Abstract: Cathelicidins comprise a family of antimicrobial peptides sharing a highly conserved cathelin domain， they play a critical role in the innate immune system of chicken. In order to investigate the antibacterial activity of recombinant Cathelicidins， the putative mature peptide coding fragments of CathL\|1， CathL\|2， CathL\|3 genes were amplified from the plasmid pMD\|CathL containing Cathelicidins cDNA sequences， and then subcloned into pET\|30a（+） plasmid respectively. The recombinant vectors named pET30\|CathL1S， pET30\|CathL2S and pET30\|CathL3S were transformed into the competent cell of E.coli Rosetta（DE3）. The positive clones were cultured and induced to express target protein by addition of 10 mmol·L-1 IPTG in LB. SDS\|PAGE and Western blot analysis demonstrated that cathelicidins genes were expressed in the form of fusion protein， and the apparent molecular weight of expression products were 70 kD， 80 kD， 75 kD， respectively. The recombinant Cathelicidins were able to kill both Gram negative bacteria and Gram positive bacteria by the means of agar well diffusion assay （AWDA）， especially for the antibiotic\|resistant strains.

Key words: Silkie, Cathelicidins antimicrobial peptide, fusion expression, purification, antibacterial activity