Evaluation of the Antimicrobial Efficacy of Epidermal Mucus Extract from Air-Breathing Fish (Channa punctatus) and Identification of the Peptides Serving as Immune Components

Fish and other members of aquatic habitats are in constant contact with the microbes that trigger their immune system to produce immune components along with mucus. Compounds like lysozymes, proteases, lectins and peroxidase were reported in many studies. The study aims to identify and characterize the immune components present in the epidermal mucus of Channa punctatus. For this, antibacterial and antifungal efficacy was tested first using agar well diffusion assay and MIC was measured. Maximum activity against bacteria's E. coli, S. aureus and Fungus H. gramineum was observed. FESEM analysis was performed to reveal the mechanism of the antimicrobial activity. Physico-chemical stability of mucus was also checked by exposing to various parameters such as (temperature, pH, proteases and surfactants). Precipitated proteins of mucus were separated using 12% SDS-PAGE assay. The band was digested using trypsin digestion and digested peptides were subjected to LCMSMS analysis for identification and on characterization using MASCOT servers 2 proteins (Hemoglobin subunit beta-A-globin chain and Galactose specific lectins nattectin) with number of fragmented unique peptides were obtained. Insilico predictions of antibacterial, antifungal, antiviral and anticancerous properties of peptides were also determined to support the role of mucus in microbial defense and therapeutical applications using the servers AMPfun, DBAASP and APD3.