Antimicrobial activity in the cuticle of the American lobster, Homarus americanus

• Antibacterial activity in lobster cuticle was investigated.
• Cuticle homogenates inhibited the growth of Gram-negative and -positive bacteria.
• The antibacterial activity was due to heat-stable molecules less than 10 kDa.
• MALDI MS revealed peptide peaks at 1.6, 2.8, 4.6, and 5.6 kDa.
• Data suggest the activity is due to antimicrobial peptides present in cuticle.

American lobster, Homarus americanus, continues to be an ecologically and socioeconomically important species despite a severe decline in catches from Southern New England and Long Island Sound (USA) and a high prevalence of epizootic shell disease in these populations. A better understanding of lobster immune defenses remains necessary. Cuticle material collected from Long Island Sound lobsters was found to be active against a broad spectrum of bacteria, including Gram-negative and -positive species. The antimicrobial activity was characterized by boiling, muffling, and size fractioning. Boiling did not significantly reduce activity, while muffling did have a significant effect, suggesting that the active component is organic and heat stable. Size fractioning with 3 and 10 kDa filters did not significantly affect activity. Fast protein liquid chromatography fractions were also tested for antimicrobial activity, and fractions exhibiting protein peaks remained active. MALDI mass spectrometry revealed peptide peaks at 1.6, 2.8, 4.6, and 5.6 kDa. The data presented suggest that one or several antimicrobial peptides contribute to antimicrobial activity present in the American lobster cuticle.