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1.
J Agric Food Chem ; 67(42): 11584-11590, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31566380

RESUMO

Ureolytic microbes play a pivotal role in the maintenance of soil fertility. Soil aggregates are supposed to provide heterogeneous habitats for microorganisms, which may result in distinct metabolic functions. However, limited information is available regarding the distribution patterns, driving factors, and activity of ureolytic microbiota at the aggregate scale. In this study, we characterized the ureolytic microbiota and urease activity of three soil aggregate fractions from an Inceptisol subjected to 5 years of different fertilization regimes. Correlations between soil chemical characteristics and ureolytic microbial communities were analyzed. The results showed that the total abundance as well as the relative abundance of copiotrophic ureolytic microbes generally increased with the increasing soil aggregate size. This trend was in line with the nutrient distribution patterns, including labile carbon, NH4+, total carbon, nitrogen, and phosphorus. Soil urease activity also increased significantly with the increasing soil aggregate size and was positively correlated with copiotrophic ureolyric microbes, such as Betaproteobacteria, Alphaproteobacteria, and Gammaproteobacteria. Thus, we speculated that larger size soil aggregates with greater availability of labile carbon support more copiotrophic ureolyric microbes with a high growth rate, leading to a high density of total ureolytic microbes and higher urease activity. Smaller aggregates with less available carbon were associated with more oligotrophs, higher abundances of total ureolytic microbes, and higher urease activity. Our results suggest that larger soil aggregates and associated ureolyric microbes play a more important role in nutrient cycling for crop growth in this Inceptisol ecosystem.


Assuntos
Bactérias/enzimologia , Proteínas de Bactérias/metabolismo , Microbiologia do Solo , Solo/química , Ureia/metabolismo , Urease/metabolismo , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Microbiota , Nitrogênio/metabolismo , Tamanho da Partícula , Fósforo/metabolismo
2.
J Agric Food Chem ; 67(39): 10984-10993, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31525294

RESUMO

The objective of the present study was to reveal the effects of four types of nitrogen sources (soymeal, yeast extract, KNO3, and ammonium tartrate) on the lipid metabolism of the oleaginous fungus Mortierella alpina using untargeted lipidomics, targeted fatty acid, and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis. Our results showed clear differences in the contents and compositions of lipids between four types of nitrogen sources. Soymeal and ammonium tartrate supplementation favored the accumulation of triglycerides with arachidonic acid (ARA) and C16-18 fatty acids, respectively. These results were further validated by our targeted fatty acid analysis. RT-qPCR analysis of related genes in M. alpina between the four nitrogen source conditions found that soymeal supplementation dramatically increased the expression of GPAT, ELOVL, and Δ12/Δ6 desaturase. Our findings provided new insights into the regulation of lipid biosynthesis in M. alpina and potential avenues for genetic manipulation and highlighted the importance of an optimal nitrogen source for ARA-rich oil production.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Lipídeos/biossíntese , Lipídeos/química , Espectrometria de Massas/métodos , Mortierella/metabolismo , Nitrogênio/metabolismo , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos/biossíntese , Ácidos Graxos/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Mortierella/química , Mortierella/enzimologia , Mortierella/genética
3.
Life Sci ; 233: 116752, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31415770

