OBJECTIVES: The overall objectives of this ongoing investigation are elucidation of fundamental biological mechanisms involved in the formation, propagation, and genetic control of antibiotic resistance factors and other plasmids -- and modification of these processes as a result of the information obtained. Objectives Set During the Current Year: (1) Continued study of transposable genetic elements involved in the structural evolution of bacterial plasmids, (2) investigation of expression of inserted fragments of foreign DNA introduced into plasmid cloning vehicles, (3) construction of Streptomyces-E. coli and Bacillus-E. coli hybrid plasmids and development of a cloning system in Streptomyces using transformation or cell fusion techniques, and (4) investigation of site-specific genetic recombination in vivo mediated by "restriction" endonucleases and other site-specific recombination systems.