Proteomic responses to ocean acidification of the marine diazotroph Trichodesmium under iron-replete and iron-limited conditions

Abstract(#br)Growth and dinitrogen (N 2 ) fixation of the globally important diazotrophic cyanobacteria Trichodesmium are often limited by iron (Fe) availability in surface seawaters. To systematically examine the combined effects of Fe limitation and ocean acidification (OA), T. erythraeum strain IMS101 was acclimated to both Fe-replete and Fe-limited concentrations under ambient and acidified conditions. Proteomic analysis showed that OA affected a wider range of proteins under Fe-limited conditions compared to Fe-replete conditions. OA also led to an intensification of Fe deficiency in key cellular processes (e.g., photosystem I and chlorophyll a synthesis) in already Fe-limited T. erythraeum . This is a result of reallocating Fe from these processes to Fe-rich nitrogenase to..

Reduced nitrogenase efficiency dominates response of the globally important nitrogen fixer Trichodesmium to ocean acidification

工业革命以来，海洋吸收了约三分之一人为排放的CO2，以迄今3亿年来最快的速度酸化（CO2升高、pH下降），这势必影响海洋生态系统的关键过程和功能。研究团队创新性地从区分海洋酸化过程中CO2上升和pH下降的双重效应入手，揭示了海水CO2升高的正效应小于pH下降的负效应，故酸化的净效应为抑制束毛藻的固氮作用。这是因为酸化引起束毛藻胞质 pH下降，从而降低固氮酶效率、干扰胞内pH稳态、影响细胞产能。在上述研究工作的基础上，进一步系统地测定了固氮和光合系统蛋白的表达量及其含铁量，建立了一个束毛藻的“资源最优化分配”细胞模型。实现了实验数据和数值模型的紧密结合：实验数据是构筑模型的坚实基础，并提高了模型的预测水平；通过模型模拟，加深了对实验发现的认知，并对实验结论进行了时空拓展。 罗亚威博士和史大林博士为论文的共同第一作者和共同通讯作者，史大林课题组的洪海征教授、研究助理沈容和博士生张福婷为共同作者。论文的共同作者还包括美国佛罗里达州立大学助理教授Sven Kranz博士和乔治亚大学副教授Brian Hopkinson博士。【Abstract】The response of the prominent marine dinitrogen (N2)-fixing cyanobacteria Trichodesmium to ocean acidification (OA) is critical to understanding future oceanic biogeochemical cycles. Recent studies have reported conflicting findings on the effect of OA on growth and N2 fixation of Trichodesmium. Here, we quantitatively analyzed experimental data on how Trichodesmium reallocated intracellular iron and energy among key cellular processes in response to OA, and integrated the findings to construct an optimality-based cellular model. The model results indicate that Trichodesmium growth rate decreases under OA primarily due to reduced nitrogenase efficiency. The downregulation of the carbon dioxide (CO2)-concentrating mechanism under OA has little impact on Trichodesmium, and the energy demand of anti-stress responses to OA has a moderate negative effect. We predict that if anthropogenic CO2 emissions continue to rise, OA could reduce global N2 fixation potential of Trichodesmium by 27% in this century, with the largest decrease in iron-limiting regions.This work was funded by the National Key R&D Program of China (2016YFA0601404 and 2016YFA0601203), NSFC (41476093, 41721005, 41890802, 31861143022 and 41376116), and the MEL internal research fund (MELRI1502).本项研究得到了国家重点研发计划（2016YFA0601404 和2016YFA0601203）以及国家自然科学基金系列项目（41476093, 41721005, 41890802, 31861143022 和41376116）的资助

Patterns and drivers of prokaryotic communities in thermokarst lake water across Northern Hemisphere

