Cold desert soil microbiomes thrive despite severe moisture and nutrient limitations. In Eastern Antarctic soils, bacterial primary production is supported by trace gas oxidation and the light-independent RuBisCO form IE. This study aims to determine if atmospheric chemosynthesis is widespread within Antarctic, Arctic and Tibetan cold deserts, to identify the breadth of trace gas chemosynthetic taxa and to further characterize the genetic determinants of this process. H2 oxidation was ubiquitous, far exceeding rates reported to fulfill the maintenance needs of similarly structured edaphic microbiomes. Atmospheric chemosynthesis occurred globally, contributing significantly (p < 0.05) to carbon fixation in Antarctica and the high Arctic. Taxonomic and functional analyses were performed upon 18 cold desert metagenomes, 230 dereplicated medium-to-high-quality derived metagenome-assembled genomes (MAGs) and an additional 24,080 publicly available genomes. Hydrogenotrophic and carboxydotrophic growth markers were widespread. RuBisCO IE was discovered to co-occur alongside trace gas oxidation enzymes in representative Chloroflexota, Firmicutes, Deinococcota and Verrucomicrobiota genomes. We identify a novel group of high-affinity [NiFe]-hydrogenases, group 1m, through phylogenetics, gene structure analysis and homology modeling, and reveal substantial genetic diversity within RuBisCO form IE (rbcL1E), and high-affinity 1h and 1l [NiFe]-hydrogenase groups. We conclude that atmospheric chemosynthesis is a globally-distributed phenomenon, extending throughout cold deserts, with significant implications for the global carbon cycle and bacterial survival within environmental reservoirs.

• MeSH
• hydrogenasa * genetika   MeSH
• koloběh uhlíku MeSH
• půda chemie   MeSH
• půdní mikrobiologie MeSH
• ribulosa-1,5-bisfosfát-karboxylasa MeSH
• Verrucomicrobia MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hydrogenasa * MeSH
• půda MeSH
• ribulosa-1,5-bisfosfát-karboxylasa MeSH

Trichomonads, represented by the highly prevalent sexually transmitted human parasite Trichomonas vaginalis, are anaerobic eukaryotes with hydrogenosomes in the place of the standard mitochondria. Hydrogenosomes form indispensable FeS-clusters, synthesize ATP, and release molecular hydrogen as a waste product. Hydrogen formation is catalyzed by [FeFe] hydrogenase, the hallmark enzyme of all hydrogenosomes found in various eukaryotic anaerobes. Eukaryotic hydrogenases were originally thought to be exclusively localized within organelles, but today few eukaryotic anaerobes are known that possess hydrogenase in their cytosol. We identified a thus-far unknown hydrogenase in T. vaginalis cytosol that cannot use ferredoxin as a redox partner but can use cytochrome b5 as an electron acceptor. Trichomonads overexpressing the cytosolic hydrogenase, while maintaining the carbon flux through hydrogenosomes, show decreased excretion of hydrogen and increased excretion of methylated alcohols, suggesting that the cytosolic hydrogenase uses the hydrogen gas as a source of reducing power for the reactions occurring in the cytoplasm and thus accounts for the overall redox balance. This is the first evidence of hydrogen uptake in a eukaryote, although further work is needed to confirm it. Assembly of the catalytic center of [FeFe] hydrogenases (H-cluster) requires the activity of three dedicated maturases, and these proteins in T. vaginalis are exclusively localized in hydrogenosomes, where they participate in the maturation of organellar hydrogenases. Despite the different subcellular localization of cytosolic hydrogenase and maturases, the H-cluster is present in the cytosolic enzyme, suggesting the existence of an alternative mechanism of H-cluster assembly.

• Klíčová slova
• H-cluster, Trichomonas, cytosolic hydrogenase, hydrogenosome,
• MeSH
• cytosol metabolismus   MeSH
• ferredoxiny metabolismus   MeSH
• hydrogenasa * metabolismus   MeSH
• Trichomonas vaginalis * enzymologie   ultrastruktura   MeSH
• vodík * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ferredoxiny MeSH
• hydrogenasa * MeSH
• vodík * MeSH

Naegleria gruberi is a free-living heterotrophic aerobic amoeba well known for its ability to transform from an amoeba to a flagellate form. The genome of N. gruberi has been recently published, and in silico predictions demonstrated that Naegleria has the capacity for both aerobic respiration and anaerobic biochemistry to produce molecular hydrogen in its mitochondria. This finding was considered to have fundamental implications on the evolution of mitochondrial metabolism and of the last eukaryotic common ancestor. However, no actual experimental data have been shown to support this hypothesis. For this reason, we have decided to investigate the anaerobic metabolism of the mitochondrion of N. gruberi. Using in vivo biochemical assays, we have demonstrated that N. gruberi has indeed a functional [FeFe]-hydrogenase, an enzyme that is attributed to anaerobic organisms. Surprisingly, in contrast to the published predictions, we have demonstrated that hydrogenase is localized exclusively in the cytosol, while no hydrogenase activity was associated with mitochondria of the organism. In addition, cytosolic localization displayed for HydE, a marker component of hydrogenase maturases. Naegleria gruberi, an obligate aerobic organism and one of the earliest eukaryotes, is producing hydrogen, a function that raises questions on the purpose of this pathway for the lifestyle of the organism and potentially on the evolution of eukaryotes.

