Addition of cellulose and hemicellulose degrading microorganisms intensified nitrous oxide emission during composting.

This study aims to clarify the mechanisms underlying effects of inoculating cellulose and hemicellulose-degrading microorganisms on nitrous oxide (N2O) emissions during composting with silkworm excrement and mulberry branches. Inoculation with cellulose and hemicellulose-degrading microorganisms resulted in significant increases of total N2O emission by 10.4 ± 2.0 % (349.1 ± 6.2 mg N kg-1 dw) and 26.7 ± 2.1 % (400.6 ± 6.8 mg N kg-1 dw), respectively, compared to the control (316.3 ± 3.6 mg N kg-1 dw). The stimulation of N2O emission was attributed to the enhanced contribution of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria to N2O production, as evidenced by the increased AOB amoA and denitrifying nirK gene abundances. Moreover, microbial inoculation stimulated N2O reduction to N2 owing to increased abundances of nosZⅠ and nosZⅠⅠ genes. These findings highlight the necessity to develop cost-effective and environmentally friendly strategies to reduce N2O emissions when cellulose and hemicellulose-degrading microorganisms are inoculated during composting.

Tree species diversity increases soil microbial carbon use efficiency in a subtropical forest.

Plant communities strongly influence soil microbial communities and, in turn, soil carbon (C) cycling. Microbial carbon use efficiency (CUE) is an important parameter for predicting soil C accumulation, yet how plant and soil microbial community traits influence microbial CUE remains poorly understood. Here, we determined how soil microbial CUE is influenced by plant and soil microbial community traits, by studying a natural gradient of plant species diversity in a subtropical forest. Our results showed that microbial CUE increased with increasing tree species diversity, suggesting a correlation between plant community traits and soil C storage. The specific soil properties that explained the greatest variation in microbial CUE were associated with microbial communities (biomass, enzyme activities and the ratio of oligotrophic to copiotrophic taxa); there were weaker correlations with plant-input properties, soil chemistry and soil organic C quality and its mineral protection. Overall, high microbial CUE was associated with soil properties correlated with increased tree species diversity: higher substrate availability (simple SOM chemical structures and weak mineral organic associations) and high microbial growth rates despite increased community dominance by oligotrophic strategists. Our results point to a mechanism by which increased tree species diversity may increase the forest C sink by affecting carbon use with the soil microbial community.

Mechanisms of mitigating nitrous oxide emission during composting by biochar and calcium carbonate addition.

To investigate the mechanisms underlying effects of biochar and calcium carbonate (CaCO3) addition on nitrous oxide (N2O) emissions during composting, this paper conducted a systematic study on mineral nitrogen (N), dissolved organic carbon (C) and N, sources of N2O, and functional genes. Biochar and CaCO3 addition decreased N2O emissions by 26.5-47.8% (9.5-96.9 mg N kg-1 dw) and 13.9-37.4% (12.0-121.0 mg N kg-1 dw) compared to the control (14.3-179.7 mg N kg-1 dw), respectively. The mitigation of N2O emission was caused by decreased contribution of ammonia-oxidizing bacteria (AOB) and fungi to N2O production due to diminished AOB amoA, fungal nirK and P450 gene abundances, or by stimulated N2O reduction to N2 owing to increased abundances of nosZⅠ and nosZⅠⅠ genes under biochar and CaCO3 addition. The findings suggest that the addition of biochar or CaCO3 is effective in mitigating N2O emission during composting.

Study on Properties and Micro-Mechanism of RHB-SBS Composite-Modified Asphalt.

Rice husk biochar (RHB) is a renewable agricultural waste, and its fixation on pavements helps develop environmentally friendly, economical, and sustainable asphalt pavements. This paper used RHB to replace part of styrene-butadiene-styrene (SBS) for the composite modification study of matrix asphalt. The high- and low-temperature properties and microscopic mechanisms of the composite-modified asphalt were studied through a series of tests. The results showed that, compared with SBS-modified asphalt, the softening point, viscosity, complex shear modulus, stiffness modulus, and rutting factors of RHB-SBS composite-modified asphalt were improved. In contrast, the ductility and creep rate were slightly decreased, indicating an improvement in the high-temperature performance of composite-modified asphalt, but a slight decrease in its low-temperature performance. The process of RHB and SBS composite modification was mainly physical blending, with only a small number of chemical reactions, and no new functional groups were generated. The porous structure of RHB enables it to adhere better to the network crosslinked continuous phase system formed by SBS and matrix asphalt. This results in composite-modified asphalt with good high-temperature storage stability and rheological properties. Therefore, RHB-SBS composite-modified asphalt can be applied to high-temperature areas and rice-producing areas, and the optimal content of RHB is suggested to be 15%.