RESUMO

AIMS: Few studies have compared the interaction of single and repeated administration of amitriptyline (amit) with the nitrergic system and glutamatergic system in the experimental model of neuropathic pain. We aimed to evaluate the antinociceptive effect of single and repeated administration of amit and to assess whether glutamate preceded inducible nitric oxide synthase (iNOS) inhibition as a mechanism of the analgesic effect of amit in the neuropathic model of pain. MATERIALS AND METHODS: Male Wistar rats were subjected to left sciatic nerve ligation. The effect of single (25 mg kg-1) and repeated (10 mg kg-1 daily for 3 weeks) administration of amit intraperitoneally (i.p.) alone or in combination with aminoguanidine (AG i.p., 100 mg kg-1 for 3 days, a selective iNOS inhibitor) and MK-801 (0.05 mg kg-1 i.p., NMDA antagonist) on resting paw posture and mechanical hyperalgesia were studied. Glutamate level and iNOS protein expression in hippocampus were detected. KEY FINDINGS: Single and repeated administration of amit alone or in combination with AG or MK-801 demonstrated a significant decrease in resting pain score and increase in the pain threshold. Both glutamate and nitrite levels decreased in the hippocampi of single and repeated amit + MK-801 groups. Immunohistochemistry showed a marked decrease in iNOS immunoreactivity in rats treated with single and repeated amit + MK-801. SIGNIFICANCE: Our results suggest that glutamate-dependent mechanisms are involved in the analgesic responses to amit administration. Importantly, glutamatergic system and its upstream nitrergic system play an important role in the antinociceptive action of amit.


Assuntos
Amitriptilina/farmacologia , Analgésicos não Entorpecentes/farmacologia , Ácido Glutâmico/metabolismo , Neuralgia/tratamento farmacológico , Nitrogênio/metabolismo , Amitriptilina/administração & dosagem , Analgésicos não Entorpecentes/administração & dosagem , Animais , Modelos Animais de Doenças , Masculino , Neuralgia/metabolismo , Neuralgia/patologia , Óxido Nítrico Sintase Tipo II/antagonistas & inibidores , Limiar da Dor , Ratos , Ratos Wistar
4.
Ying Yong Sheng Tai Xue Bao ; 30(8): 2667-2674, 2019 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-31418191

RESUMO

With a greenhouse pot experiment, we investigated the effects of nitrogen (N) and plant growth promoter (brassinolide, BR) addition on the growth and competitive ability of three common plant species of typical steppe in Inner Mongolia, including Leymus chinensis, Astragalus adsurgens and Stipa krylovii. We added N at rates of 0, 0.1, 0.2, 0.4, 0.8 mg·g-1 soil and BR at rates of 0 and 0.005 mg·g-1 soil during plant growth in monoculture or with L. chinensis being planted in mixing with other two species, respectively. There were significant effects on biomass of L. chinensis and A. adsurgens, but not on that of S. krylovii with increase of N and BR addition. The effects of N addition on the growth of L. chinensis varied with accompanying plant species. Nitrogen addition increased aboveground biomass production of L. chinensis when growing in monoculture and mixed with A. adsurgens, but decreased its belowground biomass when growing mixed with S. krylovii. With increasing soil N availability, plant biomass allocation of L. chinensis showed significant decrease in root-shoot ratio when it was in monoculture or mixed with S. krylovii, but similar changes were not found when it was planted in mixing with A. adsurgens. The significant effects of BR addition on plant growth appeared occasionally. BR addition significantly reduced belowground biomass of A. adsurgens in its monoculture and significantly increased aboveground biomass of L. chinensis when it was planted in mixing with A. adsurgens. The results indicated that the appropria-tely combined addition of N and BR could effectively enhance biomass production of specific species combinations in grasslands, which has application prospects in the restoration of degraded grassland.


Assuntos
Nitrogênio/metabolismo , Poaceae/crescimento & desenvolvimento , Biomassa , China , Desenvolvimento Vegetal , Solo
5.
Bioresour Technol ; 291: 121886, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31377046

RESUMO

The objective of this study was to identify the effect of clay additive to explore the nitrogen cycling related ammonification, denitrifying genes and their relation N2O and ammonia emission during the chicken manure (CM) composting. The consequences indicated that the additive clay could optimize the environment and improve the NH4+-N into NO3--N transformation. Meanwhile, the results observed that 8% clay amendment was significant correlated the abundance of nifH and nosZ genes. Compared with the other treatments, the 6% and 10% clay treatments observed low abundance of nifH. The heat map indicated that clay amendment could enhance the function genes abundance. The redundancy analysis showed that N2O and ammonia emission among all physiochemical parameters had great relationship with functional genes. Therefore, the addition of 10% clay into CM composting system could efficiently enhance the abundance of nirK and narG genes, and improve the composting with its application.


