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1.
Nature ; 613(7944): 449-459, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36653564

RESUMO

River networks represent the largest biogeochemical nexus between the continents, ocean and atmosphere. Our current understanding of the role of rivers in the global carbon cycle remains limited, which makes it difficult to predict how global change may alter the timing and spatial distribution of riverine carbon sequestration and greenhouse gas emissions. Here we review the state of river ecosystem metabolism research and synthesize the current best available estimates of river ecosystem metabolism. We quantify the organic and inorganic carbon flux from land to global rivers and show that their net ecosystem production and carbon dioxide emissions shift the organic to inorganic carbon balance en route from land to the coastal ocean. Furthermore, we discuss how global change may affect river ecosystem metabolism and related carbon fluxes and identify research directions that can help to develop better predictions of the effects of global change on riverine ecosystem processes. We argue that a global river observing system will play a key role in understanding river networks and their future evolution in the context of the global carbon budget.


Assuntos
Ciclo do Carbono , Dióxido de Carbono , Ecossistema , Rios , Dióxido de Carbono/análise , Sequestro de Carbono , Gases de Efeito Estufa/análise
2.
Nature ; 613(7942): 90-95, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36600067

RESUMO

Organic carbon buried in marine sediment serves as a net sink for atmospheric carbon dioxide and a source of oxygen1,2. The rate of organic carbon burial through geologic history is conventionally established by using the mass balance between inorganic and organic carbon, each with distinct carbon isotopic values (δ13C)3,4. This method is complicated by large uncertainties, however, and has not been tested with organic carbon accumulation data5,6. Here we report a 'bottom-up' approach for calculating the rate of organic carbon burial that is independent from mass balance calculations. We use data from 81 globally distributed sites to establish the history of organic carbon burial during the Neogene (roughly 23-3 Ma). Our results show larger spatiotemporal variability of organic carbon burial than previously estimated7-9. Globally, the burial rate is high towards the early Miocene and Pliocene and lowest during the mid-Miocene, with the latter period characterized by the lowest ratio of organic-to-carbonate burial rates. This is in contrast to earlier work that interpreted enriched carbonate 13C values of the mid-Miocene as massive organic carbon burial (that is, the Monterey Hypothesis)10,11. Suppressed organic carbon burial during the warm mid-Miocene is probably related to temperature-dependent bacterial degradation of organic matter12,13, suggesting that the organic carbon cycle acted as positive feedback of past global warming.


Assuntos
Sequestro de Carbono , Sedimentos Geológicos , Oceanos e Mares , Ciclo do Carbono , Carbonatos/análise , Sedimentos Geológicos/química , Sedimentos Geológicos/microbiologia , Oxigênio/análise , História Antiga , Bactérias/metabolismo , Temperatura , Aquecimento Global , Retroalimentação
3.
Science ; 379(6630): eabp8622, 2023 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-36701452

RESUMO

Approximately 2.5 × 106 square kilometers of the Amazon forest are currently degraded by fire, edge effects, timber extraction, and/or extreme drought, representing 38% of all remaining forests in the region. Carbon emissions from this degradation total up to 0.2 petagrams of carbon per year (Pg C year-1), which is equivalent to, if not greater than, the emissions from Amazon deforestation (0.06 to 0.21 Pg C year-1). Amazon forest degradation can reduce dry-season evapotranspiration by up to 34% and cause as much biodiversity loss as deforestation in human-modified landscapes, generating uneven socioeconomic burdens, mainly to forest dwellers. Projections indicate that degradation will remain a dominant source of carbon emissions independent of deforestation rates. Policies to tackle degradation should be integrated with efforts to curb deforestation and complemented with innovative measures addressing the disturbances that degrade the Amazon forest.


