Ecological determinants of 17a-ethynylestradiol biodegradation: Unveiling unique microbial community assemblages in lake sediments under nitrate or sulfate reduction

Nitrate and sulfate, as electron acceptors (EAs), influence microbial communities and the subsequent biodegradation of emerging contaminants, such as 17a-ethynylestradiol (EE2) in anaerobic sediments. Results of this study showed that nitrate amendment significantly raised nitrate reduction intensity within a short period (<5 days) and greatly influenced microbial community succession compared with sulfate amendment. Nitrate reduction induced deterministic selections that narrowed the niche widths of the microbial community, creating direct correlations between functional members, including denitrifiers and potential estrogen degraders like Pseudomonas. The facilitative coordination of microbes and increased denitrification resulted in greater EE2 biodegradation under nitrate -reducing (0.19 +/- 0.02 g g-1) and combined nitrate- and sulfate -reducing conditions (0.23 +/- 0.01 mu g g-1) after 120 days. Moreover, natural organic matter enhanced interspecies syntrophic cooperation (the number of direct connectors increased from 9 to 25 in the microbial network) in the microbial community and further improved EE2 biodegradation efficiency to 0.26 +/- 0.03 mu g g(-1). Conversely, sulfate reduction required longer adaptation (>20 days) with a higher contribution of stochastic processes in community assembly, yielding fewer connections with estrogen degraders and weaker EE2 biodegradation (0.15 +/- 0.03 mu g g(-1)). These mechanistic understandings can guide EA selection in the bioremediation of emerging contaminants.