For a constantly growing human population, healthy and productive soil is critical for sustainable delivery of agricultural products. The soil microorganisms play a crucial role in soil structure and functioning. They...For a constantly growing human population, healthy and productive soil is critical for sustainable delivery of agricultural products. The soil microorganisms play a crucial role in soil structure and functioning. They are responsible for soil formation, ecosystem biogeochemistry, cycling of nutrients and degradation of plant residues and xenobiotics. Certain agricultural treatments, such as fertilizers and pesticides applications, crop rotation, or soil amendment addition, influence the composition, abundance and function of bacteria and fungi in the soil ecosystems. Some of these practices have rather negative effects;others can help soil microorganisms by creating a friendlier habitat or providing nutrients. The changes in microbial community structure cannot be fully captured with traditional methods that are limited only to culturable organisms, which represent less than 1% of the whole population. The use of new molecular techniques such as metagenomics offers the possibility to better understand how agriculture affects soil microbiota. Therefore, the main goal of this review is to discuss how common farming practices influence microbial activity in the soil, with a special focus on pesticides, fertilizers, heavy metals and crop rotation. Furthermore, potential practices to mitigate the negative effects of some treatments are suggested and treatments that can beneficially influence soil microbiota are pointed out. Finally, application of metagenomics technique in agriculture and perspectives of developing efficient molecular tools in order to assess soil condition in the context of microbial activities are underlined.展开更多
Oceans are important sources of microbes in atmospheric aerosols;however, information about the characteristics of airborne microbes and their influencing factors over oceans is lacking. Here we report the characteris...Oceans are important sources of microbes in atmospheric aerosols;however, information about the characteristics of airborne microbes and their influencing factors over oceans is lacking. Here we report the characteristics of the microbial abundance and activity in aerosols sampled near the sea surface over the South China Sea(SCS) from May to June 2016. The airborne microbial concentration range in the aerosols was 1.68?105 to 4.84?105 cells m-3 over the SCS, reflecting an average decrease of 40% – 54% over the SCS compared with that in the samples from the coastal region of Qingdao. About 63% – 76% of the airborne microbes occurred in coarse particles(> 2.1 ?m), with a variable size distribution over the SCS. The microbial activity range in aerosols, measured by the fluorescein diacetate(FDA) hydrolysis method, was 2.09 – 11.97 ng m-3 h-1 sodium fluorescein(SF) over the SCS, which was 15% – 79% lower than that over the coastal region. These values reflected a different spatial distribution over the SCS from that of the microbial concentration. Except for certain samples, all samples had 68% of the microbial activity occurring in coarse particles. Correlation analysis showed that the microbial abundance and activity were positively correlated with the aerosol, organic carbon(OC), and water-soluble organic carbon(WSOC) concentrations, indicating that the airborne microbes may be related to the reactions of certain water-soluble organic chemicals in the atmosphere. Moreover, the concentrations of airborne microbes were significantly negatively correlated with the horizontal offshore distance. The microbial concentration and activity were significantly correlated with wind speed.展开更多
The impact of dissolved oxygen(DO)at aerobic phase on the nitrogen removal,extracellular polymeric substances(EPS),microbial activity and microbial community of sequencing batch biofilm reactor(SBBR)have been evaluate...The impact of dissolved oxygen(DO)at aerobic phase on the nitrogen removal,extracellular polymeric substances(EPS),microbial activity and microbial community of sequencing batch biofilm reactor(SBBR)have been evaluated in treating mariculture wastewater.The oxygen uptake rate and nitrification rate declined with DO concentration from 3–4 to 1–1.5mgL^(-1),whereas the denitrification rate had an increment.The activities of nitrifying enzymes reduced with the decrease of DO concentration at aerobic phase,but those of denitrifying enzymes illustrated opposite results.The nitrification and denitrification rates displayed the similar variation tendency with the relevant enzymatic activities as DO concentration decreased.The protein(PN)and polysaccharide(PS)content in EPS decreased as DO concentration declined,whereas the PN/PS ratio increased.The microbial community showed obvious difference as DO concentration decreased from 3–4 to 1–1.5mgL^(-1).The microbial co-occurrence,keystone taxa and sig-nificant difference illustrated some variations at different DO concentrations.展开更多
A new favane,bropapyriferol(1),and eleven known ones were isolated from the EtOAc part of Broussonetia papyrifera under the guidance of bioassay.The structure of compound 1 was determined by extensive 1D and 2D NMR,[...A new favane,bropapyriferol(1),and eleven known ones were isolated from the EtOAc part of Broussonetia papyrifera under the guidance of bioassay.The structure of compound 1 was determined by extensive 1D and 2D NMR,[α]_(D) spectroscopic data and quantum computation.Daphnegiravan F(2)and 5,7,3′,4′-tetrahydroxy-3-methoxy-8,5′-diprenylfavone(3)showed signifcantly anti-oral microbial activity against fve Gram-positive strains and three Gram-negative strains in vitro.Especially,compound 3 was more potent in suppressing Actinomyces naeslundii and Porphyromonas gingivalis(MIC=1.95 ppm)than the positive control,triclosan.展开更多
Microbial enhanced oil recovery (MEOR) is the research focus in the field of energy development as an environmentally friendly and low cost technology. MEOR can bes divided into indigenous microbial oil recovery and e...Microbial enhanced oil recovery (MEOR) is the research focus in the field of energy development as an environmentally friendly and low cost technology. MEOR can bes divided into indigenous microbial oil recovery and exogenous microbial oil recovery. The ultimate goal of indigenous microbial flooding is to enhance oil recovery via stimulation of specific indigenous microorganisms by injecting optimal nutrients. For studying the specific rule to activate the indigenous community during the long-term injection period, a series of indigenous displacement flooding experiments were carried out by using the long-core physical simulation test. The experimental results have shown that the movement of nutrients components (i.e., carbon/nitrogen/phosphorus) differed from the consumption of them. Moreover, there was a positive relationship between the nutrients concentration and bacteria concentration once observed in the produced fluid. And the trend of concentration of acetic acid was consistent with that of methanogens. When adding same activators, the impacts of selective activators to stimulate the indigenous microorganisms became worse along with the injection period, which led to less oil recovery efficiency.展开更多