Assuntos
Conservação dos Recursos Naturais , Florestas , Humanos , Biodiversidade , Ciclo do Carbono , Carbono
4.
Water Res ; 229: 119499, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36549186

RESUMO

Erosion is the most widespread form of soil degradation and an important pathway of carbon transfer from land into aquatic systems, with significant impact on water quality and carbon cycle. However, it remains debatable whether erosion induces a carbon source or sink, and the fate of eroded soil carbon in aquatic systems remains poorly constrained. Here, we collect 41 representative soils from seven erosion-influenced basins and conduct microcosm simulation experiments to examine the fate of soil carbon under three different scenarios. We showed that soil carbon mineralization was generally promoted (by up to 10 times) in water under turbulence relative to in soils, but suppressed under static conditions upon entering into aquatic systems. Moreover, the enhancement of mineralization in turbulent systems is primarily related to soil aggregate content, while suppression in static systems positively relates to macromolecule abundance, indicating that soil geochemistry affects the magnitude of hydrodynamic effects on carbon mineralization. Random forest model further predicts that erosion may induce significant carbon sources in basins dominated by turbulent waters and aggregate-rich soils. Our findings demonstrate hydrodynamic and geochemical controls on soil carbon mineralization upon delivery into aquatic systems, which is a non-negligible part of the boundless carbon cycle and must be considered when making region-specific conservation strategies to reduce CO2 emissions from inland waters.


Assuntos
Carbono , Solo , Solo/química , Carbono/química , Hidrodinâmica , Ciclo do Carbono , Qualidade da Água
5.
Sci Total Environ ; 862: 160805, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-36502982

RESUMO

Non-photosynthetic chemoautotrophic microorganisms in deep-sea hydrothermal vent can obtain energy by oxidation reducing substances and synthesize CO2 into organic carbon, and the development and utilization of microbial resources in this environment for CO2 fixation under ordinary environmental conditions is of great significance to understand the carbon cycle and microbial carbon fixation in deep-sea hydrothermal vent. In this study, a set of spiral-stirred bioreactor (SSB) was developed to cultivate a group of non-photosynthetic chemoautotrophic CO2 assimilation microorganisms (NPCAM), mainly Sphingomonadaceae (unclassified, the mean of which was 31.16 %), from deep-sea hydrothermal vent sediments, which have the characteristics of halophilic, acid-base and heavy metal resistant. The maximum carbon fixation efficiency (calculated by CO2) was 6.209 mg·CO2/(L·h) after 96 h of incubation in the presence of mixed electron donors (MEDs, 0.46 % NaNO2, 0.50 % Na2S2O3 and 1.25 % Na2S, w/v), mixed inorganic carbon sources (CO2, Na2CO3 and NaHCO3) and aerobic conditions. The detection of NPCAM synthetic organic fraction in SSB system, the study of single bacteria culturability and carbon fixation efficiency, the analysis of CO2 fixation pathway and the development of coupled carbon fixation technology are the prospective works that need to be further developed.


Assuntos
Dióxido de Carbono , Fontes Hidrotermais , Dióxido de Carbono/metabolismo , Fontes Hidrotermais/microbiologia , Estudos Prospectivos , Carbono/metabolismo , Ciclo do Carbono
6.
New Phytol ; 237(1): 88-99, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36059142

RESUMO

Soil organic carbon (SOC) is a mixture of various carbon (C) compounds with different stability, which can be distinctly affected by the priming effect (PE). However, little is known about how the PE changes with SOC stability. We address this issue by combining results from two experiments and a metaanalysis. We found that the PE increased with the prolongation of soil preincubation, suggesting that higher PE occurred for more stable SOC than for labile SOC. This was further supported by the metaanalysis of 42 observations. There were significant negative relationships between the difference in PE (ΔPE) between labile and more stable SOC and their differences in SOC, microbial biomass C and soil C : N ratio, indicating that soil C availability exerts a vital control on ΔPE. We conclude that, compared with labile SOC, stable SOC can be more vulnerable to priming once microbes are provided with exogenous C substrates. This high vulnerability of stable SOC to priming warrants more attention in future studies on SOC cycling and global change.


