A truncated peptide Spgillcin derived from mud crab exerting multiple antibacterial activities.

Antimicrobial peptides (AMPs) may be the most promising substitute for antibiotics due to their effective bactericidal activity and multiple antimicrobial modes against pathogenic bacteria. In this study, a new functional gene named was identified in , which encoded 216 amino acids of mature peptide. , Spgillcin was dominantly expressed in the gills of male and female crabs, offering the highest expression level among all tested organs or tissues. The expression pattern of Spgillcin was significantly altered when challenged by , indicating a positive immune response. , a functional truncated peptide Spgillcin derived from the amino acid sequence of Spgillcin was synthesized and showed a broad-spectrum and potent antibacterial activity against several bacterial strains, including the clinical isolates of multidrug-resistant (MDR) strains, with a range of minimum inhibitory concentrations from 1.5 to 48 μM. Spgillcin also showed rapid bactericidal kinetics for and but did not display any cytotoxicity to mammalian cells and maintained its antimicrobial activity in different conditions. Mechanistic studies indicated that Spgillcin was mainly involved in the disruption of cell membrane integrity where the membrane components lipoteichoic acid and lipopolysaccharide could significantly inhibit the antimicrobial activity in a dose-dependent manner. In addition, Spgillcin could change the membrane permeability and cause the accumulation of intracellular reactive oxygen species. No resistance was generated to Spgillcin when the clinical isolates of methicillin-resistant and MDR were treated with Spgillcin and then subjected to a long term of continuous culturing for 50 days. In addition, Spgillcin exerted a strong anti-biofilm activity by inhibiting biofilm formation and was also effective at killing extracellular in the cultural supernatant of RAW 264.7 cells. Taken together, Spgillcin has strong potential as a substitute for antibiotics in future aquaculture and medical applications.