Inhibitory action of erythromycin on bacteriophage SPO1 multiplication in sporulating cells of Bacillus subtilis 168

Summary Erythromycin (2–4 g/ml) was found to inhibit specifically multiplication of SPO1 in sporulating cells of an erythromycin-resistant, conditional asporogenous mutant of Bacillus subtilis 168 thy ^- trp ^-, Ery1040. In contrast, streptomycin (150–200 g/ml) which inhibits protein synthesis to a similar extent as erythromycin did not inhibit SPO1 multiplication severely, suggesting that the inhibition of SPO1 multiplication by erythromycin is not caused by an overall inhibition of protein synthesis. Neither phage DNA synthesis nor phage messenger RNA synthesis was affected appreciably under these conditions. However, the synthesis of three phage proteins that are synthesized 15 min after infection was preferentially inhibited by erythromycin. In addition, the inhibition of SPO1 multiplication has been correlated with the stimulation of host stable RNA synthesis exhibited by erythromycin. Possible mechanisms for the inhibition of SPO1 multiplication in Ery1040 cells are discussed.