Metagenomic analysis reveals hidden links between gut microbes and habitat adaptation among cave and surface dwelling Sinocyclocheilus species

Intestinal microbes are closely related to vital host functions such as digestion and nutrient absorption,which play important roles in enhancing host adaptability.As a natural“laboratory”,caves provide an outstanding model for understanding the significance of gut microbes and feeding habits in the habitat adaptability of hosts.However,research on the relationship between gut microbes,feeding habits,and the adaptability of troglobites remains insufficient.In this study,we compared the characteristics of the intestinal microbes of Sinocyclocheilus cavefish and surface fish and further established the relationship between intestinal and habitat microbes.Furthermore,we conducted environmental DNA(eDNA)(metabarcoding)analysis of environmental samples to clarify the composition of potential food resources in the habitats of the Sinocyclocheilus cavefish and surface fish.Results showed that the structure of the Sinocyclocheilus gut microbes was more related to ecological type(habitat type)than phylogenetic relationships.While horizontal transfer of habitat microbes was a source of gut microbes,hosts also showed strong selection for inherent microbes as dominant microorganisms.Differences in the composition and structure of gut microbes,especially dominant microbes,may enhance the adaptability of the two Sinocyclocheilus fish types from the perspectives of food intake,nutrient utilization,and harmful substance metabolism,suggesting that food resources,predation patterns,intestinal flora,digestive and absorptive capacity,and feeding habits and preferences are linked to habitat adaptability.These results should facilitate our understanding of the significance of fish gut microbes to habitat adaptation and provide a new perspective for studying the adaptive mechanisms of cavefish.

Dietary supplementation of bilberry anthocyanin on growth performance,intestinal mucosal barrier and cecal microbes of chickens challenged with Salmonella Typhimurium

Background Anthocyanins(AC)showed positive effects on improving the intestinal health and alleviating intestinal pathogen infections,therefore,an experiment was conducted to explore the protective effects of supplemented AC on Salmonella-infected chickens.Methods A total of 240 hatchling chickens were randomly allocated to 4 treatments,each with 6 replicates.Birds were fed a basal diet supplemented with 0(CON,and ST),100(ACL)and 400(ACH)mg/kg of AC for d 60,and orally challenged with PBS(CON)or 10^(9) CFU/bird(ST,ACL,ACH)Salmonella Typhimurium at d 14 and 16.Results(1)Compared with birds in ST,AC supplementation increased the body weight(BW)at d 18 and the average daily gain(ADG)from d 1 to 18 of the Salmonella-infected chickens(P<0.05);(2)AC decreased the number of Salmonella cells in the liver and spleen,the contents of NO in plasma and inflammatory cytokines in ileal mucosa of Salmonella-infected chickens(P<0.05);(3)Salmonella infection decreased the ileal villi height,villi height to crypt depth(V/C),and the expression of zonulaoccludins-1(ZO-1),claudin-1,occludin,and mucin 2(MUC2)in ileal mucosa.AC supplementation relieved these adverse effects,and decreased ileal crypt depth(P<0.05);(4)In cecal microbiota of Salmonella-infected chickens,AC increased(P<0.05)the alpha-diversity(Chao1,Pd,Shannon and Sobs indexes)and the relative abundance of Firmicutes,and decreased(P<0.05)the relative abundance of Proteobacteria and Bacteroidota and the enrichment of drug antimicrobial resistance,infectious bacterial disease,and immune disease pathways.Conclusions Dietary AC protected chicken against Salmonella infection via inhibiting the Salmonella colonization in liver and spleen,suppressing secretion of inflammatory cytokines,up-regulating the expression of ileal barrier-related genes,and ameliorating the composition and function of cecal microbes.Under conditions here used,100 mg/kg bilberry anthocyanin was recommended.

Vaginal microbes confounders and implications on women's health

The vagina has diverse vaginal microbes(Vm).A disturbance in the delicate balance maintained in Vm is linked to women's obstetrical and reproductive tract problems.Vaginal microbes play an essential role in protecting the health of the female reproductive tract by alleviating gynecological infection.However,Vm profiling has many confounders that need to be addressed during sampling,including age,race,pregnancy,medical illness,and smoking.Vm profiling improves reproduction odds,may serve as a marker for genital malignancies and have a therapeutic application in menopausal women and women with cervical cancers.

