title: Carbon catabolite repression and cell dispersal affect degradation of the xenobiotic compound 3,4-dichloroaniline in Comamonas testosteroni WDL7 biofilms.
abstract: Organic pollutant degrading biofilms in natural ecosystems and water treatment systems are often exposed to other carbon sources in addition to the pollutant. The availability of auxiliary carbon sources can lead to surplus biomass growth, changes in biofilm structure and carbon catabolite repression (CCR) which together will affect pollutant degradation rate and efficiency of the system. To understand the interplay between these processes, continuous biofilms of the 3,4-dichloroaniline (3,4-DCA) degrading Comamonas testosteroni WDL7-RFP were grown in single- and dual-substrate conditions with 3,4-DCA and/or citrate and reciprocal effects on 3,4-DCA/citrate degradation, biofilm biomass and biofilm structure were examined. The main mechanism affecting 3,4-DCA degradation in biofilms in dual-substrate conditions was citrate-mediated CCR as reflected by a decrease in specific 3,4-DCA degrading activity. Growth on citrate partially compensated for the lowered specific 3,4-DCA degradation activity under dual substrate conditions but not to the extent expected from growth observed under single-substrate conditions with citrate. This was explained by higher residual 3,4-DCA concentrations in the presence of citrate that increased cell dispersal in the biofilms. Our results show hampered pollutant removal in biofilms due to a complex interplay of auxiliary organic C source utilization for growth affecting the specific pollutant degradation rate and changes in cell physiology due to increased exposure to the pollutant as a result of lowered pollutant degradation rates.
authors.affiliation: KU Leuven, Department of Earth and Environmental Sciences, Division of Soil and Water Management, 3001 Leuven, Belgium.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Horemans
authors.affiliation: KU Leuven, Department of Earth and Environmental Sciences, Division of Soil and Water Management, 3001 Leuven, Belgium.
authors.forename: Philip
authors.initials: P
authors.lastname: Breugelmans
authors.affiliation: KU Leuven, Molecular Imaging and Photonics, Department of Chemistry, 3001 Leuven, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Hofkens
authors.affiliation: KU Leuven, Department of Earth and Environmental Sciences, Division of Soil and Water Management, 3001 Leuven, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Springael
mesh_terms: D000814:Aniline Compounds / Q000378:metabolism*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D057465:Catabolite Repression / Q000187:drug effects; D020604:Comamonas testosteroni / Q000502:physiology*; D017753:Ecosystem
chemical_list: D000814:Aniline Compounds; C014464:3,4-dichloroaniline; D002244:Carbon
keywords: 3,4-dichloroaniline; Comamonadeceae; bacterial biofilms; biodegradation; carbon catabolite repression