Soil salinization is a major challenge in soil management, and remediating saline soils is crucial for sustainable soil resource development. Although vermicompost and biochar are frequently employed as soil amendments, their micro-ecological remediation mechanism for acid saline soils needs further verification. This study aimed to investigate whether vermicompost co-applied with coconut-shell biochar exerts a synergistic positive impact on coastal saline soil micro-ecology. A pot experiment was conducted to examine the microecological regulation effect of vermicompost co-applied with coconut-shell biochar on coastal saline soil. The study revealed that applying the amendment containing vermicompost and coconut-shell biochar significantly improved the quality of coastal saline soils by reducing soil salinity, increasing the soil pH and organic matter (OM), and enhancing nutrient availability and enzyme activity. The soil salinity changed from moderate to mild, and total water-soluble salts (TS) significantly decreased by 72.8%. The soil pH raised significantly by 6.5%. The contents of OM, alkali-hydrolyzed nitrogen (AN), available phosphorus (AP), and available potassium (AK) increased by 20.8%, 50.4%, 80.9%, and 41.6%, respectively. Moreover, the three enzyme activities of urease (UE), acid phosphatase (ACP), and catalase (CAT) increased by 835%, 17.1%, and 130%, respectively. Additionally, vermicompost co-applied with coconut-shell biochar significantly impacted bacterial diversity and community composition. Notably, vermicompost co-applied with coconut-shell biochar boosted the growth of key salttolerant bacterial groups. Specifically, the relative abundance of Acidobacteriota, Gemmatimonadetes, Actinobacteria, and Chloroflexi increased by 167%, 888%, 86.7%, and 123%, respectively. Redundancy analysis showed that vermicompost co-applied with coconutshell biochar could reduce TS by increasing pH, available nutrients, bacterial diversity, and enzyme activities in coastal soils. To sum up, vermicompost co-applied with coconut-shell biochar played a crucial role in positively influencing the soil micro-ecological environment. It effectively reduced soil salinity and would hold great potential for improving saline soil conditions.

Abstract The aim of the study was to assess the effect of grazing native sheep breeds on soil condition. Methods: The study was conducted on soils of xerothermic grasslands in eastern Poland, within four Natura 2000 sites: Ostoja Nadbużańska PLH140011, Zachodniowołyńska Dolina Bugu PLH060035, Stawska Góra PLH060018 and Kąty PLH060010. Soil samples were collected over three years, twice annually: before and after grazing. The intensity of biochemical N transformations was determined based on the activity of nitrogen cycle enzymes, i.e. urease (UrA) and proteases (PrA), as well as N resources (total N, ammonium N and nitrate N) in soils under conditions of extensive sheep grazing. Results: In the soils of all studied habitats, a beneficial effect of extensive sheep grazing on the activity of soil enzymes, the content of total N and mineral forms of N was found. A noticeable improvement in the soil’s biochemical condition was observed in the habitat, which had been subjected to continuous sheep grazing since 2008. The soil of the grazed site was characterized by two times higher PrA and four times higher UrA than the soil of wastelands. Still, long-term studies are needed to investigate better enzyme activity changes and N content fluctuations.

Cowpea (Vigna unguiculata) is a nutritious vegetable and a key crop in China, encompassing a sizeable cultivation area. However, continuous cropping has led to declines in yield and quality, limiting sustainable development in the protected cowpea industry. This study investigated the effects of combining organic fertilizer with soil conditioner (an amendment containing beneficial microbes and organic components) on protected cowpea production, soil physicochemical properties, and microbial community structure in soils subjected to five consecutive cowpea cropping cycles. The results demonstrated that combined application significantly improved cowpea yield and quality. Specifically, soil pH decreased by 5.4%, while soil organic matter (OM) content increased markedly, especially during the vegetative growth stage, displaying a 70.4% increase. The activities of key soil enzymes, including sucrase (SC), protease (PT), nitrate reductase (NR), dehydrogenase (DHO), and phosphatase, were enhanced, while the urease (UE) activity decreased. Additionally, the combined application improved bacterial and fungal abundance and diversity. Operational taxonomic unit (OTU) richness exhibited positive correlations with various soil nutrient indicators, enzyme activities, and physicochemical properties. Moreover, cowpea protein, carbohydrate, and energy contents were positively correlated with specific soil enzyme activities and nutrient levels. The combined treatment increased the cowpea yield by nearly 32,849kg per ha and protein content by 32.3% compared with applying only organic fertilizer while optimizing the soil microbial community, improving soil structure and fertility, and effectively mitigating the issues of continuous cropping in protected cowpea production.

