Figure 3. Hydrolysis of hemoglobin.

Culture supernatants from mid-exponential phase cultures of the isogenic strains described in Fig. 1 were used to assay for hemoglobin (Hb) hydrolysis. Culture supernatants (n = 4) were mixed with equal volumes of human hemoglobin (1 mg/ml) and incubated for 24 h. Trypsin (0.5%) was used as a positive control. Hemoglobin was precipitated using 3% TCA and the absorbance of the supernatants analysed at 410 nm. The results are shown relative to the amount of hemoglobin hydrolysed by trypsin after 24 h. Error bars indicate S.E.M.