Overview of microbes in hypertension

High blood pressure(BP),known as hypertension,is a major contributing factor to the development of cardiovascular disease.The development and pathogenesis of hypertension involve a wide array of factors including genetics,environment,hormones,hemodynamics,and inflammation.There is a significantly positive association between higher levels of colonization by Aggregatibacter actinomycetemcomitans,Porphyromonas gingivalis,Tannerella forsythia,and Treponema denticola(etiologic bacterial burden)below the gum line,and the presence of hypertension.The use of antibiotics during pregnancy,which is likely indicative of bacterial infections severe enough to require antibiotic treatment,is associated with a slight increase in average arterial BP.Cytomegalovirus infection is a risk factor for heightened arterial BP and acts as a co-factor in the development of aortic atherosclerosis.The relationship between hypertension and coronavirus disease 2019 involves endothelial dysfunction and dysregulation of the renin-angiotensin system.The effects of gut microbiota on BP,whether beneficial or harmful,are influenced by multiple factors including genetics,epigenetics,lifestyle choices,and antibiotic usage.These variables collectively contribute to overall BP levels and the control of hypertension.Several reports have examined the BP levels of patients infected with the Zika virus.In regions with a high incidence of nasopharyngeal carcinoma,hypertension has been linked to a higher risk of Epstein-Barr virus reactivation.Also,a potential causal link has been found between malaria and elevated BP.Also,the elevated prevalence of hypertension among dengue patients during their initial visit suggests that relying solely on BP measurements to predict severe infection may not be clinically reliable.

Visualization Analysis of the Impact of Rubber Agroforestry Ecosystem on Soil Microbial Community

Rubber agroforestry systems positively impact soil microbial communities. This study employed a bibliometric approach to explore the research status, hotspots, and development trends related to these effects. Using CiteSpace software, we visually analyzed research literature from the Web of Science (WOS) core database, spanning 2004 to 2024. The focus was on the impact of rubber agroforestry ecosystems on soil microbial communities. The results indicate significant attention from Chinese researchers, who have published numerous influential papers in this field. Authors Liu Wenjie have contributed the most papers, although no stable core author group exists. The Chinese Academy of Sciences is the leading research institution in terms of publication volume. While there is close collaboration between different institutions and countries, the intensity of researcher cooperation is low. The most cited literature emphasizes soil nutrients and structure in rubber agroforestry, laying a foundation for soil microorganism studies. Most cited journals are from countries like Netherlands and the United Kingdom. Key research areas include the effects of rubber intercropping on soil microbial communities, agroforestry management, and soil health. Research development can be divided into three stages: the initial stage (2010-2015), the development stage (2015-2020), and the mature stage (2020-2024). Current studies show that rubber intercropping and rubber-based agroforestry systems enhance soil microbial communities, positively impacting soil health. This paper provides a theoretical basis for the sustainable development of rubber agroforestry systems and improved management plans. Future research could explore the effects of species composition on soil microbiological characteristics and develop methods for species interactions. An in-depth study of the soil microbial community’s structure and function, and its relationship with rubber trees, is crucial. Developing effective, rationally designed rubber agroforestry systems and underground soil microbiome technology will promote sustainability and improve plantation productivity.

Effects of land-use patterns on soil microbial diversity and composition in the Loess Plateau,China

In the Loess Plateau of China,land-use pattern is a major factor in controlling underlying biological processes.Additionally,the process of land-use pattern was accompanied by abandoned lands,potentially impacting soil microbe.However,limited researches were conducted to study the impacts of land-use patterns on the diversity and community of soil microorganisms in this area.The study aimed to investigate soil microbial community diversity and composition using high-throughput deoxyribonucleic acid(DNA)sequencing under different land-use patterns(apricot tree land,apple tree land,peach tree land,corn land,and abandoned land).The results showed a substantial difference(P<0.050)in bacterial alpha-diversity and beta-diversity between abandoned land and other land-use patterns,with the exception of Shannon index.While fungal beta-diversity was not considerably impacted by land-use patterns,fungal alpha-diversity indices varied significantly.The relative abundance of Actinobacteriota(34.90%),Proteobacteria(20.65%),and Ascomycota(77.42%)varied in soils with different land-use patterns.Soil pH exerted a dominant impact on the soil bacterial communities'composition,whereas soil available phosphorus was the main factor shaping the soil fungal communities'composition.These findings suggest that variations in land-use pattern had resulted in changes to soil properties,subsequently impacting diversity and structure of microbial community in the Loess Plateau.Given the strong interdependence between soil and its microbiota,it is imperative to reclaim abandoned lands to maintain soil fertility and sustain its function,which will have significant ecological service implications,particularly with regards to soil conservation in ecologically vulnerable areas.