The proliferation of glyphosate-resistant weeds has resulted in significant losses in the productivity of crops such as corn, soybean, and cotton. As a result, new crop varieties with resistance genes from other herbi...The proliferation of glyphosate-resistant weeds has resulted in significant losses in the productivity of crops such as corn, soybean, and cotton. As a result, new crop varieties with resistance genes from other herbicides, such as 2,4-D and dicamba, have been developed as part of alternative weed control cropping systems. However, little is known about how the application of these herbicides impacts the microorganisms that carry out nutrient cycling in the soil of these cropping systems, particularly in the rhizosphere, the soil compartment immediately adjacent to the root system which is pivotal to plant nutrient uptake. The purpose of the current study was to assess the effects of dicamba on soil enzyme activities linked to C, N, and P cycling in the rhizosphere of </span><span style="font-family:Verdana;">resistant soybean plants. While dicamba had no significant effects on the ac</span><span style="font-family:Verdana;">tivities of enzymes linked to C or P cycling in the rhizosphere, N-acetylglucosaminidase activity was temporarily inhibited, but recovered by three days after application. These results suggest there are no long-lasting negative effects of dicamba in the rhizosphere of treated plants when applied at field rates.展开更多
The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and st...The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and stores massive soil carbon.展开更多
The antibacterial activity of copper is well-known from an ancient civilization, however, its biocidal mechanism has not been necessarily elucidated. Notwithstanding up to now, mainly 4 processes have been proposed. A...The antibacterial activity of copper is well-known from an ancient civilization, however, its biocidal mechanism has not been necessarily elucidated. Notwithstanding up to now, mainly 4 processes have been proposed. Among them, it is cleared that 4 kinds of reactive oxygen species (ROS): hydroxyl radical ·OH, hydrogen per oxide H<sub>2</sub>O<sub>2</sub>, superoxide anion ·O<sup>-</sup>2</sub></sub> and singlet oxygen <sup>1</sup>O<sub>2</sub>, play an important role for contact-killing of bacteria, viruses and fungi. In this paper, generation of ROS on the surfaces of copper plates heated from room temperature to 673 K for 4.2 × 10<sup>2</sup> s in air, was investigated using the chemiluminescence. ROS have been evaluated by selecting the most suitable scavengers, such as 2-propanol for ·OH, sodium pyruvate for H<sub>2</sub>O<sub>2</sub>, nitro blue tetrazolium for ·O<sup>-</sup>2</sub></sub>, and sodium azide NaN<sub>3</sub> for <sup>1</sup>O<sub>2</sub>. At the same time the outermost surface of copper, on which thin film of cuprous oxide Cu<sub>2</sub>O was first formed and then cupric oxide CuO was laminated on Cu<sub>2</sub>O, was examined by thin-film XRD and TEM analysis to estimate the amounts and kinds of copper oxides. It was found that the most amounts of ROS were obtained for the 573 K-heated Cu plate and they were composed of ·OH, H<sub>2</sub>O<sub>2</sub>, and ·O<sup>-</sup>2.</sub></sub>.展开更多
Beech stands are considered part of the ancient forest ecosystems in the northern hemisphere.In mixed stands in beach forest ecosystems,the type of associated tree species can signifi cantly aff ect soil functions,but...Beech stands are considered part of the ancient forest ecosystems in the northern hemisphere.In mixed stands in beach forest ecosystems,the type of associated tree species can signifi cantly aff ect soil functions,but their infl uence on microbial activity,nutrient cycling and belowground properties is unknown.Here,we considered forest patches in northern Iran that are dominated by diff erent tree species:Fagus orientalis Lipsky,Quercus castaneifolia C.A.Mey.,Pterocarya fraxinifolia(Lam.),Tilia begonifolia Stev.,Zelkova carpinifolia Dippe,Acer cappadocicum Gled,Acer velutinum Boiss.,Fraxinus excelsior L.,Carpinus betulus L.,and Alnus subcordata C.A.Mey.For each forest patch–tree species,litter and soil samples(25×25×10 cm,100 of each)were analyzed for determine soil and litter properties and their relationship with tree species.The litter decomposition rate during a 1-year experiment was also determined.A PCA showed a clear diff erence between selected litter and soil characteristics among tree species.F.orientalis,Q.castaneifolia,P.fraxinifolia,T.begonifolia,Z.carpinifolia,A.cappadocicum,and A.velutinum enhanced soil microbial biomass of carbon,whereas patches with F.excelsior,C.betulus and A.subcordata had faster litter decomposition and enhanced biotic activities and C and N dynamics.Thus,soil function indicators were species-specifi c in the mixed beech forest.A.subcordata(a N-fi xing species),C.betulus and F.excelsior were main drivers of microbial activities related to nutrient cycling in the old-growth beech forest.展开更多
Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underly...Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underlying mechanisms are not well understood. This study is designed to evaluate the efficacy of biochar amendment for controlling tomato bacterial wilt caused by Ralstonia solanacearum, and to explore the interactions between biochar-induced changes in rhizosphere compound composition, the pathogen and tomato growth. The results showed that biochar amendment decreased disease incidence by 61–78% and simultaneously improved plant growth. The positive ‘biochar effect' could be associated with enhanced microbial activity and alterations in the rhizosphere organic acid and amino acid composition. Specifically, elevated rhizosphere citric acid and lysine, but reduced salicylic acid, were induced by biochar which improved microbial activity and rendered the rhizosphere unsuitable for the development of R. solanacearum. In addition, nutrients which were either made more available by the stimulated microbial activity or supplied by the biochar could improve plant vigor and potentially enhance tomato resistance to diseases. Our findings highlight that biochar's ability to control tomato bacterial wilt could be associated with the alteration of the rhizosphere organic acid and amino acid composition, however, further research is required to verify these ‘biochar effects' in field conditions.展开更多
Recently, under the circumstances of pandemic of COVID-19 much attention has been paid to titanium dioxide TiO<sub>2</sub> as bactericidal agent;however, conventional TiO<sub>2</sub> requires u...Recently, under the circumstances of pandemic of COVID-19 much attention has been paid to titanium dioxide TiO<sub>2</sub> as bactericidal agent;however, conventional TiO<sub>2</sub> requires ultraviolet radiation or visible light to exercise its photocatalytic properties and its induced antimicrobial activity. In order to expand its applications directed at wide civil life, antibacterial TiO<sub>2</sub> being usable under dark conditions has been demanded. The present paper describes the powder characterization of newly developed potassium K and phosphorous P co-doped nanometer-size anatase TiO<sub>2</sub> powders using X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM & TEM), Brunauer-Emmett-Teller method (BET), fourier-transform infrared spectroscopy (FT-IR), X-ray absorption fine structure (XAFS), electron spin resonance (ESR) and chemiluminescence (CL). It was found for the first time that thus prepared anatase TiO<sub>2</sub> could submit much reactive oxygen species (ROS) even in the dark, which has close relation with bactericidal activity in light interception.展开更多
