Mucus-Associated Bacteria from Two Freshwater Fish Species (Monopterus albus and Oreochromis niloticus) and Their Antibacterial Activities
DOI:
https://doi.org/10.24191/bioenv.v4i3.170Keywords:
Fish mucus , Antimicrobial activity , Freshwater microbiota , Asian swamp eel , Nile tilapiaAbstract
The increasing prevalence of antibiotic-resistant pathogens has intensified the search for antimicrobial agents from natural sources. This study isolated and characterised bacteria associated with the skin mucus of Monopterus albus (Asian swamp eel) and Oreochromis niloticus (Nile tilapia) and evaluated their antibacterial potential. Six bacterial isolates were obtained from three individuals of each fish species. The isolates were characterised using colony morphology, Gram staining, motility, starch and gelatine hydrolysis, and methyl red and Voges–Proskauer tests. Antibacterial activity was initially screened using the cross-streak method, followed by disc diffusion assays of co-culture-derived supernatants against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. Two isolates exhibited the most promising activity. The supernatant from the co-culture involving Isolate 1 showed inhibition against E. coli, whereas that involving Isolate 2 inhibited S. aureus. Both isolates were characterised as Gram-negative, rod-shaped bacteria. These findings identify freshwater fish mucus as a source of bacterial isolates warranting further investigation for antibacterial activity. However, because the tested supernatants originated from co-cultures, the inhibitory effects could not be attributed solely to the mucus-associated isolates. Further studies should establish isolate identity, determine the origin of the inhibitory activity, and characterise the active compounds.
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