Mitigation of N_(2)O emissions in water-saving paddy fields:Evaluating organic fertilizer substitution and microbial mechanisms

Water-saving irrigation strategies can successfully alleviate methane emissions from rice fields,but significantly stimulate nitrous oxide(N_(2)O)emissions because of variations in soil oxygen level and redox potential.However,the relationship linking soil N_(2)O emissions to nitrogen functional genes during various fertilization treatments in water-saving paddy fields has rarely been investigated.Furthermore,the mitigation potential of organic fertilizer substitution on N_(2)O emissions and the microbial mechanism in rice fields must be further elucidated.Our study examined how soil N_(2)O emissions were affected by related functional microorganisms(ammonia-oxidizing archaea(AOA),ammonia-oxidizing bacteria(AOB),nirS,nirK and nosZ)to various fertilization treatments in a rice field in southeast China over two years.In this study,three fertilization regimes were applied to rice cultivation:a no nitrogen(N)(Control),an inorganic N(Ni),and an inorganic N with partial N substitution with organic manure(N_(i)+N_(o)).Over two rice-growing seasons,cumulative N_(2)O emissions averaged 0.47,4.62 and 4.08 kg ha^(−1)for the Control,Ni and N_(i)+N_(o)treatments,respectively.In comparison to the Ni treatment,the N_(i)+N_(o)fertilization regime considerably reduced soil N_(2)O emissions by 11.6%while maintaining rice yield,with a lower N_(2)O emission factor(EF)from fertilizer N of 0.95%.Nitrogen fertilization considerably raised the AOB,nirS,nirK and nosZ gene abundances,in comparison to the Control treatment.Moreover,the substitution of organic manure for inorganic N fertilizer significantly decreased AOB and nirS gene abundances and increased nosZ gene abundance.The AOB responded to N fertilization more sensitively than the AOA.Total N_(2)O emissions significantly correlated positively with AOB and nirS gene abundances while having a negative correlation with nosZ gene abundance and the nosZ/nirS ratio across N-fertilized plots.In summary,we conclude that organic manure substitution for inorganic N fertilizer decreased soil N_(2)O emissions primarily by changing the soil NO_(3)^(−)-N,pH and DOC levels,thus inhibiting the activities of ammonia oxidation in nitrification and nitrite reduction in denitrification,and strengthening N_(2)O reduction in denitrification from water-saving rice paddies.

Effects of Urbanization on the Quantity Changes of Microbes in Urban-to-rural Gradient Forest Soil

Three typical rural-suburban-urban artificial wetlands Pinus elliottii forest in Nanchang City were selected as research objects to mensurate the soil nutrient content.And the annual average values and seasonal changes of microbes in forest soil were analyzed.The results showed that soil bulk density,total phosphorus （TP） and pH increased,while soil organic carbon （SOC）,total nitrogen （TN） declined with rural-to-urban gradient.At different eco-boundary,annual average values showed that actinomycetes quantity bacteria quantity fungi quantity.Total microbe number was urban suburb rural areas.The number of bacteria and fungi was urban suburbs rural areas,but the number of actinomycetes was suburb urban rural areas.Eco-boundary,season and microbes actinomycetes and fungi reached an extreme significant level （P 0.001）.Bacteria in soil at different eco-boundary had significant effects,but season had no significant effect on bacteria.Eco-boundary and season had a very significant interaction on actinomycetes and fungi （P 0.001）,but they had no significant interaction on bacteria （P 0.05）.Eco-boundary showed significantly positive correlation with actinomycetes and fungi （P 0.001）,but season had no significant corelation with microbes.In conclusion,urbanization process caused the physical-chemical properties changes of forest soil and affected the amount of soil microbes obviously.

Isolation,Screening and Identification of High-temperature Cellulolytic Microbes in Pig Manure

[Objective] The research aimed to lay the foundation for high-efficiency biological degradation microbial inoculums. [Method] under the 60℃ temperature the cellulolytic microbes in pig manure were isolated and determined the CMCase and Fpase,then proceeded the 16S rRNA gene analysis. [Result]The results showed that:BC1 and BC3 strains characterized higher carboxymethyl cellulose enzyme activity and higher filter paper activity,but their difference was small,then the 16S rDNA sequence of BC1 and BC3 strains were related to pseudomonas sp. (98% and 99% similarities,respectively).[Conclusion] the experiment laid foundation for high-efficiency biological heating agent.

