Exploring the gut microbiome of Mugil cephalus for antibacterial agents using liquid chromatography

Due to the global challenge of antimicrobial resistance, there is an urgent need for the development of new drugs to combat infections. We hypothesize that bacteria isolated from untapped sources, namely from the gut microbiome of species living in unhygienic environments likely produce antimicrobials. Herein, gut bacteria from Mugil cephalus, an Egyptian fish, were isolated and identified using 16S rDNA amplification and sequencing. The isolated bacterial colonies were cultured in minimal media, and conditioned media containing metabolites were prepared and tested against selected Gram-positive and Gram-negative multiple drug-resistant bacteria using antibacterial assays. The conditioned media were also tested against  human colorectal cancer (HCT-116) cells using lactate dehydrogenase assays. Results from antibacterial analysis revealed that conditioned media from bacterial strain: Bacillus aerophilus and Staphylococcus xylosus showed broad-spectrum antibacterial effects. In particular, the conditioned media from bacterial strain: Bacillus aerophilus significantly inhibited bacterial viability. The conditioned media containing metabolites from bacterial strains produced minimal cytotoxicity toward human cells. Mass spectrometry analysis revealed several antibacterial, antifungal, flavonoids, neurotransmitters, sphingolipids, steroids and anticancer compounds. These results are indicative that bacteria from unique environments are a potential source to isolate molecule(s) with antibacterial properties, albeit in vivo studies are needed to validate these findings.