Background nutrients and bacterial community evolution determine 13C-17β-estradiol mineralization in lake sediment microcosms

Microbial biodegradation plays a key role in determining the fate of estrogens and can be affected by the background nutrients in natural environments. However, information on how microbial community and nutrient conditions influence estrogen biodegradation is very limited. In this study, C-13-17 beta-estradiol (C-13-E2) was supplied to sediments from the Central Area (CA), Gonghu (GH), Meiliang (ML), and Zhushan (ZS) Bays of Taihu Lake to investigate shifts in bacterial community structure associated with C-13-E2 mineralization over a 30-day incubation period, and the relationships between the background nutrients and cumulative C-13-E2 mineralization rates. The cumulative C-13-E2 mineralization rate for ZS Bay was 87.40% on Day 30, which was significantly greater (P < 0.05) than the rates for ML Bay (67.74%), GH Bay (62.79%), and the CA (52.60%). A correlation analysis suggested that the cumulative C-13-E2 mineralization rate was significantly and positively related to the concentrations of total organic carbon (P < 0.01), nitrate-nitrogen (P < 0.05), ammonia-nitrogen (P < 0.001), and dissolved phosphorus (P < 0.001) in the sediments. Although the highest relative abundances of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes (contain most estrogen-degrading bacteria) were not initially in the ZS Bay sediment, the addition of C-13-E2 stimulated their growth in all sediments, with the greatest increases observed for ZS Bay. At the genus level, the cumulative increases of seven genera (Nitrosomonas, Bacillus, Pseudomonas, Sphingomonas, Novosphingobium, Alcaligenes and Mycobacterium) considered to be associated with E2 degradation were also highest for ZS Bay (80.2 times), followed by ML Bay (39.8 times), GH Bay (28.1 times), and CA (19.0 times). Besides the higher nutrient concentrations, the responses of bacteria to C-13-E2 addition in ZS Bay could also explain it having the highest cumulative C-13-E2 mineralization rate. These results indicate both the background nutrients and bacterial community evolution in the sediments determined the C-13-E2 mineralization rates. (C) 2018 Elsevier B.V. All rights reserved.