Abstract:Microbes belonging to the genus Metallosphaera oxidize sulfidic minerals. These organisms thrive at temperature extremes and are members of the archaeal phylum Crenarchaeota. Because they can employ a lithoautotrophic metabolism, energy availability likely limits their activity raising questions about how they conduct biogeochemical activity. Vesicles are membrane encapsulated structures produced by all biological lineages but using very different mechanisms. Across the Crenarchaeota, it has been proposed that… Show more
“…Collectively, these results indicate that cells require direct contact with FeS 2 to catalyze its reduction and/or that cells require direct access to FeS 2 to acquire Fe and S following the coupled reductive dissolution-precipitation reaction. Alternatively, these results could point to high molecular weight (>100 kDa) extracellular proteins, metabolites, or other cellular assemblages (such as enzyme containing vesicles) as being involved in catalyzing FeS 2 reduction or in acquiring mineral-associated Fe and S. The involvement of vesicles in mineral sulfide oxidation has been demonstrated in the crenarchaeote Metallosphaera sedula , where they were shown to adhere to and promote the oxidation and solubilization of chalcopyrite (CuFeS 2 ) [ 38 ]. Fig.…”
The formation and fate of pyrite (FeS2) modulates global iron, sulfur, carbon, and oxygen biogeochemical cycles and has done so since early in Earth’s geological history. A longstanding paradigm is that FeS2 is stable at low temperature and is unavailable to microorganisms in the absence of oxygen and oxidative weathering. Here, we show that methanogens can catalyze the reductive dissolution of FeS2 at low temperature (≤38 °C) and utilize dissolution products to meet cellular iron and sulfur demands associated with the biosynthesis of simple and complex co-factors. Direct access to FeS2 is required to catalyze its reduction and/or to assimilate iron monosulfide that likely forms through coupled reductive dissolution and precipitation, consistent with close associations observed between cells and FeS2. These findings demonstrate that FeS2 is bioavailable to anaerobic methanogens and can be mobilized in low temperature anoxic environments. Given that methanogens evolved at least 3.46 Gya, these data indicate that the microbial contribution to the iron and sulfur cycles in ancient and contemporary anoxic environments may be more complex and robust than previously recognized, with impacts on the sources and sinks of iron and sulfur and other bio-essential and thiophilic elements such as nickel and cobalt.
“…Collectively, these results indicate that cells require direct contact with FeS 2 to catalyze its reduction and/or that cells require direct access to FeS 2 to acquire Fe and S following the coupled reductive dissolution-precipitation reaction. Alternatively, these results could point to high molecular weight (>100 kDa) extracellular proteins, metabolites, or other cellular assemblages (such as enzyme containing vesicles) as being involved in catalyzing FeS 2 reduction or in acquiring mineral-associated Fe and S. The involvement of vesicles in mineral sulfide oxidation has been demonstrated in the crenarchaeote Metallosphaera sedula , where they were shown to adhere to and promote the oxidation and solubilization of chalcopyrite (CuFeS 2 ) [ 38 ]. Fig.…”
The formation and fate of pyrite (FeS2) modulates global iron, sulfur, carbon, and oxygen biogeochemical cycles and has done so since early in Earth’s geological history. A longstanding paradigm is that FeS2 is stable at low temperature and is unavailable to microorganisms in the absence of oxygen and oxidative weathering. Here, we show that methanogens can catalyze the reductive dissolution of FeS2 at low temperature (≤38 °C) and utilize dissolution products to meet cellular iron and sulfur demands associated with the biosynthesis of simple and complex co-factors. Direct access to FeS2 is required to catalyze its reduction and/or to assimilate iron monosulfide that likely forms through coupled reductive dissolution and precipitation, consistent with close associations observed between cells and FeS2. These findings demonstrate that FeS2 is bioavailable to anaerobic methanogens and can be mobilized in low temperature anoxic environments. Given that methanogens evolved at least 3.46 Gya, these data indicate that the microbial contribution to the iron and sulfur cycles in ancient and contemporary anoxic environments may be more complex and robust than previously recognized, with impacts on the sources and sinks of iron and sulfur and other bio-essential and thiophilic elements such as nickel and cobalt.