Assessment of fungal species associated with a multicultural orchard and cultivated land in Bingham University landscape was carried out,with the ultimate aim of identifying the fungi species present in soil under dif...Assessment of fungal species associated with a multicultural orchard and cultivated land in Bingham University landscape was carried out,with the ultimate aim of identifying the fungi species present in soil under different agricultural practices.A total of 30 soil samples were collected and the composite from each land use pattern was analyzed in the laboratory using standard methods.Soil type,percentage Soil Moisture(SM),percentage Organic Carbon(OC)and percentage Organic Matter(OM)were measured using standard methods;fungi species were isolated and identified on the basis of mycelia and spore characteristics,after staining with lactophenol-in-cotton blue.The results showed that,four types of soil exist in the sites including sandy,clayey,silt and loamy.SM ranges between 3.6%-5.7%,and OC in the sandy soil was the highest 1.01%in the orange plantation(Op5)followed closely by loamy soil on cultivated site C with 0.97%OM and 0.56%OC and least in clay soil with 0.72%OM and 0.42%OC.The results of colony forming unit per gram(cfu/g)in relation to land use type,Cultivated Site C(CC1-CC5)had the highest(262 cfu/g)and mango plantation(Mp1-Mp5)had the least with 156 cfu/g.Pictorial representation of isolated fungal species are indicative of suspected presence of Aspergillus Spp,Mucor Spp,Cladosporium Spp,Fusarium Spp,Aspergillus Spp etc.This qualitative study concluded that fungal species population in the soil depends on the management practice in place and the moisture content of the soil.展开更多
Background:Nitrogen(N)deposition alters litter decomposition and soil carbon(C)sequestration by influencing the microbial community and its enzyme activity.Natural atmospheric N deposition comprises of inorganic N(IN)...Background:Nitrogen(N)deposition alters litter decomposition and soil carbon(C)sequestration by influencing the microbial community and its enzyme activity.Natural atmospheric N deposition comprises of inorganic N(IN)and organic N(ON)compounds.However,most studies have focused on IN and its effect on soil C cycling,whereas the effect of ON on microbial enzyme activity is poorly understood.Here we studied the effects of different forms of externally supplied N on soil enzyme activities related to decomposition in a temperate steppe.Ammonium nitrate was chosen as IN source,whereas urea and glycine were chosen as ON sources.Different ratios of IN to ON(Control,10:0,7:3,5:5,3:7,and 0:10)were mixed with equal total amounts of N and then used to fertilize the grassland soils for 6 years.Results:Our results show that IN deposition inhibited lignin-degrading enzyme activity,such as phenol oxidase(POX)and peroxidase(PER),which may restrain decomposition and thus induce accumulation of recalcitrant organic C in grassland soils.By contrast,deposition of ON and mixed ON and IN enhanced most of the C-degrading enzyme activities,which may promote the organic matter decomposition in grassland soils.In addition,theβ-N-acetyl-glucosaminidase(NAG)activity was remarkably stimulated by fertilization with both IN and ON,maybe because of the elevated N availability and the lack of N limitation after long-term N fertilization at the grassland site.Meanwhile,differences in soil pH,soil dissolved organic carbon(DOC),and microbial biomass partially explained the differential effects on soil enzyme activity under different forms of N treatments.Conclusions:Our results emphasize the importance of organic N deposition in controlling soil processes,which are regulated by microbial enzyme activities,and may consequently change the ecological effect of N deposition.Thus,more ON deposition may promote the decomposition of soil organic matter thus converting C sequestration in grassland soils into a C source.展开更多
The growth and metabolism of microbial communities on biologically activated carbon(BAC) play a crucial role in the purification of drinking water.To gain insight into the growth and metabolic characteristics of micro...The growth and metabolism of microbial communities on biologically activated carbon(BAC) play a crucial role in the purification of drinking water.To gain insight into the growth and metabolic characteristics of microbial communities and the efficiency of drinking water treatment in a BAC filter,we analyzed the heterotrophic plate count(HPC),phospholipid,dehydrogenase,metabolic function and water quality parameters during start-up and steady-state periods.In the start-up process of the filter with natural biofilm colonization,the variation in heterotrophic plate count levels was S-curved.The total phospholipid level was very low during the first 5 days and reached a maximum value after 40 days in the filter.The activity of dehydrogenase gradually increased during the first 30 days and then reached a plateau.The functional diversity of the microbial community in the filter increased,and then reached a relatively stable level by day 40.After an initial decrease,which was followed by an increase,the removal rate of NH4+-N and COD Mn became stable and was 80% and 28%,respectively,by day 40.The consumption rate of dissolved oxygen reached a steady level after 29 days,and remained at 18%.At the steady operation state,the levels of HPC,phospholipid,dehydrogenase activity and carbon source utilization had no significant differences after 6 months compared to levels measured on day 40.The filter was shown to be effective in removing NH4+-N,NO2--N,COD Mn,UV 254,biodegradable dissolved organic carbon and trace organic pollutants from the influent.Our results suggest that understanding changes in the growth and metabolism of microorganisms in BAC filter could help to improve the efficiency of biological treatment of drinking water.展开更多
The water-wind erosion crisscross region of the northern Loess Plateau in China is under constant pressure from severe erosion due to its windy and dry climate and intensive human activities. Identifying sustainable l...The water-wind erosion crisscross region of the northern Loess Plateau in China is under constant pressure from severe erosion due to its windy and dry climate and intensive human activities. Identifying sustainable land use patterns is key to maintaining ecosystem sustainability in the area. Our aim was to appraise the impacts of different land use regimes on the dynamics of soil total organic C(TOC), total N(TN), and microbes in a typical watershed in the northern Loess Plateau to identify suitable land use types that can maintain soil fertility and sustainability. A field experiment was performed in Liudaogou watershed in Shenmu City, Shaanxi Province, China, where the dynamics of soil TOC and TN, microbial biomass C and N, microbial respiration, and net N mineralization in six typical land use types, dam land, rainfed slope land, deciduous broadleaf forest, evergreen coniferous forest, shrubland, and grassland,were measured in three different growing seasons. Land use type and season significantly affected TOC, TN, and the dynamics of microbial biomass and activity. As the most anthropogenically disturbed land use pattern, dam land was an optimal land use pattern for TOC sequestration due to its higher TOC and TN, but lower microbial activity. Soil TOC, TN, and microbial properties demonstrated a decreasing trend after natural grassland was converted to shrubland,forest, and rainfed slope land. Shrubland with exotic N-fixing Korshinsk peashrub(Caragana korshinskii Kom.) can maintain TOC, TN, and microbial properties similar to those in grassland. Soil TOC, NH_(4+)^(-)N, TN, moisture, and extractable C were the principal indexes for soil microbial biomass and activity and explained 88.90% of the total variance. Thus, grassland was the optimal land use pattern in the water-wind erosion crisscross region of the northern Loess Plateau to maintain ecosystem stability and sustainability.展开更多
