Antifungal peptides in marine invertebrates

A majority of terrestrial and marine organisms use to fend off a wide range of microorganisms, including bacteria and fungi by employing “antimicrobial peptides (AMPs)” that are ribosomally synthesized from proteinogenic amino acids. AMPs are a primary component of innate immune mechanisms in marine invertebrates. In contrast, marine sponges seem to contain no AMPs, but often contain nonribosomal peptides consisting of unusual amino acids that exhibit potent cytotoxic and antifungal activity. Most of these peptides are considered to be of symbiotic bacterial origin. Similarly opisthobranch molluscs sequester unusual bioactive nonribosomal peptides from their prey organisms, cyanobacteria. However, roles of these peptides are unknown.