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Cobalamin (B12), an essential nutrient and growth cofactor for many living organisms on Earth, can be fully synthesized only by selected prokaryotes in nature. Therefore, microbial communities related to B12 biosynthesis could serve as an example subsystem to disentangle the underlying ecological mechanisms balancing the function and taxonomic make-up of complex functional assemblages. By anchoring microbial traits potentially involved in B12 biosynthesis, we depict the biogeographic patterns of B12 biosynthesis genes and the taxa harboring them in the global ocean, despite the limitations of detecting de novo B12 synthesizers via metagenomes alone. Both the taxonomic and functional composition of B12 biosynthesis genes were strongly shaped by depth, differentiating the epipelagic zones from the mesopelagic layers. Functional genes related to B12 biosynthesis were relatively stably distributed across different oceans, but the taxa harboring them varied considerably, showing clear functional redundancy among microbial systems. Microbial taxa carrying B12 biosynthesis genes in the surface water were influenced by environmental factors such as temperature, oxygen, and nitrate. However, the composition of functional genes was only weakly associated with these environmental factors. Null model analyses demonstrated that determinism governed the variations in B12 biosynthesis genes, whereas a higher degree of stochasticity was associated with taxonomic variations. Significant associations were observed between the chlorophyll a concentration and B12 biosynthesis, confirming its importance in primary production in the global ocean. The results of this study reveal an essential ecological mechanism governing the assembly of microbes in nature: the environment selects for function rather than taxonomy; functional redundancy underlies stochastic community assembly.

In order to study the relationship between the corrosion behavior of steel rails and the concentration and corrosion time of NaCl solution, U71Mn steel rails were taken as the object, and the initial corrosion behavior and mechanism of steel rail materials immersed in neutral NaCl solutions (different concentrations of 1.0%, 2.0%, 2.5%, 3.5%, 4.0% and 5.0%) for 144 h, and in neutral 3.5% NaCl solutions for various immersion times (12, 48, 96, 144, 192, 288 h) were investigated by full immersion test and electrochemical tests.Results showed that the average corrosion rate of initial steel rail materials was positively correlated with NaCl concentration and immersion time.With the increase of NaCl concentration, the Ecorr of the steel rail specimen moved negatively from－0.651 V to－0.717 V, and the Jcorr increased from 5.71 μA/cm2 to 67.48 μA/cm2.With the increase of corrosion time, the Ecorr of the steel rail specimen moved negatively from－0.692 V to－0.720 V, and the Jcorr increased from 7.54 μA/cm2 to 74.59 μA/cm2.Furthermore, the reduction of corrosion products γ-FeOOH could destroy the original stable rust layer structure, and finally causing the acceleration of corrosion.

BackgroundChronic kidney disease (CKD) is increasingly recognized as a stroke risk factor, but its exact relationship with cerebrovascular disease is not well-understood. We investigated the development of cerebral small vessel disease using in vivo and in vitro models of CKD.MethodsCKD was produced in aged C57BL/6J mice using an adenine-induced tubulointerstitial nephritis model. We analyzed brain histology using Prussian blue staining to examine formation of cerebral microhemorrhage (CMH), the hemorrhagic component of small vessel disease and the neuropathological substrate of MRI-demonstrable cerebral microbleeds. In cell culture studies, we examined effects of serum from healthy or CKD patients and gut-derived uremic toxins on brain microvascular endothelial barrier.ResultsCKD was induced in aged C57BL/6J mice with significant increases in both serum creatinine and cystatin C levels (p

In order to study the corrosion behavior of ER8 wheel steel in coastal neutral chlorine salt environment，the electrochemical corrosion behavior of ER8 wheel steel in neutral NaCl solutions with three different concentrations were analyzed through electrochemical tests， corrosion weight loss tests，scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques.The polarization curve results showed that the self-corrosion current density (Jcorr) was the largest in 5.0%(mass fraction， the same below) NaCl solution at the initial stage of immersion.After immersed for 576 h， Jcorr continued to increase at 2.0%and 3.5%NaCl solutions， and the average corrosion rate was more than 0.12 mm/a for 2 160 h.The SEM results indicated that the morphology of corrosion products were mainly flake and cluster structures.Because the morphology of corrosion products at the initial stage had more pores， it’s difficult to prevent Cl- from reacting with the substrate.The structure of corrosion products was more uniform and denser for 2 160 h.Moreover，the XRD results showed that the corrosion products were mainly composed of γ-FeOOH， α-FeOOH and Fe3O4.

The integration of railway facilities and use of new energies is an important way to achieve the carbon peaking and carbon neutrality goals. After analyzing the demand for the integrated development of railway and new energies, this study summarizes the natural conditions of various new energy sources along railways, including solar, wind, geothermal, acoustic, braking, and vibrational energies. The current integration forms, technical characteristics, and equipment levels are then reviewed. The specific integration scenarios between the railway service facilities, carriers, infrastructures, and new energy sources are summarized by category, and the developmental scales and problems of major scenarios, such as photovoltaic systems at the top of railway stations, new-energy locomotives, and self-power supply monitoring equipment, are discussed. Based on the classification of potentials to supply new energies for railways, a series of new integration scenarios and methods are introduced considering the new energy systems of different scales (e.g., micro, small- and medium-sized, as well as large and super-large). A new major scenario that integrates electricequipment for railway infrastructure defects control and small- and medium-sized distributed off-grid photovoltaic systems is proposed. Furthermore, the future trends, core technologies, and key developmental directions for the integration of railway and new energies are proposed from the aspects such as energy capture and conversion, load, energy storage, and energy management.

Cobalamin (vitamin B12; VB12) is an indispensable nutrient for all living entities in the Earth's biosphere and plays a vital role in both natural and host environments. Currently in the metagenomic era, gene families of interest are extracted and analyzed based on functional profiles by searching shotgun metagenomes against public databases. However, critical issues exist in applying public databases for specific processes such as VB12 biosynthesis pathways. We developed a curated functional gene database termed VB12Path for accurate metagenomic profiling of VB12 biosynthesis gene families of microbial communities in complex environments. VB12Path contains a total of 60 VB12 synthesis gene families, 287,731 sequences, and 21,154 homology groups, and it aims to provide accurate functional and taxonomic profiles of VB12 synthesis pathways for shotgun metagenomes and minimize false-positive assignments. VB12Path was applied to characterize cobalamin biosynthesis gene families in human intestines and marine environments. The results demonstrated that ocean and human intestine had dramatically different VB12 synthesis processes and that gene families belonging to salvage and remodeling pathway dominated human intestine but were lowest in the ocean ecosystem. VB12Path is expected to be a useful tool to study cobalamin biosynthesis processes via shotgun metagenome sequencing in both environmental and human microbiome research. IMPORTANCE Vitamin B12 (VB12) is an indispensable nutrient for all living entities in the world but can only be synthesized by a small subset of prokaryotes. Therefore, this small subset of prokaryotes controls ecosystem stability and host health to some extent. However, critical accuracy and comprehensiveness issues exist in applying public databases to profile VB12 synthetic gene families and taxonomic groups in complex metagenomes. In this study, we developed a curated functional gene database termed VB12Path for accurate metagenomic profiling of VB12 communities in complex environments. VB12Path is expected to serve as a valuable tool to uncover the hidden microbial communities producing this precious nutrient on Earth.