Low level chemiluminescence from liquid culture media

Low level chemiluminescence (CL) can be observed from autoclaved liquid culture media, as used in microbiology. The light emission is oxygen-dependent and arises from reactions following auto-oxidation of reducing Maillard products which are formed during autoclaving. The inhibition of this CL by radical scavengers and antioxidants has been studied. As superoxide radicals and hydrogen peroxide are predominantly involved in the initiation of the CL, the investigation of CL from culture media offers a convenient tool for the detection of exogenous (medium-mediated) oxidative stress being imposed onto micro-organisms in culture. Transition metal ions showed, dependent on concentration, both inhibitory and stimulating effects on the CL, which was also affected by the presence of complexing agents. Iron porphyrins and related complexes displayed a very efficient quenching of the CL, which may be of particular importance, as aerobic micro-organisms have been previously shown to be very efficient in quenching the CL from culture media.