Publications by authors named "Arjan Pol"

The Aeolian archipelago is known worldwide for its volcanic activity and hydrothermal emissions, of mainly carbon dioxide and hydrogen sulfide. Hydrogen, methane, and carbon monoxide are minor components of these emissions which together can feed large quantities of bacteria and archaea that do contribute to the removal of these notorious greenhouse gases. Here we analyzed the metagenome of samples taken from the Levante bay on Vulcano Island, Italy.

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Terrestrial geothermal ecosystems are hostile habitats, characterized by large emissions of environmentally relevant gases such as CO , CH , H S and H . These conditions provide a niche for chemolithoautotrophic microorganisms. Methanotrophs of the phylum Verrucomicrobia, which inhabit these ecosystems, can utilize these gases and grow at pH levels below 1 and temperatures up to 65°C.

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The outer membrane (OM) protects Gram-negative bacteria against a hostile environment. The proteins embedded in the OM fulfil a number of tasks that are crucial to the bacterial cell. In this study, we identified and characterised a major outer membrane protein (WP_009059494) from Methylacidiphilum fumariolicum SolV.

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We present the extremophilic bacterium SolV as a platform for the recovery of rare earth elements (REE). Strain SolV is able to selectively extract the light REE from artificial industrial waste sources, natural REE-containing and post-mining waters. Upscaling, different media composition and accumulation over several cycles were successfully implemented, underlining the potential for bio-recovery of REE.

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Article Synopsis
  • Bacterial lipoproteins, like WP_009060351, contain a lipid-modified cysteine that anchors them to cell membranes and are crucial for various physiological functions.
  • Transcriptomic analysis of the methanotroph Methylacidiphilum fumariolicum SolV identified WP_009060351 as a highly expressed lipoprotein, with specific amino acid sequences indicating its unique role in methanotrophs and verrucomicrobial species.
  • Experiments in Escherichia coli showed that WP_009060351 forms dimeric and tetrameric proteins, and its presence in membrane and peptidoglycan fractions suggests it may help connect the outer membrane to the peptidoglycan layer.
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Hydrogen sulfide (HS) and methane (CH) are produced in anoxic environments through sulfate reduction and organic matter decomposition. Both gases diffuse upwards into oxic zones where aerobic methanotrophs mitigate CH emissions by oxidizing this potent greenhouse gas. Although methanotrophs in myriad environments encounter toxic HS, it is virtually unknown how they are affected.

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Certain f-block elements-the lanthanides-have biological relevance in the context of methylotrophic bacteria. The respective strains incorporate these 4 f elements into the active site of one of their key metabolic enzymes, a lanthanide-dependent methanol dehydrogenase. In this study, we investigated whether actinides, the radioactive 5 f elements, can replace the essential 4 f elements in lanthanide-dependent bacterial metabolism.

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Production of organic molecules is largely depending on fossil fuels. A sustainable alternative would be the synthesis of these compounds from CO and a cheap energy source, such as H, CH, NH, CO, sulfur compounds or iron(II). Volcanic and geothermal areas are rich in CO and reduced inorganic gasses and therefore habitats where novel chemolithoautotrophic microorganisms for the synthesis of organic compounds could be discovered.

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Article Synopsis
  • Lanthanides, crucial for high-tech devices and renewable energy, demonstrate potential biological roles, particularly in certain bacteria that depend on them for growth.
  • These elements have been identified in key enzymatic processes, specifically in XoxF-type methanol dehydrogenases, highlighting their significance in biochemistry.
  • Research is ongoing to understand the gene expression regulation and uptake of lanthanides in bacteria, along with exploring their applications in element recovery.
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A variety of luminescent dyes including the most common indicators for optical oxygen sensors were investigated in regard to their stability and photophysical properties in the presence of nitrogen dioxide. The dyes were immobilized in polystyrene and subjected to NO concentrations from 40 to 5500 ppm. The majority of dyes show fast degradation of optical properties due to the reaction with NO.

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Pyrroloquinoline quinone (PQQ) is a redox cofactor in calcium- and lanthanide-dependent alcohol dehydrogenases that has been known and studied for over 40 years. Despite its long history, many questions regarding its fluorescence properties, speciation in solution and in the active site of alcohol dehydrogenase remain open. Here we investigate the effects of pH and temperature on the distribution of different PQQ species (HPQQ to PQQ in addition to water adducts and in complex with lanthanides) with NMR and UV-Vis spectroscopy as well as time-resolved laser-induced fluorescence spectroscopy (TRLFS).

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Methanotrophs aerobically oxidize methane to carbon dioxide to make a living and are known to degrade various other short chain carbon compounds as well. Volatile organic sulfur compounds such as methanethiol (CHSH) are important intermediates in the sulfur cycle. Although volatile organic sulfur compounds co-occur with methane in various environments, little is known about how these compounds affect methanotrophy.

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The methane-oxidizing bacterium Methylacidimicrobium thermophilum AP8 thrives in acidic geothermal ecosystems that are characterized by high degassing of methane (CH), H, HS, and by relatively high lanthanide concentrations. Lanthanides (atomic numbers 57 to 71) are essential in a variety of high-tech devices, including mobile phones. Remarkably, the same elements are actively taken up by methanotrophs/methylotrophs in a range of environments, since their XoxF-type methanol dehydrogenases require lanthanides as a metal cofactor.