Mechanisms underlying the responses of microbial carbon and nitrogen use efficiencies to nitrogen addition are mediated by topography in a subtropical forest.

Microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE) are key parameters determining the fate of C and N in soils. Atmospheric N deposition has been found to heavily impact multiple soil C and N transformations, but we lack understanding of the responses of CUE and NUE to N deposition, and it remains uncertain whether responses may be mediated by topography. Here, a N addition experiment with three treatment levels (0, 50 and 100 kg N ha-1 yr-1) was conducted in the valley and on the slope of a subtropical karst forest. Nitrogen addition increased microbial CUE and NUE at both topographic positions, but the underlying mechanisms differed. In the valley, the increase in CUE was associated with an increase in soil fungal richness:biomass and lower litter C:N, whereas on the slope, the response was linked with a reduced ratio of dissolved soil organic C (DOC) to available phosphorus (AVP) which reduced respiration, and increased root N:P stoichiometry. In the valley, the increase in NUE was explained by stimulated microbial N growth relative to gross N mineralization, which was associated with increased ratios of soil total dissolved N:AVP and fungal richness:biomass. In contrast, on the slope, the increase in NUE was attributed to reduced gross N mineralization, linked to increased DOC:AVP. Overall, our results highlight how topography-driven soil substrate availability and microbial properties can regulate microbial CUE and NUE.

[Abundance of denitrifying genes and their driving factors in soil under different land use types in the karst region of Northwest Guangxi]. / æ¡‚è¥¿åŒ—å²©æº¶åŒºä¸åŒåœŸåœ°åˆ©ç”¨æ–¹å¼ä¸‹åœŸå£¤åç¡åŒ–åŸºå› ä¸°åº¦åŠå ¶é©±åŠ¨å› ç´ .

To understand the role of denitrifying microbes during vegetation recovery in karst regions, we determined the basic physicochemical properties and abundance of denitrifying microbial functional genes (nirS, nirK, fungal nirK, p450nor, and nosZ) of 13 collected soil samples under three land use types (cropland, grassland, and plantation) in Northwest Guangxi, and investigated the changes in the abundance of denitrifying microbial functional genes and their driving factors. Results showed that soil pH, soil organic carbon, total nitrogen (TN), and exchangeable calcium (Caexe) in plantation soil were significantly higher than those in cropland and grassland. The abundance of nirS, nirK, p450nor, and nosZ in plantation soil were significantly higher than those in cropland and grassland. Soil pH, TN, and Caexe were positively correlated with the abundance of denitrifying functional genes nirS, nirK, and p450nor. Results of redundancy analysis showed that soil Caexe, pH and TN were the primary factors influencing the abundance of denitrifying functional genes, which accounted for 34.1%, 20.1%, and 16.1% of the total variation, respectively. Such a result suggested that Caexe was the main driver of changes in denitrifying functional genes under different land use types. Overall, vegetation restoration (plantation) could effectively increase soil denitrifying microbe genes abundance in the karst region of Northwest Guangxi, and consequently influence soil nitrogen cycling.

Synergistically mitigating nitric oxide emission by co-applications of biochar and nitrification inhibitor in a tropical agricultural soil.

Agricultural soils are the hotspots of nitric oxide (NO) emissions, which are related to atmospheric pollution and greenhouse effect. Biochar application has been recommended as an important countermeasure, however, its mitigation efficiency is limited as biochar, under certain conditions, can stimulate soil nitrification. Therefore, biochar co-applied with nitrification inhibitor could optimize the mitigation potential of biochar. Herein, a laboratory-scale experiment was conducted to investigate the effects of co-application of biochar and nitrification inhibitor on NO emission, nitrogen cycling function and bacterial community in a tropical vegetable soil. Results showed that a single application of biochar or nitrification inhibitor significantly decreased NO emissions, and this mitigation effectiveness was amplified by their co-applications. Soil NO2--N intensity, along with abundances of AOB-amoA and nirK were significantly and positively correlated with cumulative NO emissions. The stimulated activity of ammonia monooxygenase and growths of AOB and total comammox Nitrospira by biochar were weakened by nitrification inhibitor, implying decreased nitrification-driven NO production. The nitric oxide reductase activity and related qnorB abundance in nitrification inhibitor-added soils were increased by biochar, indicating promoted NO consumption during denitrification. The nirK abundance and NO2--N intensity were decreased more by co-applications of biochar or nitrification inhibitor. Moreover, both biochar and nitrification inhibitor changed bacterial ß-diversity, and their co-application synergistically enriched Armatimonadetes and Verrucomicrobia abundances and decreased WPS-2 abundance. This study highlights that co-applications of biochar and nitrification inhibitor can make their respective advantages complementary to each other, thereby achieving a larger mitigation of NO emissions from agricultural soils in tropical regions.

