Deletion of Crotonobetaine Reductase Gene in Escherica coli

This work reports that the construction of a 5.2 kb DNA fragment in which the caiA gene was replaced by kanamycin resistant gene(Km~r), which was then transferred into JM83 and BL21(DE3). The No.4 and 22 strains from BL21(DE3) and JM83 respectively, were proved to be caiA-defective through the experiment of genetic stability, polymerase chain reaction(PCR) and southern blotting; and enzyme assays indicated that strains 4 and 22 have lost their crotonobetaine reductase activities.