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151.
152.
Caitlin Petro Alyssa A. Carrell Rachel M. Wilson Katherine Duchesneau Sekou Noble-Kuchera Tianze Song Colleen M. Iversen Joanne Childs Geoff Schwaner Jeffrey P. Chanton Richard J. Norby Paul J. Hanson Jennifer B. Glass David J. Weston Joel E. Kostka 《Global Change Biology》2023,29(11):3159-3176
Peat mosses (Sphagnum spp.) are keystone species in boreal peatlands, where they dominate net primary productivity and facilitate the accumulation of carbon in thick peat deposits. Sphagnum mosses harbor a diverse assemblage of microbial partners, including N2-fixing (diazotrophic) and CH4-oxidizing (methanotrophic) taxa that support ecosystem function by regulating transformations of carbon and nitrogen. Here, we investigate the response of the Sphagnum phytobiome (plant + constituent microbiome + environment) to a gradient of experimental warming (+0°C to +9°C) and elevated CO2 (+500 ppm) in an ombrotrophic peatland in northern Minnesota (USA). By tracking changes in carbon (CH4, CO2) and nitrogen (NH4-N) cycling from the belowground environment up to Sphagnum and its associated microbiome, we identified a series of cascading impacts to the Sphagnum phytobiome triggered by warming and elevated CO2. Under ambient CO2, warming increased plant-available NH4-N in surface peat, excess N accumulated in Sphagnum tissue, and N2 fixation activity decreased. Elevated CO2 offset the effects of warming, disrupting the accumulation of N in peat and Sphagnum tissue. Methane concentrations in porewater increased with warming irrespective of CO2 treatment, resulting in a ~10× rise in methanotrophic activity within Sphagnum from the +9°C enclosures. Warming's divergent impacts on diazotrophy and methanotrophy caused these processes to become decoupled at warmer temperatures, as evidenced by declining rates of methane-induced N2 fixation and significant losses of keystone microbial taxa. In addition to changes in the Sphagnum microbiome, we observed ~94% mortality of Sphagnum between the +0°C and +9°C treatments, possibly due to the interactive effects of warming on N-availability and competition from vascular plant species. Collectively, these results highlight the vulnerability of the Sphagnum phytobiome to rising temperatures and atmospheric CO2 concentrations, with significant implications for carbon and nitrogen cycling in boreal peatlands. 相似文献
153.
Katalin Tenger Petro Khoroshyy Gábor Rákhely László Zimányi 《Journal of bioenergetics and biomembranes》2010,42(2):125-133
Maturation of c-type cytochromes involves the covalent and stereospecific enzymatic attachment of a heme b via thioether linkages to two conserved cysteines within apocytochromes. Horse cytochrome c is readily matured into its native holoform in the cytoplasm of E. coli when co-expressed with yeast cytochrome c heme lyase. Here we report the low yield formation of holocytochrome with covalently attached heme also in the absence of
heme lyase. This is the first demonstration of in vivo maturation of a eukaryotic cytochrome c in a prokaryotic cytoplasm without the assistance by a dedicated enzymatic maturation system. The assembled cytochrome c can be oxidized by cytochrome c oxidase, indicating the formation of a functional protein. The absorption spectrum is typical of a low spin, six coordinated
c-type heme. Nevertheless, minor spectral differences relative to the native cytochrome c, deviation of the midpoint reduction potential and slightly altered kinetic parameters of the interaction with cytochrome
c oxidase emphasize the importance of cytochrome c heme lyase in folding cytochrome c into its native conformation. 相似文献
154.
The potential of reverse-phase high-performance liquid chromatography for the separation of closely related proteins has been investigated. Using an octadecasilyl silica stationary phase and a propanol/pyridine formate solvent system normal α- and β-chains of human hemoglobin have been separated from several of their respective mutant chains which differ by single amino acid residues only. The results suggest that reverse-phase high-performance liquid chromatography is a powerful tool for the separation of medium-sized proteins with minimal structural difference. 相似文献