We investigated the effects of adding up to 11% rice bran(RB) in corn-soybean meal diets fed to broiler chickens without or with a multi-enzyme supplement(MES). The MES supplied xylanase, b-glucanase invertase, protea...We investigated the effects of adding up to 11% rice bran(RB) in corn-soybean meal diets fed to broiler chickens without or with a multi-enzyme supplement(MES). The MES supplied xylanase, b-glucanase invertase, protease, cellulase, a-amylase and mannanase with targeted activity of 2,500, 300, 700, 10,0001,200, 24,000, and 20 U/kg of feed, respectively. The study used a two-phase feeding program(starter d 0 to 24; finisher, d 25 to 35) with RB added at 5% and 11%, respectively creating 4 diets in each phase Diets were iso-caloric and iso-nitrogenous and contained phytase(500 FTU/kg) and TiO_2 as a digestibility marker. Three hundred and sixty d-old male Ross 708 broiler chicks were placed in cages based on BW(15 birds/cage) and allocated to 4 diets(n = 6). Birds had free access to feed and water. Body weight and feed intake were recorded. Excreta samples were collected 3 d prior to the end of each phase for apparent retention(AR) of components. Samples of birds were sacrificed on d 24 and 35 for gut weight and ceca digesta for organic acid content. There was no interaction(P > 0.10) between RB and MES on BWG and FCR in starter or finisher phase. In finisher phase, birds fed MES had better BWG(961 versus 858 g) and FCR(1.69 versus 1.86) than birds fed non-MES diets(P < 0.01). Feeding RB reduced(P = 0.02) BWG in finisher phase resulting in lower d 35 BW. Birds fed RB had higher(P 0.01) gizzard weight on d 24 and 35 than non-RB birds. An interaction(P 0.01) between RB and MES on concentrations of propionic and iso-butyric acids in ceca digesta showed that MES reduced these acids in non-RB diet. The AR of gross energy was higher(P < 0.02) for MES versus non-MES birds in starter and finisher phases. In conclusion independently, RB increased gizzard weight and reduced final BW whereas MES improved growth and energy utilization.展开更多
Soil amendment with biochar alleviates the toxic effects of heavy metals on microbial functions in single-metal contaminated soils.Yet,it is unclear how biochar application would improve microbial activity and enzymat...Soil amendment with biochar alleviates the toxic effects of heavy metals on microbial functions in single-metal contaminated soils.Yet,it is unclear how biochar application would improve microbial activity and enzymatic activity in soils co-polluted with toxic metals.The present research aimed at determining the response of microbial and biochemical attributes to addition of sugarcane bagasse biochar(SCB)in cadmium(Cd)-lead(Pb)co-contaminated soils.SCBs(400 and 600°C)decreased the available concentrations of Cd and Pb,increased organic carbon(OC)and dissolved organic carbon(DOC)contents in soil.The decrease of metal availability was greater with 600°C SCB than with 400°C SCB,and metal immobilization was greater for Cd(16%)than for Pb(12%)in co-spiked soils amended with low-temperature SCB.Biochar application improved microbial activity and biomass,and enzymatic activity in the soils co-spiked with metals,but these positive impacts of SCB were less pronounced in the co-spiked soils than in the single-spiked soils.SCB decreased the adverse impacts of heavy metals on soil properties largely through the enhanced labile C for microbial assimilation and partly through the immobili-zation of metals.Redundancy analysis further confirmed that soil OC was overwhelmingly the dominant driver of changes in the properties and quality of contaminated soils amended with SCB.The promotion of soil microbial quality by the low-temperature SCB was greater than by high-temperature SCB,due to its higher labile C fraction.Our findings showed that SCB at lower temperatures could be applied to metal co-polluted soils to mitigate the combined effects of metal stresses on microbial and biochemical functions.展开更多
Shortcut nitrification-denitrification(SCND)is widely concerned because of its low energy consumption and high nitrogen removal efficiency.However,the current difficulty lies in the stable maintenance of SCND performa...Shortcut nitrification-denitrification(SCND)is widely concerned because of its low energy consumption and high nitrogen removal efficiency.However,the current difficulty lies in the stable maintenance of SCND performance,which leads to the challenge of large-scale application of this new denitrification technology.In this study,the nitrogen removal pathway from complete nitrification-denitrification(CND)to SCND was rapidly realized under high free ammonia(FA),high pH and low dissolved oxygen(DO)conditions.The variations of specific oxygen uptake rate(SOUR)of activated sludge in both processes were investigated by an online SOUR monitoring device.Different curves of SOUR from CND to SCND process were observed,and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process.Accordingly,the SOUR ratio of ammonia oxidizing bacteria(AOB)to nitrite oxidizing bacteria(NOB)(SOURAOB/SOURNOB)was increased from 1.40 to 2.93.16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB,and the ratio of relative abundance(AOB/NOB)was increased from 1.03 to 3.12.Besides,SOURAOB/SOURNOB displayed significant correlations to ammonia removal rate(P<0.05),ammonia oxidation rate/nitrite oxidation rate(P<0.05),nitrite accumulation rate(P<0.05)and the relative abundance of AOB/NOB(P<0.05).Thus,a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed,which provides a theoretical basis for optimizing the SCND performance.展开更多
Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil...Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil feedback(PSF),driving community succession remains limited.In this work,we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment.Setaria viridis,Stipa bungeana,and Bothriochloa ischemum were selected to represent dominant and representative early-,mid-,and late-successional stage species,respectively,of semiarid grasslands on the Loess Plateau.In response to the different soil origin,the shoot biomass of early-,mid-,and late-species were all higher when grown in their own soil than in other species’soils,which indicated that the PSF of three species were positive.Over two growth periods,the early-species experienced a negative PSF,but the mid-and late-species experienced negative,neutral and positive PSF in the soil of early-,mid-and late-species,respectively.Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.展开更多
文摘For a constantly growing human population, healthy and productive soil is critical for sustainable delivery of agricultural products. The soil microorganisms play a crucial role in soil structure and functioning. They are responsible for soil formation, ecosystem biogeochemistry, cycling of nutrients and degradation of plant residues and xenobiotics. Certain agricultural treatments, such as fertilizers and pesticides applications, crop rotation, or soil amendment addition, influence the composition, abundance and function of bacteria and fungi in the soil ecosystems. Some of these practices have rather negative effects;others can help soil microorganisms by creating a friendlier habitat or providing nutrients. The changes in microbial community structure cannot be fully captured with traditional methods that are limited only to culturable organisms, which represent less than 1% of the whole population. The use of new molecular techniques such as metagenomics offers the possibility to better understand how agriculture affects soil microbiota. Therefore, the main goal of this review is to discuss how common farming practices influence microbial activity in the soil, with a special focus on pesticides, fertilizers, heavy metals and crop rotation. Furthermore, potential practices to mitigate the negative effects of some treatments are suggested and treatments that can beneficially influence soil microbiota are pointed out. Finally, application of metagenomics technique in agriculture and perspectives of developing efficient molecular tools in order to assess soil condition in the context of microbial activities are underlined.
