Exploration of potentiality of algal extracts as antibacterial, antibiofilm agent and down-regulation of quorum sensing against Pseudomonas aeruginosa and Escherichia coli

Antimicrobial resistance is an ever-growing global concern for public health with no immediate solution. In the study, the antimicrobial and antibiofilm activities of two algal extracts, Arthrospira platensis and Macrocystis pyrifera, were evaluated against two biofilm producers, Pseudomonas aeruginosa and Escherichia coli. The extracts possessed notable antimicrobial activity, showing the zone of inhibition from a range of 12 mm to 35 mm. They exhibited potent antioxidant activity against DPPH and H₂O₂ radicals. The algal extracts showed a biofilm reduction ability of more than 90 % and became an effective anti-quorum-sensing agent by inhibiting the AHL and elastase activity. MTT assay showed eradication of biofilms by 91.49 % in P. aeruginosa and 91.30 % in E. coli. The algae are also able to restrict the bacterial movement, as observed through the motility assay. Scanning electron microscopy revealed severe structural changes regarding biofilm formation. Gel electrophoresis showed a significant decrease in the nucleic acid content. Further, spectroscopic analysis results confirm a decrease in nucleic acid up to 90 %. In silico data, particularly the drug ability, binding energies, and molecular interactions of the chemicals from the algal sources with the targeted proteins of the bacteria under study, have corroborated the experimental findings. Through docking investigations and molecular dynamics simulations revealed eicosapentaenoic acid as the best inhibitory compound with the binding score of −11.2 kcal/mol. In conclusion, the study demonstrates the potential of algal extracts as antibacterial and antibiofilm agents against drug-resistant diseases.