Abstract

Endogenous antimicrobial peptides are exciting candidates as new antibacterial agents due to their broad antimicrobia spectra, highly selective toxicities and the difficulty for bacteria to develop resistance to these peptides. Marine invertebrates, which rely solely on innate immune system for host defense, are the spectacular resources for new antimicrobial compounds. In order to seek for new effective antibiotics, tissue homogenate of Bullacta exarata was treatedwith trypsin, and was isolated following ultrafiltration, gel chromatography and reverse phase high performance liquid chromatography (reverse-phase HPLC). Antibacterial activities of the peptides purified from B. exarata were measured by the agar diffusion test and minimal inhibitory concentration (MIC). Three isolated peptides, BEP-1, BEP-2 and BEP-3, showed activity against Escherichia coli, Staphylococcus aureus and Bacillus subtilis. BEP-1 also showed activity against human pathogen strains (Staphylococcus epidermidis, E. coli and Methecillin-Resistant S. aureus). This research picked out three candidates for new effective antibiotics.

Key words: Bullacta exarata, antimicrobial peptides, isolation and purification, antibacterial activity, minimal inhibitory concentration.