Assuntos
Argila , Compostagem , Esterco , Ciclo do Nitrogênio , Nitrogênio/metabolismo , Amônia/metabolismo , Animais , Galinhas , Desnitrificação/genética , Esterco/análise
6.
Environ Monit Assess ; 191(9): 531, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31375926

RESUMO

Microbially produced biosurfactants are fast catching up due to their environment-friendly approach over chemical surfactants. But their commercial production is restricted due to poor economy of the production process which could be improved by using high yielding microbial strains and optimizing the process parameters. The present research was directed to optimize the biosurfactant production monitored in terms of oil displacement and emulsification (E24) index, using a promising yeast Meyerozyma guilliermondii YK32. Maximum oil displacement equaling 7.5 cm was obtained with olive oil at 8% (v/v) concentration as carbon source under shaking conditions (150 rpm). Diesel being a complex hydrocarbon was not utilized easily by yeast and showed poor biosurfactant production. Yeast extract at 1.5% (w/v) concentration yielded maximum biosurfactant as evident from maximum oil displacement and E24 index equal to 8.1 cm and 52.6%, respectively. Sodium chloride at the rate of 3% (w/v) supported maximum oil displacement (8.8 cm) using the production broth containing optimized carbon and nitrogen sources. Any increase beyond this level negatively influenced the biosurfactant production. The yield was at its maximum at 30 °C as a shift in temperature either to 35 °C or 25 °C decreased the oil displacement from 8.8 to 5.2 or 7.6 cm, respectively. At 40 °C, oil displacement was decreased to 2.5 cm. Biosurfactant production appeared to be sensitive to varying pH as evident from the E24 index as high as 67.3% at pH 6.0 as compared with 60.2%, 60.1%, and 52.4% at pH 5.0, 5.5, and 7.0, respectively. Yeast biomass yield equivalent to 10.3 g/L and 8.3 g/L was recorded at pH 6 and 7, respectively, during the production process. Elimination of shaking reduced the E24 index from 67.3 to 34.8% under optimized conditions.


Assuntos
Monitoramento Ambiental/métodos , Saccharomycetales/metabolismo , Tensoativos/metabolismo , Biomassa , Carbono/metabolismo , Hidrocarbonetos/metabolismo , Nitrogênio/metabolismo , Saccharomycetales/crescimento & desenvolvimento , Temperatura Ambiente
7.
Bioresour Technol ; 291: 121865, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31369926

RESUMO

Bacterial community structure and metabolic function during solid waste decomposition were investigated using Illumina MiSeq sequencing and phylogenetic investigation of communities by reconstruction of unobserved states, respectively. Results showed that bacterial community diversity and structure differed in aerobic phase, anaerobic acid phase, and methanogenic phase. Anaerobic acid phase had significantly (p < 0.05) higher richness. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant representatives with significant (p < 0.05) difference between three phases. Total nitrogen of solid waste and pH of leachate were the important factors in shaping bacterial community composition. Bacterial metabolism, information storage and processing, and cellular processes and signaling were the primary functions during solid waste decomposition. Key function genes (amo, nar, nis, and nos) profiles suggested that nitrification and denitrifiation mainly occurred in AP and both AP and MP, respectively.


Assuntos
Microbiota , Filogenia , Resíduos Sólidos , Bacteroidetes/genética , Biodiversidade , Euryarchaeota/genética , Firmicutes/genética , Nitrificação , Nitrogênio/metabolismo , Proteobactérias/genética
8.
Bioresour Technol ; 291: 121867, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376671

RESUMO

Nitrous oxide (N2O) is a strong greenhouse gas that is produced in significant quantities through biological nitrogen removal processes in wastewater treatment plants; however, N2O generation within the internal micro-environment of activated sludge flocs (ASFs) is poorly understood. In this study, microelectrodes and molecular techniques were employed to investigate the concentrations of N2O and other chemicals and the composition and distribution of microbes within ASFs, respectively. The results showed that N2O generation was correlated with the ASF micro-environment, and was significantly influenced by the dissolved oxygen (DO) concentration of the bulk wastewater. Equal N2O, DO, NH4+-N, and NO3--N concentrations were found in small flocs (<100 µm). By contrast, higher N2O generation rates and lower DO, NH4+-N, and NO3--N concentrations were detected in the center of large flocs (>200 µm) compared with those at their surfaces. Microbial structures of varying particle sizes were distinct and depended on the micro-environmental characteristics.


