Figure 1.

In vivo cytotoxicity assays of mutant colicin E3-Im3 complexes. Cytotoxicity of the purified colicin E3 alanine mutants was assessed by spotting a fivefold serial dilution of purified colicin E3-Im3 complex from a starting concentration of 1 mg mL⁻¹ onto a growing lawn of E. coli JM83 cells (see Materials and Methods). Clear zones in the cell lawn indicate cell killing by colicin E3, and hazy zones indicate partial toxicity.