Assuntos
Carbono , Solo , Solo/química , Ciclo do Carbono , Biomassa , Microbiologia do Solo
7.
Chaos ; 32(11): 113140, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36456320

RESUMO

Many natural systems exhibit tipping points where changing environmental conditions spark a sudden shift to a new and sometimes quite different state. Global climate change is often associated with the stability of marine carbon stocks. We consider a stochastic carbonate system of the upper ocean to capture such transition phenomena. Based on the Onsager-Machlup action functional theory, we calculate the most probable transition pathway between the metastable and oscillatory states via a neural shooting method. Furthermore, we explore the effects of external random carbon input rates on the most probable transition pathway, which provides a basis to recognize naturally occurring tipping points. Particularly, we investigate the transition pathway's dependence on the transition time and further compute the optimal transition time using a physics-informed neural network, toward the maximum carbonate concentration state in the oscillatory regimes. This work may offer some insights into the effects of noise-affected carbon input rates on transition phenomena in stochastic models.


Assuntos
Ciclo do Carbono , Carbono , Mudança Climática , Redes Neurais de Computação , Física
8.
Artigo em Inglês | MEDLINE | ID: mdl-36497518

RESUMO

Canada goldenrod (Solidago canadensis L.) is considered one of the most deleterious and invasive species worldwide, and invasion of riparian wetlands by S. canadensis can reduce vegetation diversity and alter soil nutrient cycling. However, little is known about how S. canadensis invasion affects soil carbon cycle processes, such as soil respiration, in a riparian wetland. This study was conducted to investigate the effects of different degrees of S. canadensis invasion on soil respiration under different moisture conditions. Soil respiration rate (heterotrophic and autotrophic respiration) was measured using a closed-chamber method. S. canadensis invasion considerably reduced soil respiration under all moisture conditions. The inhibition effect on autotrophic respiration was higher than that on heterotrophic respiration. The water level gradient affects the soil autotrophic respiration, thereby affecting the soil respiration rate. The changes in soil respiration may be related to the alteration in the effective substrate of the soil substrate induced by the invasion of S. canadensis. While the effects of S. canadensis invasion were regulated by the fluctuation in moisture conditions. Our results implied that S. canadensis invasion could reduce the soil respiration, which further potentially affect the carbon sequestration in the riparian wetlands. Thus, the present study provided a reference for predicting the dynamics of carbon cycling during S. canadensis invasion and constituted a scientific basis for the sustainable development and management of riparian wetlands invaded by alien plants.


Assuntos
Espécies Introduzidas , Solo , Microbiologia do Solo , Áreas Alagadas , Ciclo do Carbono
9.
Nat Commun ; 13(1): 7676, 2022 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-36509763

RESUMO

Soil carbon dynamics is strongly controlled by depth globally, with increasingly slow dynamics found at depth. The mechanistic basis remains however controversial, limiting our ability to predict carbon cycle-climate feedbacks. Here we combine radiocarbon and thermal analyses with long-term incubations in absence/presence of continuously 13C/14C-labelled plants to show that bioenergetic constraints of decomposers consistently drive the depth-dependency of soil carbon dynamics over a range of mineral reactivity contexts. The slow dynamics of subsoil carbon is tightly related to both its low energy density and high activation energy of decomposition, leading to an unfavourable 'return-on-energy-investment' for decomposers. We also observe strong acceleration of millennia-old subsoil carbon decomposition induced by roots ('rhizosphere priming'), showing that sufficient supply of energy by roots is able to alleviate the strong energy limitation of decomposition. These findings demonstrate that subsoil carbon persistence results from its poor energy quality together with the lack of energy supply by roots due to their low density at depth.


