Degradation of p-chlorotoluene by a mutant of Pseudomonas sp. strain JS6.
Pseudomonas sp. strain JS6 grows on chlorobenzene, p-dichlorobenzene, or toluene as a sole source of carbon and energy. It does not grow on p-chlorotoluene (p-CT). Growth on glucose in the presence of p-CT resulted in the accumulation of 4-chloro-2,3-dihydroxy-1-methylbenzene (3-chloro-6-methylcatechol), 4-chloro-2,3-dihydroxy-1-methylcyclohexa-4,6-diene (p-CT dihydrodiol), and 2-methyl-4-carboxymethylenebut-2-en-4-olide (2-methyl dienelactone). Strain JS21, a spontaneous mutant capable of growth on p-CT, was isolated from cultures of strain JS6 after extended exposure to p-CT. In addition to growing on p-CT, JS21 grew on all of the substrates that supported growth of the parent strain, including p-dichlorobenzene, chlorobenzene, benzene, toluene, benzoate, p-hydroxybenzoate, phenol, and ethylbenzene. The pathway for degradation of p-CT by JS21 was investigated by respirometry, isolation of intermediates, and assay of enzymes in cell extracts. p-CT was converted to 3-chloro-6-methylcatechol by dioxygenase and dihydrodiol dehydrogenase enzymes. 3-Chloro-6-methylcatechol underwent ortho ring cleavage catalyzed by a catechol 1,2-dioxygenase to form 2-chloro-5-methyl-cis,cis-muconate, which was converted to 2-methyl dienelactone. A dienelactone hydrolase converted 2-methyl dienelactone to 2-methylmaleylacetic acid. Preliminary results indicate that a change in wild-type induction patterns allows JS21 to grow on p-CT.
Haigler
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BE
Air Force Engineering and Services Center, Tyndall Air Force Base, Florida 32403.
Spain
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JC
D001711:Biotransformation; D013058:Mass Spectrometry; D009154:Mutation; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011549:Pseudomonas / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet