Mechanism Of CO2 Fixation Research Articles

Heterologous assembly of red-type Rubisco and functional identification of chaperonin in Porphyridium purpureum

In the natural growth process of organisms, Ribulose 1,5-diphosphate carboxylase/oxygenase (Rubisco) is the rate-limiting enzyme for carbon fixation in photosynthesis. However, its carboxylation is low and the reaction can be competitively inhibited by O2. Red-type Rubiscos are known with higher catalytic rates and CO2/O2 specificity, but their incompatibility with chaperonins in the green lineage pose challenges for them to be assembled and accumulated in C3 plants. In this study, we systematically explored the factors and conditions required for heterologous accumulation Rubisco from Porphyridium purpureum and that from Phaeodactylum tricornutum. We found that P. purpureum Rubisco required less co-factors to be produced in Escherichia coli than the P. tricornutum needed. In addition, the amino acid sequences of the co-chaperonin Cpn10 and Cpn20 in P. purpureum were retrieved, and they can assist in GroEL to fold the red-type Rubisco large subunits in vitro and in E. coli. Heterogeneous system research on Rubisco assembly conditions are of great significance for humans to understand CO2 fixation mechanism, improve crop yield and mitigate global climate change.

Bioelectricity facilitates carbon dioxide fixation by Alcaligenes faecalis ZS-1 in a biocathodic microbial fuel cell (MFC)

The CO2 fixation mechanism by Alcaligenes faecalis ZS-1 in a biocathode microbial fuel cell (MFC) was investigated. The closed-circuit MFC (CM) exhibited a significantly higher CO2 fixation rate (10.7%) compared to the open-circuit MFC (OC) (2.0%), indicating that bioelectricity enhances CO2 capture efficiency. During the inward extracellular electron transfer (EET) process, riboflavin concentration increased in the supernatant while cytochrome levels decreased. Genome sequencing revealed diverse metabolic pathways for CO2 fixation in strain ZS-1, with potential dominance of rTCA and C4 pathways under electrotrophic conditions as evidenced by significant upregulation of the ppc gene. Differential metabolite analysis using LC-MS demonstrated that CM promoted upregulation of various lipid metabolites. These findings collectively highlight that ZS-1 simultaneously generated electricity and fixed CO2 and that the ppc associated with bioelectricity played a critical role in CO2 capture. In conclusion, bioelectricity resulted in a significant enhancement in the efficiency of CO2 fixation and lipid production.

Optimization and Process Effect for Microalgae Carbon Dioxide Fixation Technology Applications Based on Carbon Capture: A Comprehensive Review

Microalgae carbon dioxide (CO2) fixation technology is among the effective ways of environmental protection and resource utilization, which can be combined with treatment of wastewater and flue gas, preparation of biofuels and other technologies, with high economic benefits. However, in industrial application, microalgae still have problems such as poor photosynthetic efficiency, high input cost and large capital investment. The technology of microalgae energy development and resource utilization needs to be further studied. Therefore, this work reviewed the mechanism of CO2 fixation in microalgae. Improving the carbon sequestration capacity of microalgae by adjusting the parameters of their growth conditions (e.g., light, temperature, pH, nutrient elements, and CO2 concentration) was briefly discussed. The strategies of random mutagenesis, adaptive laboratory evolution and genetic engineering were evaluated to screen microalgae with a high growth rate, strong tolerance, high CO2 fixation efficiency and biomass. In addition, in order to better realize the industrialization of microalgae CO2 fixation technology, the feasibility of combining flue gas and wastewater treatment and utilizing high-value-added products was analyzed. Considering the current challenges of microalgae CO2 fixation technology, the application of microalgae CO2 fixation technology in the above aspects is expected to establish a more optimized mechanism of microalgae carbon sequestration in the future. At the same time, it provides a solid foundation and a favorable basis for fully implementing sustainable development, steadily promoting the carbon peak and carbon neutrality, and realizing clean, green, low-carbon and efficient utilization of energy.

CO2 fixation mechanism of kaolin treated with organic amines at varied temperatures and pressure

CO2 capture and storage is an effective way to control CO2 levels in the atmosphere. However, the adsorption technology is determined by many factors, such as temperature, pressure, and material cost. In this study, a clay-based CO2 adsorbent was designed to monitor the possible factors that affect the geological condensation of CO2 under varied conditions. The effect of molecular chain length on the CO2 adsorption performance of intercalated kaolinite was discussed in detail. The prepared kaolinite/n-hexylamine complex achieved a 17.0 (±0.4) mL/g CO2 adsorption capacity when 6.35% (±0.05) n-hexylamine was loaded, which has significantly improved the utilization rate of organic amines. A higher relative CO2 adsorption capacity (in proportion to the amount of amine) was obtained at lower temperatures and higher pressures. The mechanism of CO2 adsorption of organic amine-intercalated kaolinite was discussed based on Fourier transform infrared spectroscopy and specific surface area measurements. The enhanced relative CO2 adsorption capacity at low-temperature and high-pressure conditions may provide a hint to the geological condensation of CO2 at high latitude positions.

Polymerization-like mechanism for fixation of CO2 with epoxides by multifunctional organocatalysts.

The commonly accepted mechanism of CO2 fixation of epoxides to cyclic carbonates catalyzed by multifunctional non-halide organocatalysts is challenged by our computational DFT-D3 study, which revealed a new polymerization-like mechanism comprising alternate epoxide and CO2 activation steps and a nested CO2 activation pathway. We investigated a recently reported CO2 coupling with epoxide reaction catalyzed by a bis-phenolic multifunctional catalyst. The predicted cis/trans product ratio is in excellent agreement with experimental results. The general applicability of the new mechanism is supported by another diamine-diacid catalyzed CO2 fixation reaction.

Microalgae as a solution of third world energy crisis for biofuels production from wastewater toward carbon neutrality: An updated review

The boost of the greenhouse gases (GHGs, largely carbon dioxide – CO2) emissions owing to anthropogenic activity is one of the biggest global threats. Bio-CO2 emission reduction has received more and more attention as an environmentally sustainable approach. Microalgae are very popular in this regard because of excellent speed of growth, low costs of production, and resistance to extreme environments. Besides, most microalgae can undergo photosynthesis, where the CO2 and solar energy can be converted into sugar, and subsequently become biomass, providing a renewable and promising biofuel strategy with a few outstanding benefits. This review focuses on presenting CO2 sequestration by microalgae towards wastewater treatment and biodiesel production. First, the CO2 fixation mechanism by microalgae viz., sequestration and assimilation of CO2 in green microalgae as well as cyanobacteria were introduced. Besides, factors affecting CO2 sequestration in microalgae, containing microalgae species and cultivation conditions, such as light condition, photobioreactor, configuration, pH, CO2 concentration, temperature, and medium composition, were then comprehensively discussed. Special attention was given to the production of biodiesel as third-generation biofuel from various wastewater (CO2 biofixation), including processing steps of biodiesel production by microalgae, biodiesel production from wastewater, and improved methods. Furthermore, current life cycle assessment (LCA) and techno-economic analysis (TEA) used in biodiesel production were discussed. Finally, the research challenges and specific prospects were considered. Taken together, this review provides useful and updated information to facilitate the development of microalgal “green chemistry” and “environmental sustainability”.

Structural insights of catalytic intermediates in dialumene based CO2 capture: Evidences from theoretical resonance Raman spectra

CO2 capture is considered as one of the most ideal strategies for solving the environmental issues and against global warming. Recently, experimental evidence has suggested that aluminum double bond (dialumene) species can capture CO2 and further convert it into value-added products. However, the catalytic application of these species is still in its infancy. Both the dynamics mechanism of CO2 fixation and the detailed structures of catalytic intermediates are not well understood. In this work, we investigate the structure dependent resonance Raman (RR) signals for different reaction intermediates. Ab-initio simulations of spontaneous resonance Raman (spRR) and time-domain stimulated resonance Raman (stRR) give spectral signatures correlated to the existence of different intermediates during the CO2-dialumene binding process. The unique Raman vibronic features contain rich structural information with high temporal resolution, enabling to monitor the transient catalytic intermediates under reaction conditions. Our work shows that RR can be used to monitor intermediates during the dialumene based CO2 capture reaction. The spectral features not only provide insight into the structural information of intermediate species, but also allow a deeper understanding of the dynamical details of this kind of catalytic process.

The regulating mechanisms of CO2 fixation and carbon allocations of two Chlorella sp. strains in response to high CO2 levels

The extreme high CO2 in industrial exhaust gas cannot be tolerated by microalgae is the key challenge for the application of microalgae in CO2 bio-sequestration. To provide better insights for this challenge, we chose one high CO2 tolerant (Chlorella sp. LAMB 31) and non-tolerant (Chlorella sp. LAMB 122) Chlorella sp. to examine their different CO2 fixation and carbon allocation responses to 40% CO2. The results indicated LAMB 31 had a 24-h “lag phase” of biomass increase, during which the transition from PSII–PSI and the increase of lipid synthesis happened to acclimate high CO2 conditions, followed by the increase of pigments synthesis, carbon fixation rates and polysaccharide productions. However, no acclimating mechanism was observed in LAMB 122, whose biomass, photosynthesis and material synthesis were all gradually collapsed under 40% CO2. Finally, four parameters including Chl a, polysaccharides, carbon fixation rates and MDA were selected to be good physiological biomarkers for high CO2 tolerant strains screenings in the future.

Desert soil sequesters atmospheric CO2 by microbial mineral formation

Microbial carbonate formation in soil may play a critical role in sequestering atmospheric CO2, specifically in drylands with sparse vegetation and harsh environments. However, few studies have examined the mechanism of CO2 fixation by soil microbes. Here, we investigated the sign of soil inorganic carbon (SIC) formed by microbial populations recovered from soil in the Mu Us Desert and identified the carbon source of this process by tracking the isotope profile of atmospheric CO2 in the SIC pool. In addition, we used high-throughput sequencing to predict the function of soil microbial genes involved in metabolic pathways associated with the formation of carbonaceous minerals, and characterised these minerals using scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction spectrometry. We found that atmospheric CO2 was incorporated into SIC via microbial processes at a rate of approximately 52.13 μg C kg−1 d−1 during a 2.5-month labelling period under 13CO2, and that microbial genes predicted to function in metabolic pathways for carbonaceous mineral formation were widespread among desert soil microbes. Moreover, the composition of microbial populations, along with the predicted metabolic pathways for microbial mineral formation, correlated significantly with rate of microbial CO2 incorporation into SIC. Importantly, we observed the formation of carbonaceous minerals such as calcite in desert soil samples inoculated with indigenous microbes. To our knowledge, we demonstrated for the first time that desert soil microbes are directly involved in fixing atmospheric CO2 via biomineralisation. Our findings provide empirical evidence for soil microbe-driven sequestration of atmospheric carbon and further reveal the potential capacity of desert soil for carbon sequestration.

Protic Quaternary Ammonium Ionic Liquids for Catalytic Conversion of CO2 into Cyclic Carbonates: A Combined Ab Initio and MD Study

The mechanism of CO2 fixation catalyzed by protic hydroxyl-functionalized quaternary ammonium ionic liquids (ILs) is investigated by two different models, the Single-IL model and the Double-IL model. The relative sequence of catalytic activity calculated by the Single-IL model is contradictory with the experimental result. The situation is totally varied when the Double-IL model is utilized. In this system, ILs are not limited to the catalyst but solvent. The ILs are incorporated into the catalytic system to consider the solvent effect rather than by the existing solvent model. When the solvent effect is included, it is better to distinguish the catalytic activity of three ILs. According to the noncovalent interaction and the atoms in molecules analysis, the highest catalytic activity of tris(2-hydroxyethyl)ammonium bromide ([HTEA]Br) is attributed to its strongest nucleophilic attack and moderate hydrogen bond interaction between IL and reactant. It is necessary to consider the interaction between ILs to...

Long noncoding RNA (lncRNA) as possible tumour marker also for bladder cancer

The biotechnologically important Gram-negative β-proteobacterium Ralstonia eutropha H16 is able to grow lithoautotrophically by utilizing CO2 and H2 as sole carbon and energy sources, respectively. CO2 is fixed by the CBB cycle, which is encoded in duplicate on the genome of R. eutropha H16. The transcription of both cbb operons is controlled by the transcription regulator CbbR dependent on intracellular PEP levels as a response to the carbon-state of the cell. As demonstrated in this study transcription control of both cbb operons appears to be more complex and additionally involves, next to CbbR, the transcription regulator RegA as part of the global transcription regulation system RegA/RegB. The identification of a highly conserved RegA/RegB homologue in R. eutropha H16 and experimental evidence gathered in this study reveal that RegA plays a crucial role in the transcription control of both cbb promoters. RegA is able to induce cbb promoter activity and controls transcription in combination with CbbR dependent on cellular PEP concentrations. These results clearly demonstrate that RegA plays an important role in cbb operon transcription regulation and may also be relevant for the control of other energy-utilizing and energy-generating pathways of R. eutropha H16. In addition to promoting a more complete understanding of the CO2 fixation mechanism of R. eutropha H16 these findings also provide crucial insights for the utilization of this bacterium in biotechnological applications with respect to CO2 fixation.

CbbR and RegA regulate cbb operon transcription in Ralstonia eutropha H16

The biotechnologically important Gram-negative β-proteobacterium Ralstonia eutropha H16 is able to grow lithoautotrophically by utilizing CO2 and H2 as sole carbon and energy sources, respectively. CO2 is fixed by the CBB cycle, which is encoded in duplicate on the genome of R. eutropha H16. The transcription of both cbb operons is controlled by the transcription regulator CbbR dependent on intracellular PEP levels as a response to the carbon-state of the cell. As demonstrated in this study transcription control of both cbb operons appears to be more complex and additionally involves, next to CbbR, the transcription regulator RegA as part of the global transcription regulation system RegA/RegB. The identification of a highly conserved RegA/RegB homologue in R. eutropha H16 and experimental evidence gathered in this study reveal that RegA plays a crucial role in the transcription control of both cbb promoters. RegA is able to induce cbb promoter activity and controls transcription in combination with CbbR dependent on cellular PEP concentrations. These results clearly demonstrate that RegA plays an important role in cbb operon transcription regulation and may also be relevant for the control of other energy-utilizing and energy-generating pathways of R. eutropha H16. In addition to promoting a more complete understanding of the CO2 fixation mechanism of R. eutropha H16 these findings also provide crucial insights for the utilization of this bacterium in biotechnological applications with respect to CO2 fixation.

Integration of Metagenomic and Stable Carbon Isotope Evidence Reveals the Extent and Mechanisms of Carbon Dioxide Fixation in High-Temperature Microbial Communities.

