Gene disruption methods are useful to construct bacteria lacking a specific gene especially when a gene’s function is unknown. In the 1980s, complementation techniques were used as the first step in cloning a gene. With the advances made through genome projects, gene identification and cloning have allowed easier construction of deficient bacterial strains with cloned genes. In this report, I describe three methods of disrupting specific genes on chromosomes in a strain of interest, namely linear transformation, preligation and the ‘one-step’ method. Moreover, several genetic techniques which are necessary for conducting these methods are also reviewed.