The PsrA transcriptional regulator is involved in stationary phase induced transcriptional regulation of rpoS and in negative auto-regulation in Pseudomonas aeruginosa. This study was designed to determine whether other loci were regulated by PsrA in P. aeruginosa. Computer search was performed of the PsrA binding motif (G/CAAAC N(2-4) GTTTG/C) against the P. aeruginosa genome sequence. Four of 14 analysed promoters responded to and bound PsrA; (i) divergent promoters controlling PA2952/PA2951 and PA2953, (ii) promoter of PA0506 and (iii) upstream region of PA3571. Promoters PA0506 and PA2952-PA2951 were regulated negatively whereas promoters of PA2953 and PA3571 were regulated positively by PsrA. Two dimensional sodium dodecyl sulphate polyacrylamide gel electrophoresis (2D SDS-PAGE) analysis on total proteins from P. aeruginosa PAO1 and psrA knock-out derivative was also performed resulting in the identification of 11 protein spots which were differentially regulated. These studies have indicated PsrA as a global regulator.