AHLs-mediated quorum sensing enhances biofilm development and autotrophic denitrification on pyrite as electron donor

Pyrite-driven autotrophic denitrification (PAD) is an emerging process for completely autotrophic nitrogen removal from water and wastewater. However, biofilm development on pyrite has been identified as the major challenge for a larger application of this process and strategies to enhance biofilm formation are needed. In this context, quorum sensing (QS) molecules such as acyl homoserine lactones (AHLs) are known to regulate biofilm attachment, communication and growth in biological systems and might be improve PAD if added exogenously. Moreover, the role of AHLs in PAD systems is still unexplored and may help understanding the mechanisms of biofilm development on pyrite toward the enhancement of PAD performance for (waste)water treatment. To investigate the impact of AHL signaling molecules on the performance of the PAD system and to identify the optimal type and concentration of signaling molecules for enhancing denitrification efficiency, this study examines the effects of 8 AHLs signaling molecules at 3 different concentrations on the PAD system in batch conditions. Microscopic, genetic, and metabolomic investigations were employed to characterize biofilm growth, microbial community structure, absolute denitrifying gene abundance, and metabolic products to understand the enhancement mechanisms of QS on PAD performance.