Microbial metabolism of chlorosalicylates: accelerated evolution by natural genetic exchange.

Methylsalicylate-grown cells of Pseudomonas sp. WR401 cometabolized 3-, 4- and 5-substituted halosalicylates to the corresponding halocatechols. Further degradation was unproductive due to the presence of high levels of catechol 2,3-dioxygenase. This strain acquired the ability to utilize 3-chlorobenzoate following acquisition of genes from Pseudomonas sp. B13 which are necessary for the assimilation of chlorocatechols. This derivative (WR4011) was unable to use 4- or 5-chlorosalicylates. Derivatives able to use these compounds were obtained by plating WR4011 on 5-chlorosalicylate minimal medium; one such derivative was designated WR4016. The acquisition of this property was accompanied by concomitant loss of the methylsalicylate phenotype. During growth on 4- or 5-chlorosalicylate the typical enzymes of chlorocatechol assimilation were detected in cell free extracts, whereas catechol 2,3-dioxygenase activity was not induced. Repeated subcultivation of WR4016 in the presence of 3-chlorosalicylate produced variants (WR4016-1) which grew on all three isomers.