PINK1/Parkin-Mediated Mitophagy Plays a Protective Role in Albumin Overload-Induced Renal Tubular Cell Injury.

BACKGROUND: Proteinuria is an important symptom of chronic kidney disease irrespective of its initial pathogenesis. Mitochondrial dysfunction is an early pathophysiological event in proteinuria-induced tubular damage. Mitophagy, the selective degradation of damaged mitochondria targeted by autophagy, contributes to mitochondrial homeostasis and is primarily regulated by the PTEN-induced kinase 1 (PINK1)/Parkin pathway. In this study, we evaluated the function of mitophagy in proteinuria-induced tubular injury and mechanism. METHODS: HK-2 cells were transfected with Parkin siRNA or Parkin overexpression plasmids for 48 h followed by treatment with albumin (8 mg/mL) for 8 h. JC-1 staining, ATP detection, and reactive oxygen species (ROS) detection were used to determine mitochondrial function. Immunoblot, LC3/mitochondria co-localization analyses, and Mito-Keima were employed to detect mitophagy. Immunoblot analysis and TUNEL were used to detect apoptosis. RESULTS: Albumin overload induced mitochondrial dysfunction and mitophagy activation in HK-2 cells. Parkin knockdown inhibited albumin overload induced-mitophagy. Parkin overexpression further upregulated albumin overload induced-mitophagy. Parkin deficiency aggravated albumin overload-induced mitochondrial dysfunction and the overproduction of ROS, resulting in increased cell injury. Contrarily, Parkin overexpression helped maintain mitochondrial function and attenuate ROS generation, contributing to cell protection. CONCLUSIONS: Our results suggest that by clearing damaged mitochondria and maintaining mitochondrial function, PINK1/Parkin-mediated mitophagy contributed to tubular cell survival during albumin overload. PINK1/Parkin-mediated mitophagy may be a potential therapeutic target for proteinuria in tubular epithelial cells.

Residual effects of four-year amendments of organic material on N2O production driven by ammonia-oxidizing archaea and bacteria in a tropical vegetable soil.

Organic material (OM) applied to cropland not only enhances soil fertility but also profoundly affects soil nitrogen cycling. However, little is known about the relative contributions of soil ammonia-oxidizing archaea (AOA) and bacteria (AOB) to nitrous oxide (N2O) production during ammonia oxidation in response to the additions of diverse types of OMs in the tropical soil for vegetable production. Herein, the soils were sampled from a tropical vegetable field subjected to 4-year consecutive amendments of straw or manure. All the soils were amended with ammonium sulfate ((NH4)2SO4, applied at a dose of 150 mg N kg-1) and incubated aerobically for four weeks under 50% water holding capacity. 1-octyne or acetylene inhibition technique was used to differentiate the relative contributions of AOA and AOB to N2O production. Results showed that AOA dominated N2O production in soil managements of unfertilized control (CK), chemical fertilization (NPK), and NPK with straw (NPKS), whereas AOB contributed more in soil under NPK with manure (NPKM). Straw addition stimulated AOA-dependent N2O production by 94.8% despite the decreased AOA-amoA abundance. Moreover, manure incorporation triggered both AOA- and AOB-dependent N2O production by 147.2% and 233.7%, respectively, accompanied with increased AOA and AOB abundances. Those stimulating effects were stronger for AOB, owing to its sensitivity to the alleviated soil acidification and decreased soil C/N ratio. Our findings highlight the stimulated N2O emissions during ammonia oxidation by historical OM amendments in tropical vegetable soil, with the magnitude of those priming effects dependent on the types of OM, and appropriate measures need to be taken to counter this challenge in tropical agriculture ecosystems.

