Molecular Modifications of the Pseudomonas Quinolone Signal in the Intermicrobial Competition with .

The Pseudomonas quinolone signal (PQS) is an important quorum-sensing molecule for that regulates virulence factors, chelates iron, and is an important factor in interactions with eukaryotes, including fungi and mammalian hosts. It was previously shown to inhibit or boost , depending on the milieu iron concentration. We studied several molecular modifications of the PQS molecule, and their effects on biofilm metabolism and growth in vitro, and the effects of iron supplementation. We found that most molecules inhibited at concentrations similar to that of PQS, but with relatively flat dose-responses, and all were less potent than PQS. The inhibition was reversible by iron, suggesting interference with fungal iron metabolism. Stimulation of was not noted. We conclude that the critical -inhibiting moeities of the PQS molecule were partially, but not completely, interfered with by molecular modifications at several sites on the PQS molecule. The mechanism, as with PQS, appears to relate to fungal iron metabolism.