the control cells. a Fluorescence microscopy showing that almost all cells stained positive for propidium iodide treatment. b Colony-forming units showing no significant difference between controls and electroporated samples