Exploration of the key microbes and composition stability of microbial consortium GF-20 with efficiently decomposes corn stover at low temperatures

The microbial consortium GF-20(GF-20) can efficiently decompose corn stover at low temperatures. The present study explored the key microbes of GF-20 and evaluated different culture conditions on its composition stability to promote the utilization of corn stover decomposing microbes in low temperature regions. GF-20 was subcultured to the 15 th generation under different temperatures, pHs, carbon, and nitrogen sources. Then, the dynamics of fermenting pH, cellulose enzyme activities, carbohydrate concentration, and oxidation reduction potential were determined to estimate the degradation efficiency of corn stover with GF-20. Furthermore, the structural stability and functional microbes of GF-20 were identified on the basis of PCR-denaturing gradient gel electrophoresis(DGGE) profiling and principal component analysis. The results showed that the offspring of GF-20 subcultured under different temperatures(4–30°C) and pH(6.0–9.0) conditions maintained stable growth, decomposition function, and composition structure. Furthermore, consortia GF-20 had a stable composition structure, which induced GF-20 to secrete cellulose and promote substrate decomposition as corn stover and ammonium were used as sources of carbon and nitrogen, respectively. According to the PCR-DGGE profiles, the key strains of GF-20 were determined to be Bacillus licheniformis, Cellvibrio mixtus subsp. mixtus, Bacillus tequilensis, Clostridium populeti, and Clostridium xylanolyticum.

Thermochemical Kinetics of Sm(Gly)_4Im(ClO_4)_3·2H_2O Reacting with Microbes

The thermochemical kinetics of the rare earth ternary complex Sm(Gly) 4Im(ClO 4) 3·2H 2O (Gly glycine, Im imidazole) reacting with microbes (escherichia coli, bacillus subilis, staphylococcus aureus) was studied by means of Calvet microcalorimeter. The rate constant k of microbe growth was calculated, and the inhibition effect of these complexes to microbes was compared.

The addition of microbes for treating textile wastewater

Some strains and culture of bacteria which are able to decolorize dyes and degrade polyvinyl alcohol(PVA) were isolated and selected. A pilot scale facultative anaerobic-aerobic biological process was applied for treatment of textile wastewater containing dyes and PVA. Activated carbon adsorption was used as a tertiary treatment stage, and residual sludge from clarifier returned to the anaerobic reactor again. The pilot test were carried out with two systems. One was inoculated by acclimated sludge, and the another was adding the mixed culture of dye-decoloring and PVA-degrading bacteria for forming biological films, the latter was observed to be more effective than the former. The test has run normally for ten months with a COD loading of 2.13 kg/m3/day, a BOD5 loading of 0.34 kg/m3/day in anaerobic reactor; a COD loading of 1.71 kg/m3/day, a BOD5 loading 0.44 kg/m3/day in aerobic reactor. The pollutants removal efficiency by adding microbes was about 20% higher than that by acclimated sludge. The average removal efficiency of COD stood about 92%, BOD5 97%, PVA 90% and decolorization 80%. The other parameters of effluent quality are also satisfactory.

Effect of Different Temperatures on Microbes and Its Quality of Green Pepper During Circulation

[Objective] The aim was to study on effect of different temperatures on microbes and its quality of green pepper during circulation. [Method] Measurement was conducted on change of colibacillus, salmonella, Listeria number, and its quality of green pepper stored at 9 and 20 ℃ respectively. The green peppers stored at 9 ℃ for 16 d were under simulated sale. In addition, effects of microbe number of green peppers stored at 20 ℃ for 4 d by different washing methods were measured. [Result] Indices of green pepper were different when green peppers were stored for 16 d at 9 ℃ and sold at 20 ℃ after 16 d storage. Specifically, under the former condition, sensory quality, weight-loss rate, Vc content, chlorophyll content and soluble protein were 4.1, 1.79%, 95.6, 20.3, and 93.3 mg/100 g; under the latter condition, the corresponding indices were 3.3, 3.87%, 81.2, 16.5, 85.6 mg/100 g, respectively. Colibacillus numbers for green pepper stored 16 d at 9 ℃, sold for 1 d at 20 ℃ after 16 d storage and stored for 4 d at 20 ℃ were 46, 3.2×103 and 3.1×104 cfu/g; during the test, salmonella and Listeria were not found; colibacillus in green pepper could be eliminated by 1×10-3 ml/L of chloros and most colibacillus in green pepper could be cleared away by 1 drop/L of detergent and running water. [Conclusion] Stored at 9 ℃, quality of green pepper could be better preserved and colibacillus propagation could be controlled.