Biochar amendment mitigated N2O emissions from paddy field during the wheat growing season.

Biochar may variably impact nitrogen (N) transformation and N-cycle-related microbial activities. Yet the mechanism of biochar amendment on nitrous oxide (N2O) emissions from agricultural ecosystems remains unclear. Based on a 6-year long-term biochar amendment experiment, we applied a dual isotope (15N-18O) labeling technique with tracing transcriptional genes to differentiate the contribution of nitrifier nitrification (NN), nitrifier denitrification (ND), nitrification-coupled denitrification (NCD) and heterotrophic denitrification (HD) pathway to N2O production. Then the field experiment provided quantitative data on dynamic N2O emissions, soil mineral N and key functional marker gene abundances during the wheat growing season. By using 15N-18O isotope, biochar decreased N2O emission derived from ND (by 45-94%), HD (by 35-46%) and NCD (by 30-64%) compared to the values under N application. Biochar increased the relative contribution of NN to total N2O production as evidenced by the increase in ammonia-oxidizing bacteria, but did not influence the cumulative NN-derived N2O. The field experiment found that the majority of the N2O emissions peaked following fertilization, in parallel with soil NH4+ and nitrite dynamics. Soil N2O emissions during the wheat growing stage were effectively decreased (by 38-48%) by biochar amendment. Based on the correlation analyses and random forest analysis in both microcosm and field experiments, the decrease in nitrite concentration (by 62-65%) and increase in N2O consumption were mainly responsible for net N2O mitigation, as evidenced by the decrease in the ratios of nitrite reductase genes/transcripts (nirS, nirK and fungal nirK) and N2O reductase gene/transcripts (nosZI and nosZII). Based on the extrapolation from microcosm to field, biochar significantly mitigated N2O emissions by weakening the ND processes, since NCD and HD contributed little during the N2O emission "peaks" following urea fertilization. Therefore, emphasis should be put on the ND process and nitrite accumulation during N2O emission peaks and extrapolated to all agroecosystems.

Organic substitutions aggravated microbial nitrogen limitation and decreased nitrogen-cycling gene abundances in a three-year greenhouse vegetable field.

Partially substituting chemical fertilizer with organic fertilizer has substantially changed the stoichiometric imbalances of carbon (C), nitrogen (N) and phosphorus (P) between microbial communities and their available resources in agroecosystems. However, how organic substitution alters microbial nutrient limitation and then affects soil N cycle in intensive greenhouse vegetable ecosystem, remain unknown. Thus, we performed a three-year greenhouse vegetable field experiment in China with different fertilization strategies: no N fertilization, chemical N fertilization, and substituting 20% (1M4N) or 50% (1M1N) of chemical N with organic fertilizer (organic substitutions). Our results demonstrated that the microbial communities presented N limitation, accompanying with a strong N:P but a weak C:N (or P) microbial homeostasis in response to high N:P imbalance among all treatments. Organic substitutions at 1M1N and 1M4N significantly aggravated microbial N limitation and decreased the gene abundances of nitrification and denitrification by 4.7%-27.3% than that of chemical N fertilization. Microbial N limitation was strongly influenced by N:P stoichiometric imbalance illustrated from regression analysis. The N-cycling gene abundances were not only dependent on the inorganic N pool and soil physicochemical properties (i.e. pH and electrical conductivity), but also affected by microbial nutrient limitation inferred from random forest analysis. Furthermore, the 1M1N treatment performed better than the 1M4N in terms of improved crop yield and less microbial N limitation. Overall, these results highlight the importance of ecological stoichiometry in regulating soil N cycle under different fertilization strategies for intensive greenhouse vegetable ecosystem.

The effect of long-term biochar amendment on N2O emissions: Experiments with N15-O18 isotopes combined with specific inhibition approaches.

