This document summarizes the discovery and mechanisms of bacterial conjugation. Joshua Lederberg and Edward Tatum discovered conjugation in 1946 while experimenting with E. coli strains. They found that when two auxotrophic strains were mixed on minimal media, prototrophs grew, indicating genetic transfer. Bernard Davis provided evidence for direct cell-to-cell contact in 1950 using a filter to separate strains. Conjugation involves an F plasmid transferring via pili from an F+ donor cell to an F- recipient. This can involve the whole chromosome in Hfr cells. The mechanisms of F+, F-, and Hfr conjugation and their genetic crosses are then described.