Figure 7
Amino acid complementation increased the resistance of E. coli to H 2 O 2 and reduced the difference in H 2 O 2 resistance between the wild type and ΔarcA mutant E. coli. Resistance of wild type (diamond) and the ΔarcA mutant E. coli (square) to H2O2 was assayed by the ability to grow in the presence of H2O2 and more resistant bacteria show a smaller diameter of inhibition. Various volumes of 20 mM amino acid solution was spread onto each M9 minimal medium plate containing approximately 1 × 106 c.f.u. wild type or ΔarcA mutant E. coli and a paper disc of 1/4" with 10 μl of 30% H2O2 was added to the center of each plate. Zone of inhibition was measured after overnight incubation and plotted against the volume of amino acid supplementation. At least three experiments were performed, and results from a representative experiment performed in triplicates are shown. Error bars indicate standard deviation and sometimes fall within the data label..