Numerous studies reporting a transient decrease in soil nitrous oxide (N2O) emissions after biochar amendment have mainly used short-term experiments. Thus, long-term field trials are needed to clarify the actual impact of biochar on N2O emissions and the underlying mechanisms. To address this, both a 15N18O labeling technique and gene analyses were applied to investigate how N2O production pathways and microbial mediation were affected by long term biochar amendment in field. Then, 1-octyne and 2-phenyl l-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) were used in combination with potassium chlorate to evaluate the relative contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to potential ammonia oxidation (PAO) and the associated N2O production. Acidic and alkaline greenhouse vegetable soils that had each received two separate treatments were collected (control, no biochar amendment; biochar, biochar amended in the field after 2 or 7 years). The results showed that biochar decreased N2O emissions by 48% in acidic soils and by 22% in alkaline soils compared to those in control. These results were explained by decreases in nitrifier denitrification- (by 74%) and heterotrophic denitrification-derived N2O production (by 58%), as further evidenced by a decrease in NO2- (by 87%) and the (nirK+nirS+fungal nirK):(nosZ-I + nosZ-II) ratio (by 5%) in both greenhouse vegetable soils. However, biochar increased nitrifier nitrification-derived N2O in both soils because of increases in pH and PAO, which were attributed to an increased abundance of AOB rather than AOA. The contribution of AOB to PAO (or N2O) exceeded 69% (or 68%) of the total in acidic soil and 88% (or 85%) of the total in alkaline soil after biochar amendment. Our findings demonstrated that the mitigation of N2O by biochar is linked to specific N2O production pathways.

Spatial-heterogeneous granulation of organic amendments and chemical fertilizer stimulated N2O emissions from agricultural soil: An microcosm study.

The promising application modes of organic fertilizer (OF) and chemical nitrogen (N) fertilizer (CF) could be the homogeneous granulation (HG: OF and CF are distributed spatially evenly) and spatial heterogeneous granulation (SG: OF and CF are distributed separately in space), where the N transformation processes, such as the nitrous oxide (N2O) emissions, are greatly influenced by the spatial distribution of the OF and CF, particularly. Currently, there is a lack of in-depth understanding about the microbial mechanisms of the SG and HG application on N2O emissions, and the related functional guilds (ammonia oxidizers and heterotrophic denitrifiers) respond to the granular fertilizer is yet not known. In the present study, we made CF (15N-(NH4)2SO4), cow compost and maize straw (2% or 8% based on the N proportion) into granular of 1 cm in diameter, in HG and SG forms, respectively, and then applied these granules in soils for 80 days incubation. Results showed that, compared with HG treatments, the SG treatment promoted the ammonium (NH4+), nitrate (NO3-) and microbial biomass carbon (MBC) intensities, and increased the N2O emissions possibly through ammonia oxidize bacteria dependent nitrification and fungal denitrification. In addition, the high maize residues proportion in organic fertilizer significantly mitigated N2O emissions by the coupled impacts of suppressed nitrification and enhanced denitrification enzyme activity with high C input. Overall, our results suggest that spatial heterogeneous granulation of and CF may induce higher risk of N2O emissions and the higher proportion of maize residues could potentially mitigate such increased emissions.

Temperature decouples ammonia and nitrite oxidation in greenhouse vegetable soils.

The influence of temperature on soil ammonia (NH3) and nitrite (NO2-) oxidation and related NO2- accumulation in soils remain unclear. The soil potential NH3 oxidation (PAO) and NO2- oxidation (PNO) rates were evaluated over a temperature gradient of 5-45 °C in six greenhouse vegetable soils using inhibitors. The values of temperature sensitivity traits such as temperature minimum (Tmin), temperature optimum (Topt), and maximum absolute temperature sensitivity (Tm_sens) were also fitted to the square root growth (SQRT) and macromolecular rate theory (MMRT) models. The ammonia-oxidizing archaea (AOA) and bacteria (AOB) were determined by quantifying amoA, and nitrite-oxidizing bacteria (NOB) were determined by quantifying the nxrA and nxrB. Both models identified that Topt for PAO (34.0 °C) was significantly greater than that for PNO (26.0 °C). The Tm_sens (23.4 ± 2.1 °C) and Tmin (1.0 ± 2.0 °C) for PAO were higher than those for PNO (16.8 ± 3.2 °C and - 11.7 ± 6.7 °C). PAO was positively correlated with AOB-amoA at 20-30 °C and with AOA-amoA at 30-35 °C, while PNO was positively correlated with nxrB at 5-30 °C. Additionally, NO2- and N2O were positively correlated with the (AOA + AOB amoA) to (nxrA + nxrB) ratio, and the concentration of N2O was positively correlated with NO2- accumulation. These results highlight that elevated temperatures resulted in the uncoupling of NH3 oxidation and NO2- oxidation, leading to NO2- accumulation, which could stimulate N2O emissions.

Biochar-enriched soil mitigated N2O and NO emissions similarly as fresh biochar for wheat production.

