Two different “quorum sensing” (QS) systems were defined in Pseudomonas aeruginosa: rhl and las. The signal molecules of the las (3- oxo-C12-HSL) and rhl (C4- HSL) systems are visualized by two different reporter strains ( Choromobacterium violaceum for rhl , and Agrobacterium tumefaciens for las).

In order to show the existence of QS systems, micro AHL, thin layer choromotograpy, zymography, and diffusion methods are used.

In this study, QS responses of two clinical isolates and standart P. aeruginosa strain (ATCC 27853) were compared by diffusion and micro AHL methods. As a result, micro AHL method was much easier to apply and to visualize, and was easier to repeat when compared to diffusion method. This may be the reason for widely applying this method while showing QS.