Assuntos
Carbono , Solo , Ciclo do Carbono , Agricultura , Rizosfera , Microbiologia do Solo
10.
Artigo em Inglês | MEDLINE | ID: mdl-36497999

RESUMO

With the continuous intensification of global climate warming, the carbon cycle has become the focus of global climate change, and the calculation and value evaluation of forest carbon reserves is a key link in promoting the global carbon cycle system. Considering the climatic factors, the biomass expansion factor method (BEF) is used to calculate the forest carbon reserves, selecting the best Gompertz model, adding the time change to the forecast model to predict the growth of forest stock, and the four key indexes of total forest value (TEV) are selected for comprehensive evaluation of forest value. The results show that the carbon fixation efficiency and prediction of forest farms depend largely on the trees, and products can provide more value. Accordingly, it is suggested that broad-leaved trees and younger trees should be planted, and broad-leaved trees should be planted to increase forest stock, increase the vertical distribution of forests to increase carbon reserves, and make trees into wood products with longer retention time to achieve higher total forest value.


Assuntos
Carbono , Florestas , Biomassa , Árvores , Ciclo do Carbono , Sequestro de Carbono
11.
Nature ; 612(7941): 764-770, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36477536

RESUMO

The ocean-atmosphere exchange of CO2 largely depends on the balance between marine microbial photosynthesis and respiration. Despite vast taxonomic and metabolic diversity among marine planktonic bacteria and archaea (prokaryoplankton)1-3, their respiration usually is measured in bulk and treated as a 'black box' in global biogeochemical models4; this limits the mechanistic understanding of the global carbon cycle. Here, using a technology for integrated phenotype analyses and genomic sequencing of individual microbial cells, we show that cell-specific respiration rates differ by more than 1,000× among prokaryoplankton genera. The majority of respiration was found to be performed by minority members of prokaryoplankton (including the Roseobacter cluster), whereas cells of the most prevalent lineages (including Pelagibacter and SAR86) had extremely low respiration rates. The decoupling of respiration rates from abundance among lineages, elevated counts of proteorhodopsin transcripts in Pelagibacter and SAR86 cells and elevated respiration of SAR86 at night indicate that proteorhodopsin-based phototrophy3,5-7 probably constitutes an important source of energy to prokaryoplankton and may increase growth efficiency. These findings suggest that the dependence of prokaryoplankton on respiration and remineralization of phytoplankton-derived organic carbon into CO2 for its energy demands and growth may be lower than commonly assumed and variable among lineages.


Assuntos
Organismos Aquáticos , Archaea , Bactérias , Ciclo do Carbono , Respiração Celular , Plâncton , Alphaproteobacteria/genética , Alphaproteobacteria/crescimento & desenvolvimento , Alphaproteobacteria/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Dióxido de Carbono/metabolismo , Plâncton/classificação , Plâncton/genética , Plâncton/crescimento & desenvolvimento , Plâncton/metabolismo , Água do Mar/microbiologia , Organismos Aquáticos/classificação , Organismos Aquáticos/genética , Organismos Aquáticos/crescimento & desenvolvimento , Organismos Aquáticos/metabolismo , Archaea/genética , Archaea/crescimento & desenvolvimento , Archaea/metabolismo , Respiração Celular/fisiologia , Fotossíntese
12.
Nat Plants ; 8(12): 1484-1492, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36482207

RESUMO

The seasonal dynamics of the vegetation canopy strongly regulate the surface energy balance and terrestrial carbon fluxes, providing feedbacks to climate change. Whether the seasonal timing of maximum canopy structure was optimized to achieve a maximum photosynthetic carbon uptake is still not clear due to the complex interactions between abiotic and biotic factors. We used two solar-induced chlorophyll fluorescence datasets as proxies for photosynthesis and the normalized difference vegetation index and leaf area index products derived from the moderate resolution imaging spectroradiometer as proxies for canopy structure, to characterize the connection between their seasonal peak timings from 2000 to 2018. We found that the seasonal peak was earlier for photosynthesis than for canopy structure in >87.5% of the northern vegetated area, probably leading to a suboptimal maximum seasonal photosynthesis. This mismatch in peak timing significantly increased during the study period, mainly due to the increasing atmospheric CO2, and its spatial variation was mainly explained by climatic variables (43.7%) and nutrient limitations (29.6%). State-of-the-art ecosystem models overestimated this mismatch in peak timing by simulating a delayed seasonal peak of canopy development. These results highlight the importance of incorporating the mechanisms of vegetation canopy dynamics to accurately predict the maximum potential terrestrial uptake of carbon under global environmental change.