Biochar amendment has been recommended as a potential strategy to mitigate nitrous oxide (N2O) and nitric oxide (NO) emissions for wheat production, but its mechanism and effective duration are not well understood. The 1-octyne and 2-pheny l-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) in combination with potassium chlorate were used to evaluate the relative contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to potential ammonia oxidation (PAO) and N2O and NO production as affected by biochar. Acidic and alkaline soils were collected during wheat-growing season, and four treatments were installed in each soil type: CK, urea alone; BE, biochar-enriched soil for 2-6 years; FB, fresh biochar added to CK; and AB, aged biochar added to CK. The results showed that octyne and PTIO efficiently assessed AOB and AOA activities in soil incubation. The AOB-driven PAO in acidic soil was largely enhanced by increased soil pH in BE and FB treatments, whereas AOA-driven PAO was not. And the contribution of AOB to PAO exceeded 80% in alkaline soil. The N2O and NO production were positively correlated with PAO in both soils. BE treatment decreased the direct N2O and NO production in alkaline soil, while both BE and FB treatments decreased the N2O and NO yields in acidic soil, indicating that biochar mitigated soil N2O and NO emissions for wheat production. The lack of differences between AB and CK treatments indicated that aged biochar lost its initial effects on PAO, while the biochar-enriched soil amended with biochar years earlier still functioned similarly as fresh biochar.

Aged biochar stimulated ammonia-oxidizing archaea and bacteria-derived N2O and NO production in an acidic vegetable soil.

Both nitrous oxide (N2O) and nitric oxide (NO) emissions are typically high in greenhouse-based high N input vegetable soils. Biochar amendment has been widely recommended for mitigating soil N2O emissions in agriculture. However, knowledge of the regulatory mechanisms of fresh and aged biochar for both N2O and NO production during ammonia oxidation is lacking. Two vegetable soils with different pH values were used in aerobic incubation experiments with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), 1-octyne and acetylene. The relative importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to N2O and NO production was investigated as influenced by fresh and aged biochar amendments. The results showed that AOA dominated N2O production in acidic soil, while AOB dominated N2O production in alkaline soil. Aged biochar stimulated both AOA- and AOB-derived N2O and NO production by 84.8 and 340%, respectively, in acidic soil but only increased AOA-derived N2O and NO production in alkaline soil. Fresh biochar amendment increased AOA- and AOB-derived NO in acidic soil and AOA-derived NO in alkaline soil but had negligible effects on AOA- and AOB-derived N2O in both soils. Fresh biochar decreased AOA-amoA but increased AOB-amoA gene abundances in acidic soil, whereas aged biochar increased AOA- and AOB-amoA gene abundances in both soils. These findings improved our understanding of N2O and NO production mechanisms under different biochar amendments in alkaline and acidic vegetable soils.

Potential role of exosomes in the pathophysiology, diagnosis, and treatment of hypoxic diseases.

Exosomes are extracellular vesicles that originate in the endosomal system. They perform important functions for cell-to-cell communication by transferring bioactive cargoes to recipient cells or activating signal transduction pathways in the target cells. Hypoxia is a severe cellular stress that can regulate the release of exosomes and change their contents. Exosomes have been investigated in different types of hypoxic diseases and found to have many effects from pathology to protection. Increasingly, studies have indicated that exosomes can reflect their cellular origin and disease state through the bioactive cargoes they carry, making exosomes useful as potential biomarkers for diagnosing or predicting hypoxic diseases. In this review, we summarize the effects and mechanisms of hypoxia on exosomes and introduce the basics of exosome production, release, and uptake. In addition, we also summarize current information on the involvement, diagnostic value, and therapeutic potential of exosomes in different types of hypoxic diseases, including myocardial infarction (MI), renal ischemia-reperfusion (IR) induced acute kidney injury (AKI) and hypoxic tumors.

Overdose fertilization induced ammonia-oxidizing archaea producing nitrous oxide in intensive vegetable fields.