Phosphate tailings (PTs) are typical industrial byproducts that can rapidly neutralize soil acidity. However, their acid-neutralizing efficacy, long-term application optimization mechanisms, and high-yield regulation pathways for crops remain unclear. This study conducted a corn-potato crop rotation field trial on acidic soils, investigating the effect of different PT application rates (T: CK, 0 t·ha−1; PTs-1, 6 t·ha−1; PTs-2, 9 t·ha−1; PTs-3, 15 t·ha−1) in a multiple cropping system (C: late autumn potatoes (LAP)-early spring potatoes (ESP)-summer maize (SM)). The results showed that two consecutive applications of 9 t·ha−1 of PTs produced optimal results, increasing the LAP yield by 12.82% and the soil quality by 76.51%, while improving the ESP soil quality by 46.21%. The higher yield was mainly attributed to a significant increase in the soil pH (0.72–1.58 units) and enhanced chemical and biological properties (higher exchangeable calcium (ExCa), exchangeable magnesium (ExMg), the total exchangeable salt base ion (TEB), and catalase (CAT) and urease (UE) content and lower soil exchangeable acidity (EA), exchangeable hydrogen ion (ExH), and exchangeable aluminum (ExAl) levels). Notably, a synchronized increase in the total phosphorus (TP) and total potassium (TK) during LAP cultivation, combined with simultaneous growth of TP, available nitrogen (AN), and available phosphorus (AP) during ESP cultivation, and a significant increase in TP and AP during SM cultivation, effectively promoted crop yield. Furthermore, continuous PT application significantly enriched phosphorus (P)-soluble functional bacteria, such as Actinomycetes and Chloroflexota, and enhanced the stability of bacterial-fungal cross-boundary networks. In summary, optimal acidity levels and favorable soil texture improved soil quality, consequently increasing corn and potato yields. This study reveals for the first time that PTs can substantially increase crop production via a synergistic mechanism involving acid-base balance, structural improvement, and microbial activation. Not only does this provide a novel strategy for rapidly improving acidic soils, but it also establishes a solid theoretical and technical foundation for utilizing PT resources.

Karst regions are characterized by naturally high levels of heavy metals such as cadmium (Cd), lead (Pb), and zinc (Zn). In these areas, traditional methods of non-ferrous metal smelting, which often lack treatment for wastewater, gases, and slag, frequently result in significant exogenous heavy metal contamination. This study investigates the effect of two contaminated soils; i) geological high background soil without external pollution (G) and ii) zinc smelting contaminated soil (Z) with external pollution from zinc powder factory and two Chinese cabbage (Brassica rapa L. var. pekinensis) varieties: i) Jincai No. 3 (J), and ii) Beijing Xin No. 3 (B) having high and low Cd accumulation capability on plant heavy metal accumulation, soil enzyme activities, microbial communities, and soil fauna diversity to elucidate how different plant varieties interact with distinct soil conditions. The results revealed significant variations in heavy metal uptake between cabbage varieties, influenced by soil properties. Cd concentrations in J and B varieties were 0.93 and 0.97mg/kg in Z soil, respectively, compared to 0.19 and 0.15mg/kg in G soil. Similarly, Zn concentrations were almost four times higher in Z soil. Soil enzyme activities varied between treatments, with higher catalase (CAT) and urease (URE) activities observed in Z soil, while G soil exhibited greater acid phosphatase (ACP) and sucrase (SUC) activities. High-throughput sequencing and soil fauna studies revealed substantial differences in microbial and faunal community composition and diversity associated with two soils and two cabbage varieties. Redundancy analysis (RDA) showed that As, URE, and Ni significantly influenced the bacterial community structure, whereas CEC, ACP, and pH were critical for the fungal communities. The study offers insights into phytoremediation strategies and soil health management by highlighting the complex interactions between soil contamination, heavy metal uptake by plants, and microbial community dynamics, with the goal of reducing pollution and enhancing ecosystem health in contaminated karst areas.

