Exogenous acyl homoserine lactones modulate biofilm formation in Pseudomonas aeruginosa PFL‐P1 and enhance phenanthrene degradation

BACKGROUND Quorum sensing (QS) regulates several physiological behaviors in bacteria. Acyl homoserine lactones (AHLs) are self‐synthesized auto‐inducing molecules to form biofilm. Exogenous addition of AHLs can improve the bacterial community structure and biodegradation performance in wastewater treatment systems. However, the role of the QS‐mediated interspecies interaction in phenanthrene degradation has been relatively less explored. There remains a notable research gap in understanding the effect of eavesdropping phenomena on biofilm formation, catabolic gene expression, and polycyclic aromatic hydrocarbon degradation in marine bacteria. RESULTS Two non‐cognate AHLs – N ‐hexanoyl‐ dl ‐homoserine lactone (C6‐HSL) and N ‐3‐oxo‐octanoyl‐ l ‐homoserine lactone (3OC8‐HSL) – showed affinity for LasR and RhlR QS systems in a marine bacterium, Pseudomonas aeruginosa PFL‐P1. Exogenous supplementation of AHLs improved the specific biofilm formation (SBF) index, cell surface hydrophobicity, cell auto‐aggregation, and motility. Further, the phenanthrene degradation potential of the organism increased from 85.18% to 93.82% in the presence of C6‐HSL and 96.59% in the presence of 3OC8‐HSL within 5 days. The biofilm‐associated extracellular polymeric substances (EPS) showed high emulsification activity towards several hydrocarbons. The high binding constant (4.42 L mol −1 ) and binding site number (1.38), indicating binding efficiency, suggested a strong interaction between EPS and phenanthrene. The exogenous addition of AHLs upregulated the expression of lasI , rhlI , and pslB . The phenanthrene catabolic gene, nahAc , was upregulated up to 3.07‐fold ( P < 0.01) in the presence of C6‐HSL and up to 4.7‐fold in the presence of 3OC8‐HSL ( P < 0.0001). CONCLUSION These findings suggest that QS‐mediated enhancement of pollutant biodegradation is facilitated by improved biofilm formation and catabolic gene expression.