基金financially supported by the National Natural Science Foundation of China(NSFC)(No.41775148)the Fundamental Research Funds for the Central Universities(No.201762006)+2 种基金the Program for New Century Excellent Talents in University(No.NCET-13-0531)supported by the NSFC Open Research Cruise(Cruise no.NORC2015-05)funded by the Ship Time Sharing Project of the NSFC。
文摘Oceans are important sources of microbes in atmospheric aerosols;however, information about the characteristics of airborne microbes and their influencing factors over oceans is lacking. Here we report the characteristics of the microbial abundance and activity in aerosols sampled near the sea surface over the South China Sea(SCS) from May to June 2016. The airborne microbial concentration range in the aerosols was 1.68?105 to 4.84?105 cells m-3 over the SCS, reflecting an average decrease of 40% – 54% over the SCS compared with that in the samples from the coastal region of Qingdao. About 63% – 76% of the airborne microbes occurred in coarse particles(> 2.1 ?m), with a variable size distribution over the SCS. The microbial activity range in aerosols, measured by the fluorescein diacetate(FDA) hydrolysis method, was 2.09 – 11.97 ng m-3 h-1 sodium fluorescein(SF) over the SCS, which was 15% – 79% lower than that over the coastal region. These values reflected a different spatial distribution over the SCS from that of the microbial concentration. Except for certain samples, all samples had 68% of the microbial activity occurring in coarse particles. Correlation analysis showed that the microbial abundance and activity were positively correlated with the aerosol, organic carbon(OC), and water-soluble organic carbon(WSOC) concentrations, indicating that the airborne microbes may be related to the reactions of certain water-soluble organic chemicals in the atmosphere. Moreover, the concentrations of airborne microbes were significantly negatively correlated with the horizontal offshore distance. The microbial concentration and activity were significantly correlated with wind speed.
基金supported by the National Natural Science Foundation of China(No.52070172)the Fundamental Research Funds for the Central Universities(No.201964003).
文摘The impact of dissolved oxygen(DO)at aerobic phase on the nitrogen removal,extracellular polymeric substances(EPS),microbial activity and microbial community of sequencing batch biofilm reactor(SBBR)have been evaluated in treating mariculture wastewater.The oxygen uptake rate and nitrification rate declined with DO concentration from 3–4 to 1–1.5mgL^(-1),whereas the denitrification rate had an increment.The activities of nitrifying enzymes reduced with the decrease of DO concentration at aerobic phase,but those of denitrifying enzymes illustrated opposite results.The nitrification and denitrification rates displayed the similar variation tendency with the relevant enzymatic activities as DO concentration decreased.The protein(PN)and polysaccharide(PS)content in EPS decreased as DO concentration declined,whereas the PN/PS ratio increased.The microbial community showed obvious difference as DO concentration decreased from 3–4 to 1–1.5mgL^(-1).The microbial co-occurrence,keystone taxa and sig-nificant difference illustrated some variations at different DO concentrations.
基金supported by the Program of Yunling Scholarship,the CAS“Light of West China”Program(Western Youth Scholars“A”),the Youth Innovation Promotion Association CAS(2013252)the Applied Basic Research Programs of Yunnan Province(2017FB137).
文摘A new favane,bropapyriferol(1),and eleven known ones were isolated from the EtOAc part of Broussonetia papyrifera under the guidance of bioassay.The structure of compound 1 was determined by extensive 1D and 2D NMR,[α]_(D) spectroscopic data and quantum computation.Daphnegiravan F(2)and 5,7,3′,4′-tetrahydroxy-3-methoxy-8,5′-diprenylfavone(3)showed signifcantly anti-oral microbial activity against fve Gram-positive strains and three Gram-negative strains in vitro.Especially,compound 3 was more potent in suppressing Actinomyces naeslundii and Porphyromonas gingivalis(MIC=1.95 ppm)than the positive control,triclosan.
文摘Microbial enhanced oil recovery (MEOR) is the research focus in the field of energy development as an environmentally friendly and low cost technology. MEOR can bes divided into indigenous microbial oil recovery and exogenous microbial oil recovery. The ultimate goal of indigenous microbial flooding is to enhance oil recovery via stimulation of specific indigenous microorganisms by injecting optimal nutrients. For studying the specific rule to activate the indigenous community during the long-term injection period, a series of indigenous displacement flooding experiments were carried out by using the long-core physical simulation test. The experimental results have shown that the movement of nutrients components (i.e., carbon/nitrogen/phosphorus) differed from the consumption of them. Moreover, there was a positive relationship between the nutrients concentration and bacteria concentration once observed in the produced fluid. And the trend of concentration of acetic acid was consistent with that of methanogens. When adding same activators, the impacts of selective activators to stimulate the indigenous microorganisms became worse along with the injection period, which led to less oil recovery efficiency.
