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Abstract:

The main source of carbon, energy and nutrients for heterotrophic microbial biofilm communities is the naturally available dissolved organic matter (DOM). Its quality and quantity influences enzymatic activity, growth and species composition. Research on DOM affecting specific functionality such as pesticide degradation is scarce. As a model community, a triple-species microbial biofilm which metabolically cooperates in degrading the herbicide linuron was studied in continuously fed flow chamber systems. The linuron degrading consortium consists of Variovorax sp. WDL1 transforming linuron to 3,4-dichloroaniline (3,4-DCA) and N,O-dimethylhydroxylamine (N,O-DMHA). WDL1 uses 3,4-DCA as C-source but inefficiently and its excretion supports growth of Comamonas testosteroni WDL7. Hyphomicrobium sulfonivorans WDL6 grows on N,O-DMHA. The consortium biofilm was first grown on DOM formulations of natural origin with varying biodegradability. Synergism was observed in the multi-species biofilm for a wide variety of natural organic compounds and DOM formulations of varying biodegradability, hereby extending its metabolic reach beyond each strain’s individual capabilities. Apart from niche complementarity, the consortium oxidized more carbon sources due to a synergistic cooperation between WDL1 and WDL7 making more carbon sources accessible. In addition, biofilms grown on DOM formulations, visualized with CLSM by strain specific fluorescent labelling, revealed close spatial proximity of WDL1 and WDL7. This juxtaposition of the strains was essential for the immediate removal of linuron when applied to the different DOM fed biofilms in a later stage. Natural C-sources assure a continuation of metabolic cooperation in pollutant degrading microbial communities, a necessary feature for the complete and efficient removal of pollutants.