title: Evolutions of microbial degradation pathways for parent xenobiotic and for its metabolites follow different schemes.
abstract: OBJECTIVE
  The pathways used by microorganisms for the metabolism of every xenobiotic substrate are specific. The catabolism of a xenobiotic goes through a series of intermediate steps and lower intermediates (metabolites) appear in sequence. The structure of the metabolites can be similar to the parents due to kinship. The purposes of this study were to examine if the degradation pathways that were developed for a parent xenobiotic are effective to degrade the parent's lower metabolites, and if the reverse is true.
  
  
  METHODS
  The xenobiotic substrates, 2,4-dichlorophenoxyacetic acid (2,4-D, the parent xenobiotic) and its metabolite 2,4-dichlorophenol (2,4-DCP), were independently subjected to acclimation and degradation tests by the biomasses of mixed-culture activated sludge and a pure culture of Arthrobacter sp.
  
  
  RESULTS
  Activated sludge and Arthrobacter sp. that were acclimated to 2,4-D effectively degraded 2,4-D and the lower metabolites of 2,4-D, typically 2,4-DCP. During the degradation of 2,4-D, accumulations of the lower metabolites of 2,4-D were not found. The degradation pathways acquired from acclimation to 2,4-D are effective for all the metabolites of 2,4-D. However, pathways acquired from acclimation to 2,4-DCP are not effective in the degradation of the parent 2,4-D.
  
  
  CONCLUSIONS
  Microorganisms acclimated to 2,4-D evolve their degradation pathways by a scheme that is different from the scheme the microorganisms employ when they are acclimated to the metabolites of 2,4-D.
authors.affiliation: Department of Environmental Engineering, Da-Yeh University, No. 168, University Rd., Dacun, Changhua, Taiwan 51591, Republic of China. chong@mail.dyu.edu.tw
authors.forename: Nyuk-Min
authors.initials: NM
authors.lastname: Chong
authors.forename: Chun-Shuo
authors.initials: CS
authors.lastname: Chang
authors.forename: Shiu-Ching
authors.initials: SC
authors.lastname: Tsai
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D000064:Acclimatization; D001173:Arthrobacter / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002733:Chlorophenols / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D012722:Sewage / Q000382:microbiology; D015262:Xenobiotics / Q000378:metabolism*
chemical_list: D002733:Chlorophenols; D012722:Sewage; D015262:Xenobiotics; D015084:2,4-Dichlorophenoxyacetic Acid; C004762:2,4-dichlorophenol