文摘The proliferation of glyphosate-resistant weeds has resulted in significant losses in the productivity of crops such as corn, soybean, and cotton. As a result, new crop varieties with resistance genes from other herbicides, such as 2,4-D and dicamba, have been developed as part of alternative weed control cropping systems. However, little is known about how the application of these herbicides impacts the microorganisms that carry out nutrient cycling in the soil of these cropping systems, particularly in the rhizosphere, the soil compartment immediately adjacent to the root system which is pivotal to plant nutrient uptake. The purpose of the current study was to assess the effects of dicamba on soil enzyme activities linked to C, N, and P cycling in the rhizosphere of </span><span style="font-family:Verdana;">resistant soybean plants. While dicamba had no significant effects on the ac</span><span style="font-family:Verdana;">tivities of enzymes linked to C or P cycling in the rhizosphere, N-acetylglucosaminidase activity was temporarily inhibited, but recovered by three days after application. These results suggest there are no long-lasting negative effects of dicamba in the rhizosphere of treated plants when applied at field rates.
基金financially supported by the National Natural Science Foundation of China(41871064)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0304)。
文摘The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and stores massive soil carbon.
文摘The antibacterial activity of copper is well-known from an ancient civilization, however, its biocidal mechanism has not been necessarily elucidated. Notwithstanding up to now, mainly 4 processes have been proposed. Among them, it is cleared that 4 kinds of reactive oxygen species (ROS): hydroxyl radical ·OH, hydrogen per oxide H<sub>2</sub>O<sub>2</sub>, superoxide anion ·O<sup>-</sup>2</sub></sub> and singlet oxygen <sup>1</sup>O<sub>2</sub>, play an important role for contact-killing of bacteria, viruses and fungi. In this paper, generation of ROS on the surfaces of copper plates heated from room temperature to 673 K for 4.2 × 10<sup>2</sup> s in air, was investigated using the chemiluminescence. ROS have been evaluated by selecting the most suitable scavengers, such as 2-propanol for ·OH, sodium pyruvate for H<sub>2</sub>O<sub>2</sub>, nitro blue tetrazolium for ·O<sup>-</sup>2</sub></sub>, and sodium azide NaN<sub>3</sub> for <sup>1</sup>O<sub>2</sub>. At the same time the outermost surface of copper, on which thin film of cuprous oxide Cu<sub>2</sub>O was first formed and then cupric oxide CuO was laminated on Cu<sub>2</sub>O, was examined by thin-film XRD and TEM analysis to estimate the amounts and kinds of copper oxides. It was found that the most amounts of ROS were obtained for the 573 K-heated Cu plate and they were composed of ·OH, H<sub>2</sub>O<sub>2</sub>, and ·O<sup>-</sup>2.</sub></sub>.
基金Tarbiat Modares University for the financial support of the study reported in this paper
文摘Beech stands are considered part of the ancient forest ecosystems in the northern hemisphere.In mixed stands in beach forest ecosystems,the type of associated tree species can signifi cantly aff ect soil functions,but their infl uence on microbial activity,nutrient cycling and belowground properties is unknown.Here,we considered forest patches in northern Iran that are dominated by diff erent tree species:Fagus orientalis Lipsky,Quercus castaneifolia C.A.Mey.,Pterocarya fraxinifolia(Lam.),Tilia begonifolia Stev.,Zelkova carpinifolia Dippe,Acer cappadocicum Gled,Acer velutinum Boiss.,Fraxinus excelsior L.,Carpinus betulus L.,and Alnus subcordata C.A.Mey.For each forest patch–tree species,litter and soil samples(25×25×10 cm,100 of each)were analyzed for determine soil and litter properties and their relationship with tree species.The litter decomposition rate during a 1-year experiment was also determined.A PCA showed a clear diff erence between selected litter and soil characteristics among tree species.F.orientalis,Q.castaneifolia,P.fraxinifolia,T.begonifolia,Z.carpinifolia,A.cappadocicum,and A.velutinum enhanced soil microbial biomass of carbon,whereas patches with F.excelsior,C.betulus and A.subcordata had faster litter decomposition and enhanced biotic activities and C and N dynamics.Thus,soil function indicators were species-specifi c in the mixed beech forest.A.subcordata(a N-fi xing species),C.betulus and F.excelsior were main drivers of microbial activities related to nutrient cycling in the old-growth beech forest.
基金supported by the National Natural Science Foundation of China (31870420 and 41807084)the Natural Science Foundation of Guangdong Province, China (2017A030313177 and 2018A030310214)the Science and Technology Project of Guangdong Province, China (2019B030301007)。
文摘Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underlying mechanisms are not well understood. This study is designed to evaluate the efficacy of biochar amendment for controlling tomato bacterial wilt caused by Ralstonia solanacearum, and to explore the interactions between biochar-induced changes in rhizosphere compound composition, the pathogen and tomato growth. The results showed that biochar amendment decreased disease incidence by 61–78% and simultaneously improved plant growth. The positive ‘biochar effect' could be associated with enhanced microbial activity and alterations in the rhizosphere organic acid and amino acid composition. Specifically, elevated rhizosphere citric acid and lysine, but reduced salicylic acid, were induced by biochar which improved microbial activity and rendered the rhizosphere unsuitable for the development of R. solanacearum. In addition, nutrients which were either made more available by the stimulated microbial activity or supplied by the biochar could improve plant vigor and potentially enhance tomato resistance to diseases. Our findings highlight that biochar's ability to control tomato bacterial wilt could be associated with the alteration of the rhizosphere organic acid and amino acid composition, however, further research is required to verify these ‘biochar effects' in field conditions.
文摘Recently, under the circumstances of pandemic of COVID-19 much attention has been paid to titanium dioxide TiO<sub>2</sub> as bactericidal agent;however, conventional TiO<sub>2</sub> requires ultraviolet radiation or visible light to exercise its photocatalytic properties and its induced antimicrobial activity. In order to expand its applications directed at wide civil life, antibacterial TiO<sub>2</sub> being usable under dark conditions has been demanded. The present paper describes the powder characterization of newly developed potassium K and phosphorous P co-doped nanometer-size anatase TiO<sub>2</sub> powders using X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM & TEM), Brunauer-Emmett-Teller method (BET), fourier-transform infrared spectroscopy (FT-IR), X-ray absorption fine structure (XAFS), electron spin resonance (ESR) and chemiluminescence (CL). It was found for the first time that thus prepared anatase TiO<sub>2</sub> could submit much reactive oxygen species (ROS) even in the dark, which has close relation with bactericidal activity in light interception.
