Nutrients that leach out from roots constitute a major source of food for root-colonizing bacteria. The role of specific nutrients in this interaction is unclear. The aim of the present study was to examine whether colonization ability could be attributed to specific nutrient utilization profiles. Twenty fluorescent pseudomonads were tested for colonization ability of 48-h-old wheat seedlings. Analyses of RFLPs of amplified 165 rRNA gene and of BIOLOG GN2 data demonstrated that colonization ability did not associate with any particular RFLP or metabolic group. The best colonizers PPS96, PSR2, PSR21, good colonizer PSR6 and four of ineffective colonizers were identified through 16S sequence analysis as Pseudomonas reactans. The best and good colonizers distinguished themselves from the less efficient colonizers by specifically utilizing: p-hydroxyphenylacetic acid, bromosuccinic acid, benzoic acid, methyl pyruvate. N-acetyl-D-glucosamine, D-trehalose and adonitol. However, there was no specific sole nutrient utilization profile that predicted excellent root colonization ability of wheat, since the best colonizers did not have identical profiles. This work indicates that strains of P. reactans are present in the rhizosphere of oil seed rape and wheat and that some of them are effective colonizers of wheat roots.