Assuntos
Óxido Nitroso/metabolismo , Oxigênio/metabolismo , Esgotos , Nitrogênio/metabolismo , Tamanho da Partícula , Esgotos/química
9.
Environ Pollut ; 253: 974-980, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31352189

RESUMO

Thiocyanate (SCN-)-based autotrophic denitrification (AD) has recently been demonstrated as a promising technology that could be integrated with anaerobic ammonium oxidation (Anammox) to achieve simultaneous removal of nitrogen and SCN-. However, there is still a lack of a complete SCN--based AD model, and the potential microbial competition/synergy between AD bacteria and Anammox bacteria under different operating conditions remains unknown, which significantly hinders the possible application of coupling SCN--based AD with Anammox. To this end, a complete SCN--based AD model was firstly developed and reliably calibrated/validated using experimental datasets. The obtained SCN--based AD model was then integrated with the well-established Anammox model and satisfactorily verified with experimental data from a system coupling AD with Anammox. The integrated model was lastly applied to investigate the impacts of influent NH4+-N/NO2--N ratio and SCN- concentration on the steady-state microbial composition as well as the removal of nitrogen and SCN-. The results showed that the NH4+-N/NO2--N ratio in the presence of a certain SCN- level should be controlled at a proper value so that the maximum synergy between AD bacteria and Anammox bacteria could be achieved while their competition for NO2- would be minimized. For the simultaneous maximum removal (>95%) of nitrogen and SCN-, there existed a negative relationship between the influent SCN- concentration and the optimal NH4+-N/NO2--N ratio needed.


Assuntos
Compostos de Amônio/metabolismo , Desnitrificação , Nitrogênio/metabolismo , Tiocianatos/metabolismo , Processos Autotróficos , Bactérias , Modelos Químicos , Oxirredução
10.
J Sci Food Agric ; 99(14): 6431-6443, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31294831

RESUMO

BACKGROUND: Noodles and steamed bread are popular wheat products consumed worldwide, particularly in China and other Asian countries. We performed the first comprehensive study of the influence of water deficits and different nitrogen fertilizer applications on two elite Chinese bread wheat cultivars, Zhongmai 175 and Jimai 22, which are distinct in gluten strength. These wheat cultivars were tested to determine the qualities that are optimal for the production of Chinese fresh white noodles (CFWN) and northern-style Chinese steamed bread (NCSB), and storage protein composition. RESULTS: Water deficit and high nitrogen (N) fertilizer application promoted total grain protein content and the accumulation of gliadins and glutenins, while low N resulted in the opposite results. Water deficit and high N fertilizer in Jimai 22, with medium-to-strong gluten strength significantly improved NCSB and CFWN qualities. The quality of CFWN under low N, and that of NCSB under both high and low N conditions, was significantly reduced. However, NCSB and CFWN quality in Zhongmai 175 with weak-to-medium gluten strength was not significantly affected by water deficit and different N fertilizer applications. Grain subproteome analysis revealed that considerable cultivar-specific gliadins and glutenins showed significant accumulation changes in response to water deficit and high / low N fertilizer treatment, which could be responsible for NCSB and CFWN quality changes under different treatments. CONCLUSION: Water deficit and high / low N fertilizer treatments caused changes in cultivar-specific storage protein composition, resulting in differences in the accumulation of gliadins, glutenins, and the quality of NCSB and CFWN. © 2019 Society of Chemical Industry.


