Penicillin: reversible inhibition of forespore septum development in Bacillus megaterium cells.

Benzylpenicillin inhibits the development of the forespore septum in sporulating Bacillus megaterium cells. The inhibitory effect is a function of the duration of exposure to the antibiotic and is completely reversible by penicillinase. Under the incubation conditions employed, less than 20% of the covalently bound antibiotic is released from the cells. The penicillin which remains bound to the cells after treatment with penicillinase may be necessary but is not sufficient for the effect; unbound antibiotic in the sporulation medium is also required.