The widespread occurrence of nano-plastics (NPs) in aquatic environments poses emerging challenges to the pollutant removal performance and ecological stability of constructed wetlands (CWs). This study investigates the performance of calcium-modified (Ca-MBF) and manganese-modified basalt fiber (Mn-MBF) bio-nests as novel substrates to mitigate NP-induced inhibition of CWs. Laboratory-scale CWs were operated for 180 days to evaluate substrate-associated enzyme activities, microbial community structure, and functional gene profiles. Results showed that Mn-MBF bio-nests enhanced the activities of dehydrogenase (DHA), urease (UR), ammonia monooxygenase (AMO), nitrite oxidoreductase (NOR), nitrate reductase (NAR), nitrite reductase (NIR), and phosphatase (PST) by 86.2%, 65.5%, 127.0%, 62.8%, 131.5%, 65.3%, and 107.0%, respectively, compared with the control. In contrast, Ca-MBF bio-nests increased these enzyme activities by 48.6%, 53.5%, 67.0%, 30.6%, 95.0%, 45.3%, and 54.6%, respectively. MBF bio-nests also enhanced microbial diversity, enriched denitrifying and phosphorus-removing bacteria (e.g., Thauera, Plasticicumulans), and promoted extracellular polymeric substance secretion. Functional gene prediction indicated elevated abundances of nitrogen cycle-related genes, thereby enhancing nitrification, denitrification, and phosphorus removal processes. These synergistic effects collectively improved nitrification, denitrification, and phosphorus removal efficiency, with Mn-MBF showing superior performance. This study highlights MBF bio-nests as a sustainable strategy to enhance the resilience and long-term operational stability of CWs in environments impacted by nano-plastic pollution.

In recent years， microplastics （MPs） contamination in agroecosystems and its adverse effects on soil health and plants has attracted increasing concern. Biological nitrogen fixation is an important source of nitrogen for the agroecosystem， and soil fertility maintenance can be affected greatly by the diazotrophs. However， there are few studies on the evolution characteristics and interrelationships of MPs and diazotrophs in greenhouse vegetable fields with different planting years in karst areas. This study aimed to analyze the changes in MPs and diazotroph community in different planting years （1， 5， 10， and 12） in karst areas. The results showed that the contents of total nitrogen （TN）， ammonium nitrogen （NH4+-N）， and nitrate nitrogen （NO3--N） increased with prolongation of growth. Soil urease （URE） and sucrase （SUC） activities first increased and then decreased with prolongation of growth， and the pH value， organic carbon （SOC）， available potassium （AK）， C/N， and catalase activities （CAT） of soils decreased with prolongation of growth. MPs were detected in all greenhouse vegetable field soil samples at concentrations ranging from （286.67±72.23） to（2 454.33±309.73） n·kg-1， with a mean abundance of （1 518.58±174.03） n·kg-1. The abundance of MPs increased with increase of planting years. MPs in greenhouse vegetable fields with different planting years had mostly small size （0?1 mm）， accounting for 55.59% of the distribution. The small size （0-0.1 mm） increased with increase of planting year. Fibers， fragments， and films were the main shapes of MPs， occupying 40.81%， 27.34%， and 23.74% of the MPs， respectively. The color was mainly transparent， accounting for 24.78% of MPs， and the most common polymer type was polypropylene， accounting for 20.83%. With increase in planting years in the greenhouse vegetable fields， the nifH gene and diversity index α changed significantly， with the abundances of nifH gene and diversity index α being promoted significantly to year 5 but being significantly inhibited after year 5. The dominant phyla in the soil diazotrophic community included mainly Pseudomonadota （48.60%） and Thermodesulfobacteriota （44.54%）. Desulfuromonas， Bradyrhizobium， Citrifermentans， and Azohydromonas were the dominant genera. After 5 years of planting， the abundances of Pseudomonadota， Desulfuromonas，Bradyrhizobium， and Citrifermentans were significantly increased， but their relative abundances decreased with increase after planting year thereafter. The pH， SOC， NO3--N， C/N， AK， NH4+-N， CAT， and MPs values were the main factors affecting the structure of the bacterial community. Partial least squares path modeling （PLS-PM） analysis showed that planting years have a significant inhibitory effect on the diazotrophic community due to enrichment of MPs. Thus， utilizing a reasonable number of planting years and reducing the input of microplastics would improve microbial activity and provide a basis for sustainable utilization and high-quality production in greenhouse vegetable fields.