Degradation of Microbes for the Crude Oil Contaminants

Production and storage-transportation of crude oil can not only give rise to soil pollution but also destroy ecological environment. Degradation of microbes for oily soil was studied with the instnunent, Geofina Hydrocarbon Meter (GHM), by experimental analysis qualitatively and quantitatively in the paper. Analytical result showed that the crude oil could be considerably degraded by eating-oil microbes in oily soil and the number of eating-oil microbes increased while the working hours of oil-well risi...

Study on Microbes and Their Effects on Rare Earth Extraction in Weathering Crust of Granite

Microbes were cultured from the samples at various depths in a weathering profile of RE-bearing granite in Gonghe RE mine, Guangdong Province. The cultured microbes, existing at a depth of 0.2 similar to 12 in and being more plentiful within 3 in in the profile, include bacteria ( Bacillus, Enterobacter, Escherichia, Alkaligenes, Neisseria, Staphylococcus and anaerobic bacteria such as Clostridium), fungi ( Aspergillus niger, Aspergillus flavus, Penicillium, Mucor and Saccharomycete) and actinomyces. Experiments were made under room temperature by using solutions of the cultured microbes and their metabolites, compared with distilled water and the culture solution without microbes, to leach RE from the sample of the weathering crust. The results are shown by the experiments: (1) The mixed microbes cultured from the profile and their metabolites increase the quantity of RE leached from the sample and reduce the pH of the solutions. (2) The ability to leach RE from the sample varies with various microbes, decreasing in a sequence of fungi ( Mucor, saccharomycete, Aspegillus and Penicillium), zymotic bacilli (Enterobacter, Escherichia etc.), Staphylococcus, zymotic Bacillus, actinomyces and Alkaligenes. (3) The RE leached with bacteria is mainly related to the pH value of the solutions influenced by the metabolites of the bacteria; whereas that leached with fungi is mainly related to the adsorption and imbibition of RE by the fungi and the complexing of RE with their metabolites. (4) Compared with that leached with ammonium sulfate, the fractionation of the RE leached with microbes is characterized by higher delta (Ce), lower delta (Eu) and lower ratios of N-La/Sm and N-Gd/Yb . The result of the fractionation of RE accords with the distribution of RE in the various layers of a profile of weathering crust of granite in South China. The experimental results indicate that microbes and their metabolites should play a positive role in the mobilization, migration and fractionation of RE in the weathering crust in South China.

Effect of Different Fertilizer Treatments on Quantity of Soil Microbes and Structure of Ammonium Oxidizing Bacterial Community in a Calcareous Purple Paddy Soil

The quantity of soil microbes and the structure of ammonium oxidizing bacterial （AOB） community were analyzed using the dilution plate counting and most probable number method （MPN）, and denaturing gradient gel electrophoresis （DGGE）, respectively. Fertilizer application tended to increase the number of soil microbes and alter the AOB community compared to the control with no fertilizer application （CK）. Among the eight fertilizer treatments, soil samples from the treatments of mineral fertilizers （e.g., N, P, K） in combination with farmyard manure （M） had greater number.s of soil microbes and more complex structure of AOB community than those receiving mineral fertilizers alone. The principal component analyses （PCA） for ammonium oxidizing bacterial community structure showed that the eight fertilizer treatments could be divided into two PCA groups （PCA1 and PCA2）. For the soil sampled after rice harvest, PCA1 included NP, NM, NPM and NPKM fertilizer treatments, while PCA2 was consisted of CK, N, M and NPK fertilizer treatments. For soil samples collected after wheat harvest, PCA1 was consisted of M, NM, NPM and NPKM fertilizer treatments, while PCA2 was composed of CK, N, NP and NPK fertilizer treatments. For a given rotation, the richness of AOB community in PCA1 was greater than that in PCA2. In addition, AOB community structure was more complex in the soil after rice harvest than that after wheat harvest. The results indicated that different fertilizer treatments resulted in substantial changes of soil microbe number and AOB community. Furthermore, mineral fertilizers （N, NP, NPK） combined with farmyard manure were effective for increasing the quantity of soil microbes, enriching AOB community, and improving the soil biofertility.

