Abstract：
The microbe-mediated conversion of nitrate (NO3-) to ammonium (NH4+) in the nitrogen cycle has strong implications for soil health and crop productivity. The role of prokaryotes, eukaryotes and their phylogeny, physiology, and genetic regulations are essential for understanding the ecological significance of this empirical process. Several prokaryotes (bacteria and archaea), and a few eukaryotes (fungi and algae) are reported as NO3- reducers under certain conditions. This process involves enzymatic reactions which has been catalysed by nitrate reductases, nitrite reductases, and NH4+-assimilating enzymes. Earlier reports emphasised that single-cell prokaryotic or eukaryotic organisms are responsible for this process, which portrayed a prominent gap. Therefore, this study revisits the similarities and uniqueness of mechanism behind NO3- -reduction to NH4+ in both prokaryotes and eukaryotes. Moreover, phylogenetic, physiological, and genetic regulation also shed light on the evolutionary connections between two systems which could help us to better explain the NO3--reduction mechanisms over time. Reports also revealed that certain transcription factors like NtrC/NtrB and Nit2 have shown a major role in coordinating the expression of NO3- assimilation genes in response to NO3- availability. Overall, this review provides a comprehensive information about the complex fermentative and respiratory dissimilatory nitrate reduction to ammonium (DNRA) processes. Uncovering the complexity of this process across various organisms may further give insight into sustainable nitrogen management practices and might contribute to addressing global environmental challenges.
摘要：
在氮循环中，微生物介导的硝酸盐（NO3-）向铵（NH4）的转化对土壤健康和作物生产力具有重要意义。原核生物的作用，真核生物及其系统发育，生理学,遗传调控对于理解这一经验过程的生态意义至关重要。几种原核生物（细菌和古细菌），在某些条件下，一些真核生物（真菌和藻类）被报道为NO3-还原剂。此过程涉及硝酸盐还原酶催化的酶促反应，亚硝酸盐还原酶，和NH4+同化酶。早期的报道强调单细胞原核或真核生物负责这一过程，这描绘了一个突出的差距。因此,这项研究重新审视了原核生物和真核生物中NO3-还原为NH4的机制的相似性和独特性。此外，系统发育，生理,遗传调控也揭示了两个系统之间的进化联系，这可以帮助我们更好地解释随着时间的推移NO3-减少机制。报告还显示，某些转录因子，如NtrC/NtrB和Nit2，在协调NO3-同化基因的表达以响应NO3-可用性方面发挥了重要作用。总的来说,这篇综述提供了有关复杂的发酵和呼吸异化硝酸盐还原成铵（DNRA）过程的全面信息。在各种生物中发现这一过程的复杂性可能会进一步深入了解可持续的氮管理实践，并可能有助于应对全球环境挑战。