13 páginas.- 5 figuras.- 81referencias.Aim: The formation of thermokarst lakes could make a large amount of carbon accessible to microbial degradation, potentially intensifying the permafrost carbon-climate feedback via carbon dioxide/methane emissions. Because of their diverse functional roles, prokaryotes could strongly mediate biogeochemical cycles in thermokarst lakes. However, little is known about the large-scale patterns and drivers of these communities. Location: Permafrost regions in the Northern Hemisphere. Time period: Present day. Major taxa studied: Prokaryotes. Methods: Based on a combination of large-scale measurements on the Tibetan Plateau and data syntheses in pan-Arctic regions, we constructed a comprehensive dataset of 16S rRNA sequences from 258 thermokarst lakes across Northern Hemisphere permafrost regions. We also used the local contributions to beta diversity (LCBD) to characterize the variance of prokaryotic species composition and screened underlying drivers by conducting a random forest modelling analysis. Results: Prokaryotes in thermokarst lake water were dominated by the orders Burkholderiales, Micrococcales, Flavobacteriales and Frankiales. The relative abundance of dominant taxa was positively associated with dissolved organic matter (DOM) properties, especially for the chromophoric/aromatic compounds. Microbial structure differed between high-altitude and high-latitude thermokarst lakes, with the dominance of Flavobacterium in high-altitude lakes, and the enrichment of Polynucleobacter in high-latitude lakes. More importantly, climatic variables were among the main drivers shaping the large-scale variation of prokaryotic communities. Specifically, mean annual precipitation was the best predictor for prokaryotic beta diversity across the Northern Hemisphere, as well as in the high-altitude permafrost regions, while mean annual air temperature played a key role in the high-latitude thermokarst lakes. Main conclusions: Our findings demonstrate significant associations between dominant taxa and DOM properties, as well as the important role of climatic factors in affecting prokaryotic communities. These findings suggest that climatic change may alter DOM conditions and induce dynamics in prokaryotic communities of thermokarst lake water in the Northern Hemisphere. © 2023 John Wiley & Sons Ltd.This work was supported by the National Key Research and Development Program of China (2022YFF0801903), National Natural Science Foundation of China (31988102, and 31825006), and Tencent Foundation through the XPLORER PRIZE. M.D‐B. acknowledges support from TED2021‐130908B‐C41/AEI/10.13039/501100011033/Unión Europea NextGenerationEU/PRTR and from the Spanish Ministry of Science and Innovation for the I + D + i project PID2020‐115813RA‐I00 funded by MCIN/AEI/10.13039/501100011033.Peer reviewe

Coupled Thermo-Structural Analysis Model of Solid Rocket Motor Nozzle considering the Variation of Friction Coefficient under Operating Conditions

Multi-interface is a typical feature of solid rocket motor nozzles, and the interface evolution law is an important aspect to analyze the thermo-structural response of solid rocket motor nozzles. In this paper, based on the friction coefficient test at different temperatures, a coupled thermo-structural analysis model of solid rocket motor nozzle considering the variation of friction coefficient under operating conditions was established. Firstly, the friction coefficient was tested to model the variation at different temperatures. Then, by adopting structure gap, variable friction coefficient, thermal contact resistance, and friction heat production, a strongly coupled non-linear model was established. Simulations using the non-linear model and traditional model were performed, in which the stress of the throat insert was within the required stress range of the material. The ground firing test result demonstrated the validity of the analysis model, and the non-linear model was in a better agreement with the firing test than the traditional model. Therefore, it can be concluded that with a more specific friction coefficient to represent the friction behaviour of the different parts of the nozzle, the strongly coupled non-linear model established in this paper can reflect the essence of thermo-structural response of solid rocket motor nozzle

The extremity localized classic osteosarcomas have better survival than the axial non-classics

Abstract Background Osteosarcoma is one of the most malignant primary bone cancers, while is rarely reported in China. Of note, very few data of prognosis has been documented in this region. Thus, we carried a retrospective study to identify prognostic factors and to analyze outcomes in patients of both classic and non-classic high-grade osteosarcomas. Classic osteosarcoma is defined as of high-grade histology, age below 40 years, with extremity localized primary tumor, and without detectable metastasis at primary diagnosis. Methods A total of 98 patients (68 classic and 30 non-classic) aged from 4 to 64 years old were diagnosed as high-grade osteosarcoma from 2008 to 2015 in Nanfang Hospital, Guangzhou, China. Univariate and multivariate analyses were performed to identify the independent predictors for overall survival and event-free survival. Kaplan-Meier method was used for survival analysis. Results The median overall survival was 117 vs. 21 months, and the median event-free survival was 31 vs. 6 months in classic and non-classic osteosarcoma, respectively. The most frequently found tumor site was around the knee. The classic osteosarcoma had better overall survival and event-free survival than the non-classics. Tumor site and primary metastasis were found to be associated with overall survival and event-free survival in the univariate analysis. In the multivariate Cox regression analysis, tumor site and primary metastasis were each verified as independent prognostic factors. However, no similar result was found in elevated serum alkaline phosphatase or lactate dehydrogenase. Amputation or limb salvage surgery had no significant effect on overall survival and event-free survival in the extremity osteosarcomas. Classic osteosarcomas with extremity tumor site and free of primary metastasis exhibited better overall survival and event-free survival, while the axial and metastatic non-classics exhibited the worse. Conclusions The extremity classic osteosarcomas have better survivals than the axial non-classic cases. Amputation and limb salvage surgery make no significant change in overall survival and event-free survival in the extremity osteosarcomas. Trial registration Nanfang2013071; Date of registration: 7 September 2013 (retrospectively registered)

Effect of Yb2O3 on superplastic behavior of laser welded joint of TC4 titanium alloy

