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This study verified the potential use of nitric oxide (NO) as a useful engineering indicator for controlling and predicting nitrous oxide (N2O) production in wastewater treatment processes. Nitrifying bacteria were cultivated on inorganic substrates in a laboratory-scale batch reactor, and we examined the effects of artificially NO supply control on N2O production by ammonia-oxidizing bacteria (AOB) and bacterial communities during the nitrification process. Furthermore, we attempted to extract only the direct effects of NO on N2O production of AOB by eliminating the effects of nitrite concentration and dissolved oxygen, which are conventionally known to affect N2O production, by using the "conversion model," a mathematical model developed in this study. The results showed that exogenous NO supply suppressed N2O production under nitrification-accelerating conditions and increased N2O production under nitrification-suppressing conditions. Furthermore, experiments using syringes as microbial reactors indicated that AOB may regulate NO production according to their NO demand, which is required as electron acceptors in ammonia oxidation. Hence, when NO supply is excessive, NO production is suppressed, and the excess NO is converted to N2O. Conversely, when NO supply is insufficient, N2O production is not activated until NO production exceeds demand. These findings indicate the possibility of suppressing N2O production by appropriately NO concentration control in biological reactors in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

AbstractBioretention cells (BRCs) are increasingly used to treat nutrients in stormwater runoff, with plants known to enhance nitrogen (TN) and phosphorus (TP) uptake. This study investigated the role of rhizosphere microbial communities in TN, TP, and COD removal across three BRCs: an unvegetated control (CP), one vegetated with vetiver (P1), and another with cattail (P2). Detailed microbiome profiling revealed key taxa across phylum, family, and genus levels contributing to nutrient cycling, with P2 showing the highest species richness and diversity based on OTU counts and diversity indices. Proteobacteria, Acidobacteria, and Verrucomicrobiota were the most prominent phyla, aligning with their known roles in nutrient uptake. Key functional taxa included denitrifiers (e.g., Ramlibacter, TRA3-20), Ammonia Oxidizing Bacteria (AOBs) (e.g., MND1, Ellin 6067), and Phosphate Accumulating Organisms (PAOs) (e.g., Comamonadaceae, Vicinamibacteria), supporting TN (>79%) and TP (>84%) removal rates. Distinct microbial compositions between vegetated BRCs confirmed the role of root exudates in microbial selection and enhanced nutrient removal. These findings emphasize the importance of plant-specific rhizosphere effects and microbial selection in optimizing BRC design for stormwater treatment applications. [ABSTRACT FROM AUTHOR]

The application of nitrification inhibitors (NIs) is an effective way to reduce soil nitrogen (N) losses and increase crop N uptake. Yet, the efficacy of NIs commonly varies with dosages, crop systems and soil environmental conditions. Hence, clarifying the suitable type and dosage of NIs is extremely important for structuring the best N management regime at a regional scale. Here, based on microcosm experiments, we evaluated the influence of three widely used NIs [Dicyandiamide, DCD; 3,4-Dimethylpyrazole phosphate, DMPP; 2-chloro-6-(trichloromethyl) pyridine, Nitrapyrin] on the nitrification activity of an intensively cultivated greenhouse soil. The results showed that both DCD and DMPP imposed a transient inhibition on nitrification (less than five days) regardless of the dosages applied, and, on the contrary, Nitrapyrin presented a persistent suppression, with a longer duration of the inhibition action by a higher dosage. Accordingly, the incorporation of Nitrapyrin at 2% of the applied N rate (w/w) is a recommendable dosage for local intensive greenhouse production. Further, we assessed the influence of various dosages of Nitrapyrin incorporation (0%, 0.25%, 0.5%, 2% and 5%) on the abundance and community of three groups of soil ammonia oxidizers [i.e., ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB) and completely ammonia-oxidizing bacteria (Comammox Nitrospira)] by qPCR and high-throughput amplicon sequencing. Nitrapyrin incorporation strongly lowered both the AOB and Comammox Nitrospira abundances and their community richness even at the lowest dosage. Nitrapyrin incorporation also significantly altered the community structure of all of the tested ammonia oxidizers, and the average relative abundance of some major community members (i.e., the Nitrososphaerales Clade Nitrososphaera, Nitrososphaerales Clade A, Nitrosospira briensis Clade, Nitrosospira multiformis Clade, Comammox Nitrospira Clade A.2 and Comammox Nitrospira Clade A-associated) obviously responded to Nitrapyrin incorporation. Overall, our findings indicated that AOB and Comammox Nitrospira were more sensitive to Nitrapyrin incorporation as compared with AOA. The results obtained here highlight the importance of optimizing the type and dosage of NIs for N fertilization management in intensive greenhouse vegetable production. Nitrapyrin incorporation inhibits soil nitrification probably by suppressing the Nitrosospira multiformis Clade in the AOB community at the level tested herein. [ABSTRACT FROM AUTHOR]

Nitrification, the oxidation of ammonium to nitrate via nitrite, links nitrogen fixation and nitrogen loss processes, playing key roles in coastal nitrogen cycle. However, few studies have simultaneously examined both ammonia-oxidizing and nitrite-oxidizing microbes. This work investigated the abundance and community structure of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) using archaeal amoA gene, bacterial amoA gene, and NOB nxrB gene, respectively, through q-PCR and Sanger sequencing along the Changjiang Estuary salinity gradient. Results showed that ammonia oxidizers were dominated by AOB and had higher abundance than NOB. AOA had a higher diversity at high-salinity stations, and AOB diversity decreased along the estuarine salinity gradient. The communities of AOA differed among freshwater, estuarine mixing and seawater zones, indicating a narrow ecological niche. AOB compositions displayed a wide niche, changing from Nitrosomonas-like sequences dominated to Nitrosospira-like sequences dominated along the salinity gradient. The RDA showed that sand and nitrate contents had significant impacts on the AOA community compositions, while the AOB communities were governed by clay and nitrate contents. This research provides insight into the understanding of the niche of ammonia oxidizers in the estuarine zones. [ABSTRACT FROM AUTHOR]

