A genetically engineered strain of Pseudomonas putida U designed for the identification of new therapeutic herbicides has been obtained. In this bacterium, deletion of the homogentisate gene cluster (hmgRABC) confers upon this mutant huge biotechnological possibilities since it can be used: (i) as a target for testing new specific herbicides (p-hydroxy-phenylpyruvate dioxygenase inhibitors); (ii) to identify new therapeutic drugs-effective in the treatment of alkaptonuria and other related tyrosinemia - and (iii) as a source of homogentisic acid in a plant-bacterium association.