Although the biological fixation of CO2 by chemolithoautotrophs provides a diverse suite of organic compounds utilized by chemoorganoheterotrophs as a carbon and energy source, the relative amounts of autotrophic C in chemotrophic microbial communities are not well-established. The extent and mechanisms of CO2 fixation were evaluated across a comprehensive set of high-temperature, chemotrophic microbial communities in Yellowstone National Park by combining metagenomic and stable 13C isotope analyses. Fifteen geothermal sites representing three distinct habitat types (iron-oxide mats, anoxic sulfur sediments, and filamentous “streamer” communities) were investigated. Genes of the 3-hydroxypropionate/4-hydroxybutyrate, dicarboxylate/4-hydroxybutyrate, and reverse tricarboxylic acid CO2 fixation pathways were identified in assembled genome sequence corresponding to the predominant Crenarchaeota and Aquificales observed across this habitat range. Stable 13C analyses of dissolved inorganic and organic C (DIC, DOC), and possible landscape C sources were used to interpret the 13C content of microbial community samples. Isotope mixing models showed that the minimum fractions of autotrophic C in microbial biomass were >50% in the majority of communities analyzed. The significance of CO2 as a C source in these communities provides a foundation for understanding community assembly and succession, and metabolic linkages among early-branching thermophilic autotrophs and heterotrophs.

Extensive Turnover of Compatible Solutes in Cyanobacteria Revealed by Deuterium Oxide (D2O) Stable Isotope Probing.

Cyanobacteria are important primary producers of organic matter in diverse environments on a global scale. While mechanisms of CO2 fixation are well understood, the distribution of the flow of fixed organic carbon within individual cells and complex microbial communities is less well characterized. To obtain a general overview of metabolism, we describe the use of deuterium oxide (D2O) to measure deuterium incorporation into the intracellular metabolites of two physiologically diverse cyanobacteria: a terrestrial filamentous strain (Microcoleus vaginatus PCC 9802) and a euryhaline unicellular strain (Synechococcus sp. PCC 7002). D2O was added to the growth medium during different phases of the diel cycle. Incorporation of deuterium into metabolites at nonlabile positions, an indicator of metabolite turnover, was assessed using liquid chromatography mass spectrometry. Expectedly, large differences in turnover among metabolites were observed. Some metabolites, such as fatty acids, did not show significant turnover over 12-24 h time periods but did turn over during longer time periods. Unexpectedly, metabolites commonly regarded to act as compatible solutes, including glutamate, glucosylglycerol, and a dihexose, showed extensive turnover compared to most other metabolites already after 12 h, but only during the light phase in the cycle. The observed extensive turnover is surprising considering the conventional view on compatible solutes as biosynthetic end points given the relatively slow growth and constant osmotic conditions. This suggests the possibility of a metabolic sink for some compatible solutes (e.g., into glycogen) that allows for rapid modulation of intracellular osmolarity. To investigate this, uniformly 13C-labeled Synechococcus sp. PCC 7002 were exposed to 12C glucosylglycerol. Following metabolite extraction, amylase treatment of methanol-insoluble polymers revealed 12C labeling of glycogen. Overall, our work shows that D2O probing is a powerful method for analysis of cyanobacterial metabolism including discovery of novel metabolic processes.

Mechanism of CO2 Fixation by IrI–X Bonds (X = OH, OR, N, C) (Eur. J. Inorg. Chem. 28/2015)

Mechanism of CO₂ Fixation by Ir^I–X Bonds (X = OH, OR, N, C) (Eur. J. Inorg. Chem. 28/2015)

Mechanism of CO2 Fixation by IrI–X Bonds (X = OH, OR, N, C)

AbstractDensity functional theory calculations have been used to investigate the CO2 fixation mechanism proposed by Nolan et al. for the IrI complex [Ir(cod)(IiPr)(OH)] (1; cod = 1,5‐cyclooctadiene; IiPr = 1,3‐diisopropylimidazol‐2‐ylidene) and its derivatives. For 1, our results suggest that CO2 insertion is the rate‐limiting step rather than the dimerization step. Additionally, in agreement with the experimental results, our results show that CO2 insertion into the Ir–OR1 (R1 = H, methyl, and phenyl) and Ir–N bonds is kinetically facile, and the calculated activation energies span a range of only 12.0–23.0 kcal/mol. Substantially higher values (35.0–50.0 kcal/mol) are reported for analogous Ir–C bonds.

