Changes in the pattern of protein synthesis during the first three hours of sporulation in Bacillus subtilis

Abstract

Cultures were labelled with L-[35S]methionine for 5 min periods immediately after resuspension in sporulation medium (t0) or at hourly intervals thereafter (t1, t2 or t3). Cells were harvested and lysed very rapidly at low temperature in the presence of inhibitors of protease, cell extracts were subjected to high-resolution two-dimensional gel electrophoresis, and radioactive proteins were revealed by fluorography. Comparisons of fluorograms from wild-type cells labelled at various times after resuspension showed that 35 proteins were synthesized at t1 that were not seen at t0, ten at t2 that were not seen at t1, and seven at t3 that were not seen at t2. Conversely, nine proteins ceased to be synthesized in the first hour of resuspension, eight in the second hour and five in the third hour. Experiments with the same protocol were done with cells of a strain carrying spo-43, a mutation that blocks sporulation at a very early stage. The results show that the mutation prevents about two-thirds of the total number of changes that occur in the wild-type in the first hour, about one-third of those that occur in the second hour, but only two out of 12 of those that occur in the third hour.