Assuntos
Pão/análise , Nitrogênio/metabolismo , Proteínas de Plantas/química , Triticum/química , Água/análise , China , Fertilizantes/análise , Gliadina/análise , Gliadina/metabolismo , Glutens/análise , Glutens/metabolismo , Proteínas de Plantas/metabolismo , Triticum/metabolismo , Água/metabolismo
11.
Environ Pollut ; 252(Pt B): 1659-1670, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31284208

RESUMO

The Yangtze River, which is the largest in Euro-Asian, receives tremendous anthropogenic nitrogen input and is typically characterized by severe eutrophication and hypoxia. Two major processes, denitrification and anaerobic ammonium oxidation (anammox), play vital roles for removing nitrogen global in nitrogen cycling. In the current study, sediment samples were collected from both latitudinal and longitudinal transects along the coastal Yangtze River and the East China Sea (ECS). We investigated community composition and distributions of nosZ gene-encoded denitrifiers by high throughput sequencing, and also quantified the relative abundances of both denitrifying and anammox bacteria by q-PCR analysis. Denitrifying communities showed distinct spatial distribution patterns that were impacted by physical (water current and river runoffs) and chemical (nutrient availability and organic content) processes. Both denitrifying and anammox bacteria contributed to the nitrogen removal in Yangtze Estuary and the adjacent ECS, and these two processes shifted from coastal to open ocean with reverse trends: the abundance of nosZ gene decreased from coastal to open ocean while anammox exhibited an increasing trend based on quantifications of hzsB and 16S rRNA genes. Further correspondence correlation analysis revealed that salinity and nutrients were the main factors in structuring composition and distribution of denitrifying and anammox bacteria. This study improved our understanding of dynamic processes in nitrogen removal from estuarine to open ocean. We hypothesize that denitrification is the major nitrogen removal pathway in estuaries, but in open oceans, low nutrient and organic matter concentrations restrict denitrification, thus increasing the importance of anammox as a nitrogen removal process.


Assuntos
Amônia/metabolismo , Estuários , Ciclo do Nitrogênio , Nitrogênio/metabolismo , Rios/microbiologia , Água do Mar/microbiologia , China , Desnitrificação , Genes Bacterianos , Ciclo do Nitrogênio/genética , Oceanos e Mares , Oxirredução , Rios/química , Salinidade , Água do Mar/química
12.
Bioresour Technol ; 291: 121783, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31326682

RESUMO

Microalgae are feedstocks for multiple product development based on algal biorefinery concept. The effects of light quality (white, red and blue light emitting diodes) and macro-element starvations on Chlorella sp. AE10 were investigated under 20% CO2 and 850 µmol m-2 d-1. Nitrogen and phosphorus starvations had negative effects on its growth rate. The biomass productivities were decreased from day 1 and the highest one was 1.90 g L-1 d-1 under white light conditions. Phosphorus starvation promoted carbohydrate accumulation under three LED light sources conditions and the highest carbohydrate content was 75.9% using red light. Blue light increased lutein content to 9.58 mg g-1. The content of saturated fatty acids was significantly increased from 37.51% under blue light and full culture medium conditions to 77.44% under blue light and nitrogen starvation conditions. Chlorella sp. AE10 was a good candidate for carbohydrate and lutein productions.


Assuntos
Carboidratos/biossíntese , Chlorella/metabolismo , Ácidos Graxos/biossíntese , Luteína/biossíntese , Biomassa , Chlorella/crescimento & desenvolvimento , Ácidos Graxos/análise , Luz , Nitrogênio/metabolismo , Fósforo/metabolismo
13.
Bioresour Technol ; 291: 121803, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31326686

RESUMO

This study investigated the effects of tylosin (0, 10, and 100 mg/kg dry weight) on the denitrification genes and microbial community during the anaerobic digestion of cattle manure. N2 emissions were reduced and N2O emissions were increased by 10 mg/kg tylosin. Adding 100 mg/kg tylosin increased the emission of both N2O and N2. The different responses of denitrifying bacteria and genes to tylosin may have been due to the presence of antibiotic resistance genes (ARGs). Network analysis indicated that denitrification genes and ARGs had the same potential host bacteria. intI1 was more important for the horizontal transfer of denitrification genes and ARGs during anaerobic digestion than intI2. The anaerobic digestion of manure containing tylosin may increase nitrogen losses and the associated ecological risk.