[Display omitted] • AMC showed higher NH 3 removal efficiency than SC. • Both biofilters filled with AMC and SC realized low N 2 O generation. • Nitrification started earlier in AMC than in SC. • AMC took longer time to reach stable community composition than SC. • Community composition converged with the operation in AMC and SC. Biofiltration is an important method for composting off -gas treatment. Compost-based materials are widely used as the filling media for biofilter. To expand the application of compost from different composting materials in off-gas control for organic waste aerobic composting, the NH 3 removal efficiency, N 2 O generation, and microbial communities of ammonia monooxygenase (amoA functional gene was selected) and nitrite reductase (nirS functional gene was selected) were investigated using the animal manure compost (AMC) and sludge compost (SC) as filling materials. AMC showed a higher NH 3 removal efficiency (average 82.9 ± 12.1 %) than SC (average 58.9 ± 21.9 %). Achieving stable NH 3 removal took longer with the AMC biofilter than with the SC biofilter. More N 2 O was emitted from the AMC than from the SC. The ammonia-oxidizing bacteria (AOB) community composition in the AMC changed significantly after 30 days, whereas the denitrifying bacterial communities changed minimally. The AOB community structure in the SC was more stable than that in the AMC; however, the community compositions in the AMC and SC gradually converged with the extension of operation. These results indicate that the AMC is more suitable than the SC as biofilter filling material for NH 3 control. This study provides a significant reference for optimizing the application of compost-based biofilter off-gas control technology. [ABSTRACT FROM AUTHOR]

The contrasting response of AOA, AOB, and comammox Nitrospira amoA transcript abundance to temperature, moisture, and nitrogen was investigated using soil microcosms. The moisture, temperature, and nitrogen treatments were selected to represent conditions typically found in a New Zealand (NZ) dairy farm. AOB dominated all synthetic urine treated soils. Peak AOB amoA transcript abundance was positively correlated with estimated soil ammonia availability. While AOB gDNA abundance and nitrification rate trends were similar. AOA were strongly influenced by soil temperature. At 20°C, AOA amoA peak transcript abundance averaged over 1 order of magnitude higher than at 8°C. Within the AOA community a member of the Nitrosocosmicus clade was positively correlated with ammonium and estimated ammonia concentrations. The presence and relative increase of an AOA community member in a high nitrogen environment poses an interesting contrast to current scientific opinion in NZ. Comammox Nitrospira abundance showed no correlation with soil moisture. This suggests that previously found associations are more complex than originally thought. Further research is required to determine the drivers of comammox Nitrospira abundance in a high moisture environment. Overall, these results indicate that AOB are the main drivers of nitrification in New Zealand dairy farm soils. [ABSTRACT FROM AUTHOR]

Methane-and ammonia-oxidizing bacteria play key roles in the global carbon and nitrogen cycles, respectively. These bacteria use homologous copper membrane monooxygenases to accomplish the defining chemical transformations of their metabolisms: the oxidations of methane to methanol by particulate methane monooxygenase (pMMO) and ammonia to hydroxylamine by ammonia monooxygenase (AMO), enzymes of prime interest for applications in mitigating climate change. However, investigations of these enzymes have been hindered by the need for disruptive detergent solubilization prior to structure determination, confounding studies of pMMO and precluding studies of AMO. Here, we overcome these challenges by using cryoEM to visualize pMMO and AMO directly in their native membrane arrays at 2.4 to 2.8 Å resolution. These structures reveal details of the copper centers, numerous bound lipids, and previously unobserved components, including identifiable and distinct supernumerary helices interacting with pMMO and AMO, suggesting a widespread role for these helices in copper membrane monooxygenases. Comparisons between these structures, their metallocofactors, and their unexpected protein-protein interactions highlight features that may govern activity or the formation of higher-order arrays in native membranes. The ability to obtain molecular insights within the native membrane will enable further understanding of these environmentally important enzymes. [ABSTRACT FROM AUTHOR]

Ammonia oxidation plays a vital role in regulating soil nitrogen (N) cycle in agricultural soil, which is significantly influenced by different fertilizer regimes. However, there is still need to further investigate the effects of different fertilizer managements on rhizosphere soil ammonia-oxidizing archaea (AOA) and bacteria (AOB) community in the double-cropping rice field. Therefore, the effects of different long-term (37 years) fertilizer managements on rhizosphere soil potential nitrification activity (PNA), AOA and AOB community structure, and its relationship under the double-cropping rice system in southern of China were studied in the present paper. The field experiment included without fertilizer input as a control (CK), inorganic fertilizer (MF), rice straw and inorganic fertilizer (RF), 30% organic manure and 70% inorganic fertilizer (OM). This result indicated that rhizosphere soil organic carbon (SOC) (SOC), total N and ammonium N (NH4+-N) contents in paddy field with RF and OM treatments were increased. Rhizosphere soil PNA, potential nitrification rate (PNR) and abundance of AOB in paddy field with MF treatment were increased, and abundance of AOA in paddy field with RF and OM treatments were increased, respectively. The result also showed that rhizosphere soil diversity index of AOA and AOB with RF and OM treatments were enhanced, compared with CK treatment. Rhizosphere soil AOB and AOA community composition was dominated by Proteobacteria, Actinobacteria and Acidobacteria with all fertilizer treatments. There had significantly positively correlation between the abundance of AOA and SOC, total N, and NH4-N contents. However, there had significantly negatively correlation between soil pH and abundance of AOA, soil PNA, PNR. As a result, long-term application of rice straw and organic manure was benefit for increasing community structure of rhizosphere soil ammonia oxidizer under the double-cropping rice system in southern of China. [ABSTRACT FROM AUTHOR]

[Display omitted] • AOB and SOB reduced NH 3 and H 2 S by 38.90 % and 46.24 %, respectively. • Combined addition of microbial agents could reduce the sulfur loss by 34.69%. • The abundance of soxB gene was increased by 1.72 times in the coupling treatment. • Microbial inoculation enhanced the correlation between bacteria and soxB gene. Ammonia (NH 3) and hydrogen sulfide (H 2 S) are the main odor components in the composting process. Controlling their emissions is very important to reduce environmental pollution and improve the quality of composting products. This study explored the effects of functional bacteria on nitrogen and sulfur metabolism in the composting process of food waste (FW) by adding ammonia-oxidizing bacteria (AOB, A treatment), sulfur-oxidizing bacteria (SOB, S treatment), and combined AOB and SOB (AS treatment), respectively. The key bacterial species involved in nitrogen and sulfur transformation were identified, and the intrinsic mechanisms by which ammonia oxidation drove sulfur oxidation during composting were deciphered. Compared with control treatment (CK), the combined addition of functional microorganisms increased the maximum of soxB gene abundance by 1.72 times, thus resulting in the increase in the SO 4 2- content by 44.00 %. AS treatment decreased the cumulative H 2 S emission and total sulfur (TS) loss by 40.24 % and 34.69 %, respectively, meanwhile lowering NH 3 emission. Correlation network analysis showed that the simultaneous addition of AOB and SOB enhanced the correlation between microorganisms and sulfur oxidation genes, and Acinetobacter , Aeribacillus , Brevibacterium and Ureibacillus might be involved in the ammonia oxidation-promoted sulfur oxidation process. In summary, the optimized inoculation strategy of AOB and SOB could drive biological transformation of nitrogen and sulfur by regulating microbial community, ultimately reducing odor emissions and improving sulfur conservation. [ABSTRACT FROM AUTHOR]