Prescribed burning significantly influences the microbial communities and physicochemical characteristics of forest soils. However, studies on the impacts of prescribed burning on the stability of soil microbial co-occurrence networks, as well as on the combined effects of post-fire soil depth gradients and their interactions on soil physicochemical properties and microbial communities, remain poorly understood. This study was conducted in a subtropical Pinus yunnanensis plantation that has undergone annual prescribed burns since 2007. Using 16S and ITS rRNA gene sequencing techniques alongside analyses of soil physicochemical properties, we collected and examined soil samples from different depths (0–5 cm, 5–10 cm, and 10–20 cm) in June 2024. The study found that prescribed burning enhanced the complexity and stability of bacterial co-occurrence networks, boosting both the diversity (prescribed burning/unburned control: 3/1) and the abundance (prescribed burning/unburned control: 8/2) of key taxa, which were essential for maintaining bacterial community network stability. However, it also intensified competitive interactions (prescribed burning/unburned control: 0.3162/0.0262) within the community. Moreover, prescribed burning had a significant effect on the diversity, structure, and composition of microbial communities and the physicochemical properties in the 0–5 cm soil layer, while also showing notable effects in the 5–20 cm layer. Prescribed burning also enhanced the coupling between the soil environment and bacterial community composition. The bacterial community showed negative correlations with most physicochemical properties. Soil organic matter (SOM) (p = 0.002) and available potassium (AK) (p = 0.042) were identified as key determinants shaping the post-fire bacterial community structure. The relationship between physicochemical parameters and fungal community composition was weaker. Urease (UE) (p = 0.036) and total potassium (TK) (p = 0.001) emerged as two key factors influencing the composition of post-fire fungal communities. These results elucidate the distinct functional roles of bacteria and fungi in post-fire ecosystem recovery, emphasizing their contributions to maintaining the stability and functionality of microbial communities. The study provides valuable insights for refining prescribed burning management strategies to promote sustainable forest ecosystem recovery.

Effects of PBAT biodegradable mulch on lettuce (Lactuca sativa L.) physiology and soil microbial community: Based on a long-term degradation trial.

This study evaluated the effects of different doses of the herbicide fluroxypyr on soil microbial communities under controlled laboratory conditions. Specific enzymatic activities ((dehydrogenase (DA), urease (UA), catalase (CA), phosphatase (PA)) and quantitative variations in bacterial and fungal populations were measured regarding key physico-chemical soil parameters (temperature, pH, electrical conductivity, moisture, organic matter, ammonium, nitrate nitrogen, and available phosphate content). The effects of the herbicide on the targeted parameters were dose- and time-dependent. Fluroxypyr induced a clear decrease in DA, CA, and PA during the first 14 days after administration, while UA showed a decrease in the first 7 days, followed by a slight increase starting on day 14, closely related to the applied dose. Microbial populations decreased in direct relation to the fluroxypyr dose. Organic matter content exhibited a positive correlation with DA, UA, CA, as well as with microbial populations. In addition, three natural compounds structurally similar to fluroxypyr were identified via 3D virtual screening, demonstrating potential herbicidal activity. Fluroxypyr can alter soil metabolic activity and disrupt microbial communities, thereby affecting soil fertility. Used as a reference in 3D screening, fluroxypyr helped identify three natural compounds with potential herbicidal activity as safer alternatives to synthetic herbicides.

Urease (urea amidohydrolase, EC 3.5.1.5) is a metalloenzyme that catalyzes the hydrolysis of urea into ammonia and carbamate, playing a pivotal role in numerous biotechnological applications. Initially sourced from plants (such as Canavalia ensiformis), followed by bacteria (Sporosarcina pasteurii, Bacillus subtilis), fungi (Aspergillus niger), and cyanobacteria, urease has become increasingly significant across a wide range of sectors. This review explores the diverse origins of urease, its intricate catalytic mechanisms, and the regulatory roles of accessory genes that modulate its activity. Special emphasis is placed on microbial ureases and its applications in agriculture, heavy metal remediation, clinical diagnostics, and geotechnical engineering. The review also investigates ureolysis-induced calcium carbonate precipitation (UICP), with a focus on the environmental and biochemical factors that influence this process. A comparison between microbial-induced carbonate precipitation (MICP) and enzyme-induced carbonate precipitation (EICP) is provided, highlighting their respective advantages and limitations. Additionally, recent advancements in optimizing UICP through machine learning techniques are discussed, aiming to enhance process efficiency and scalability. Overall, this review underscores the substantial potential of urease-driven technologies in offering sustainable solutions across a variety of industrial and environmental applications.

