The swarming motility is considered

The swarming motility is considered a crucial feature for the surfaceattachment during the early steps of biofilm formation as well as forbiofilm maturation [55,56]. In fact, previous studies showed that P.aeruginosa mutants with altered swarming motility had impaired biofilm formation [57,58], whereas swarming strains of P. aeruginosa showhigher resistance to antibiotics than swimming cells [59]. The resultsreported above were obtained with P. aeruginosa ATCC27853, becauseoptimized culture medium composition and time for read-outs havealready been described in the literature and are currently in use in ourlab [60–62]. Contrastingly, optimal conditions for biofilm andswarming motility assays have been reported for PA14 [37] and areroutinely used in our groups. For that reason, the swarming motility ofP. aeruginosa PA14 was evaluated by spotting cultures on swarmingagar plates containing or not calycopterin and measuring the swarmingarea of the colonies. Swarming inhibition, evidenced by a smaller dispersion as compared to the control, were observed on plates containing140 μM of calycopterin. The effect of this molecule on swarming motility was not significant at concentrations at 70 μM or below (Fig. 3),whereas at 140 μM there is a significant reduction (38.4%) of P. aeruginosa motility