The study summarizes the necessary revisions for initiating the nitrification process in a full-scale leachate treatment plant that operates in a warm climate including dynamic simulation and kinetic characterization studies that were conducted to determine the nitrification kinetics. Following its commissioning, the process temperature in the plant reached high temperatures during the first six months of operation and failed to achieve complete nitrification. The process temperature was lowered from 40°C to 30°C with the aid of surface aerators installed in the anoxic volume of the bioreactor. With the selection of appropriate aerator capacity, besides reducing the temperature of the activated sludge, an 80% total nitrogen removal was achieved. Furthermore, as a result of dynamic simulation and kinetic studies, the maximum specific growth rates for ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) at a process temperature of 30°C were determined to be 0.85 day−1 and 0.56 day−1, respectively, around neutral pH. [ABSTRACT FROM AUTHOR]

Abstract Ammonia-oxidizing microorganisms (AOM) are vital for soil nitrogen cycling, nutrient availability, and soil health during sustainable agriculture. Long-term continuous cultivation of bananas and improper chemical fertilization affect the adaptability of AOM; however, the underlying basis for this phenomenon is unclear. This study utilized 16S rRNA gene and metagenomic sequencing techniques to examine soil from banana plantations that were continuously cultivated for 2, 3, 7, 10, 12, and 13 years (Y2, Y3, Y7, Y10, Y12, and Y13, respectively). The results indicated a significant decrease in soil acidity buffering capacity (pHBC) with increasing years of continuous cropping. Furthermore, compared with forest soil (Y0), Y7, Y10, Y12, and Y13 soils exhibited a significantly increased potential nitrification rate (PNR) as well as an abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), with no significant difference in complete ammonia oxidizers (comammox). Principal component analysis (PCA) further demonstrated marked differences in chemical properties and ammonia-oxidizing microbial community structures between the soils under long-term (Y7, Y10, Y12, Y13) and short-term (Y2, Y3) banana cultivation. In addition, metagenome analysis results indicated that the relative abundance of Nitrososphaera-AOA and Ca. Nitrosocosmicus-AOA as well as Nitrosospira-AOB, Nitrosovibrio-AOB, Nitrosomonas-AOB, and comammox Nitrospira jacus was significantly higher in Y7 and Y13 soils than in Y0 controls. Redundancy analysis (RDA) identified pHBC, CEC, and NH4 + as the primary chemical factor responsible for the differences in AOM microbial communities, whereas random forest analysis revealed that Nitrosospira-AOB significantly contributed to PNR. In summary, long-term continuous banana cultivation primarily stimulates AOB promote soil ammonia oxidation, leading to soil acidification. Graphical Abstract

The Arctic fjords are currently experiencing the effects of glacier discharge, which may affect the nitrogen cycle and associated microbial communities in the benthic sediments. However, there remain a lack of understanding regarding nitrogen transformation processes in Arctic fjords. Here, we collected benthic sediment samples from Arctic Kongsfjorden subject to glacier discharge and then examined the spatial variability in the biogeochemical properties, nitrogen transformation processes and associated microbial community structures. Results showed that potential nitrogen transformation rates showed significant spatial differences (P < 0.05), and no significant correlation (P > 0.05) with TOC, TN, NH4+-N, NO3−-N, and NO2−-N in benthic sediments. Relatively higher contributions of anammox to nitrogen removal (48.5–62.7%) and DNRA to nitrate reduction (27.3–67.3%) occurred in Kongsfjorden sediments, compared with most of marine sediments. The gene abundances of AOB amoA, anammox 16S rRNA, and nirS showed significant positive correlations (P < 0.05) with TOC:N, TOC, TN, and TP in the sediments. All detected ammonia-oxidizing archaea (AOA) belonged to the group 1.1a Nitrosopumilus cluster with the group 1.1b Nitrososphaera cluster at the site closest to the glacier. The detected ammonia-oxidizing bacteria (AOB) and anammox bacteria belongs to β-Proteobacteria Nitrosospira and Planctomycetes Candidatus Scalindua, respectively. AOB has a comparative advantage over AOA in the Kongsfjorden sediments. Overall, our results indicated that the glacier discharge had an important effect on the biogeochemical properties of the Kongsfjorden sediments, which further influenced benthic potential nitrogen transformation rates and associated microbial communities. [ABSTRACT FROM AUTHOR]

To investigate the effects of kitchen waste on the chemical properties of acidic red soil and the community structure of ammonia–oxidizing archaea (AOA) and ammonia–oxidizing bacteria (AOB), a study was conducted in the flue–cured tobacco farmland ecosystem of the Erlongtan small watershed in central Yunnan. Eight fertilization methods were applied: no fertilization control CK, single application of chemical fertilizer T1 (1 t·hm−2), kitchen waste combined with a chemical fertilizer (T2:12 t·hm−2 + 1 t·hm−2, T3:15 t·hm−2 + 1 t·hm−2, T4:18 t·hm−2 + 1 t·hm−2), and single application of kitchen waste (T5:12 t·hm−2, T6:15 t·hm−2, T7:18 t·hm−2). The numbers twelve, fifteen, and eighteen in brackets represent the amount of food waste applied, and one represents the amount of chemical fertilizer applied. The study evaluated the effects of kitchen waste on soil chemical properties, the community structure and composition of AOA and AOB, and the relationship between soil chemical properties and these microbial communities in acidic red soil. The results showed that: (1) single application of kitchen waste (T5, T6, T7) effectively improved soil nutrient status (SOC increased by 15.79–217.24%; TN increased by 1.53–92.99%; NH4+–N increased by 18.19–520.74%; NO3−–N) increased by 15.54–750.61%), and alleviated acidification. (2) Temporal variations had a more significant effect on the community structure of AOA and AOB than different treatments. The dominant phyla of AOA were Thaumarchaeota, Crenarchaeot. The dominant phylum of AOB was Proteobacteria, and the dominant genera were Nitrosospira and norank_Bacteri. (3) The number of AOA co–occurrence network nodes were equivalent to that of AOB, but AOB had more connection edges, indicating a more complex interaction network. In contrast, AOA exhibited higher modularity, reflecting tighter internal connections and greater stability. The AOA co–occurrence network showed stronger performance during the maturity and fallow stages, while AOB interactions were most active during the topping stage. (4) AOA demonstrated a strong correlation with soil chemical properties during the topping and maturity stages, whereas AOB showed a stronger correlation at the rosette and fallow stages. Among soil chemical factors, pH and SOC were identified as the primary drivers influencing AOA and AOB community abundance and structural differentiation. In conclusion, kitchen waste application enhances the nutrient content of acidic red soil and influences the niche differentiation of AOA and AOB, thereby affecting nitrogen recycling. This approach represents an environmentally friendly and sustainable fertilization method. [ABSTRACT FROM AUTHOR]