文摘Assessment of fungal species associated with a multicultural orchard and cultivated land in Bingham University landscape was carried out,with the ultimate aim of identifying the fungi species present in soil under different agricultural practices.A total of 30 soil samples were collected and the composite from each land use pattern was analyzed in the laboratory using standard methods.Soil type,percentage Soil Moisture(SM),percentage Organic Carbon(OC)and percentage Organic Matter(OM)were measured using standard methods;fungi species were isolated and identified on the basis of mycelia and spore characteristics,after staining with lactophenol-in-cotton blue.The results showed that,four types of soil exist in the sites including sandy,clayey,silt and loamy.SM ranges between 3.6%-5.7%,and OC in the sandy soil was the highest 1.01%in the orange plantation(Op5)followed closely by loamy soil on cultivated site C with 0.97%OM and 0.56%OC and least in clay soil with 0.72%OM and 0.42%OC.The results of colony forming unit per gram(cfu/g)in relation to land use type,Cultivated Site C(CC1-CC5)had the highest(262 cfu/g)and mango plantation(Mp1-Mp5)had the least with 156 cfu/g.Pictorial representation of isolated fungal species are indicative of suspected presence of Aspergillus Spp,Mucor Spp,Cladosporium Spp,Fusarium Spp,Aspergillus Spp etc.This qualitative study concluded that fungal species population in the soil depends on the management practice in place and the moisture content of the soil.
基金supported by the National Natural Science Foundation of China(32022054,31901137)China Postdoctoral Science Foundation(2018M640263)+2 种基金Instrument Developing Project of CAS(YJKYYQ20190079)Strategic Priority Research Program of CAS(Grant No.XDA28120100)Youth Innovation Promotion Association of CAS(2019198)。
文摘Background:Nitrogen(N)deposition alters litter decomposition and soil carbon(C)sequestration by influencing the microbial community and its enzyme activity.Natural atmospheric N deposition comprises of inorganic N(IN)and organic N(ON)compounds.However,most studies have focused on IN and its effect on soil C cycling,whereas the effect of ON on microbial enzyme activity is poorly understood.Here we studied the effects of different forms of externally supplied N on soil enzyme activities related to decomposition in a temperate steppe.Ammonium nitrate was chosen as IN source,whereas urea and glycine were chosen as ON sources.Different ratios of IN to ON(Control,10:0,7:3,5:5,3:7,and 0:10)were mixed with equal total amounts of N and then used to fertilize the grassland soils for 6 years.Results:Our results show that IN deposition inhibited lignin-degrading enzyme activity,such as phenol oxidase(POX)and peroxidase(PER),which may restrain decomposition and thus induce accumulation of recalcitrant organic C in grassland soils.By contrast,deposition of ON and mixed ON and IN enhanced most of the C-degrading enzyme activities,which may promote the organic matter decomposition in grassland soils.In addition,theβ-N-acetyl-glucosaminidase(NAG)activity was remarkably stimulated by fertilization with both IN and ON,maybe because of the elevated N availability and the lack of N limitation after long-term N fertilization at the grassland site.Meanwhile,differences in soil pH,soil dissolved organic carbon(DOC),and microbial biomass partially explained the differential effects on soil enzyme activity under different forms of N treatments.Conclusions:Our results emphasize the importance of organic N deposition in controlling soil processes,which are regulated by microbial enzyme activities,and may consequently change the ecological effect of N deposition.Thus,more ON deposition may promote the decomposition of soil organic matter thus converting C sequestration in grassland soils into a C source.
基金supported by the National High Technology Research and Development Program (863) of China (No.2008AA06A412)the National Key Projects of Water Pollution Control and Treatment (No. 2008ZX07421-004)
文摘The growth and metabolism of microbial communities on biologically activated carbon(BAC) play a crucial role in the purification of drinking water.To gain insight into the growth and metabolic characteristics of microbial communities and the efficiency of drinking water treatment in a BAC filter,we analyzed the heterotrophic plate count(HPC),phospholipid,dehydrogenase,metabolic function and water quality parameters during start-up and steady-state periods.In the start-up process of the filter with natural biofilm colonization,the variation in heterotrophic plate count levels was S-curved.The total phospholipid level was very low during the first 5 days and reached a maximum value after 40 days in the filter.The activity of dehydrogenase gradually increased during the first 30 days and then reached a plateau.The functional diversity of the microbial community in the filter increased,and then reached a relatively stable level by day 40.After an initial decrease,which was followed by an increase,the removal rate of NH4+-N and COD Mn became stable and was 80% and 28%,respectively,by day 40.The consumption rate of dissolved oxygen reached a steady level after 29 days,and remained at 18%.At the steady operation state,the levels of HPC,phospholipid,dehydrogenase activity and carbon source utilization had no significant differences after 6 months compared to levels measured on day 40.The filter was shown to be effective in removing NH4+-N,NO2--N,COD Mn,UV 254,biodegradable dissolved organic carbon and trace organic pollutants from the influent.Our results suggest that understanding changes in the growth and metabolism of microorganisms in BAC filter could help to improve the efficiency of biological treatment of drinking water.
基金supported by the National Natural Science Foundation of China(Nos.41201259 and41671269)the Open Fund of the State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau,China(No.10501-1207)+1 种基金the National Science Foundation of Shaanxi Province,China(No.2013JQ5001)the CAS“Light of West China”Program。
文摘The water-wind erosion crisscross region of the northern Loess Plateau in China is under constant pressure from severe erosion due to its windy and dry climate and intensive human activities. Identifying sustainable land use patterns is key to maintaining ecosystem sustainability in the area. Our aim was to appraise the impacts of different land use regimes on the dynamics of soil total organic C(TOC), total N(TN), and microbes in a typical watershed in the northern Loess Plateau to identify suitable land use types that can maintain soil fertility and sustainability. A field experiment was performed in Liudaogou watershed in Shenmu City, Shaanxi Province, China, where the dynamics of soil TOC and TN, microbial biomass C and N, microbial respiration, and net N mineralization in six typical land use types, dam land, rainfed slope land, deciduous broadleaf forest, evergreen coniferous forest, shrubland, and grassland,were measured in three different growing seasons. Land use type and season significantly affected TOC, TN, and the dynamics of microbial biomass and activity. As the most anthropogenically disturbed land use pattern, dam land was an optimal land use pattern for TOC sequestration due to its higher TOC and TN, but lower microbial activity. Soil TOC, TN, and microbial properties demonstrated a decreasing trend after natural grassland was converted to shrubland,forest, and rainfed slope land. Shrubland with exotic N-fixing Korshinsk peashrub(Caragana korshinskii Kom.) can maintain TOC, TN, and microbial properties similar to those in grassland. Soil TOC, NH_(4+)^(-)N, TN, moisture, and extractable C were the principal indexes for soil microbial biomass and activity and explained 88.90% of the total variance. Thus, grassland was the optimal land use pattern in the water-wind erosion crisscross region of the northern Loess Plateau to maintain ecosystem stability and sustainability.
