Halocidins are isolated from the haemocytes of the tunicate, Halocynthia aurantium (Sea peach). They are dimeric in structures, which are found via a disulphide linkage between cysteines of two different- sized monomers. Halocidins have been shown to have strong antimicrobial activities against a wide variety of pathogenic bacteria and could be ideal candidates as peptide antibiotics against multidrug-resistant bacteria [PMID: 12067731].