Characterization of novel linuron‐mineralizing bacterial consortia enriched from long‐term linuron‐treated agricultural soils

Linuron‐mineralizing cultures were enriched from two linuron‐treated agricultural soils in the presence and absence of a solid support. The cultures contained linuron‐degrading bacteria, which coexisted with bacteria degrading either 3,4‐dichloroaniline (3,4‐DCA) or N,O ‐dimethylhydroxylamine ( N,O ‐DMHA), two common metabolites in the linuron degradation pathway. For one soil, the presence of a solid support enriched for linuron‐degrading strains phylogenetically related to but different from those enriched without support. Most linuron‐degrading consortium members were identified as Variovorax , but a Hydrogenophaga and an Achromobacter strain capable of linuron degradation were also obtained. Several of the linuron‐degrading isolates also degraded 3,4‐DCA. Isolates that degraded 3,4‐DCA but not linuron belonged to the genera Variovorax , Cupriavidus and Afipia. Hyphomicrobium spp. were involved in the metabolism of N,O ‐DMHA. Whereas several isolates degraded linuron independently, more efficient degradation was achieved by combining linuron and 3,4‐DCA‐degraders or by adding casamino acids. These data suggest that (1) linuron degradation is performed by a group of metabolically interacting bacteria rather than by individual strains, (2) there are other genera in addition to Variovorax that degrade linuron beyond 3,4‐DCA, (3) linuron‐degrading consortia of different origins have a similar composition, and (4) interactions between consortium members can be complex and can involve exchange of both metabolites and other nutrients.