“…6a). The monolayers of M. sedula vesicles have been shown to catalyze iron oxidation and solubilization of mineralized copper from chalcopyrite under the energy-limited lithoautotrophic conditions 25 . Apart from metal transformation, synthesis and secretion of membrane vesicles might serve as a general mechanism of extracellular metal sequestration by binding with chelating agents, e.g ., proteins, and enzymatic detoxification of the metal to a less toxic form.…”
exploration of microbial-meteorite redox interactions highlights the possibility of bioprocessing of extraterrestrial metal resources and reveals specific microbial fingerprints left on extraterrestrial material. in the present study, we provide our observations on a microbial-meteorite nanoscale interface of the metal respiring thermoacidophile Metallosphaera sedula. M. sedula colonizes the stony meteorite Northwest Africa 1172 (NWA 1172; an H5 ordinary chondrite) and releases free soluble metals, with Ni ions as the most solubilized. We show the redox route of Ni ions, originating from the metallic ni° of the meteorite grains and leading to released soluble ni 2+. nanoscale resolution ultrastructural studies of meteorite grown M. sedula coupled to electron energy loss spectroscopy (EELS) points to the redox processing of Fe-bearing meteorite material. Our investigations validate the ability of M. sedula to perform the biotransformation of meteorite minerals, unravel microbial fingerprints left on meteorite material, and provide the next step towards an understanding of meteorite biogeochemistry. Our findings will serve in defining mineralogical and morphological criteria for the identification of metal-containing microfossils.
“…EVs carry proteins, nucleic acids and metabolites which they can transfer between cells. While they function in cell-cell and cell-microenvironment communication [1,2], EVs are also emerging as universal agents in intra-and cross-organism communication for mammals [3][4][5][6][7], viruses [8,9], bacteria [10], archaea [11], microbes [12,13], parasites [14], fungi [15,16] and plants [17]. Cells have been shown to release different types of EVs which include exosomes, shedding microvesicles (sMVs) [18] or oncosomes [19], apoptotic blebs (ABs) and gesicles [20].…”
Extracellular vesicles (EVs) are membrane-enclosed vesicles released by cells. They carry proteins, nucleic acids and metabolites which can be transferred to a recipient cell, locally or at a distance, to elicit a functional response. Since their discovery over 30 years ago, the functional repertoire of EVs in both physiological (e.g., organ morphogenesis, embryo implantation) and pathological (e.g., cancer, neurodegeneration) conditions has cemented their crucial role in intercellular communication. Moreover, because the cargo encapsulated within circulating EVs remains protected from degradation, their diagnostic as well as therapeutic (such as drug delivery tool) applications have garnered vested interest. Global efforts have been made to purify EV subtypes from biological fluids and in vitro cell culture media using a variety of strategies and techniques, with a major focus on EVs of endocytic origin called exosomes (30-150 nm in size). Given that the secretome comprises of soluble secreted proteins, protein aggregates, RNA granules and EV subtypes (such as exosomes, shed microvesicles, apoptotic bodies), it is imperative to purify exosomes to homogeneity if we are to perform biochemical and biophysical characterization and importantly, functional dissection. Besides understanding the composition of EV-subtypes, defining molecular bias of how they reprogram target cells also remains of paramount importance in this area of active research. Here, we outline a systematic "how to" protocol (along with useful insights/tips) to obtain highly purified exosomes and perform their biophysical and biochemical characterization. This protocol employs a mass spectrometry-based proteomics approach to characterize the protein composition of exosomes. We also provide insights on different isolation strategies and their usefulness in various downstream applications. We outline protocols for lipophilic-labelling of exosomes to study uptake by a recipient cell, investigating cellular reprogramming using proteomics and studying functional response to exosomes in the Transwell-Matrigel TM Invasion assay.
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