The inhomogeneity of joints during superplastic deformation greatly limits the application of laser beam welding/superplastic forming (LBW/SPF). In order to adjust the deformation uniformity of the joint, Yb2O3 with different mass fractions was added to the laser welded joint of TC4 titanium alloy, and the effect of Yb2O3 on the superplastic deformation behavior of the laser welded joint of TC4 titanium alloy was studied. The results showed that the addition of Yb2O3 can effectively refine β grains. At Yb2O3 content of 6 wt%, the refinement effect of Yb2O3 on the weld grains is the most obvious. At this time, the peak flow stress of the longitudinal weld sample reaches a minimum value of 25.6 MPa, and the superplasticity of the joint is significantly improved. The elongation of the transverse welded sample reached 29% of that of the base metal and the joint deformation uniformity was significantly improved. The prior β grain of weld broke during superplastic deformation, and the acicular martensite structure in the weld was gradually transformed into a lamellar structure. After the addition of Yb2O3, the lamellar structure inside the weld becomes short and disordered, which promotes occurrence of superplastic deformation

Microstructure analysis of 7050 aluminum alloy joint fabricated by linear friction weld

The microstructure of a linear friction welded joint of 7050 aluminum alloy was investigated through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The analysis focused on grain boundary types, microstructure, and mechanical properties of the joint. The results reveal that fine equiaxed crystals are generated in the welded zone through dynamic recrystallization. The average grain size is 6.8 μm, with a volume fraction of large angle grain boundaries reaching 69.5%. The microstructure primarily consists of Cube {001} texture, {111} Brass recrystallization texture, and a small amount of copper {112} deformation texture. The thermo-mechanically affected zone (TMAZ) presents a linear structure with an average grain size of 15.8 μm and a volume fraction of 36.1% at large grain boundary, resulting in a deformed Brass {011} texture and a small amount of {236} as well as {111} Brass recrystallization texture. The welded joint exhibits a tensile strength of 492 MPa and a yield strength of 380 MPa, which represents 94.2% and 78.5% of the base material, respectively. Furthermore, the elongation of the joint is 10.2% and 98% of the base material, respectively. The fracture of the tensile sample is observed in the TMAZ, showing good mechanical properties with a mixed fracture mode with some degrees of ductility and brittleness

Thermo-Structural Response Caused by Structure Gap and Gap Design for Solid Rocket Motor Nozzles

The thermo-structural response of solid rocket motor nozzles is widely investigated in the design of modern rockets, and many factors related to the material properties have been considered. However, little work has been done to evaluate the effects of structure gaps on the generation of flame leaks. In this paper, a numerical simulation was performed by the finite element method to study the thermo-structural response of a typical nozzle with consideration of the structure gap. Initial boundary conditions for thermo-structural simulation were defined by a quasi-1D model, and then coupled simulations of different gap size matching modes were conducted. It was found that frictional interface treatment could efficiently reduce the stress level. Based on the defined flame leak criteria, gap size optimization was carried out, and the best gap matching mode was determined for designing the nozzle. Testing experiment indicated that the simulation results from the proposed method agreed well with the experimental results. It is believed that the simulation method is effective for investigating thermo-structural responses, as well as designing proper gaps for solid rocket motor nozzles

Ultraviolet radiation rather than inorganic nitrogen increases dissolved organic carbon biodegradability in a typical thermo-erosion gully on the Tibetan Plateau

Permafrost thaw could lead to frozen carbon (C) being laterally transferred to aquatic systems as dissolved organic carbon (DOC). If this part of DOC has high biodegradability, it could be decomposed during the delivery process, release greenhouse gases to the atmosphere and trigger positive C-climate feedback. Thermokarst is an abrupt permafrost thaw process that can enhance DOC export and also impact DOC processing through increased inorganic nitrogen (N) and ultraviolet (UV) light exposure. Especially on the Tibetan Plateau, where thermokarst develops widely and suffers from serious UV radiation and N limitation. However, it remains unclear how thermokarst-impacted biodegradable DOC (BDOC) responds to inorganic N addition and UV radiation. Here, we explored the responses of DOC concentration, composition and its biodegradability to inorganic N and UV amendments in a typical thermokarst on the Tibetan Plateau, by using laboratory incubations with spectral analyses (UV-visible absorption and three-dimensional fluorescence spectra) and parallel factor analyses. Our results showed that BDOC in thermokarst outflows was significantly higher than in reference water. Our results also revealed that inorganic N addition had no influence on thermokarst-impacted BDOC, whereas exposure to UV light significantly increased BDOC by as much as 2.3 times higher than the dark-control. Moreover, N addition and UV radiation did not generate additive effects on BDOC. Our results further illustrated that dissolved organic matter (DOM) composition explained more of the variability in BDOC, while the nutrients and other physicochemical properties played a minor role. Overall, these results imply that UV light rather than inorganic N significantly increases thermokarst-derived BDOC, potentially strengthening the positive permafrost C-climate feedback. (c) 2018 Published by Elsevier B.V