Trace organic chemicals (TOrCs) such as pharmaceuticals, personal care products and pesticides, have raised emerging concerns regarding their effects on the aquatic environment. These anthropogenic compounds usually enter the wastewater systems, and may finally end up in the receiving water bodies, leading to their frequent detection in surface, ground, and even drinking water at a concentration ranging from few ng/L to several µg/L. Residuals of these chemicals at such low concentrations can still have adverse effects on aquatic ecosystems. In general, wastewater treatment plants provide the initial opportunity for removing TOrCs. On the other hand, conventional wastewater treatment processes are not originally designed to eliminate chemical pollution. Microbial communities bearing a high potential to remove TOrCs via enzymatic degradation processes could serve as a promising and cost effective treatment method. To better apply and control the biological treatment process, a comprehensive understanding of the TOrCs biotransformation mechanisms and interactions within microbial communities is necessary. However, it is a challenging task as the immense taxonomic and functional diversity of most natural microbial communities render them intractable for comprehensive mechanistic studies, hence creating a need for tractable and less complex model communities. A model community is defined as a closed assembly of microorganisms that represents or mimics the systemic behaviour of ecological communities under controlled conditions. In this project, we establish model communities from different sources of environment that are able to biotransform diverging TOrCs. The objectives of this project are:

1. To investigate the effects of environmental factors (e.g. carbon source quality/quantity, inoculumn biodiversity/origin) on the growth of model communities and their removal performance of TOrCs.

2. To decipher the biotransformation pathways of TOrCs and involved enzymes and functional genes.

3. To investigate the interspecies interactions in the community and the influence of cross-domain interactions on TOrCs biotransformation.

To achieve these goals, the dilution to extinction method is used to cultivate model communities. Subsequently, metagenomic and metatranscriptomic analyses are applied to identify the taxonomic composition, microbial interactions and functions. LC-MS/MS measurements are applied to investigate the degradation and byproducts of different TOrC classes. The results of this project will contribute to our knowledge on the biotransformation mechanisms of diverging TOrCs, and help provide fundamental theoretical support for the removal of TOrCs by biological treatment in WWTPs.