Bacteriophage SPO1 is chosen as a model system for development. Coordinate in vivo studies and in vitro studies of RNA and DNA-dependent protein synthesis will be directed at understanding how blocks of genes are regulated in transcription. Ultimately the system can be used to compare the alteration in transcription machinery underlying two different developmental processes, sporulation and virus infection, in the same bacterium. A biochemical-genetic approach will be used, in which viral mutants will be employed to determine gene functions. Specific mechanisms under study will be regulation of host cell metabolic activity, repression of early phage genes, and the positive control mechanism determining initiation at new viral promotors.