ABSTRACTIntercropping significantly affects soil microbial communities and nutrient content; however, the influence of intercropping with fertilizer application on them has yet to be elucidated. A pot experiment was performed with three planting patterns: P (poplar monoculture; Populus deltoides ), S (soybean monoculture; Glycine max ) and PS (poplar–soybean intercropping), with three fertilizer application rates of 0, 5, and 10 g (10 kg of soil per pot). The soil properties and fungal community under different treatments were analyzed. Planting patterns and fertilizer application rates significantly influenced soil properties and fungal communities. The PS pattern exhibited significantly higher soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), and ammonium nitrogen (NH4 +‐N) contents; greater urease (UR) and sucrase (SUR) activities; and greater soil fungal diversity than did the S and P patterns. Soil nitrate nitrogen (NO3 −‐N), available phosphorus (NH4 +‐N, AP), available potassium (AK) contents, UR, SUR activities; and fungal diversity increased with a higher fertilizer application rate, with the highest values occurring in the 10 g fertilizer treatment. Structural equation modeling revealed that intercropping and fertilizer application affected soil nutrients by altering fungal community and enzyme activity. Soil water content and NO3 −‐N content were the dominant factors affecting the soil fungal community (p < 0.05). The PS pattern significantly decreases the relative abundance of soil pathogenic fungi and increases the relative abundance of soil fungi related to SOM transformation and nutrient utilization efficiency. In conclusion, these findings emphasize the importance of poplar intercropping and fertilizer application on soil quality, providing guidance for the selection and management of planting patterns in agriculture to improve soil quality.

Current nanoparticle-based drug delivery systems for tumor therapy face significant challenges in intratumoral penetration and cellular internalization, leading to poor therapeutic efficacy. Herein, it is demonstrated that the sequential integration of glucose oxidase (GOx), catalase (CAT), and urease (URE) onto the half surface of biotin-modified Janus nanoparticles via the chemical coupling way produces nanorobots of multifunctionality and synergistic effect (denoted as UCGPJNRs). They can autonomously and powerfully move in tumor microenvironment (TME) by using endogenous urea as a fuel, enabling to penetrate deeper than 0.55 mm into tumor tissues, ≈5.5-fold of the previous counterparts. The UCGPJNRs perform motion-enhanced biotin receptor-mediated endocytosis and endoplasmic reticulum/Golgi apparatus pathway-mediated exocytosis, greatly improving the internalization efficiency of tumor cells. They release NH3 when moving to produce selective toxicity against tumor cells in hypoxic TME. Further, they enhance the glucose consumption by ≈threetimes due to the motion-accelerated GOx/CAT cascade reaction, disrupting the metabolism against tumor cells on a large area. After intratumorally injecting into tumor-bearing mice, UCGPJNRs can significantly amplify the in vivo tumor growth inhibition rate through their synergistic effect. This work provides a plausible strategy to overcome current limitations in tumor treatment by anchoring multiple bioenzymes on one nanoparticle.

Aim of study: We investigated how changes in forest gap size influence soil enzyme activities in both the rhizosphere and bulk soils, mediated by rhizosphere effects (RE). Area of study: Xuzhou, Jiangsu Province, China. Material and methods: The study was conducted in a 46-year-old Platycladus orientalis (L.) Franco, 1950 plantation in Xuzhou and its aim was accomplished by sampling soils, one year after forest gaps establishment, from three levels of forest gap sizes: small (S, with a radius of 4 m), medium (M, with a radius of 8 m), and large (L, with a radius of 12 m), as well as control plots (CK, without any gaps). Soil enzyme activities, including peroxidase (PER), dehydrogenase (DEH), urease (URE), and invertase (INV), were quantified. Main results: Gap size and season strongly affected the RE on DEH and URE. The interaction of gap size, location and season significantly affected the RE on DEH, URE, and INV. Enzyme activities in bulk soils were more sensitive to changes in nutrient availability than in rhizosphere soils, and microbial biomass played a crucial role in modulating enzyme activity. Furthermore, both L and S forest gaps exerted an influence on the RE of enzyme activity, with L gaps exhibiting the most extensive impact. Research highlights: This study observed that the RE of soil enzyme activity did not increase with the enlargement of forest gap size. However, in L forest gaps, its impact range was more extensive.

