Effect of synthetic N-acylhomoserine lactones on cell–cell interactions in marine Pseudomonas and biofilm mediated degradation of polycyclic aromatic hydrocarbons

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Effect of exogenous N-acyl homoserine lactones (AHLs) on biofilm growth, cell surface hydrophobicity, auto-aggregation and polycyclic aromatic hydrocarbons (PAHs) degradation potential of two marine Pseudomonas isolates (Pseudomonas pseudoalcaligenes NP103 and Pseudomonas aeruginosa N6P6) were evaluated in the present study. Increased biofilm growth, auto-aggregation and swarming motility was observed in the presence of exogenous AHLs (3OC8-HSL and 3OC12-HSL) resulting in enhanced phenanthrene and pyrene degradation. P. pseudoalcaligenes NP103 biofilm was able to degrade up to 79% of phenanthrene and 49% pyrene in 7d whereas 85.6% phenanthrene and 47.56% pyrene degradation was achieved using P. aeruginosa N6P6 biofilm. 3OC8-HSL significantly (P<0.05; Tukey’s HSD test) potentiated the phenanthrene and pyrene degradation by P. pseudoalcaligenes NP103 biofilm (89% and 65.5%), whereas the phenanthrene and pyrene degradation potential of P. aeruginosa N6P6 biofilm increased significantly (P<0.05; Tukey’s HSD test) in presence of 3OC12-HSL (97.4% and 54.39%). Furthermore, the degradation achieved by both the isolates in presence of tannic acid, a quorum sensing inhibitor (QSI), was highest in presence of 3OC12-HSL suggesting the most pronounced effect of long chain AHL in degradation of phenanthrene and pyrene. Both the isolates followed catechol pathway for PAHs degradation. The findings suggest that AHL can significantly affect the biodegradation performance specifically when bacteria are present in abundant numbers in biofilms.