Effect of Penicillin Irradiation on Bacterial Growth and Penicillin Resistance

The interaction between benzylpenicillin and the specific bacterial cell wall receptor(s) is influenced in a noncontinuous manner through the antibiotic irradiation with λ = 546 nm. The growth of two B. subtilis strains, one sensitive and the other resistant to penicillin, presents a different response pattern to the irradiated antibiotic. For both strains, the inhibitory activity of the antibiotic is increased for 5, 25 and 45 sec penicillin irradiation times. For the resistant strain, the inhibitory activity of the antibiotic is decreased for 15, 35 and 55 sec penicillin irradiation times. This decrease is correlated with the enhancements induced in penicillinase activity, which appear also for 15, 35 and 55 sec of benzylpenicillin irradiation times.