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Biochar effects on the abundance, activity and diversity of the soil biota
Published in Johannes Lehmann, Stephen Joseph, Biochar for Environmental Management, 2015
Janice E. Thies, Matthias C. Rillig, Ellen R. Graber
Among the more intriguing aspects of amending soil and compost with biochar is the potential to decrease N2O emissions (Chapter 17) that result from nitrification, denitrification and dissimilatory nitrate reduction to ammonia (DNRA) processes. Denitrification is the sequential reduction of NO3- to NO2-, nitric oxide (NO), N2O and N2 during anaerobic respiration. Enzymes catalyzing these reactions are nitrate reductase (Nar), nitrite reductase (Nir), nitric oxide reductase (Nor) and nitrous oxide reductase (Nos), respectively. Changes in the abundance of denitrifiers have been assessed by quantifying the number of copies of genes coding for these key enzymes in the denitrification pathway (i.e., narG, nirS and nirK, and nosZ) by qPCR (Table 13.3) and in one study (Harter et al, 2014) by quantifying the number of gene transcripts (qPCR of RNA extracts) of these enzymes.
Denitrification-induced carbonate precipitation by bio-composite material with Pseudomonas aeruginosa for simultaneous nitrate and cadmium remediation
Published in Human and Ecological Risk Assessment: An International Journal, 2023
Chaolin Fang, Ruitao Lin, Kaixuan Xu, Varenyam Achal
Common methods for such water pollution treatment mainly include bioremediation, permeable reactive barriers, air sparging, and adsorption (He et al. 2020a; Zhao et al. 2021). Among them, biological denitrification, a type of bioremediation, has gained increasing interest for nitrate removal; however, it’s efficiency in simultaneous remediation of heavy metals is often in question. Denitrification is sensitive to heavy metals, and the inhibition of denitrification is dependent on the amount of heavy metals in surrounding medium (He et al. 2020b). It has been found that aerobic denitrifying activity decreases with increasing heavy metal concentrations due to their corresponding inhibition on the related enzymes (Gui et al. 2017). The process of denitrification is catalyzed mainly by denitrifying enzymes including nitrite reductase, nitric oxide reductase, and nitrous oxide reductase, from nitrate to nitrogen gas (Heylen et al. 2006). However, these enzyme activities have not been documented at large in heavy metal remediation with denitrification.
Nitrite removal by Acinetobacter sp.TX: a candidate of curbing N2O emission
Published in Environmental Technology, 2022
Shuqian Sun, Xiaohui Bi, Bin Yang, Weihong Zhang, Xinyu Zhang, Shujing Sun, Jibo Xiao, Yunlong Yang, Zhida Huang
In general, the nitrite nitrogen consumed by microorganisms is subjected to assimilation and dissimilation processes. For assimilation (nitrite as the sole nitrogen source), nitrogen is incorporated into biomass and some nitrogen-containing metabolites, whereas nitrite could be transformed to gaseous products by some denitrifying reductases such as nitrite reductase, nitric oxide reductase and nitrous oxide reductase in the course of dissimilation. In our previous study, a denitrifying nitrite reductase was isolated satisfactorily from TX5 [28], and no other products generated by this enzyme are detected except nitric oxide. As a consequence, the nitrite removal pathway (dissimilation) in TX5 is proposed as follows: nitrite is reduced to nitric oxide by nitrite reductase, followed by a rapid reduction of nitric oxide to nitrous oxide through nitric oxide reductase due to a great toxicity of nitric oxide to cells [46], and subsequently nitrous oxide is converted to nitrogen gas by the means of nitrous oxide reductase. This pathway is different from that found in Bacillus licheniformis, which lacks a nitrite reductase to nitric oxide but is capable of reducing nitrite to ammonium with concomitant production of N2O [47]. To further corroborate the proposed nitrite removal pathway for TX5, however, either the identification of nitric oxide reductase gene or the purification of nitric oxide reductase should be conducted in the future.
Changes of bacterial community in arable soil after short-term application of fresh manures and organic fertilizer
Published in Environmental Technology, 2022
Chunmei Ye, Shenfa Huang, Chenyan Sha, Jianqiang Wu, Changzheng Cui, Jinghua Su, Junjie Ruan, Juan Tan, Hao Tang, Jiajia Xue
Moreover, OF had the highest relative abundance of genes encoding nitrous-oxide reductase (N2ORs, EC1.7.2.4) and nitric oxide reductase (cytochrome c) (EC1.7.2.5). The relative abundance of genes encoding N2ORs in OF was significantly higher than in CK, CM and PM (p < 0.05), which was 44.86%, 42.81% and 53.51% higher respectively. Compared with CK, CM and PM, the relative abundance of genes encoding EC1.7.2.5 in OF was 3.01%, 10.15% and 10.81% higher, respectively. EC1.7.2.4 and EC1.7.2.5 are constituents of the important bacterial denitrification processes. EC1.7.2.4 is a terminal reductase that reduces N2O to N2 in the respiratory chain [63]. And EC1.7.2.5, a protein that catalyzes NO to N(2)O, is a key enzyme in the nitrate respiration process of denitrifying bacteria [64]. The application of OF increased the relative abundance of genes encoding EC1.7.2.4 and EC1.7.2.5, was beneficial to promote denitrification, in order to reduce the accumulation of nitrite nitrogen in soil and its toxic effect on crops.