Soilborne pathogens significantly impact potato productivity by altering rhizosphere enzymatic activities and microbial communities. Pathogen-induced changes in enzyme activities are correlated with shifts in microbial community composition, but causal relationships remain unclear. This study investigates the effects of five key pathogens-Phytophthora infestans, Streptomyces scabies, Spongospora subterranea, Ralstonia solanacearum and Globodera rostochiensis-on soil enzyme activities and microbial community structure in potato rhizosphere soils under continuous cropping. This experiment involved pathogen inoculation and soil sampling in potato rhizosphere soils, with treatments replicated three times. Potatoes were planted on March 22, 2023, and harvested on August 25, 2023. Enzymatic activities were measured at different growth stages, and microbial communities were analyzed using high-throughput sequencing. Pathogen-induced variations in enzymatic activities were observed, potentially promoting disease proliferation. For instance, under S. scabies stress, urease (URE) activity increased significantly at the full flowering and post-flowering stages, while catalase (CAT) activity decreased significantly during the seedling and full flowering stages. Under S. subterranea stress, activities of urease, sucrase (SUC), and alkaline phosphatase (ALP) decreased. M. nematode stress led to a decline in URE and sucrase activities. P. infestans infection led to a decrease in URE activity at the sowing stage. Furthermore, microbial community composition was significantly correlated with disease incidence, with specific taxa such as Planctomycetes and Basidiomycota showing negative correlations with S. subterranea incidence, while Candidatus Dormibacteraeota and Ascomycota were positively associated with P. infestans. These results suggest that pathogen-induced changes in enzymatic activities play a critical role in disease dynamics and microbial interactions. The findings highlight the importance of understanding the effects of soilborne pathogens on soil enzyme activities and microbial communities, providing insights into disease management strategies in potato farming.

Recycled wheat straw biochar enhances nutrient-poor soil: Enzymatic kinetics of carbon, nitrogen, and phosphorus cycling.

Excessive soil cadmium (Cd) and the accumulation of pathogens pose serious threats to legume growth. However, it remains unclear whether intercropping (IFcd) and its combined treatment with silicon nanoparticles (Si-NPs) (IFcd + Si) can alleviate these challenges under Cd stress, as well as the underlying mechanisms involved. This study systematically elucidated the mechanism of faba bean-wheat intercropping and Si-NPs regulating faba bean growth under Cd stress using rhizosphere metabolomics and 16 S rRNA microbiome analysis. The results showed that IFcd and IFcd + Si treatments significantly reduced Cd accumulation by 17.3% and 56.2%, and Fusarium wilt incidence by 11.1% and 33.3%, respectively, compared with monoculture faba bean (MFcd) while promoting root and plant growth. These treatments reduced oxidative stress markers, including H2O2, MDA, and O2−, and increased the activity of defense enzymes, such as SOD, APX, and POD in plants. Furthermore, they increased NH4+-N and available potassium levels in rhizosphere soils. Interestingly, the NH4+-N content increased and was significantly positively correlated with urease (URE) activity and negatively correlated with Cd. Beneficial bacteria and functional metabolites were enriched in the rhizosphere of faba bean. Joint analysis revealed increased relative abundances of Sphingomonas, Intrasporangium, and Streptomyces, which were positively correlated with antibacterial metabolites, such as sordarin, lactucin, and 15-methylpalmate. This explains the reduced Cd accumulation and Fusarium wilt in plants. These findings provide mechanistic insights into how intercropping with Si-NPs mitigates Cd stress and controls soil-borne diseases by regulating rhizosphere metabolites, bacterial communities, and plant resistance.Graphical