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Verrucomicrobial methanotrophs are a group of aerobic bacteria isolated from volcanic environments. They are acidophiles, characterized by the presence of a particulate methane monooxygenase (pMMO) and a XoxF-type methanol dehydrogenase (MDH). Metagenomic analysis of DNA extracted from the soil of Favara Grande, a geothermal area on Pantelleria Island, Italy, revealed the presence of two verrucomicrobial Metagenome Assembled Genomes (MAGs).

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Methane and ammonia have to be removed from wastewater treatment effluent in order to discharge it to receiving water bodies. A potential solution for this is a combination of simultaneous ammonia and methane oxidation by anaerobic ammonia oxidation (anammox) bacteria and nitrite/nitrate-dependent anaerobic methane oxidation (N-damo) microorganisms. When applied, these microorganisms will be exposed to oxygen, but little is known about the effect of a low concentration of oxygen on a culture containing these microorganisms.

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Article Synopsis
  • The Favara Grande is a geothermal area in Italy with extreme conditions (high temperature, low pH) that may support unique microbial life, particularly chemolithotrophic thermoacidophiles.
  • Researchers successfully isolated a new methanotrophic strain (AP8) from soil samples taken from this region, which thrives in hot, acidic environments and shows potential for methane utilization.
  • The study provides insights into the genetic and physiological characteristics of this strain, highlighting its adaptations to harsh conditions and contributing to the broader understanding of microbial ecology in geothermal settings.
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The genus Methylobacter is considered an important and often dominant group of aerobic methane-oxidizing bacteria in many oxic ecosystems, where members of this genus contribute to the reduction of CH emissions. Metagenomic studies of the upper oxic layers of geothermal soils of the Favara Grande, Pantelleria, Italy, revealed the presence of various methane-oxidizing bacteria, and resulted in a near complete metagenome assembled genome (MAG) of an aerobic methanotroph, which was classified as a Methylobacter species. In this study, the Methylobacter sp.

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Methanotrophs are an important group of microorganisms that counteract methane emissions to the atmosphere. Methane-oxidising bacteria of the Alpha- and Gammaproteobacteria have been studied for over a century, while methanotrophs of the phylum Verrucomicrobia are a more recent discovery. Verrucomicrobial methanotrophs are extremophiles that live in very acidic geothermal ecosystems.

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Volcanic areas emit a number of gases including methane and other short chain alkanes, that may serve as energy source for the prevailing microorganisms. The verrucomicrobial methanotroph SolV was isolated from a volcanic mud pot, and is able to grow under thermoacidophilic conditions on different gaseous substrates. Its genome contains three operons encoding a particulate methane monooxygenase (pMMO), the enzyme that converts methane to methanol.

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Ammonia oxidation was considered impossible under highly acidic conditions, as the protonation of ammonia leads to decreased substrate availability and formation of toxic nitrogenous compounds. Recently, some studies described archaeal and bacterial ammonia oxidizers growing at pH as low as 4, while environmental studies observed nitrification at even lower pH values. In this work, we report on the discovery, cultivation, and physiological, genomic, and transcriptomic characterization of a novel gammaproteobacterial ammonia-oxidizing bacterium enriched via continuous bioreactor cultivation from an acidic air biofilter that was able to grow and oxidize ammonia at pH 2.

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Volcanic and geothermal environments are characterized by low pH, high temperatures, and gas emissions consisting of mainly CO and varied CH, HS, and H contents which allow the formation of chemolithoautotrophic microbial communities. To determine the link between the emitted gases and the microbial community composition, geochemical and metagenomic analysis were performed. Soil samples of the geothermic region Favara Grande (Pantelleria, Italy) were taken at various depths (1 to 50 cm).

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Aerobic and nitrite-dependent methanotrophs make a living from oxidizing methane via methanol to carbon dioxide. In addition, these microorganisms cometabolize ammonia due to its structural similarities to methane. The first step in both of these processes is catalyzed by methane monooxygenase, which converts methane or ammonia into methanol or hydroxylamine, respectively.

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Article Synopsis
  • Industrial methanol production typically requires high temperatures and pressures to convert methane from natural gas into methanol, while biological methods using methanotrophs, like the bacterium SolV, provide a more environmentally friendly alternative under moderate conditions.
  • The study focused on optimizing conditions to minimize the activity of methanol dehydrogenase, which can inhibit methanol production, achieving a high conversion efficiency of 63% and a production rate of 0.88 mmol/g/h during optimal growth.
  • Full-scale applications will need improvements in methanol yield and efficiency, which could be achieved through reduced lanthanide concentrations and better reactor designs to ensure adequate gas supply.
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Article Synopsis
  • Volcanic and geothermal areas provide hot, acidic environments that support unique microorganisms capable of oxidizing hydrogen (H) and carbon monoxide (CO) for energy.
  • Two strains, FAVT5 and COOX1, were isolated from volcanic soils in Italy and can grow autotrophically using these gases, with FAVT5 showing optimal growth at 55°C and pH 5.0.
  • The strains possess specialized hydrogenases and a CO dehydrogenase in their genomes, indicating they are well adapted to survive and thrive in harsh geothermal conditions.
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3B and 4AC are Gram-negative rod-shaped mesophilic methanotrophs isolated from soil samples with low pH at the Solfatara Crater, near Naples, Italy. The genomes of these extremophilic verrucomicrobia were sequenced using Illumina technology, and both species possess one operon and two genes.

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