The adaptive response of bacteria to stress is variable owing to the effects of various environmental factors and the time of exposure to stress conditions. We have studied the morphological and biochemical characters of resuscitated Pseudomonas aeruginosa ATCC 27853 that had been incubated for 14 years in natural sterilized seawater. The resuscitated cells were identified by PCR analysis of the internal transcribed spacer region. The biochemical profile of the resuscitated cells was partially inactive according to the API-20NE system. The cells had lost the ability to reduce nitrate and hydrolyse gelatin but acquired urease activity. In addition, the atomic force micrographs showed a reduction in cell size and an evolution to coccoid shapes. After incubation in a rich medium, the resuscitated cells regained their initial biochemical characters and their original rod shape. The differential display “DDRT-PCR” technique was used to determine the effects of stress on gene expression in this P. aeruginosa strain. The genes algU and iscR were successfully identified in stressed P. aeruginosa ATCC 27853 as two differentially expressed gene fragments. Our results demonstrate that the DDRT-PCR technique can be a useful tool in gene expression analysis studies looking at the stress response in P. aeruginosa.