Cloning and expression of the bacteriophage-derived endolysin against Aeromonas hydrophila

Abstract Hemorrhagic septicemia disease in striped catfish is caused by Aeromonas hydrophila bacterium. Antibiotics are commonly used to treat this disease, however, due to antibiotic resistance in A. hydrophila , it is necessary to have an alternative antibacterial agent to antibiotics. Endolysins are bacteriophage-encoded peptidoglycan hydrolases that are synthesized at the end of the lytic phage replication cycle, they lyse the host bacterial cell wall and release new bacteriophage virions. In this study, an endolysin (cell wall hydrolase) derived from A. hydrophila phage PVN02 was artificially synthesized, cloned into pET28a(+) and successfully expressed in E. coli BL21 (DE3). The recombinant endolysin, cell wall hydrolase strongly exhibited antimicrobial activity against A. hydrophila with a reduction of 3-log CFU/ml of A. hydrophila after 30 minutes of mixing and further 30 minutes of incubation, the bacterial cells were lysed completely. It should be emphasized that the lytic activity by the recombinant endolysin to A. hydrophila bacteria did not require a pretreatment with an outer-membrane permeabilizer. The results of our study showed a potential of use this recombinant endolysin as a novel antibacterial agent to replace antibiotics in the treatment of hemorrhagic septicemia diseases in striped catfish.