QUORUM-SENSING AND SIDEROPHORE BIOSYNTHESIS IN PSEUDOMONAS-AERUGINOSA- LASR LASI MUTANTS EXHIBIT REDUCED PYOVERDINE BIOSYNTHESIS/

Cell density-dependent gene expression in Pseudomonas aeruginosa is co ntrolled, in part, by the quorum-sensing regulator LasR. lasR null mut ants exhibited a reproducible 2-fold decrease in production of the cat echolate-hydroxamate siderophore pyoverdine during grown under iron-li miting conditions. Similarly, lasI mutants defective in the biosynthes is of the autoinducer PAI-1 also exhibited a 2-fold decrease in pyover dine production which could be largely restored upon addition of exoge nous PAI-1. lasR mutants were not altered with respect to expression o f the pvdD gene involved in the synthesis of the peptide portion of py overdine, indicating that some other pyoverdine biosynthetic gene(s) w ere affected by the LasRI status of the cell. This represents the firs t report of quorum-sensing regulation of siderophore production in bac teria and highlights the fact that cell density, while not an essentia l signal for pyoverdine expression, does enhance production of this si derophore. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.