To select strains for the bioremediation of Cr(VI)-polluted environments, four highly Cr( VI)resistant bacterial isolates were identified and characterized using both traditional techniques and a novel approach called phenotype microarrays. The isolates were identified as members of Pseudomonas mendocina ( strains 34 and 56) and members of Pseudomonas corrugata ( strains 22 and 28). Results showed that it was possible, by varying the carbon/energy source, to decouple bacterial growth and Cr( VI) reduction, inasmuch as some carbon/energy sources were more effective electron donors for chromate reduction, whereas other sources supported growth but not an effective chromate reduction. The isolates were characterized by a novel high-throughput technique, phenotype microarrays (PM)-Biolog, which can test up to 2000 cellular phenotypes simultaneously. The isolates belonging to P. corrugata had PM profiles different from those of the isolates belonging to P. mendocina. Such differences were related to the capacity of the isolates to resist various chemicals, pH values, and osmolytic substances. With the PM technique a very large amount of information about the fitness of isolates in the presence of different stressors could be obtained.