Background
The skin mucus layer of fish is endowed with biologics that offer a first line of immune defense against pathogens. This study evaluated the antibacterial activity of extracts from skin mucus of two fresh water fish; Protopterus annectens (African lungfish) and Claris griepinus (African catfish).
Method
A 10% acetic acid extracts of the 24 P. annectens and 24 C. griepinus sourced from Lake Victoria, Albert and Kyoga were ultra-filtered using 5 kDa 5kDa molecular weight cut-off ultrafiltration membrane. The antibacterial activity was later determined using Agar Well Diffusion method utilizing Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922). Later, the profiles of the extract was determined using a 15% Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE).
Results
Results indicate that extractive yield was influenced by Lake (F2,18=528.65, p<0.05), fish species (F1,18=88.20, p<0.05) and the interaction between the two factors (F2,18=49.65, p<0.05). P. annectens produced higher yield (29.89±0.35 %, p<0.05) compared to C. griepinus (25.22±0.35 %); concentration 7.05±0.33 µg/mL). Lake Kyoga fish gave the highest peptide yield (44.67±0.61 %, p<0.05). All the peptide extracts studied exhibited antimicrobial activity on E. coli and S. aureus. However, peptides from C. griepinus were more active on both E. coli (Zone of inhibition [ZOI], 15.00±0.58 mm, p<0.05) and S. aureus (ZOI, 11.67±0.33 mm, p<0.05) as compared to those from P. annectens (E. coli ZOI, 12.00±0.58 mm; S. aureus ZOI, 11.33±0.33 mm). Generally, E. coli was more susceptible to extracted peptides compared to S. aureus. The most active extract was approximately 4 kDa in molecular weight.
Conclusion & Recommendation
The ?nding of this study points out that skin mucus of P. annectens and C. griepinus are potential sources of antimicrobial peptide candidates, however, further studies are still needed especially to identify the actual peptide-residues responsible for this observed activity.