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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↗

bioRxiv2019

The Signature Microbiota Driving Rumen Function Shifts in Goat Kids Introduced Solid Diet Regimes

The feeding regime of early supplementary solid diet improved rumen development and ruminant production. However, the signature microbiota linking dietary regimes to rumen function shifts and hosts are still unclear. We analyzed the rumen microbiome and functions affected by supplementation of solid diet using a combination of machine learning algorithms. The volatile fatty acids (i.e., acetate, propionate and butyrate) fermented by microbes increased significantly in the supplementary solid diet groups. The predominant genera altered significantly from unclassified Sphingobacteriaceae (non-supplementary group) to Prevotella (supplementary solid diet groups) RandomForest classification model revealed signature microbiota for solid diet that positively correlated with macronutrient intake, and linearly increased with volatile fatty acids production. The nutrient specific bacteria for carbohydrate and protein were also identified. According to FishTaco analysis, a set of intersecting core species contributed with rumen function shifts by solid diet. The core community structures consisted of specific signature microbiota and their symbiotic partners are manipulated by extra nutrients from concentrate and/or forage, and then produce more volatile fatty acids to promote rumen development and functions eventually host development. Our study provides mechanism of microbiome governing by solid diet and highlights the signatures microbiota for animal health and production.\n\nImportanceSmall ruminants are essential protein sources for human, so keeping them health and increasing their production are important. The microbial communities resided in rumen play key roles to convert fiber resources to human food. Moreover, rumen physiology experience huge changes after birth, and understanding its microbiome roles could provide insights for other species. Recently, our studies and others have shown that diet changed rumen microbial composition and goat performance. In this study, we identified core community structures that were affected by diet and associated to the rumen development and goat production. This outcome could potentially allow us to select specific microbiome to improve rumen physiology and functions, maintain host health and benefit animal production. Therefore, it gives a significant clue that core microbiome manipulation by feeding strategies can increase animal products. To our knowledge, we firstly used FishTaco for determination of link between signatures abundances and rumen function shifts.

microbiology↗