Integrating network and in-silico simulation insights into the ecological interactions shaped by carbon sources in...

The underlying ecological mechanism of microbial communities shaped by carbon source in partial denitrification and anammox (PDA) systems remains poorly understood, despite the potential of multiple carbon sources to support the partial denitrification process. Herein, the integrated network and in-silico simulation methods were used to evaluate the considerable impact of carbon sources on the dynamics of ecological interactions. The fluctuation of carbon source (from acetate to glucose and ethanol) significantly destabilized the performance of PDA system (total nitrogen removal efficiency decreased from 96.8% to 69.1%). Glucose simultaneously altered the composition of denitrifying bacteria, resulting in a significant enrichment of the genus Elstera (from 0% to 12.7%). By contrast, genus Thauera re-dominated for partial denitrification with ethanol as carbon source. Importantly, heterotrophic bacteria (e.g., genus Calditrichia) gradually enriched by utilizing ethanol. The presence of acetate in phase IV further enhanced the competitive advantage of heterotrophic bacteria over denitrifying bacteria, thereby resulting in the deteriorated performance of the PDA system. The in-silico simulation of co-culture further revealed that the overgrowth of auxotrophic species Calditrichia utilized amounts of nutrients and limited other functional bacteria. Additionally, the whole co-occurrence network indicated that positive interactions likely improved the adaptability of anammox bacteria under the unsteady conditions. This study provides profound insights into the ecological interactions shaped by carbon sources in PDA systems and underscores the necessity of comprehensive review of the external carbon source to ensure optimal performance.