(1) Background: A vegetable eel co-culture system is an economically efficient way of agricultural cultivation, which can have an impact on the soil microbial environment and play a pivotal role in the soil nutrient cycle, but there is little research on its impact on soil ammonia-oxidizing microorganisms. (2) Methods: NovaSeq platform sequencing was employed to investigate the richness, structure, and diversity of soil ammonia-oxidizing microbial communities, exploring the effects of a vegetable eel co-culture system on soil nitrogen cycling. Four different planting treatments were set up: unfertilized without vegetable eel (CCK), fertilized without vegetable eel (CRT), unfertilized with vegetable eel (ICK), and fertilized with vegetable eel (IRT). (3) Results: A vegetable eel co-culture system significantly increased soil pH and decreased bulk density under fertilization conditions. The soil nitrification potential rate was enhanced by a vegetable eel co-culture system to an average of 26.3%. A vegetable eel co-culture system significantly altered the community structure of all ammonia-oxidizing microorganisms, with a significant increase in the richness and diversity of ammonia-oxidizing bacteria (AOB) and comammox clade-A, while fertilization significantly increased the diversity of all ammonia-oxidizing microbial communities. Structural equation modeling (SEM) analysis showed that the main environmental factors affecting the structure of the ammonia-oxidizing microbial community were nitrate and total nitrogen. The number of amoA genes in AOB and comammox clade-B was significantly positively correlated with the soil potential N nitrification rate (PNR), which played a leading role in the nitrification of alkaline vegetable soil. The network analysis revealed that a vegetable eel co-culture system improved the modularity of AOB and comammox clade-B by 13.14% and 5.66%. (4) Conclusions: This study showed that the vegetable eel co-culture system stimulated the evolution of ammonia-oxidizing microbial communities by changing the physicochemical properties, which in turn promoted the soil nitrification reaction. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of predominantly chemoautotrophic and heterotrophic biofloc systems on ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and planktonic microorganisms in an integrated Penaeus vannamei and Oreochromis niloticus integrated multitrophic culture. Shrimp and tilapia were stocked at a density of 400 shrimp m−2 and 45 fish m−3, respectively. The trial consisted of two biofloc treatments, with three replicates each: chemoautotrophic and heterotrophic. The identification and quantification of the planktonic microorganisms (ciliates, flagellates, microalgae, and total bacteria) and nitrifying bacteria were carried out through direct counting and fluorescence in situ hybridization, respectively. At the end of the trial, heterotrophic treatment had resulted in higher total abundance of bacteria. The relative abundance of AOB and NOB in relation to the total abundance was less than 0.1% for both treatments. The system was dominated by flagellates in both treatment groups. The abundance of microalgae and ciliates was higher with chemoautotrophic treatment. After 43 days, the shrimp weights were higher in the chemoautotrophic group, while the final weights of the tilapia were not significantly different between the two treatments. The type of biofloc system (Chemoautotrophic vs. Heterotrophic) did not significantly alter the establishment of AOB and NOB in a Penaeus vannamei and Oreochromis niloticus integrated multitrophic culture. The two treatments proved to be equally efficient for maintaining good water quality, but the chemoautotrophic treatment resulted in better shrimp growth. Thus, our study demonstrated that chemoautotrophic biofloc is a promising approach in integrated multitrophic aquaculture. [ABSTRACT FROM AUTHOR]

Objective］ To investigate the effects of inoculating heterotrophic ammonia-oxidizing bacteria (HAOB) on yield and water use efficiency of dryland maize. Methods］ A two-year field experiment was conducted in a drought-prone area using HAOB strain S2_8_ 1 as the test strain and maize as the plant material. Four treatments were set up, inoculation with HAOB strain without irrigation (T)T), non-irrigated control (TKX), inoculation with HAOB strain with irrigation (WT), and irrigated control (WCK). Results］ Inoculation with the HAOB strain enhanced the nitrification rate in the rhizosphere soil and the photosynthetic rate of dryland maize, significantly promoted maize growth and increased the yield (p ().05). The above-ground biomass at different stages and the yield at harvest in the T)T and WT treatments were significantly higher than those in the DCK and WCK treatments, especially in the T)T treatment. Tn both the drier 2022 and the wetter 2023, maize yields in the T)T treatment exceeded those in the DCK and WCK treatments by at least 24. 98%; in 2023, the yield of the T)T treatment was comparable to that of the WT treatment, exceeding that of WCK by more than 11.29%. Additionally, inoculation of HAOB improved the water use efficiency of maize, with T)T showing at least a 4.84% increase compared to DCK, and WT showing at least a 3.()6% increase compared to WCK. The nitrification rates in the rhizosphere soil and the yields of T)T and WT were similar, but T)T did not require irrigation and had a higher water use efficiency. _Conclusion］ The application of HAOB strains in dryland agriculture is an effective method for improving maize yield, and it can provide a new technological pathway and research direction for the development of dryland agriculture. [ABSTRACT FROM AUTHOR]

Anaerobic ammonia oxidation (anammox) process is regarded as an efficient and cost-effective technology for nitrogen removal. Anammox bacteria typically coexist with other microorganisms, which highlights the necessity to optimize the system, improve the pollutant removal efficiency and maintain the system stability. This review mainly focused on the interaction effects of anammox bacteria with other functional bacteria, such as aerobic ammonia-oxidizing bacteria, sulphur-oxidizing bacteria, sulphate-reducing ammonia oxidation bacteria, denitrifying bacteria, denitrifying anaerobic methane oxidation microorganisms, denitrifying phosphate-accumulating organisms. This review provided support for the emerging insights that the synergistic effects of various functional bacteria related to nitrogen, phosphorus, sulphur, and carbon within the anammox system could be a promising direction for the development of wastewater treatment technologies. By considering the interplay and cooperation of these microorganisms, wastewater treatment systems could potentially achieve more comprehensive and efficient removal of multiple pollutants. Continued in-depth research and understanding of these interactions would be instrumental in exploring innovative and integrated solutions, ultimately aiming for a more effective and holistic approach to wastewater treatment. [ABSTRACT FROM AUTHOR]

