Abstract: The immunized hemolymph was produced from Musca domestica larvae by the inducing of challenging injury and bacteria. The antimicrobial peptide was purified by means of boiled water bath, dialysis and concentration, Tricine-SDS-PAGE preparation, retrieval and renaturation of peptides. The results of amino acids an alysis showed that the molecule weight of the antimicrobial peptide 1 (MDL-1) was 6 200 D. It contained abundant Gly and alkaline amino acids, which had potential activity against Gramnegative bacteria, Escherichia coli. Preparative electrophoresis was an effective way to produce antimicrobial peptides. The anti microbial mechanism of MDL-1 was tentatively studied. The results showed that MDL-1 caused a series of pathological changes on E. coli. MDL-1 was located on the plasma membrane observed with transmission electron microscopy. MDL-1 adhered to bacterial cells by static electricity gravitation in the early stage, and then it was observed that MDL-1 affected on the plasma membrane, disturbed the ordered arrangement of membrane lipid and changed permeability of plasma membrane, with irregular holes appearing in the plasmalemma and cytoplasmic contents of the cells leaking out. Finally, the affected bacteria disintegrated into small fragments and died.

Key words: Musca domestica, Escherichia coli, antimicrobial peptides, purification, antimicrobial activity