 In bacterial conjugation , where DNA is transferred between bacteria through direct cell @-@ to @-@ cell contact , homologous recombination helps integrate foreign DNA into the host genome via the RecBCD pathway . The RecBCD enzyme promotes recombination after DNA is converted from single @-@ strand DNA – in which form it originally enters the bacterium – to double @-@ strand DNA during replication . The RecBCD pathway is also essential for the final phase of transduction , a type of horizontal gene transfer in which DNA is transferred from one bacterium to another by a virus . Foreign , bacterial DNA is sometimes <unk> in the capsid head of bacteriophage virus particles as DNA is packaged into new bacteriophages during viral replication . When these new bacteriophages infect other bacteria , DNA from the previous host bacterium is injected into the new bacterial host as double @-@ strand DNA . The RecBCD enzyme then incorporates this double @-@ strand DNA into the genome of the new bacterial host . 