Biological nitrogen removal is a classic technique for removing nitrogen from wastewater that has been studied extensively and gives high nitrogen removal rate, energy efficiency, and is relatively environmentally benign. Using biological nitrogen removal processes to treat the diverse components of wastewater requires a thorough understanding of the microorganisms and pathways involved. However, information regarding the diverse microorganisms participating in nitrogen removal processes remains limited. This review presents the current knowledge of the researches into these microorganisms, including ammonia oxidizing bacteria, archaea, complete ammonia oxidation bacteria, nitrite-oxidizing bacteria, anaerobic ammonium oxidation bacteria, denitrifying bacteria, and heterotrophic nitrification-aerobic denitrification bacteria. The metabolic pathways and enzymatic reactions involved in nitrogen cycle of abovementioned microorganisms are demonstrated. The key enzymes, functional genes, and metabolic pathways of the nitrogen removal-related microorganisms were extensively discussed. Additionally, the advantages of the different microorganisms for the ammonia oxidation, denitrifying, and HN-AD are described. Finally, the limitations and strategies in unraveling the nitrogen metabolic pathways were presented. The aim of the review is to improve our understanding of the principle involved in advanced nitrogen removal processes to allow possible improvements to wastewater treatment processes to be identified. [ABSTRACT FROM AUTHOR]

Ammonia-oxidizing microorganisms (AOM) are vital for soil nitrogen cycling, nutrient availability, and soil health during sustainable agriculture. Long-term continuous cultivation of bananas and improper chemical fertilization affect the adaptability of AOM; however, the underlying basis for this phenomenon is unclear. This study utilized 16S rRNA gene and metagenomic sequencing techniques to examine soil from banana plantations that were continuously cultivated for 2, 3, 7, 10, 12, and 13 years (Y2, Y3, Y7, Y10, Y12, and Y13, respectively). The results indicated a significant decrease in soil acidity buffering capacity (pHBC) with increasing years of continuous cropping. Furthermore, compared with forest soil (Y0), Y7, Y10, Y12, and Y13 soils exhibited a significantly increased potential nitrification rate (PNR) as well as an abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), with no significant difference in complete ammonia oxidizers (comammox). Principal component analysis (PCA) further demonstrated marked differences in chemical properties and ammonia-oxidizing microbial community structures between the soils under long-term (Y7, Y10, Y12, Y13) and short-term (Y2, Y3) banana cultivation. In addition, metagenome analysis results indicated that the relative abundance of Nitrososphaera-AOA and Ca. Nitrosocosmicus-AOA as well as Nitrosospira-AOB, Nitrosovibrio-AOB, Nitrosomonas-AOB, and comammox Nitrospira jacus was significantly higher in Y7 and Y13 soils than in Y0 controls. Redundancy analysis (RDA) identified pHBC, CEC, and NH4+ as the primary chemical factor responsible for the differences in AOM microbial communities, whereas random forest analysis revealed that Nitrosospira-AOB significantly contributed to PNR. In summary, long-term continuous banana cultivation primarily stimulates AOB promote soil ammonia oxidation, leading to soil acidification. [ABSTRACT FROM AUTHOR]

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Certain plant species have developed the ability to express biological nitrification inhibition (BNI), suppressing the activity of nitrifying microbes and thereby reducing the conversion of ammonium to nitrate. This study assessed the BNI capacity and the rhizosphere ammonia-oxidizing microbiome of two grass species: the endemic Australian Barley Mitchell grass (Astrebla pectinata) and the introduced koronivia grass (Urochloa humidicola), using soils from both agricultural land and native vegetation. In agricultural soil, koronivia grass exhibited significantly higher BNI capacity compared with Barley Mitchell grass. However, in native soil, this trend was reversed, with Barley Mitchell grass demonstrating a significantly greater BNI capacity than koronivia grass (52% vs. 38%). Koronivia grass significantly altered the composition of the ammonia-oxidizing bacteria community in its rhizosphere, leading to a decrease in the Shannon index and bacteria number. Conversely, Barley Mitchell grass reduced the Shannon index (1.2 vs. 1.7) and population size (3.28 × 107 vs. 7.43 × 107 gene copy number g−1 dry soil) of the ammonia-oxidizing archaea community in its rhizosphere to a greater extent. These findings suggest that Australian Barley Mitchell grass may have evolved mechanisms to suppress soil archaeal nitrifiers, thereby enhancing its BNI capacity and adapting to Australia's nutrient-poor soils. [ABSTRACT FROM AUTHOR]

Nitrogen cycling in freshwater ecosystems is critical for maintaining water quality, and understanding the processes of nitrification and denitrification is essential for effective nitrogen management, particularly in areas with diverse pollution sources. This study investigated the nitrification and denitrification processes in three tributaries of the Jinjing River—Tuojia (agricultural), Jinjing (residential), and Guanjia (woodland)—during both the wet and dry seasons. The potential nitrification rates (PNRs) and potential denitrification rates (PDNRs) were measured across these sites. The highest rates were observed in Tuojia during the wet season, with the PNR reaching 39.7 μg·kg−1 h−1 and the PDNR reaching 3.25 mg·kg−1·h−1, while the rates were considerably lower in Jinjing and Guanjia. The ammonia-oxidizing archaea (AOA) abundance was higher than the ammonia-oxidizing bacteria (AOB) abundance at all sites, with Tuojia exhibiting the highest AOA abundance (5.9 × 10⁷ copies·g−1) during the wet season. The nitrate-nitrogen (NO₃−-N) content was a key factor influencing denitrification, and the AOA abundance was significantly correlated with nitrification rates (r = 0.69; p < 0.05). These findings highlight the spatial and seasonal variability in nitrogen cycling and emphasize the importance of developing targeted nitrogen management strategies in regions with mixed land uses and pollution sources. [ABSTRACT FROM AUTHOR]

This study investigates the impact of different nutritional regimes on the bacterial communities within the root-growing substrate of a soilless tomato production system and the effects on crop quality. The experiment was conducted with two tomato varieties, Conchita and Sweetelle, under three nutritional treatments: standard, nutrient solution with 20% increased salts and nitrogen and supplementation with the biostimulant Bio-algeen S-90. Bacterial communities in the root substrate were influenced by both the tomato variety and the nutritional regime. Sweetelle exhibited more pronounced shifts in bacterial communities compared to Conchita. An overall increase in bacterial populations with time was observed (+0.38 Log). Specifically, the 20% enhanced nutrient solution had varying effects on bacterial counts in the two tomato varieties, while the biostimulant promoted an increase in ammonia-oxidizing bacteria (+0.4 Log). Microbial community analysis highlighted the distinct impact of each nutritional regime on nitrogen-cycling bacteria, which correlated with differences in quality parameters such as the L-ascorbic acid and lycopene contents. In the first case, a decrease (25–30%) was observed, while the lycopene content decreased after harvest (−51% in Conchita variety) but was more stable in the postharvest phase (66–70% lycopene retained, only 44% in the control). This study highlights how increased sources of nutrients and the differential responses of microbial communities to nutritional regimes do not necessarily increase the crop quality and that tailored approaches are required for different tomato varieties. [ABSTRACT FROM AUTHOR]