Assuntos
Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/efeitos dos fármacos , Esterco/microbiologia , Tilosina/farmacologia , Anaerobiose/efeitos dos fármacos , Animais , Bovinos , Desnitrificação/efeitos dos fármacos , Resistência Microbiana a Medicamentos/genética , Microbiota/efeitos dos fármacos , Nitrogênio/metabolismo
14.
World J Microbiol Biotechnol ; 35(7): 110, 2019 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-31280381

RESUMO

Carbon sources whether types or magnitudes were fateful in terms of stimulating growth and lipids accumulation in microalgae applied for biodiesel production. The set scenario of this work was to investigate the feasibilities of glucose (G) combining with sodium acetate (SA) carbon sources in enhancing biomass and lipid accumulation in Coccomyxa subellipsoidea. The results demonstrated that C. subellipsoidea subjected to the combination feeding of G (20 g/L) and SA (12 g/L) achieved the favorable biomass (5.22 g/L) and lipid content (52.16%). The resulting lipid productivity (388.96 mg/L/day) was 1.33- to 7.60-fold more than those of sole G or SA as well as other combinations of G and SA. Even though the total fatty acids of C. subellipsoidea cells treated with the optimal combination of G and SA showed no noticeable increment in comparison with sole G or SA, the proportion of monounsaturated C18:1 (over 48.69%) and the content of C18:3 (< 12%) were commendable in high-quality algal biodiesel production. Further, such fascinating lipid accumulation in C. subellipsoidea cells treated with G combining with SA might be attributed to that G promoted glycolysis as well as SA activated glyoxylate shunt and TCA cycle to synergistically provide sufficient acetyl-CoA precursors for lipid accumulation. These findings hinted the potential of the combination of carbon sources in enhancing the overall lipid productivity to offset alga-based biodiesel production cost and would guide other alga strains cultivation.


Assuntos
Clorófitas/crescimento & desenvolvimento , Clorófitas/metabolismo , Glucose/metabolismo , Lipídeos/biossíntese , Acetato de Sódio/metabolismo , Biocombustíveis , Biomassa , Carbono/metabolismo , Clorófitas/citologia , Meios de Cultura/química , Ácidos Graxos/biossíntese , Metabolômica , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Nitrogênio/metabolismo
15.
World J Microbiol Biotechnol ; 35(7): 112, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31286266

RESUMO

Microorganisms have evolved permeases to incorporate various essential nutrients and exclude harmful products, which assists in adaptation to different environmental conditions for survival. As permeases are directly involved in the utilization of and regulatory response to nutrient sources, metabolic engineering of microbial permeases can predictably influence nutrient metabolism and regulation. In this mini-review, we have summarized the mechanisms underlying the general regulation of permeases, and the current advancements and future prospects of metabolic engineering strategies targeting the permeases in Saccharomyces cerevisiae. The different types of permeases and their regulatory mechanisms have been discussed. Furthermore, methods for metabolic engineering of permeases have been highlighted. Understanding the mechanisms via which permeases are meticulously regulated and engineered will not only facilitate research on regulation of global nutrition and yeast metabolic engineering, but can also provide important insights for future studies on the synthesis of valuable products and elimination of harmful substances in S. cerevisiae.


