Exploring the lower concentration limits of micropollutant biodegradation in oligotrophic microbiota

Objective

Organic micropollutants (OMPs) such as pesticides, pharmaceuticals, and synthetic hormones, are emerging contaminants in environmental freshwaters including drinking water resources. OMPs occur at extremely low concentrations (μg – ng/L range), but they may have adverse ecotoxicological and/or human health effects. The EU therefore strives to minimize OMP pollution in freshwaters and introduced stringent concentration limits in drinking water (100 ng/L or lower). Many bacterial strains have been reported that use OMPs for growth and hence mineralize them. Therefore, biodegradation is considering an important mechanism for OMP removal in freshwater systems. However, recent research has shown that the intrinsic trace concentrations of OMPs compose a major bottle neck of OMP biodegradation, since they poorly sustain the energetics of degraders’ cells and leading to physiological adaptions that eventually affect microbial degradation activity. OMP biodegradation has been exclusively studied using copiotrophic strains that thrive well at high pollutant concentrations while the oligotrophic degraders adapted to low substrate concentrations have been largely neglected. The Micropol_Oligo project aims to comparatively study the capacities of oligotrophic and copiotrophic bacteria to degrade OMPs at relevant trace concentrations and to explore the mechanisms underlying the lower concentration limits of OMP biodegradation. To this end, we will examine whether differences in lower concentration limits exist between copiotrophic and oligotrophic 4-chloro-2-methylphenoxyacetic acid (MCPA) catabolic bacterial strains, and investigate the roles of mass transfer limitation and the molecular mechanisms of physiological adaptations in biodegradation of trace MCPA. The outcome of the project is of major interest for understanding the biogeochemical cycling of OMPs in environmental waters and the improvement of biological water treatment systems for OMP removal.