This study investigates the mechanisms driving maize compensatory growth upon post-drought, to reveal how the root's original cytokinins are regulated by the two-fold roles of heterotrophic bacteria with ammonia-oxidizing (HAOB) capabilities. The HAOB' dual roles encompass influencing root cytokinin synthesis and transport through nitrification and a direct pathway. Experiment 1 involved introducing the application of varying amounts of NO3− to the roots to examine how nitrification affects cytokinin roots-to-leaves transport. Results demonstrate that the 30–40 mmol·L−1 NO3− concentration had ideal effects on enhancing post-drought growth in maize by facilitating cytokinin synthesis and transport. In experiment 2, an HAOB strain, S2_8_1, was utilized and NO3− was supplemented alongside HAOB inoculation to assess the joint impacts of nitrification and the direct pathway on the production and transportation of cytokinins. Results demonstrate that the HAOB strain S2_8_1 increases nitrification rates in rhizosphere soil, thereby promoting the transport of cytokinins from roots to leaves. In addition, the HAOB strain promotes root cytokinin transport to leaves autonomously, showcasing its direct pathway. Inoculation with the HAOB strain increased leaf cytokinin content and improved water use efficiency compared to the addition of NO3−; however, the combination of NO3− and HAOB strains resulted in a synergistic effect and further improvement. These findings elucidate how HAOB can enhance maize compensatory growth through its dual roles, presenting promising applications in agriculture. [ABSTRACT FROM AUTHOR]

Ammonia‐oxidizing archaea (AOA) and ammonia‐oxidizing bacteria (AOB) control nitrification in terrestrial systems. Soil pH and substrate availability (NH4+) can influence community composition, which may affect the contributions of these organisms to nitrification in forest soils. Using high‐throughput sequencing, we identified the amoA of AOA and AOB from northern forest stands that occur across a natural gradient of nitrification, soil pH, and net N mineralization (i.e., NH4+ availability). Specifically, we investigated changes in relative abundance and community composition of AOA and AOB across a soil pH and net N mineralization gradient, and how turnover in community composition is linked to nitrification. We found that soil pH was a stronger driver of AOA and AOB relative abundance than was NH4+ availability. Generally, AOA and AOB turnover were positively associated with soil pH; however, some AOA taxa also displayed a negative association. Interestingly, the relative abundance of only a small number of AOA and AOB taxa was significantly associated with net nitrification rates. Our findings reveal that coexisting taxonomical groups of ammonia‐oxidizers in forest soils have diverse responses to environmental factors, which influence how ammonia‐oxidizer communities are structured, likely having direct implications for nitrification and the regulation of N cycling in forest systems. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the effect of Pseudomonas fluorescens (P) application on isofetamid (IS) dissipation; the number of specific genes of archaea, bacteria and ammonia-oxidizing bacteria (AOB); and the activity of β-Glucosidase, phosphomonoesterase, N-acetyl-glucosaminidase and arylsulfatase. It was observed that the IS concentration was lower in the P+IS than in IS throughout the entire study period, which indicates the potential of P. fluorescens to decompose isofetamid faster. IS+P application significantly influenced N-acetyl-glucosaminidase, arylsulfatase and phosphomonoesterase activity in soil compared to the control by approximately 29%, 72% and 6.5%, respectively. Moreover, it was observed that on day 21 in IS+P, the number of bacterial genes was significantly higher than in the control and IS and than on day 1, by 10% and 20%, respectively. On day 21, the number of archaea was significantly higher in all variants and ranged from 3.61 (control) to 6.88 log10 gene copies/g dm (IS+P). Correlation analysis showed a positive correlation between IS and TOC, while there was a negative correlation between IS and β-Glu and the number of archaea and AOB genes. The tested strain has the potential to be a biofertilizer and an agent in the bioremediation of contaminated soils. [ABSTRACT FROM AUTHOR]

We investigated the potential of earthworm casts to emit N2O, hypothesizing that emission levels are influenced by the species of earthworm and their ecological category. This study examined casts a broad taxonomic and ecological coverage of tropical earthworms, i.e., 16 different species across four ecological categories. We quantified the potential nitrification, N2O production and consumption as well as the abundance of N-related microbial functional groups, including ammonia-oxidizers, nitrite-reducers, and distinct clades of N2O-reducers, along with casts chemical properties to determine cast organic matter quality and substrate availability. Earthworm casts exhibited significantly higher concentrations of carbon, nitrogen, and nitrate compared to control soil, while humification index were lower. A negative correlation between humification index and potential N₂O production suggests that more labile substrates in the casts promote higher N₂O flux. Net potential N₂O emissions were higher in the casts of 7 out of 16 species compared to control soil, and all species' casts showed higher gross potential N₂O production, with substantial interspecific variability. The abundance of nitrite and N₂O reducers was significantly higher in the casts and positively correlated with potential N₂O emissions. Casts from epigeic and mixed categories displayed higher carbon and nitrogen content, abundance of nitrite and N₂O reducers, ammonia-oxidizing bacteria, and potential N₂O production compared to anecic and endogeic categories, which exhibited higher values of humification index. Structural equation modeling indicated that gross potential N₂O production was primarily explained by the abundance of nitrite reducers and substrate availability indicators such as humification index and nitrate concentration. Our study demonstrates significant interspecific variability in N₂O potential emissions from a broad range of tropical earthworm casts, influenced by species feeding behavior, microbial communities, and substrate availability. [ABSTRACT FROM AUTHOR]

Studies of the impact of nitrification inhibitors (NIs), specifically DMPP and DMPSA, on N2O emissions during "hot moments" have produced conflicting results regarding their effectiveness after rewetting. This study aimed to clarify the effectiveness of NIs in reducing N2O emissions by assessing residual DMP concentration and its influence on ammonia-oxidizing bacteria (AOB) in two pot experiments using calcareous (Soil C, Calcic Haploxerept) and acidic soils (Soil A, Dystric Xerochrepts). Fertilizer treatments included urea (U), DMPP, and DMPSA. The experiments were divided into Phase I (water application to dry period, 44 days) and Phase II (rewetting from days 101 to 121). In both phases for Soil C, total N2O emissions were reduced by 88% and 90% for DMPP and DMPSA, respectively, compared with U alone. While in Phase I, the efficacy of NIs was linked to the regulation of AOB populations, in Phase II this group was not affected by NIs, suggesting that nitrification may not be the predominant process after rewetting. In Soil A, higher concentrations of DMP from DMPP were maintained compared to Soil C at the end of each phase. Despite this, NIs had no significant effect due to low nitrification rates and limited amoA gene abundance, indicating unfavorable conditions for nitrifiers. The study highlights the need to optimize NIs to reduce N2O emissions and improve nitrogen efficiency, while understanding their interactions with the soil. This knowledge is necessary in order to design fertilization strategies that improve the sustainability of agriculture under climate change. [ABSTRACT FROM AUTHOR]

