School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China.
China Water Resources Bei Fang Investigation, Design & Research CO.LTD, Tianjin 300222, China.
Environ Sci Technol. 2023 Jul 25;57(29):10662-10672. doi: 10.1021/acs.est.2c09624. Epub 2023 Jul 14.
This study explored the response of NO-N bioreduction to Cr(VI) stress, including reduction efficiency and the pathways involved (denitrification and dissimilatory nitrate reduction to ammonium (DNRA)). Different response patterns of NO-N conversion were proposed under Cr(VI) suppress (0, 0.5, 5, 15, 30, 50, and 80 mg/L) by evaluating Cr(VI) dose dependence, toxicity accumulation, bioelectron behavior, and microbial community structure. Cr(VI) concentrations of >30 mg/L rapidly inhibited NO-N removal and immediately induced DNRA. However, denitrification completely dominated the NO-N reduction pathway at Cr(VI) concentrations of <15 mg/L. Therefore, 30 and 80 mg/L Cr(VI) (R and R) were selected to explore the selection of the different NO-N removal pathways. The pathway of NO-N reduction at 30 mg/L Cr(VI) exhibited continuous adaptation, wherein the coexistence of denitrification (51.7%) and DNRA (13.6%) was achieved by regulating the distribution of denitrifiers (37.6%) and DNRA bacteria (32.8%). Comparatively, DNRA gradually replaced denitrification at 80 mg/L Cr(VI). The intracellular Cr(III) accumulation in R was 6.60-fold greater than in R, causing more severe oxidant injury and cell death. The activated NO-N reduction pathway depended on the value of nitrite reductase activity/nitrate reductase activity, with 0.84-1.08 associated with DNRA activation and 1.48-1.57 with DNRA predominance. Although Cr(VI) increased microbial community richness and improved community structure stability, the inhibition or death of nitrogen-reducing microorganisms caused by Cr(VI) decreased NO-N reduction efficiency.
本研究探讨了 NO-N 生物还原对 Cr(VI)胁迫的响应，包括还原效率和涉及的途径（反硝化和异化硝酸盐还原为铵（DNRA））。通过评估 Cr(VI)剂量依赖性、毒性积累、生物电子行为和微生物群落结构，提出了在 Cr(VI)抑制（0、0.5、5、15、30、50 和 80mg/L）下 NO-N 转化的不同响应模式。Cr(VI)浓度>30mg/L 迅速抑制 NO-N 去除并立即诱导 DNRA。然而，在 Cr(VI)浓度<15mg/L 时，反硝化完全主导了 NO-N 还原途径。因此，选择 30 和 80mg/L Cr(VI)（R 和 R）来探索不同的 NO-N 去除途径的选择。在 30mg/L Cr(VI)下的 NO-N 还原途径表现出连续的适应，其中通过调节反硝化菌（37.6%）和 DNRA 菌（32.8%）的分布，实现了反硝化（51.7%）和 DNRA（13.6%）的共存。相比之下，DNRA 在 80mg/L Cr(VI)下逐渐取代反硝化。R 中的细胞内 Cr(III)积累是 R 的 6.60 倍，导致更严重的氧化剂损伤和细胞死亡。激活的 NO-N 还原途径取决于亚硝酸盐还原酶活性/硝酸盐还原酶活性的值，0.84-1.08 与 DNRA 激活相关，1.48-1.57 与 DNRA 占优势相关。尽管 Cr(VI)增加了微生物群落的丰富度并改善了群落结构的稳定性，但 Cr(VI)对氮还原微生物的抑制或死亡降低了 NO-N 的还原效率。