Assuntos
Ecossistema , Fotossíntese , Estações do Ano , Fotossíntese/fisiologia , Ciclo do Carbono , Carbono , Folhas de Planta
13.
FEMS Microbiol Ecol ; 98(12)2022 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-36368693

RESUMO

The microbial ecology of arctic and sub-arctic soils is an important aspect of the global carbon cycle, due to the sensitivity of the large soil carbon stocks to ongoing climate warming. These regions are characterized by strong climatic seasonality, but the emphasis of most studies on the short vegetation growing season could potentially limit our ability to predict year-round ecosystem functions. We compiled a database of studies from arctic, subarctic, and boreal environments that include sampling of microbial community and functions outside the growing season. We found that for studies comparing across seasons, in most environments, microbial biomass and community composition vary intra-annually, with the spring thaw period often identified by researchers as the most dynamic time of year. This seasonality of microbial communities will have consequences for predictions of ecosystem function under climate change if it results in: seasonality in process kinetics of microbe-mediated functions; intra-annual variation in the importance of different (a)biotic drivers; and/or potential temporal asynchrony between climate change-related perturbations and their corresponding effects. Future research should focus on (i) sampling throughout the entire year; (ii) linking these multi-season measures of microbial community composition with corresponding functional or physiological measurements to elucidate the temporal dynamics of the links between them; and (iii) identifying dominant biotic and abiotic drivers of intra-annual variation in different ecological contexts.


Assuntos
Microbiota , Solo , Regiões Árticas , Mudança Climática , Ciclo do Carbono
14.
Artigo em Inglês | MEDLINE | ID: mdl-36360951

RESUMO

Accurate monitoring of forest carbon flux and its long-term response to meteorological factors is important. To accomplish this task, the model parameters need to be optimized with respect to in situ observations. In the present study, the extended Fourier amplitude sensitivity test (eFAST) method was used to optimize the sensitive ecophysiological parameters of the Biome BioGeochemical Cycles model. The model simulation was integrated from 2010 to 2020. The results showed that using the eFAST method quantitatively improved the model output. For instance, the R2 increased from 0.53 to 0.72. Moreover, the root-mean-square error was reduced from 1.62 to 1.14 gC·m-2·d-1. In addition, it was reported that the carbon flux outputs of the model were highly sensitive to various parameters, such as the canopy average specific leaf area and canopy light extinction coefficient. Moreover, long-term meteorological factor analysis showed that rainfall dominated the trend of gross primary production (GPP) of the study area, while extreme temperatures restricted the GPP. In conclusion, the eFAST method can be used in future studies. Furthermore, eFAST could be applied to other biomes in response to different climatic conditions.


Assuntos
Ecossistema , Borracha , Florestas , China , Ciclo do Carbono , Carbono/análise
15.
Sci Rep ; 12(1): 18398, 2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-36319733

RESUMO

Historically, humans have cleared many forests for agriculture. While this substantially reduced ecosystem carbon storage, the impacts of these land cover changes on terrestrial gross primary productivity (GPP) have not been adequately resolved yet. Here, we combine high-resolution datasets of satellite-derived GPP and environmental predictor variables to estimate the potential GPP of forests, grasslands, and croplands around the globe. With a mean GPP of 2.0 kg C m-2 yr-1 forests represent the most productive land cover on two thirds of the total area suitable for any of these land cover types, while grasslands and croplands on average reach 1.5 and 1.8 kg C m-2 yr-1, respectively. Combining our potential GPP maps with a historical land-use reconstruction indicates a 4.4% reduction in global GPP from agricultural expansion. This land-use-induced GPP reduction is amplified in some future scenarios as a result of ongoing deforestation (e.g., the large-scale bioenergy scenario SSP4-3.4) but partly reversed in other scenarios (e.g., the sustainability scenario SSP1-1.9) due to agricultural abandonment. Comparing our results to simulations from state-of-the-art Earth System Models, we find that all investigated models deviate substantially from our estimates and from each other. Our maps could be used as a benchmark to reduce this inconsistency, thereby improving projections of land-based climate mitigation potentials.


