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Abstract
Biofilm formation by Pseudomonas aeruginosa has been accepted as an important determinant to its virulence and pathology in clinical settings. It has been reported that quorum sensing (QS) mediated by the rhl and las systems, along with their cognate acyl- HSL autoinducers, play a significant role in the formation of biofilm structures. Further, it has been proposed that caspase-3-like-protease in P. aeruginosa has an essential role in establishment of biofilm formation in the early stages. In this study, we have attempted to demonstrate the interplay between QS genes and recently-identified PA4576 gene, putatively encoding the caspase-3-like-protease. Wild type P. aeruginosa grown in biofilm-inhibitory M9 minimal media was found to express caspase-3-like-protease. Using the mini-Tn5- lux CDABE fusion PAO1_lux_22_A5 and PAO1_lux_81_G7 mutants, comparable or enhanced biofilm formation was observed in PA4576 mutants compared to wildtype. Perplexingly, biofilm formation in both PAO1 and mutants was not found to be enhanced by the addition of exogenous acyl-HSL. Taken together, these data suggest that PA4576 gene may not be responsible for expression of caspase-3-like-protease in P. aeruginosa, or that the protease has weak association with biofilm formation in nutrient limited growth.