基金financially provisioned by the National Sciences and Engineering Research Council of Canada(NSERC,Ottawa,Canada,#CRDPJ522371-17)Ontario Agri-Food Innovation Alliance(Ontario,Canada,#UofG2016-2531)Canadian Bio-Systems Inc.(Calgary,Canada,#053740)
文摘We investigated the effects of adding up to 11% rice bran(RB) in corn-soybean meal diets fed to broiler chickens without or with a multi-enzyme supplement(MES). The MES supplied xylanase, b-glucanase invertase, protease, cellulase, a-amylase and mannanase with targeted activity of 2,500, 300, 700, 10,0001,200, 24,000, and 20 U/kg of feed, respectively. The study used a two-phase feeding program(starter d 0 to 24; finisher, d 25 to 35) with RB added at 5% and 11%, respectively creating 4 diets in each phase Diets were iso-caloric and iso-nitrogenous and contained phytase(500 FTU/kg) and TiO_2 as a digestibility marker. Three hundred and sixty d-old male Ross 708 broiler chicks were placed in cages based on BW(15 birds/cage) and allocated to 4 diets(n = 6). Birds had free access to feed and water. Body weight and feed intake were recorded. Excreta samples were collected 3 d prior to the end of each phase for apparent retention(AR) of components. Samples of birds were sacrificed on d 24 and 35 for gut weight and ceca digesta for organic acid content. There was no interaction(P > 0.10) between RB and MES on BWG and FCR in starter or finisher phase. In finisher phase, birds fed MES had better BWG(961 versus 858 g) and FCR(1.69 versus 1.86) than birds fed non-MES diets(P < 0.01). Feeding RB reduced(P = 0.02) BWG in finisher phase resulting in lower d 35 BW. Birds fed RB had higher(P 0.01) gizzard weight on d 24 and 35 than non-RB birds. An interaction(P 0.01) between RB and MES on concentrations of propionic and iso-butyric acids in ceca digesta showed that MES reduced these acids in non-RB diet. The AR of gross energy was higher(P < 0.02) for MES versus non-MES birds in starter and finisher phases. In conclusion independently, RB increased gizzard weight and reduced final BW whereas MES improved growth and energy utilization.
文摘Soil amendment with biochar alleviates the toxic effects of heavy metals on microbial functions in single-metal contaminated soils.Yet,it is unclear how biochar application would improve microbial activity and enzymatic activity in soils co-polluted with toxic metals.The present research aimed at determining the response of microbial and biochemical attributes to addition of sugarcane bagasse biochar(SCB)in cadmium(Cd)-lead(Pb)co-contaminated soils.SCBs(400 and 600°C)decreased the available concentrations of Cd and Pb,increased organic carbon(OC)and dissolved organic carbon(DOC)contents in soil.The decrease of metal availability was greater with 600°C SCB than with 400°C SCB,and metal immobilization was greater for Cd(16%)than for Pb(12%)in co-spiked soils amended with low-temperature SCB.Biochar application improved microbial activity and biomass,and enzymatic activity in the soils co-spiked with metals,but these positive impacts of SCB were less pronounced in the co-spiked soils than in the single-spiked soils.SCB decreased the adverse impacts of heavy metals on soil properties largely through the enhanced labile C for microbial assimilation and partly through the immobili-zation of metals.Redundancy analysis further confirmed that soil OC was overwhelmingly the dominant driver of changes in the properties and quality of contaminated soils amended with SCB.The promotion of soil microbial quality by the low-temperature SCB was greater than by high-temperature SCB,due to its higher labile C fraction.Our findings showed that SCB at lower temperatures could be applied to metal co-polluted soils to mitigate the combined effects of metal stresses on microbial and biochemical functions.
基金This research was supported by Sichuan Key Point Research and Invention Program(Nos.2019YFS0502,2020YFS0026)Instrument Developing Project of the Chinese Academy of Sciences(No.YJKYYQ20180002)Project funded by China Postdoctoral Science Foundation(No.2020M673293).
文摘Shortcut nitrification-denitrification(SCND)is widely concerned because of its low energy consumption and high nitrogen removal efficiency.However,the current difficulty lies in the stable maintenance of SCND performance,which leads to the challenge of large-scale application of this new denitrification technology.In this study,the nitrogen removal pathway from complete nitrification-denitrification(CND)to SCND was rapidly realized under high free ammonia(FA),high pH and low dissolved oxygen(DO)conditions.The variations of specific oxygen uptake rate(SOUR)of activated sludge in both processes were investigated by an online SOUR monitoring device.Different curves of SOUR from CND to SCND process were observed,and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process.Accordingly,the SOUR ratio of ammonia oxidizing bacteria(AOB)to nitrite oxidizing bacteria(NOB)(SOURAOB/SOURNOB)was increased from 1.40 to 2.93.16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB,and the ratio of relative abundance(AOB/NOB)was increased from 1.03 to 3.12.Besides,SOURAOB/SOURNOB displayed significant correlations to ammonia removal rate(P<0.05),ammonia oxidation rate/nitrite oxidation rate(P<0.05),nitrite accumulation rate(P<0.05)and the relative abundance of AOB/NOB(P<0.05).Thus,a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed,which provides a theoretical basis for optimizing the SCND performance.
基金funded by the National Natural Science Foundation of China(42130717)the Shaanxi Science Fund for Distinguished Young Scholars(2021JC-50)。
文摘Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil feedback(PSF),driving community succession remains limited.In this work,we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment.Setaria viridis,Stipa bungeana,and Bothriochloa ischemum were selected to represent dominant and representative early-,mid-,and late-successional stage species,respectively,of semiarid grasslands on the Loess Plateau.In response to the different soil origin,the shoot biomass of early-,mid-,and late-species were all higher when grown in their own soil than in other species’soils,which indicated that the PSF of three species were positive.Over two growth periods,the early-species experienced a negative PSF,but the mid-and late-species experienced negative,neutral and positive PSF in the soil of early-,mid-and late-species,respectively.Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.