Assuntos
Ecossistema , Modelos Teóricos , Humanos , Florestas , Ciclo do Carbono , Clima , Mudança Climática
16.
Ying Yong Sheng Tai Xue Bao ; 33(10): 2635-2643, 2022 Oct.
Artigo em Chinês | MEDLINE | ID: mdl-36384597

RESUMO

More than 56000 check dams have been built in the Loess Plateau, which capture around 0.95 Pg of organic carbon and act as an important carbon sink. However, the decomposition mechanism of organic carbon in the sediment in these dams is still poorly understood, and thus it is difficult to quantify their role in terrestrial carbon cycling. In this study, the mineralization culture was used as a simulated environment for the natural sediment environment. With the observations in the simulated environment, the decomposition rates of sediment organic carbon (SOC) were compared under different conditions to investigate the factors influencing the decomposition rate of SOC. The results showed that the average SOC decomposition rate of sediment under anoxic and aerobic conditions was (6.47±4.06) and (56.66±17.78) mg C·kg-1·d-1, respectively. The decomposition rate of SOC in dam sedi-ment under burial conditions was only 11.4% of that under the assumed aerobic condition, indicating that burial condition significantly reduced SOC decomposition. Under anoxic conditions, chemical compositions in the sediment had a greater effect on the decomposition rate of SOC than the microorga-nisms. In contrast, the effect of microorganisms on the decomposition rate of SOC was more significant under aerobic conditions. The physical properties of sediment had little effect on the decomposition rate of SOC under both anoxic and aerobic conditions. Under natural conditions, the siltation dam acted as a carbon sink. When the dam breaks, SOC stored in the sedimentary anoxic condition would be quickly exposed to the air, followed by a significant increase in the decomposition rate, and thus acting as a carbon source.


Assuntos
Sequestro de Carbono , Carbono , Carbono/química , Ciclo do Carbono , Dióxido de Carbono/química
17.
Nat Commun ; 13(1): 7172, 2022 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-36418299

RESUMO

The changes in atmospheric pCO2 provide evidence for the release of large amounts of ancient carbon during the last deglaciation. However, the sources and mechanisms that contributed to this process remain unresolved. Here, we present evidence for substantial ancient terrestrial carbon remobilization in the Canadian Arctic following the Laurentide Ice Sheet retreat. Glacial-retreat-induced physical erosion of bedrock has mobilized petrogenic carbon, as revealed by sedimentary records of radiocarbon dates and thermal maturity of organic carbon from the Canadian Beaufort Sea. Additionally, coastal erosion during the meltwater pulses 1a and 1b has remobilized pre-aged carbon from permafrost. Assuming extensive petrogenic organic carbon oxidation during the glacial retreat, a model-based assessment suggests that the combined processes have contributed 12 ppm to the deglacial CO2 rise. Our findings suggest potentially positive climate feedback of ice-sheet retreat by accelerating terrestrial organic carbon remobilization and subsequent oxidation during the glacial-interglacial transition.