Effect of elevated CO2on growth and yield of French bean (Phaseolus vulgarisL.) genotypes

The elevated CO2 levels are known to increase crop growth. French bean (Phaseolus vulgaris L.) being an important cool season legume vegetable, with C3 CO2 fixation mechanism, is likely to be benefitted by higher CO2 level. Hence, a study was initiated to quantify the response of two promising French bean cultivars, viz., Arka Komal and Arka Anoop to elevated CO2 concentrations of 550 ppm as compared to ambient levels of 380 ppm in open top chambers (OTCs). Significantly higher leaf area, root dry weight and total dry matter accumulation was recorded at 550 ppm elevated CO2 which was translated into significant increase in number of flowers and subsequently pod yield in cv. Arka Anoop compared to Arka Komal.

Estudio de los mecanismos de fijación de CO2 en el tumor Ascítico de Ehrlich

Hemos realizado el estudio de los mecanismos de fijación de CO2 en el tumor ascítico de Ehrlich, obteniendo los siguientes resultados: 1. La ribosa-5-fosfato produjo un ligero efecto estimulante de la fijación de C14O2; sin embargo, no pudo aislarse ácido 3-fosfoglicérico radioactivo en condiciones en que se favoreció su acumulación. 2. Usando ácido pirúvico como substrato, la cuantía de la fijación fue mayor. La adición de TPNH a homogenizados incrementó enormemente dicha fijación. 3. De los ácidos orgánicos aislados, la mayor incorporación del C14 se detectó en el succínico y málico. 4. Los extractos acetónicos parcialmente purificados presentaron actividad de enzima málica. Los resultados anteriores, permiten concluir que, en el tumor ascítico de Ehrlich, la fijación de CO2 se realiza casi exclusivamente por acción de la enzima málica, no existiendo evidencia de que ella ocurra a nivel de la ribulosa-1,5-difosfato.

农田土壤自养微生物的CO2同化功能及同化碳转化的分子生态学机制

PDF HTML阅读 XML下载 导出引用 引用提醒 自养微生物同化CO2的分子生态研究及同化碳在土壤中的转化 DOI: 10.5846/stxb201211051538 作者: 作者单位: 中国科学院亚热带农业生态研究所,湖南农业大学生物科技学院,中国科学院亚热带农业生态研究所,中国科学院亚热带农业生态研究所,中国科学院亚热带农业生态研究所,中国科学院亚热带农业生态研究所,湖南农业大学生物科技学院,中国科学院亚热带农业生态研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41271279；41090283）；湖南省自然科学基金资助项目（11JJ4030）；中国科学院青年创新促进会会员资助项目（2012-2015）；中国科学院亚热带农业生态过程重点实验室开放基金资助项目（2010-2012） Molecular mechanism on carbon dioxide assimilation of autotrophic microorganism and carbon translocation in agricultural soils Author: Affiliation: Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,College of Bioscience and Biotechnology,Hunan Agricultural University,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,College of Bioscience and Biotechnology,Hunan Agricultural University,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:大气中CO2浓度持续升高和全球气候变暖是亟待解决的重大环境问题。自养微生物在环境中广泛分布，能直接参与CO2的同化，因此研究自养微生物同化CO2的分子生态学机制具有重大的科学意义。以往对自养微生物的研究多针对基因组DNA，从DNA水平揭示了不同生态系统中碳同化自养微生物的种群结构和多样性，但这些微生物在生态系统中的具体功能有待进一步的研究。近年来，随着转录组学研究技术和稳定同位素探针技术（SIP）的发展，自养微生物同化CO2的生态机理研究不断深入，这些研究明确揭示了碳同化自养微生物是河流、湖泊和海洋生态系统中CO2固定作用的驱动者，并新发现了一些具有CO2同化功能的微生物群落。基于国内外有关研究进展，从DNA和RNA水平上对自养微生物同化CO2的分子机理以及稳定同位素探针技术（SIP）在碳同化微生物研究中的应用进行了分析 和总结，初步展望了RNA-SIP技术在陆地生态系统碳同化微生物分子生态学研究中的前景。同时，探讨了陆地生态系统同化碳的转化和稳定性机理，以期为深入了解生态系统碳循环过程和应对气候变化提供理论依据。 Abstract:The increase in atmospheric carbon dioxide (CO2) concentration and global climate change are the most important environmental challenges we faced. Autotrophic bacteria, with the capability of CO2 assimilation, are widespread in diverse environments, thus studies on molecular mechanisms of autotrophic bacteria CO2 fixation are of great scientific importance. Previous researches were mainly based on genomic DNA, revealing the diversity and composition of CO2 fixation microorganism in diverse ecological systems. However, the functional implication of these autotrophies is still unknown. Transcriptomics technique and stable isotope probe technique (SIP) are successfully employed in recent studies concerning the ecological function of CO2 fixation microorganism, providing unequivocal evidence for CO2 assimilation by autotrophic microorganisms in complex aquatic environments and identifying new autotrophic bacteria capable of CO2 assimilation. Therefore, the microbial mechanisms of CO2 fixation by autotrophic mciroorganism based on SIP are summarized and the methodological considerations of RNA-SIP for molecular ecology of carbon fixation in agricultural ecosystems are presented. The translocation and stability of assimilated carbon were also discussed. This paper will offer the theoretical basis of terrestrial ecosystem carbon cycle and response to climate change. 参考文献 相似文献 引证文献

