The aim of this study is to investigate the molecular basis of the transposition and fertility of Tn916. Studies designed to examine structure and function should reveal details of a transposition process hypothesized to be significantly different from that of most other well characterized systems. i.e. transposition of Tn916 may occur by an excision-insertion event. Experiments will also test the hypothesis that Tn916 conjugal transfer actually represents an elaborate transposition event (where donor and recipient replicons are located in different cells) and begin to illuminate the mechanisms(s) by which such an event occurs and is regulated. More specifically we will: 1) construct a physical map of Tn916; 2) sequence the ends of Tn916 and those host sequences surrounding the site of the transposon insertion; 3) determine if Tn916 can transpose in E. coli; 4) isolate transposon excision products which arise in E. coli; 5) examine behavior of Tn916 in Streptococcus sanguis; 6) examine the production of Tn916 specific macromolecules; and 7) isolate and map mutants defective in Tn916 specific functions.