Alcaligenes xylosoxidans subspecies denitrificans JH1 was enriched with 2-c
hlorophenol from a mixed culture degrading different chloro- and methylphen
ols. The strain used all monochloro- and monomethylphenols apart from 2-met
hylphenol as sole source of energy and carbon with stoichiometric release o
f chloride. 4-Chlorophenol was mineralized up to a concentration of 1.3 mM.
Degradation of mixtures of monochloro- and monomethylphenols occurred at l
east partially except for the mixture of 2-chlorophenol and 3-methylphenol.
Depending upon the growth substrates used, enzymes of the ortho and/or met
a cleavage pathway catalysed the degradation of the phenols. The transforma
tion of chlorophenols was concluded to occur exclusively via the ortho clea
vage pathway because no chlorocatechol 2,3-dioxygenase activity was found i
n chlorophenol-grown cells. Degradation of 4-methylphenol in strain JH1 occ
urred both by the ortho and meta cleavage pathway as indicated by the findi
ng that the ortho- and meta-cleaving dioxygenases were expressed in 4-methy
lphenol-grown cells. Transformation of methylphenols by the ortho cleavage
pathway led to the accumulation of methyllactones as dead-end products. Mix
tures of methyl- and chlorophenols were metabolized mainly by the ortho cle
avage pathway because chlorocatechols formed inactivated the constitutive c
atechol 2,3-dioxygenase which caused channelling of methylphenols into the
ortho cleavage pathway.