Short-cut nitrification can save energy and increase efficiency of wastewater treatment plants, but achieving short-cut nitrification at medium and low temperature is still the bottleneck of the application of this process. In this paper, the start-up of short-cut nitrification at 8~16 °C was investigated with addition of four iron-based materials (Fe2O3 nanoparticles (NPs), Fe3O4 NPs, magnetite NPs and FeCl3) using actual municipal sewage as influent. The results showed that the addition of 50 mg/L Fe2O3 NPs can achieve nitrite accumulation ratio (NAR) of more than 75% within ten days, while NAR reached as high as 100% with addition of 145 mg/g MLSS FeCL3. The results of high-throughput sequencing showed that iron-based materials affected microbial community structure of activated sludge in the reactors. Nitrosomonas was the dominant ammonia-oxidizing bacteria (AOB) and Nitrospira was the dominant nitrite-oxidizing bacteria (NOB). Compared with the control group, the relative abundance of NOB in the experimental groups decreased by an average of 68.48%. The addition of iron-based materials caused selective inhibition of NOB, which resulted in the successful achievement of short-cut nitration at medium and low temperature. PLS-PM analysis further verified the regulatory pathway of NO2--N accumulation by iron-based materials. A short-cut nitrification control method for municipal wastewater at medium and low temperature by adding iron-based materials was established. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION Sorghum (Sorghum bicolor L. Moench) is a cereal crop known for its biological nitrification inhibition (BNI) capacity, a plant‐mediated activity limiting nitrification pathway. The use of BNI‐producing plants represents an environmentally friendly and cost‐effective approach to reduce nitrogen (N) losses, such as nitrate (NO3−) leaching and nitrous oxide (N2O) gas emissions. The present study aimed to test the effectiveness of different S. bicolor cultivars in rotation to retain ammonium (NH4+) in soils and promote N availability for the subsequent wheat crop. A two‐year field rotation was established with four sorghum cultivars followed by winter wheat (Triticum aestivum L.). Urea alone or combined with the urease inhibitor N‐(n‐butyl) thiophosphoric triamide was applied to promote a NH4+‐based fertilization regimes.AddingN‐(n‐butyl) thiophosphoric triamide maintained higher soil NH4+ content and reduced ammonia‐oxidizing bacteria population during sorghum cultivation. However, the benefits of the inhibitor on sorghum growth were cultivar‐dependent. Notably, the further reduction in ammonia‐oxidizing bacteria abundance for sorghum Voyenn and the increased soil NH4+ content for Vilomene suggested a BNI potential for these cultivars. Importantly, the Vilomene precedent enhanced wheat yield for both fertilization regimes.Overall, the present study confirms that sorghum is a suitable catch crop and emphasizes the importance of selecting the proper sorghum cultivar to maximize the yield of the target wheat crop, at the same time as minimizing N losses. Furthermore, developing combined strategies with selected sorghum cultivars and the application of urease inhibitors enables to enhance sorghum productivity as forage, achieving added value to the rotation. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Nitrification is a vital process in the biological removal of inorganic nitrogen compounds. In order to ensure the stability and effectiveness of this process, buffer solutions should be added to the system to maintain neutral to slightly alkaline conditions. With a focus on the newly discovered comammox Nitrospira, this research investigates the transition of the nitrifying community within a biofilm reactor under different acidic levels (initiated at pH 6 and gradually decreased to pH 5). During the 305-day continuous operation experiment, it was observed that responsible ammonia oxidizers transitioned from ammonia-oxidizing bacteria (AOB) during the initial stages (setup stage and early stage of pH 6) to comammox Nitrospira under pH 5.5 and pH 5. Further analysis using next-generation sequencing targeting both the 16S rRNA region and amoA region revealed a shift in the dominant cluster of both Nitrospirae and comammox Nitrospira under varying pH conditions. Our study identified a distinct cluster of comammox Nitrospira that is phylogenetically closed to sequences found in acidic environments, but exhibits dissimilarity from known comammox Nitrospira isolates and the majority of environmental sequences. This cluster was found to be prevalent in the acidic biofilm reactor studied and thrived particularly well at pH 5. These findings underscore the potential significance of this distinct, uncultivated group of comammox Nitrospira in performing ammonia oxidation under acidic conditions. Key points: • Ammonia was effectively removed under pH 5.5 and 5 in the biofilm reactor • The dominant ammonia oxidizer was comammox Nitrospira when pH was 5.5 and 5 • A potential acidophilic cluster of comammox Nitrospira was identified in this acidic biofilm reactor [ABSTRACT FROM AUTHOR]

Partial nitritation-anammox (PN/A) is a cost-effective technology in high ammonia–nitrogen wastewater treatment. However, PN/A is prone to instability as the ammonia–nitrogen sharply fluctuates. In this study, a packed bed reactor is employed to construct a single-stage PN/A system to investigate the operational characteristics and explore the denitrification mechanism. The effluent NH4+-N concentration, ammonia nitrogen removal rate (ARE), and total nitrogen removal rate (TNR) could be sustained at about 60 mg/L, 80%, and over 70%, respectively, when the influent nitrogen load rate (NLR) is changed from 0.733 to 0.879 kg-N/m3/day. Both ARE and TNR are decreased when NLR continues increasing to 1.026 kg-N/m3/day. The influent NLR decreases from 0.879 to 0.147 kg-N/m3/day, and ARE and TNR reached 98% and 85.4%, respectively. Therefore, the denitrification effect of the reactor could be recovered, and the excellent nitrogen removal capacity could be obtained within a wide range of influent NLR. Moreover, the high-throughput sequencing and metagenomic testing indicate that the Proteobacteria and Planctomycetes that the PN/A functional strains (i.e., ammonia-oxidizing bacteria (AOB) and anammox bacteria (AnAOB)) account for 38.8% in the sludge. The relative abundance of Nitrospira containing the nitrite-oxidizing bacteria (NOB) has dropped to 0.01%, and the functional gene nxr of the nitrite oxidation process is also inhibited. The relative expression of the functional gene is dominated by the short-range nitritation and anammox oxidation, which demonstrates that the nitrogen removal is mainly dominated by nitritation-anammox. [ABSTRACT FROM AUTHOR]

