Bacteria exchange genetic information with one another using horizontal routes of conjugation, phage transduction, and natural transformation. In conjugation (i), donor and recipient cells are physically connected through the formation of a transient bridge (pilus), and DNA copied from one cell flows to the next. Cells can transfer plasmid DNA, integrative conjugative elements (chromosomally encoded gene clusters with autonomous conjugation machinery), or chromosomal DNA through high frequency of recombination mediated by F plasmids. Phages or bacterial viruses serve as vehicles for bacterial gene transfer (ii) by transducing DNA from one host cell to another. During lysis, phages can inadvertently package bacterial DNA, either randomly incorporating pieces of the bacterial genome into phage particles (generalized transduction) or taking up bacterial DNA positioned near the phage integration site (specialized transduction). Upon lysogenic infection of a new host, genetic material can be maintained in the genome by homologous recombination or site-specific integration. In the process of natural transformation (iii), certain bacterial species can take up free DNA from the environment using membrane protein complexes. While some species exhibit competence during phases of their life cycle, others respond to extracellular cues to initiate DNA uptake.