Diversity of Secondary Metabolites from Two Antarctic Microbes Rhodococcus sp. NJ-008 and <i>Pseudomonas</i>sp. NJ-011

Diversity analysis on secondary metabolites of Antarctic microbes, Rhodococcus sp. NJ-008 and Pseudomonas sp. NJ-011, together with the structural elucidation of some purified compounds, has been carried out for understanding of their chemical constituents. The methanol extracts of Rhodococcus sp. NJ-008 and Pseudomonas sp. NJ-011 were subjected to HPLC-TOF MS test for diversity analysis on secondary metabolites, respectively. The chemical constituents of NJ-011 are mainly N-containing compounds including some alkaloids and short polypeptides, while those of NJ-008 are not N-containing ones. Three compounds were also isolated and identified from extract of NJ011 by different column chromatography and preparative HPLC, and their structures were elucidated as b-carboline (1), 3-benzylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione (2) and 3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione (3) by comparison of TOF MS, 1Hand 13C-NMR data with those reported. More microbial material of Pseudomonas sp. NJ-011 should be needed for exploration of the minor constituents with complicated structures.

BOD Exertion and OD600 Measurements in Presence of Heavy Metal Ions Using Microbes from Dairy Wastewater as a Seed

BOD measurements in presence of cobalt, nickel, copper, zinc, silver and cadmium are reported using wastewater from dairy industry as a seed. Extent of inhibition in BOD is studied for variables like, concen-tration of metal ions (0.2 mM to 1.4 mM), pH (3 to 8) and temperature of incubation (15℃, 20℃, 25℃, 30℃ and 35℃). Results of BOD inhibition are supported by absorbance measurement (OD600) studies of microbial matter preserved in Luriya broth medium. OD measurement results are used to derive minimum inhibitory concentration, i.e., threshold concentration of each metal showing toxicity towards microbes. Sil-ver is found to be the most toxic element.

Responses of Bruguiera sexangula propagules to beneficial microbes in the nursery

Bruguiera sexangula （Lout） Poir., a threatened mangrove tree, was inoculated with beneficial microbes in a nursery to assess any improvements in growth and bio- mass. From soil samples from the rhizosphere of B. sexangula in a mangrove forest in Panangadu of Kerala India, nitrogen-fixing bacteria Azotobacter chroococcum and Azospirillum brasilense were isolated. The phosphatesolubilising bacterium Bacillus megaterium and potassiummobilizing bacteria Frateruria aurantia were also isolated and cultured on suitable media. Later, ripe propagules of B. sexangula were collected from matured trees and raised in sterilized soil bags （13 × 25 cm） containing sterilized soil and sand （2：1 ratio）. The cultured beneficial microbes were propagated and used to inoculate the ripe propagules of B. sexangula and maintained in the nursery for 6 months. After 6 months, growth and biomass of the inoculated propagules were greater than for the uninoculated control propagules. Shoot length, number of leaves, stem girth and root length were also significantly greater than in the controls. This study showed that the mangrove-specific beneficial microbes influenced the growth of B. sexangula

Effects of cultivation on N_2O emission and seasonal quantitative variations of related microbes in a temperate grassland soil

Laboratory and in situ experiments were done to investigate the influences of cultivation on temperate semi arid grassland (for 17 years spring wheat planted once every two years without fertilization) on soil N 2O emission and quantitative variations of related soil microbes. In the laboratory (25℃ and soil moisture 18%), cultivation increased soil transformations of fertilizer nitrogen (100 μg N/g as NaNO 3, urea, or as urea with dicyandiamide 1 μg N/g). The N 2O emissions from the cultivated and uncultivated soils with or without nitrogen additions were relatively low, and mainly originated from the nitrification. The soil N 2O emission due to cultivation decreased somewhat upon no fertilization or NaNO 3 addition, but significantly upon urea addition. The role of dicyandiamide as nitrification inhibitor was only considerable in the cultivated soil, and had small influence on decreasing N 2O emission in the two soils. The influence of cultivation on soil N 2O emission was also reflected by the number variations of microbes related with soil nitrogen transformation in the two soils. Compared to the uncultivated grassland, in situ ammonifiers and denitrifiers in the cultivated grassland quantitatively averagely increased, and aerobic no symbiotic azotobacters were quantitatively similar, leading to the continued decrease of organic matter content and the decrease of N 2O emission from the cultivated grassland soil.