Biology subjects

han, x.

Publications and source records attributed to han, x..

2 recordsLinked to original sources

bioRxiv2025

A new nitrogen biochemical process: Oxidization of ammonium into nitrogen gas using nitrate

The nitrifying bacteria oxidize ammonium into nitrite or nitrate under aerobic conditions, while the anaerobic ammonia-oxidizing bacteria utilize nitrite to oxidize ammonium into nitrogen gas under anaerobic conditions. There is no biochemical process that can directly oxidize ammonium into nitrogen gas using nitrate under anaerobic conditions. In this study, mature anaerobic ammonium oxidation (anammox) granular sludge was inoculated in an anaerobic nitrogen-removal system, while nitrate and ammonium were used as the influent substrates. The experiment was conducted for 537 days at a temperature of 30-32{degrees}C and a pH of 8.0-9.0. The transformation from nitrite-anammox to nitrate-anammox was stably achieved on the 350th day. The experimental results showed that, nitrate directly oxidized ammonium into nitrogen gas under anaerobic conditions. The produced gas consisted of 96.3% nitrogen and 3.7% carbon dioxide. The removal ratio of ammonium to nitrate was approximately 1.67:1, and the total inorganic nitrogen removal rate reached up to 290.20 mg/(L{middle dot}d). Unlike the nitrite-anammox reaction, this reaction was accompanied by an acid production process, which caused a decrease in pH. When the substrate was changed to nitrite and ammonium, the total nitrogen removal rate of only 1.1-1.3 mg/(L{middle dot}d) was achieved. This new biochemical reaction of nitrogen was defined as nitrate-anammox. The study reveals a new pathway of nitrogen transformation, providing novel insights into the global nitrogen cycle.

microbiology↗

bioRxiv2024

Integrative multi-omics data elucidating the biosynthesis and regulatory mechanisms of furanocoumarins in Angelica dahurica

Furocoumarins (FCs) are crucial natural products playing a dual role as plant defense molecules and pharmacologically active substances. Angelica dahurica is a renowned herb with diverse and abundant FCs. However, the accumulation pattern over developmental stages, biosynthesis pathway and regulatory mechanisms of FCs in A. dahurica remain elusive, hindering the production of FCs via synthetic biology approaches. Here, we constructed a chromosome-level reference genome for A. dahurica and quantified the content dynamics of 17 coumarins across six developmental stages of its medicinal organ, root. It showed a gradual decrease in FC concentration with root enlargement. The combined analyses of transcriptomic and metabolomic data, together with in vivo enzymatic assay, confirmed that CYP71AZ18 was involved in the biosynthesis of bergaptol, whereas CYP71AZ19 and CYP83F95 contributed to the biosynthesis of xanthotoxol. Notably, CYP71AZ19 originated from a proximal duplication event of CYP71AZ18, specific to A. dahurica, subsequently undergoing neofunctionalization. Accessible chromatin regions (ACRs), especially proximal ACRs, are correlated with higher gene expression levels, including the three validated genes involved in FC biosynthesis, showing potential to regulate metabolite biosynthesis. Our findings provide new insights into the biosynthetic pathway of FCs and the epigenetic regulation of metabolite biosynthesis.

synthetic biology↗