Microbial phototrophic fixation of atmospheric CO2 in China subtropical upland and paddy soils

Autotrophic microorganisms, which can fix atmospheric CO2 to synthesize organic carbon, are numerous and widespread in soils. However, the extent and the mechanism of CO2 fixation in soils remain poorly understood. We incubated five upland and five paddy soils from subtropical China in an enclosed, continuously 14CO2-labeled, atmosphere and measured 14CO2 incorporated into soil organic matter (SOC14) and microbial biomass (MBC14) after 110days. The five upland soils supported dominant crops soils (maize, wheat, sweet potato, and rapeseed) in the region, while all paddy soils were cultivated in a regime consisting of permanently-flooded double-cropping rice cultivation. The upland and paddy soils represented typical soil types (fluvisols and ultisols) and three landforms (upland, hill, and low mountain), ranging in total carbon from low (<10gkg−1 soil organic carbon) to medium (10–20gkg−1) to high (>20gkg−1). Substantial amounts of 14CO2 were fixed into SOC14 (mean 20.1±7.1mgCkg−1 in upland soil, 121.1±6.4mgCkg−1 in paddy soil) in illuminated soils (12h light/12h dark), whereas no 14C was fixed in soils incubated in continuous darkness. We concluded that the microbial CO2 fixation was almost entirely phototrophic rather than chemotrophic. The rate of SOC14 synthesis was significantly higher in paddy soils than in upland soils. The SOC14 comprised means of 0.15±0.01% (upland) and 0.65±0.03% (paddy) of SOC. The extent of 14C immobilized as MBC14 and that present as dissolved organic C (DOC14) differed between soil types, accounting for 15.69–38.76% and 5.54–18.37% in upland soils and 15.57–40.03% and 3.67–7.17% of SOC14 in paddy soils, respectively. The MBC14/MBC and DOC14/DOC were 1.76–5.70% and 1.69–5.17% in the upland soils and 4.23–28.73% and 5.65–14.30% in the paddy soils, respectively. Thus, the newly-incorporated C stimulated the dynamics of DOC and MBC more than the dynamics of SOC. The SOC14 and MBC14 concentrations were highly significantly correlated (r=0.946; P<0.0001). We conclude that CO2 uptake by phototrophic soil microorganisms can contribute significantly to carbon assimilation in soil, and so warrants further future study.