Little is known about the effects of nitrogen (N) fertilization rates on ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) and their differential contribution to nitrous oxide (N2O) production, particularly in greenhouse based high N input vegetable soils. Six N treatments (N1, N2, N3, N4, N5 and N6 representing 0, 293, 587, 880, 1173 and 1760 kg N ha-1 yr-1, respectively) were continuously managed for three years in a typically intensified vegetable field in China. The aerobic incubation experiment involving these field-treated soils was designed to evaluate the relative contributions of AOA and AOB to N2O production by using acetylene or 1-octyne as inhibitors. The results showed that the soil pH and net nitrification rate gradually declined with increasing the fertilizer N application rates. The AOA were responsible for 44-71% of the N2O production with negligible N2O from AOB in urea unamended control soils. With urea amendment, the AOA were responsible for 48-53% of the N2O production in the excessively fertilized soils, namely the N5-N6 soils, while the AOB were responsible for 42-55% in the conventionally fertilized soils, namely the N1-N4 soils. Results indicated that overdose fertilization induced higher AOA-dependent N2O production than AOB, whereas urea supply led to higher AOB-dependent N2O production than AOA in conventionally fertilized soils. Additionally, a positive relationship existed between N2O production and NO2- accumulation during the incubation. Further mechanisms for NO2--dependent N2O production in intensive vegetable soils therefore deserve urgent attention.

Field-aged biochar stimulated N2O production from greenhouse vegetable production soils by nitrification and denitrification.

Evidence suggests that biochar is among ideal strategies for climate change mitigation and sustainable agriculture. However, the effects of soil aging on the physicochemical characteristics of biochar and nitrous oxide (N2O) production remain elusive. We set up a microcosm experiment with two greenhouse vegetable production (GVP) (alkaline and acid) soils by using the 15N tracing technique and quantitative polymerase chain reaction (qPCR) to investigate the mechanisms of N2O production as affected by fresh (FB) and aged biochar (AB) amendment. The results showed that AB increased the specific surface area, organic C, ammonium sorption capacity and cation exchange capacity, whereas decreased the pore size and pH relative to the FB. Results also demonstrated that FB effectively decreased N2O emissions from both soils while it enhanced the abundance of nirK and nosZI genes in alkaline soil and reduced the abundance of ammonia-oxidizing bacteria (AOB) amoA and increased nirK and nosZII genes in acid soil. In contrast, AB significantly stimulated nitrification and denitrification in both soils and thus significantly increased the N2O emissions by 43-78%. Furthermore, AB induced increases in ammonia-oxidizing archaeal (AOA) amoA and nirK gene abundances in alkaline soil and fungal nirK gene abundances in acid soil. These results suggest that AB may not be suitable for the mitigation of soil N2O emissions in GVP soils thus improving our understanding of the potential mechanism of biochar in N2O emissions.

Evaluation and simulation of nitrogen mineralization of paddy soils in Mollisols area of Northeast China under waterlogged incubation.

BACKGROUND: Understanding the nitrogen (N) mineralization process and applying appropriate model simulation are key factors in evaluating N mineralization. However, there are few studies of the N mineralization characteristics of paddy soils in Mollisols area of Northeast China. MATERIALS AND METHODS: The soils were sampled from the counties of Qingan and Huachuan, which were located in Mollisols area of Northeast China. The sample soil was incubated under waterlogged at 30°C in a controlled temperature cabinet for 161 days (a 2: 1 water: soil ratio was maintained during incubation). Three models, i.e. the single first-order kinetics model, the double first-order kinetics model and the mixed first-order and zero-order kinetics model were used to simulate the cumulative mineralised N (NH4+-N and TSN) in the laboratory and waterlogged incubation. PRINCIPAL RESULTS: During 161 days of waterlogged incubation, the average cumulative total soluble N (TSN), ammonium N (NH4+-N), and soluble organic N (SON) was 122.2 mg kg-1, 85.9 mg kg-1, and 36.3 mg kg-1, respectively. Cumulative NH4+-N was significantly (P < 0.05) positively correlated with organic carbon (OC), total N (TN), pH, and exchangeable calcium (Ca), and cumulative TSN was significantly (P < 0.05) positively correlated with OC, TN, and exchangeable Ca, but was not significantly (P > 0.05) correlated with C/N ratio, cation exchange capacity (CEC), extractable iron (Fe), clay, and sand. When the cumulative NH4+-N and TSN were simulated, the single first-order kinetics model provided the least accurate simulation. The parameter of the double first-order kinetics model also did not represent the actual data well, but the mixed first-order and zero-order kinetics model provided the most accurate simulation, as demonstrated by the estimated standard error, F statistic values, parameter accuracy, and fitting effect. CONCLUSIONS: Overall, the results showed that SON was involved with N mineralization process, and the mixed first-order and zero-order kinetics model accurately simulates the N mineralization process of paddy soil in Mollisols area of Northeast China under waterlogged incubation.