Assuntos
Proteínas de Membrana Transportadoras/metabolismo , Engenharia Metabólica/métodos , Saccharomyces cerevisiae/metabolismo , Transporte Biológico , Carbono/metabolismo , Glucose/metabolismo , Proteínas de Membrana Transportadoras/genética , Nitrogênio/metabolismo , Saccharomyces cerevisiae/genética
16.
Sci Total Environ ; 691: 562-571, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31325856

RESUMO

Nitrogen (N) fertilization in agricultural soils has been receiving worldwide attention due to its detrimental effects on ecosystem services, particularly on microbial N transformation. However, few studies provide a complete picture of N-fertilization effects on the N transformation cycle within a single agricultural ecosystem. Here, we explored the main steps of the microbial N cycle, using targeted gene abundances as proxies, in relation to soil properties, following 35 years of N-fertilization at increasing rates (0, 202 and 269 kg N/ha) in continuous corn (Zea mays L.) and corn-soybean [Glycine max (L.) Merr.] rotations. We used real-time quantitative polymerase chain reaction (qPCR) for the quantification of phylogenetic groups and functional gene screening of the soil microbial communities, including genes encoding critical enzymes of the microbial N cycle: nifH (N2 fixation), amoA (first step of nitrification), nirK and nirS (first step of denitrification), and nosZ (last step of denitrification). Our results showed that long term N-fertilization increased the abundance of fungal communities likely related to decreases in pH, and an enrichment of Al3+ and Fe3+ in exchange sites at the expense of critical macro and micronutrients. At the same time, long term N-fertilization damaged potential biological N2 fixation by significantly reducing the abundance of nifH genes in both continuous and rotated corn systems, while accelerating potential nitrification activities under continuous corn by increasing the abundance of bacterial amoA. Fertilization did not affect the abundance of denitrifying groups. Altogether, these results suggest that N fertilization in corn crops potentially decreases N2 acquisition by free-living soil microbes and stimulates nitrification activities, thus creating a vicious loop that makes the overall agricultural system even more dependent on external N inputs.


Assuntos
Agricultura/métodos , Fertilizantes , Nitrificação , Nitrogênio/metabolismo , Microbiologia do Solo , Microbiota , Nitrogênio/análise
17.
Sci Total Environ ; 691: 908-918, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31326814

RESUMO

Energy (photosynthetically active [PAR] and ultraviolet [UVR] radiation) and matter (organic and inorganic nutrients) fluxes regulate the ecosystem's stability. However, the mechanisms underpinning the potential interplay between resistance and resilience to shifts in nutrient inputs and UVR are poorly understood. To assess how the UVR × nutrients interaction alters ecosystem stability, we exposed in situ a microbial food web from an oligotrophic ecosystem to: (1) two light (UVR + PAR and PAR), and (2) four nutrient (ambient concentrations, phosphorus [P], carbon [C] and C × P addition) treatments for three weeks. During this period, we quantified the community composition and biomass, sestonic P and C:P ratio, primary [PP] and bacterial [BP] production, community [CR] and bacterial [BR] respiration, excreted organic carbon [EOC], as well as the commensalistic phytoplankton-bacteria interaction (i.e. bacterial carbon demand [BCD]:EOC ratio) and the metabolic balance of the ecosystem (i.e. [PP:R] ratio). The stability of all response variables under the four environmental scenarios tested (i.e. UVR, UVR × C, UVR × P, and UVR × C × P) was quantified by means of the resistance and resilience indexes. The microbial community was dominated by phototrophs during the experimental period regardless of the treatment considered. The most complex scenario, i.e. UVR × C × P, decreased the resistance for all variables, except for BR and the PP:R ratio. Despite that PP:R ratio showed the highest resistance under such scenario, it was >1 in all environmental scenarios (i.e. net autotrophic), except under the UVR × C interaction, where, concomitant with increased resilience, the balance shifted towards net heterotrophy (PP:R < 1). Under the UVR × C × P scenario, the metabolic balance of the ecosystem proved strongly resistant due mainly to high resistance of bacterial respiration and a firm stability of the commensalistic interaction. Our results evidence that the high resilience of phototrophs (favoring their predominance over mixo- and heterotrophs) may lead to the maintenance of the autotrophic nature and carbon (C) sink capacity of the ecosystem.