• Klíčová slova
• Naegleria, hydrogen hypothesis, hydrogenase, maturases, mitochondrial evolution,
• MeSH
• cytosol enzymologie   MeSH
• hydrogenasa genetika   metabolismus   MeSH
• mitochondrie genetika   metabolismus   MeSH
• Naegleria enzymologie   genetika   MeSH
• protozoální proteiny genetika   metabolismus   MeSH
• vodík metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hydrogenasa MeSH
• protozoální proteiny MeSH
• vodík MeSH

Here we report a Narf-like gene from the apicomplexan Cryptosporidium parvum (CpNARF). CpNARF is an intronless, single-copy gene of 1680 bp which encodes a putative protein of 560 amino acids with a calculated molecular mass of 63.1 kDa. This gene contains a single highly conserved N-terminal iron-sulfur cluster ([4Fe-4S]) binding site, as well as most of the H-cluster conserved residues. Reverse transcription polymerase chain reaction analysis indicates that CpNARF is expressed by the intracellular stages of C. parvum. Although the function of this gene is as yet unknown, phylogenetic analyses suggest that CpNARF belongs to the group of NARF-like proteins from aerobic protists and higher eukaryotes, which are thought to have had an ancestor in common with [Fe]-hydrogenases.

• MeSH
• aerobióza MeSH
• buněčné linie MeSH
• Cryptosporidium parvum genetika   MeSH
• fylogeneze MeSH
• genetická transkripce MeSH
• hydrogenasa genetika   MeSH
• jaderné proteiny genetika   MeSH
• lidé MeSH
• molekulární evoluce MeSH
• molekulární sekvence - údaje MeSH
• proteiny obsahující železo a síru genetika   MeSH
• protozoální proteiny genetika   MeSH
• sekvence aminokyselin MeSH
• sekvenční homologie aminokyselin MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Názvy látek
• hydrogenasa MeSH
• iron hydrogenase MeSH Prohlížeč
• jaderné proteiny MeSH
• NARF protein, human MeSH Prohlížeč
• proteiny obsahující železo a síru MeSH
• protozoální proteiny MeSH

Acquisition of iron from lactoferrin and transferrin by a parasitic protozoon Tritrichomonas foetus has been studied in vitro. Specific, time-dependent, and saturable binding of iodinated ligands to the outer membrane of T. foetus at 4 degrees C was demonstrated for 125I-labeled lactoferrin only. About 1.7 x 10(5) binding sites of a single class with Kd approximately equal to 3.6 microM was estimated by means of Scatchard analysis. Internalization of the bound lactoferrin was observed at 37 degrees C. The cell-associated radioactivity after 30 min incubation of the parasite with 125I-lactoferrin at 37 degrees C was about 3.5-fold higher than the amount bound at 4 degrees C. The majority of internalized 125I-lactoferrin was released within 15 min of cell reincubation at 37 degrees C in the presence of a 100-fold excess of nonlabeled lactoferrin. Released lactoferrin displayed unchanged mobility on autoradiography. In contrast to lactoferrin, binding of 125I-transferrin was nonspecific and did not display saturable kinetics. The growth of T. foetus in iron-restricted media was stimulated by both lactoferrin and transferrin. The ability of the cells to remove and accumulate iron from both proteins was therefore examined using 59Fe-saturated lactoferrin and transferrin. It was found that trichomonads acquired a comparable amount of iron from both lactoferrin and transferrin during 60 min incubation at 37 degrees C (495 and 577 pmole Fe/mg of protein, respectively). The pH of the assay medium (PBS) decreased from pH 7.4 to 5.6 after incubation with trichomonads. At this pH, marked release of iron from transferrin (up to 47%) but not from lactoferrin (4%) was determined in cell-free media. These results indicate that T. foetus is able to utilize both lactoferrin and transferrin to cover its iron requirements. However, mechanisms of iron acquisition from these host proteins appear to be different. Specific binding and internalization of lactoferrin suggests the possible involvement of receptor-mediated endocytosis in the acquisition of lactoferrin-bound iron, while retrieval of iron from transferrin may depend on the extracellular release of iron from this ligand.

• MeSH
• 2,2'-dipyridyl farmakologie   MeSH
• chelátory železa farmakologie   MeSH
• hydrogenasa metabolismus   MeSH
• ketonoxidoreduktasy metabolismus   MeSH
• koncentrace vodíkových iontů MeSH
• kyselina nitrilotrioctová analogy a deriváty   farmakologie   MeSH
• laktoferrin metabolismus   MeSH
• ligandy MeSH
• myši MeSH
• pyruvátsynthasa MeSH
• receptory buněčného povrchu metabolismus   MeSH
• receptory transferinu metabolismus   MeSH
• skot MeSH
• teplota MeSH
• transferin metabolismus   MeSH
• Tritrichomonas foetus účinky léků   růst a vývoj   metabolismus   MeSH
• železité sloučeniny farmakologie   MeSH
• železo metabolismus   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• skot MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2,2'-dipyridyl MeSH
• chelátory železa MeSH
• ferric nitrilotriacetate MeSH Prohlížeč
• hydrogenasa MeSH
• ketonoxidoreduktasy MeSH
• kyselina nitrilotrioctová MeSH
• lactoferrin receptors MeSH Prohlížeč
• laktoferrin MeSH
• ligandy MeSH
• pyruvátsynthasa MeSH
• receptory buněčného povrchu MeSH
• receptory transferinu MeSH
• transferin MeSH
• železité sloučeniny MeSH
• železo MeSH