The defense system of plants and animals includes , inter alia, peptides with antimicrobial or antifungal properties . Despite the large variation in terms of occurrence and sequence of amino acids, most of them are cationic amphipathic molecules with structure . Due to the spatial structure can be distinguished among them several main groups: 1 Linear , forming a- helices ; 2 Antiparallel b sheets stabilized intramolecular disulfide bonds ; 3 A + b structure stabilized by disulfide bridges ; 4 Cyclic structures ; 5 Linear sequence enriched in certain amino acids . The activity of the peptides selectively directed against microorganisms include bacteria, fungi, protozoa , some , or even cancer cells. In view of the increasing resistance of microorganisms to conventional antibiotics, antimicrobial peptides can be a rich source of the future clinical use of antibiotics .