In this proposal, experiments are outlined to investigate genetic recombination in Vibrio cholerae. Emphasis will be placed on the nature of fertility elements in donor populations, particularly those which may facilitate the isolation of Hfr-type donors. Intergeneric transfer of Resistance factors and their interaction with resident genetic elements of V. cholerae will be further investigated. The genetic basis for toxin production will be studied, particularly in relation to possible bacteriophage involvement in this process.