The salicylate hydroxylase can convert the salicylate to catechol, and catechol 2,3-dioxygenase catalizes the conversion of catechol to 2-hydroxymuconic semialdehyde. A salicylate hydroxylase gene and a catechol 2,3-dioxygenase have been cloned from chromosomal DNA of P. putida KF715. The two genes have different promoters. An open reading frame with 339 nucleotides preceded by a putative ribosome-binding sequence (GGAGG) was identified in the intergenic sequence between salicylate hydroxylase gene and catechol 2,3-dioxygenase gene of P. putida KF715 and its sequence analyzed. This open reading frame can encode a polypeptide of molecular weight 13 kDa containing 112 amino acids, whose sequence exhibited 87% homology with that of ferredoxin encoded in NAH7 of P. putida PpG7 and significant homology with those of redox components in phenol hydroxylase, benzoate 1,2-dioxygenase, toluate 1,2-dioxygenase, xylene monooxygenase, and toluene 4-monooxygenase.