FIG. 4.

(A) Luminescence of B. subtilis after addition of the luciferase substrate, d-luciferin. The cells were incubated for 90 min with no human serum (▪) or with human serum at concentrations of 3.3 μl/ml (•), 5.0 μl/ml (▴), 5.6 μl/ml (▾), 6.7 μl/ml (⧫), and 10 μl/ml (□) prior to substrate addition. (B) Luminescence of E. coli after addition of the luciferase substrate, d-luciferin. The cells were incubated for 90 min with no human serum (▪) or with human serum at concentrations of 5.0 μl/ml (•), 12.5 μl/ml (▴), 18.3 μl/ml (▾), and 25.0 μl/ml (⧫) prior to substrate addition. The values are averages from three replicate experiments.