Nitrate-dependent salicylate degradation by the denitrifying Pseudomonas butanovora was investigated and the molar ratio of the cometabolism under anaerobic circumstances was determined. The bacterium was able to utilize salicylate as an electron donor for the reduction of nitrate. Salicylate was eliminated via catechol, which is degraded by means of catechol 2,3-oxygenases (meta-cleavage), forming 2-hydroxymuconic semialdehyde. The molar ratios of NO3--N:salicylate existing during the experiment accorded well with the assumed 1:1 molar ratio. The tolerances of the growth, the salicylate degradation and the denitrification of P. butanovora to various heavy metal ions were also studied. Although the strain was tolerant to Pb2+ and CU2+ up to 1 mM in complete medium, salicylate utilization took place only up to a concentration of 0.1 mM for both heavy metal ions. Of the heavy metal ions investigated, CD2+ (at a concentration of 0.05mM) displayed the highest inhibitory effect on salicylate degradation by P. butanovora. (C) 2004 Elsevier Ltd. All rights reserved.