Temporal dissociation of late events in Bacillus subtilis sporulation from expression of genes that determine them

Abstract

During sporulation in replacement medium, resistance to toluene to heating at 65 degrees C, to lysozyme, and to heating at 80 degrees C appeared in sequence between 4 and 8 h after the induction of sporulation (i.e., between t4 and t8). The addition of sufficient chloramphenicol at t4.5 to prevent protein synthesis nevertheless allowed the emergence of all of these types of resistance except lysozyme resistance. The numbers of spores with these types of resistance (lysozyme resistance again excepted) increased about fourfold when phenylmethylsulfonyl fluoride (an inhibitor of serine protease activity) was also present. Thus, the observed increases in resistance in the 2 h after the addition of chloramphenicol resulted from the utilization of preformed protein elements. Dipicolinate did not seem to be a determining factor in the development of any of these forms of resistance. Electron micrographs showed that inhibition of protein synthesis did not prevent deposition of the outer layers of the spores. Lysozyme resistance developed differently; synthesis of the relevant proteins began later (t5), and continued synthesis was necessary up to t8. Some processing of proteins made earlier was a prerequisite for lysozyme resistance. Therefore, it appears that from the viewpoint of regulation, the expression of the genes and the production of the proteins for resistance to toluene, heating at 65 degrees C, and heating at 80 degrees C are all stage IV sporulation events, although the resistance properties themselves appear only during stages V and VI. Lysozyme resistance is the only real late event among those examined. The germination characteristics of the spores, which are also late events, are discussed in this context, as they too are dependent on proteins that are synthesized much earlier.