Parameters of growth and substrate consumption by plasmid-harbouring Pseudomonas putida strains catabolizing naphthalene via different biochemical pathways under batch cultivation on salicylate were estimated. The values of a specific growth rate, mu, and the yield coefficient, Y, for natural isolates with the functioning genes of the ortho-pathway and silent genes of meta cleavage of catechol oxidation were less than those for isogenous strains with the functioning genes of the meta-pathway. All strains under study with functioning genes of the meta-pathway were shown to possess the activities of the enzymes both of ortho- and meta pathway of catechol oxidation: catechol-1,2-dioxygenase and catechol-2,3-dioxygenase. The comparison of the functioning of the genes of the ortho- and meta-pathways was carried out in an isogenous host background. An approach to estimate the efficiency of the biodegradation process using the kinetics of microbial growth and substrate consumption under batch cultivation was proposed. (C) 2000 Elsevier Science Ltd. All rights reserved.