The rapid rise of antimicrobial resistance (AMR) and limited effective treatments in aquaculture demand novel, eco-friendly alternatives. In this study, a red pigment-producing Serratia marcescens strain (IFSMLMEK1) was isolated from the freshwater bivalve Lamellidens marginalis. The extracted pigment, prodigiosin, was characterised using UV-Vis and FTIR spectroscopy.
Functional bioassays demonstrated significant antibacterial activity against major fish pathogens, including Aeromonas hydrophila, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. Strong antibiofilm activity was observed, particularly against high biofilm-producing Pseudomonas aeruginosa, with dose-dependent inhibition.
Importantly, this is the first report of prodigiosin’s antifungal activity against aquatic oomycete pathogens Saprolegnia parasitica and Aphanomyces invadans, known for causing high mortality in freshwater fish species. Antioxidant assays further indicated the potential of prodigiosin to mitigate oxidative stress in aquaculture settings. Whole-genome analysis confirmed the presence of a complete prodigiosin biosynthetic gene cluster with 100% similarity to known references.
In silico molecular docking revealed stable binding of prodigiosin with key extended-spectrum β-lactamase (ESBL) enzymes TEM, SHV, and CTX-M, highlighting its potential as a β-lactamase inhibitor. Moreover, this study identifies prodigiosin as a promising natural compound for controlling fish pathogens and combating AMR in aquaculture.