Urea is an important source of nitrogen for many phytoplankton with the potential to stimulate harmful algal blooms, but the molecular machinery underpinning urea uptake and assimilation by algae is not fully understood. Urease (URE) is commonly regarded as the responsible enzyme, but urea amidolyase (UAL), albeit known to exist, has hardly been studied. Here, the species distribution, expression patterns and functional roles of UAL are examined. We found a widespread occurrence of UAL across six major phytoplankton lineages, along with evidence of a potential URE-independent evolutionary trajectory and lineage-specific losses. Quantitative analyses based on marine planktonic metagenomes and metatranscriptomes revealed that UAL is as prevalent as URE, but exhibits higher expression levels in phytoplankton than in bacteria, suggesting that UAL plays a crucial role in nitrogen nutrition in marine phytoplankton. Furthermore, using the CRISPR/Cas9 genome editing method and Chlamydomonas reinhardtii as the algal model, we showed that DUR2 in UAL is essential for urea utilisation, as its knockout completely abolishes the ability of algae to grow under urea as the sole nitrogen source. This study unveils an unappreciated mechanism in algae for utilising urea as a nutrient, underscores the need to consider both URE and UAL enzyme systems to model urea utilisation by algae and provides a crucial gene (DUR2) as a potential genetic marker for detecting the contribution of UAL to urea utilisation in phytoplankton.

Amide herbicides (AHs) disturbed urease (UA) activity and soil microbial community and caused soil nutrient changes. Activity of UA was inhibited by AHs via groups of chlorine, benzene ring, and peptide bond (-N-/-CO-). Differences of surface charge distribution were mainly derived from position to connected -Cl, distance of -O- from ether group and -N from peptide bond, difference of structure/length for hydrocarbon chain, and different regions of negative charge enrichment. Developmental toxicity for alachlor was strongest related to smaller structure and weaker steric hindrance effect; mutagenicity for propanil was weakest possibly related to missing ether group. Molecular mechanism and structural activity relationship for inhibition of AHs and UA were based on functional groups, amino acids with high frequency, hydrogen bonds, hydrophobic interactions, binding area (BA) of butachlor (396.3 Å2), absolute value of binding energy (|BE|) of propanil (2.93 kJ/mol; which was highest), and quantitative structural relationship between BA and |BE|, which was negative correlation. Binding area for AHs and UA had negative correlation for density with correlation coefficient (r) as -0.937 (p ≤ 0.01). Absolute value of binding energy for AHs and UA had positive correlation for density with r as 0.847 (p ≤ 0.05), and negative correlation for molecular weight with r as -0.973 (p ≤ 0.001). Results provided technological support and theoretical foundation for toxic effects of soil enzyme activity, health effects, risk regulation, and control of AHs.

Understanding the changes in soil enzyme activities and the influencing factors after forest fire distur-bances can help assess and predict the impacts of climate warming on permafrost ecosystems. We analyzed the acti-vities of extracellular enzyme, including urease (UR), acid phosphatase (AP), acetyl-glucosidase (NAG), β-glucosidase (βG), and leucine aminopeptidase (LAP), in soils (0-60 cm depth) across unburned, lightly burned and severely burned sites within the 2015 burned area in the northern Da Xing'anling Monntains. The results showed that fire intensity, soil depth, and soil physicochemical properties significantly influenced extracellular enzyme activities. Compared to that in unburned site, the activities of UR, AP, βG, and LAP increased by 59.8%-241.7%, while NAG decreased by 35.5% at lightly burned site. The activities of all soil enzymes increased, with the magnitidues ranging from 26.0% to 206.0% at severely burned site. Soil enzyme activities gra-dually decreased with increasing soil depth. Redundancy analysis identified soil temperature (ST), total phosphorus (TP), C:P, C:N, soil depth and soil water content (SWC) as important influencing factors of soil enzyme activities, contributing 70.9%, 12.2%, 4.7%, 3.6%, 2.9%, and 1.9%, respectively. Soil enzyme activities were signifi-cantly positively correlated with ST, TP, C:P, C:N, and SWC, but significantly negatively correlated with soil depth. Forest fires and the resultant changes in soil physicochemical properties jointly affected soil extracellular enzyme activities, with the effects intensifying with increasing fire intensity.