To test specific mechanisms responsible for control of initiation of sporulation in Bacillus subtilis and for sequential activation of genes during the spore-forming process, we propose to create by recombinant DNA technology a series of cloned chromosomal segments that would be appropriate as templates for in vitro transcription experiments and as probes for determining the rates of transcription of sporulation genes in vivo. Among the specific hypotheses to be tested are: (1) the rates of transcription of individual genes change during the passage from growth to sporulation; (2) glutamine synthetase protein acts as a negative regulator of transcription of some genes subject to catabolite repression and some expressed at the onset of sporulation; and (3) changes in the structure and specificity of RNA polymerase are responsible for bringing about changes in the pattern of RNA synthesis by altering the promoter-site recognition properties of the enzyme.