FIG. 5.

Antibacterial activity of bovine and human milk is mediated by XOR. Transformed E. coli, constitutively expressing the luxCDABE operon, was incubated under hypoxic conditions with a reducing substrate and inorganic nitrite. Light emission was continuously monitored as an indicator of bacterial growth. Addition of bovine milk (A) or human milk (B) led to initial artifactual variations in light emission that were succeeded by a sharp decrease (over 8 to 14 min [A] or 4 to 8 min [B]) corresponding to a loss of metabolic function. This decrease was, in turn, followed by a steady increase as the bacteria recovered and resumed growth. In the presence of the specific XOR inhibitor oxypurinol, the sharp decrease in light emission was largely abrogated. Reprinted from reference 30 with permission of the publisher.