The three ways in which genetic recombination occur in bacteria are:
Tranformation - bacteria are able to take up foreign DNA through their cell
membranes. This foreign DNA most often remains as an extrachromosomal
structure called the plasmid. Sometimes the foreign DNA can integrate into
the bacterial genome.
Transduction - The transfer of small segments of bacterial DNA by viruses.
When viruses invade the bacterial cell, they make use of the bacterial protein
machinery to produce virions. During a process called packaging where
genetic material is packed into the newly formed virus, bits of bacterial
DNA are also included. These new virions then carry the bacterial DNA into
the next cell that they infect.
Conjugation - Also termed sexual reproduction between bacteria containing
an F plasmid (F+) and one that lacks the plasmid (F-). A temporary structure
called the conjugation tube is formed between the two interacting bacteria
and the exchange of genetic material takes place.