The effect of a cell-to-cell communication molecule, Pseudomonas quinolone signal (PQS), produced by P. aeruginosa on other bacterial species.

One of the most important factors in the development of a bacterial community is whether the bacteria are able to grow in that habitat. The regulation of bacterial growth is generally studied in relation to physicochemical conditions, however, how bacterial communities regulate themselves remains unclear. In our previous study, it was demonstrated that a cell-to-cell communication molecule, 2-heptyl-3-hydroxy-4-quinolone, referred to as the Pseudomonas quinolone signal (PQS), affects respiring-activity in Pseudomonas aeruginosa without requiring its cognate receptor PqsR. The results suggested that PQS may affect other bacterial species, which was further examined in this study. PQS repressed the growth of several species including both Gram-negative and Gram-positive bacteria. In most cases, this effect differed from the bacteriostatic or bacteriolytic actions of antibiotics. The growth repression by PQS was inhibited when iron was added to the medium, indicating iron-chelating activity to be involved. In addition, PQS affected oxygen consumption in some species tested, and may have other underlying effects. Thus, this cell-to-cell communication molecule may influence the development of bacterial communities by regulating bacterial growth, and physicochemical factors such as iron would be important in determining its effect.