Effect of linear gramicidin on sporulation and intracellular ATP pools of Bacillus brevis.

When Bacillus brevis ATCC 8185 was subjected to nutritional shiftdown from a rich medium to one completely devoid of a nitrogen source, sporulation could be stimulated by the addition of linear gramicidin. Gramicidin-induced sporulation occurred after a considerably longer lag period than the earlier described tyrocidine-induced process (Ristow and Paulus 1982) but involved similar associated biochemical changes, such as extracellular protease production, rapid incorporation of radioactive precursors into RNA, and dipicolinate synthesis. The increased incorporation of [3H]leucine into tyrocidine was a characteristic element in gramicidin-induced sporulation, not being observed when spore formation was accelerated by limited nitrogen supplementation. Nitrogen supplementation (0.02-0.01% nutrient broth) caused a slow and gradual increase in dipicolinate production, in contrast to the sudden, rapid rise of dipicolinate synthesis provoked by the addition of gramicidin or tyrocidine. The induction of sporulation by gramicidin occurred at very low peptide concentrations (0.03 microM), which also brought about an acute depletion of intracellular ATP. In sporulation accelerated by nutrient broth, no depression of ATP level was observed and nonionophoric analogues of gramicidin were unable to substitute for gramicidin in inducing sporulation.