Marine Bacillus safensis DJ1 metabolites disrupt P. aeruginosa virulence: an integrated experimental and network pharmacology and dynamics approach.

Marine bioactive compounds are natural products known for diverse biological activities, including strong anti-quorum sensing (QS) properties. These compounds offer potential for developing antivirulence agents against pathogenic bacteria. Eighty-six bacterial isolates from the coastal region of Gujarat were screened for their ability to inhibit QS and virulence factors in Chromobacterium violaceum MK and Pseudomonas aeruginosa PA14. Isolate DKGJ2E6 (E6) (Bacillus safensis DJ1, identified by 16S rRNA sequencing) showed the strongest QS inhibitory activity and was selected for further analysis. The crude extract of Bacillus safensis DJ1 significantly inhibited key virulence traits in Pseudomonas aeruginosa, drastically reducing pyocyanin production and attenuating pyoverdine and biofilm formation. A similar anti-QS effect was observed in C. violaceum, where violacein production was more than halved (55.06% reduction). The extract also exhibited synergistic anti-virulence activity when combined with ciprofloxacin. Chemical profiling via GC-MS identified bioactive components such as sulfanilamide, indole, phenol, 3-methyl-4-oxo-pentanoic acid, and allantoic acid, which demonstrated potent anti-QS and antibiofilm effects. A network pharmacology approach was employed to predict and assess the molecular mechanisms, identifying core targets and target-pathway modulated by these metabolites. Molecular docking and dynamics demonstrated strong binding affinities of selected compounds towards key targets in Pseudomonas aeruginosa. Together, these findings collectively establish the potential of B. safensis DJ1 metabolites as a significant lead for the development of novel, marine-derived antivirulence therapies against drug-resistant pathogens.