Assuntos
Pergelissolo , Carbono/análise , Atmosfera , Dióxido de Carbono/análise , Canadá , Ciclo do Carbono
18.
Nat Commun ; 13(1): 7297, 2022 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-36435937

RESUMO

Quantifying the organic carbon (OC) sink in marine sediments is crucial for assessing how the marine carbon cycle regulates Earth's climate. However, burial efficiency (BE) - the commonly-used metric reporting the percentage of OC deposited on the seafloor that becomes buried (beyond an arbitrary and often unspecified reference depth) - is loosely defined, misleading, and inconsistent. Here, we use a global diagenetic model to highlight orders-of-magnitude differences in sediment ages at fixed sub-seafloor depths (and vice-versa), and vastly different BE's depending on sediment depth or age horizons used to calculate BE. We propose using transfer efficiencies (Teff's) for quantifying sediment OC burial: Teff is numerically equivalent to BE but requires precise specification of spatial or temporal references, and emphasizes that OC degradation continues beyond these horizons. Ultimately, quantifying OC burial with precise sediment-depth and sediment-age-resolved metrics will enable a more consistent and transferable assessment of OC fluxes through the Earth system.


Assuntos
Carbono , Sedimentos Geológicos , Ciclo do Carbono , Sequestro de Carbono , Planeta Terra
19.
Proc Natl Acad Sci U S A ; 119(41): e2202261119, 2022 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-36206369

RESUMO

Global change is altering the vast amount of carbon cycled by microbes between land and freshwater, but how viruses mediate this process is poorly understood. Here, we show that viruses direct carbon cycling in lake sediments, and these impacts intensify with future changes in water clarity and terrestrial organic matter (tOM) inputs. Using experimental tOM gradients within sediments of a clear and a dark boreal lake, we identified 156 viral operational taxonomic units (vOTUs), of which 21% strongly increased with abundances of key bacteria and archaea, identified via metagenome-assembled genomes (MAGs). MAGs included the most abundant prokaryotes, which were themselves associated with dissolved organic matter (DOM) composition and greenhouse gas (GHG) concentrations. Increased abundances of virus-like particles were separately associated with reduced bacterial metabolism and with shifts in DOM toward amino sugars, likely released by cell lysis rather than higher molecular mass compounds accumulating from reduced tOM degradation. An additional 9.6% of vOTUs harbored auxiliary metabolic genes associated with DOM and GHGs. Taken together, these different effects on host dynamics and metabolism can explain why abundances of vOTUs rather than MAGs were better overall predictors of carbon cycling. Future increases in tOM quantity, but not quality, will change viral composition and function with consequences for DOM pools. Given their importance, viruses must now be explicitly considered in efforts to understand and predict the freshwater carbon cycle and its future under global environmental change.


Assuntos
Gases de Efeito Estufa , Vírus , Amino Açúcares/metabolismo , Bactérias/genética , Bactérias/metabolismo , Carbono/metabolismo , Ciclo do Carbono , Gases de Efeito Estufa/metabolismo , Lagos/microbiologia , Vírus/genética , Vírus/metabolismo , Água/metabolismo
20.
J Agric Food Chem ; 70(43): 13935-13944, 2022 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-36278912

RESUMO

d-Allulose is an attractive rare sugar that can be used as a low-calorie sweetener with significant health benefits. To meet the increasing market demands, it is necessary to develop an efficient and extensive microbial fermentation platform for the synthesis of d-allulose. Here, we applied a comprehensive systematic engineering strategy in Bacillus subtilis WB600 by introducing d-allulose 3-epimerase (DAEase), combined with the deactivation of fruA, levDEFG, and gmuE, to balance the metabolic network for the efficient production of d-allulose. This resulting strain initially produced 3.24 g/L of d-allulose with a yield of 0.93 g of d-allulose/g d-fructose. We further screened and obtained a suitable dual promoter combination and performed fine-tuning of its spacer region. After 64 h of fed-batch fermentation, the optimized engineered B. subtilis produced d-allulose at titers of 74.2 g/L with a yield of 0.93 g/g and a conversion rate of 27.6%. This d-allulose production strain is a promising platform for the industrial production of rare sugar.


Assuntos
Bacillus subtilis , Frutose , Bacillus subtilis/metabolismo , Frutose/metabolismo , Racemases e Epimerases/metabolismo , Ciclo do Carbono
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