Aims: N rhizodeposition plays a vital role in regulating rhizosphere soil N dynamics. However, its effects on the rhizosphere soil N cycle in clonal plants and the underlying mechanism remain unclear. Methods: 15N solutions with different concentrations were injected into young or connected mature ramets of Moso bamboo (Phyllostachys edulis), respectively, in the field, to explore the response of rhizosphere N transformation to N rhizodeposition. Results: 15N injection increased the 15N abundance in the rhizosphere soil of both young and mature ramets, with higher 15N abundance in 20–40-cm layer than that in 0–20-cm layer. Functional genes involved in nitrification and denitrification in the rhizosphere were upregulated when young ramets received low- and medium-N solutions. However, the genes showed diverse responses to high-N treatment in young ramets, with increased abundances of ammonia-oxidizing bacteria and decreased levels of ammonia-oxidizing archaea, comammox, and denitrifiers. In contrast, the functional genes involved in denitrification in the 20–40-cm layer of rhizosphere soil were upregulated by high-N treatment in mature ramets. Additionally, partial-least-squares path modeling revealed 15N abundance in the soil indirectly affected N mineralization, N mineralization directly affected nitrification, and nitrification directly affected denitrification in a positive manner. Conclusion: The variations of N rhizodeposition and transformation process in both connected ramets is highly consistent in responding to different N treatments, but the nitrifiers and denitrifiers in the deeper rhizosphere soil were more sensitive to N rhizodeposits than those in the upper rhizosphere soil. [ABSTRACT FROM AUTHOR]

Pond aquaculture is an important aquacultural model worldwide in which ammonia-oxidizing bacteria (AOB) are crucial for the removal of ammonia from water. The influence of light irradiation on AOB in an aquaculture pond was studied using artificial simulation wastewater under dark/light cycles of 24 h/0 h (L0), 12 h/12 h (L12), and 0 h/24 h (L24). The ammonia oxidation rates (AORs) in groups L0, L12, and L24 were 9.88 ± 0.19 mg h−1, 6.01 ± 0.32 mg h−1, and 1.85 ± 0.09 mg h−1, respectively. Long-term exposure to light had a serious impact on the AOR and decreased the abundance of Nitrosomonas spp. and their ammonia monooxygenase genes. To determine the protective effect of microalgae on AOB, different doses of freeze-dried Chlorella spp. powder were added to the nitrifying bacteria community. The photoinhibition rate of chlorophyll a (Chla) in the groups with 300 and 1300 µg L−1 of added Chlorella were 32.85% and 28.77%, respectively, while the Chla in the 2200 µg L−1 Chlorella-added group was only 0.01%, with no significant differences (p > 0.05) in AOR between the dark/light treatment subgroups. Fluorescence in situ hybridization showed that AOB, nitrite-oxidizing bacteria, and algae coexist and grow together without free AOB in the nitrifying bacterial community. It was suggested that microalgae enhance the resistance of AOB to light irradiation in a pond through the shading effect provided by algal chlorophyll and the close symbiotic relationship between microalgae and AOB. [ABSTRACT FROM AUTHOR]

Biological Nitrification Inhibition (BNI) encompasses primarily NH4+‐induced release of secondary metabolites to impede the rhizospheric nitrifying microbes from performing nitrification. The intermediate wheatgrass Thinopyrum intermedium (Kernza®) is known for exuding several nitrification inhibition traits, but its BNI potential has not yet been identified. We hypothesized Kernza® to evince BNI potential through the presence and release of multiple BNI metabolites. The presence of BNI metabolites in the biomass of Kernza® and annual winter wheat (Triticum aestivum) and in the root exudates of hydroponically grown Kernza®, were fingerprinted using HPLC‐DAD and GC–MS/MS analyses. Growth bioassays involving ammonia‐oxidizing bacteria (AOB) and archaea (AOA) strains were conducted to assess the influence of the crude root metabolome of Kernza® and selected metabolites on nitrification. In most instances, significant concentrations of various metabolites with BNI potential were observed in the leaf and root biomass of Kernza® compared to annual winter wheat. Furthermore, NH4+ nutrition triggered the exudation of various phenolic BNI metabolites. Crude root exudates of Kernza® inhibited multiple AOB strains and completely inhibited N. viennensis. Vanillic acid, caffeic acid, vanillin, and phenylalanine suppressed the growth of all AOB and AOA strains tested, and reduced soil nitrification, while syringic acid and 2,6‐dihydroxybenzoic acid were ineffective. We demonstrated the considerable role of the Kernza® metabolome in suppressing nitrification through active exudation of multiple nitrification inhibitors. [ABSTRACT FROM AUTHOR]

The unique positioning of mangrove ecosystems between land and sea makes them vital in the nitrogen cycle. The role of nitrification in the nitrogen cycle is important to provide nitrogen compounds readily absorbed by mangrove plants. Nevertheless, the nitrification process and nitrifying bacteria in mangrove areas have yet to be comprehensively understood. The primary objective of this study is to provide comprehensive analysis of nitrifying bacteria in mangrove sediments by conducting a systematic review. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses method is used as a guide to help report reviews systematically and has a flow chart to show the process of selecting relevant studies. Data collection was carried out by utilizing 6 databases and journal search engines including Scopus, PubMed, ResearchGate, Google Scholar, and Springer in order to achieve more comprehensive findings. This study employed the widely recognized and commonly used technique of defining the review's scope in a focused manner by first identifying the population, intervention, comparison, and outcome. This study identified 358 studies, and 31 studies were included in the review after screening. Based on the screening results, research on nitrifying bacteria in mangrove sediments is geographically limited to several countries such as Indonesia, Vietnam, Thailand, China, Mexico, the United States, India, and Saudi Arabia. This study vealed that there is a high level of diversity among nitrifying bacteria in mangrove sediment, with five distinct groups identified: ammonia oxidizing bacteria, nitrite oxidizing bacteria, anammox bacteria, and comammox bacteria, a recently identified group. In carrying out changes in nitrogen compounds, nitrifying bacteria use functional genes from different steps of the nitrification process, such as nitrogenase, ammonia monooxygenase subunit A, nitrite oxidoreductase alpha subunit, nitrate reductase alpha chain, nitrite reductase, nitric oxide reductase, nitrous oxide reductase, hydrazine synthase, hydrazine oxidoreductase and hydroxylamine oxidoreductase genes. Ammonia-oxidizing bacteria were the predominant group in general, but various nitrifying bacteria groups were distributed diversely across different mangrove environments. This study also indicated the vegetation type and the distribution of nitrifying bacteria in mangrove sediments. The depth of these sediments typically varies from 0 to 60 centimeters, with most samples taken at a depth of 0 to 20 centimeters. The type of vegetation at the sampling location is dominated by species of Kandelia candel, Avicennia marina, Kandelia obovata, and Rhizophora mangle. Limitations regarding research on nitrifying bacteria in mangrove sediments provide opportunities for in-depth study. This comprehensive review provides an in-depth overview of the variety and spread of nitrifying bacteria, highlighting their role in nitrogen cycling and emphasizing the potential for discovering new nitrifying bacteria in mangrove sediments. [ABSTRACT FROM AUTHOR]