Ultrastructural analysis of the effect of netropsin on sporulation of Bacillus subtilis.

An electron microscopic analysis of Bacillus subtilis cells revealed that netropsin blocked sporulation ultrastructurally at stages 0-I. These observations are consistent with previous results which indicated that cells were not committed to sporulation in the presence of the drug. Further, the addition of netropsin up to stage III of sporulation prevented the normal sharp increase in dihydrodipicolinate synthase activity which results in dipicolinic acid accumulation of stage IV. The addition of netropsin after stage III had much less effect on the synthesis of dihydrodipicolinate synthase and on sporulation. Thus, morphological events in sporulation are blocked early whereas a sporulation-associated enzyme may be affected at later stages. These data indicate than netropsin affects the expression of sporulation-associated genes in a differential manner.