Assuntos
Cadeia Alimentar , Água Doce/microbiologia , Biomassa , Carbono/metabolismo , Ecossistema , Nitrogênio/metabolismo , Fósforo/metabolismo , Fitoplâncton
18.
Bioresour Technol ; 289: 121744, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323718

RESUMO

Haematococcus pluvialis is a prominent feedstock of astaxanthin. The ratio of carbon to nitrogen (C/N) strongly influences the metabolic pathways of mixotrophic-grown microalgae, however, its role involved in astaxanthin biosynthesis is still not fully understood. In this study, integrative metabolic and physiologic profiles were analyzed in elucidating how C/N affected carbon and nitrogen assimilation and thereby exerted influence on astaxanthin biosynthesis. It was demonstrated that high C/N up-regulated the activities of acetate kinase by increase of 5.76 folds in early logarithmic phase, leading a significant increase of acetyl-CoA. The increased carbon skeletons were then funneled into astaxanthin biosynthesis. Additionally, high C/N increased the proportion of carotenoid-intermediates in cytoplasm from chloroplast. Finally, a fed-batch cultivation strategy based on C/N gradient was developed. Biomass attained 9.18 g L-1 in 100% type of immotile cyst cells, which presented astaxanthin productivity at 15.45 mg L-1 d-1 afterward, exhibiting a promising paradigm in commercial production.


Assuntos
Carbono/metabolismo , Clorofíceas/metabolismo , Nitrogênio/metabolismo , Biomassa , Espaço Intracelular/metabolismo , Microalgas/metabolismo , Xantofilas/metabolismo
19.
Bioresour Technol ; 289: 121745, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323724

RESUMO

The status of heavy metals and the P fractions in compost affects their environmental risk. The present study investigated the effects of different initial carbon to nitrogen (C/N) ratios (15, 22, 27) on redistribution of Cu, Zn, and P fractions during composting. The results showed that the composting process transformed Cu, Zn and P from mobile fractions to more stable fractions. Compost with an initial C/N of 22 showed the most effective immobilization of Cu, Zn and P because of yielding greatest degree of polymerization. Multivariate statistical analysis identified organic matter as the most critical factor for explaining the redistribution of Cu, Zn, and P fractions in composting. However, the degree of organic matter degradation (organic matter content and Humic acid/Fulvic acid) better explained the change of bioavailability factor for Cu and the mobility of P during composting. This research provided guidance for providing technology to reduce environmental risk in compost.


Assuntos
Carbono/metabolismo , Compostagem , Cobre/metabolismo , Nitrogênio/metabolismo , Fósforo/metabolismo , Zinco/metabolismo , Disponibilidade Biológica
20.
Bioresour Technol ; 289: 121742, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323725

RESUMO

A novel partial nitritation-anammox (PNA) reactor configuration was piloted for 250 days. Primary effluent from full-scale municipal wastewater treatment plant was treated in a two-stage biofilm system incorporating innovative process control for cold partial nitritation. Partial nitritation was combined with carbon removal in a moving bed biofilm reactor (MBBR) to achieve high-rate treatment and nitritation was obtained with dissolved oxygen to total ammonium nitrogen (DO/TAN) ratio control and free ammonia (FA) for inhibition of nitratation. Effluent from MBBR was directed to an integrated fixed-film activated sludge (IFAS) reactor where nitrogen was removed via anammox. MBBR achieved partial nitritation at 2.0 ±â€¯0.3 g-N m-2 d-1 and nitrogen removal in the IFAS reactor reached 0.45 ±â€¯0.1 g-N m-2 d-1 (55 g-N m-3 d-1). The process performed well at 19 ±â€¯3 °C with an average effluent total inorganic nitrogen (TIN) concentration of 11 ±â€¯4 mg L-1.


Assuntos
Biofilmes , Nitrogênio/metabolismo , Esgotos , Águas Residuárias/química , Amônia/metabolismo , Compostos de Amônio/metabolismo , Reatores Biológicos , Desnitrificação , Oxirredução , Oxigênio/metabolismo , Projetos Piloto
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