scholarly journals Correlation of Key Physiological Properties of Methanosarcina Isolates with Environment of Origin

2021 ◽  
Author(s):  
Jinjie Zhou ◽  
Dawn E. Holmes ◽  
Hai-Yan Tang ◽  
Derek R. Lovley
Keyword(s):  
Electron Transfer ◽  
Electron Flux ◽  
High Energy ◽  
Metagenomic Data ◽  
Extracellular Electron Transfer ◽  
Acetate Metabolism ◽  
Type I ◽  
Type Ii ◽  
Anaerobic Digesters ◽  
Soils And Sediments

It is known that the physiology of Methanosarcina species can differ significantly, but the ecological impact of these differences is unclear. We recovered two strains of Methanosarcina from two different ecosystems with a similar enrichment and isolation method. Both strains had the same ability to metabolize organic substrates and participate in direct interspecies electron transfer, but also had major physiological differences. Strain DH-1, which was isolated from an anaerobic digester, could use H2 as an electron donor. Genome analysis indicated that it lacks an Rnf complex and conserves energy from acetate metabolism via intracellular H2 cycling. In contrast, strain DH-2, a subsurface isolate, lacks hydrogenases required for H2 uptake and cycling, and has an Rnf complex for energy conservation when growing on acetate. Further analysis of the genomes of previously described isolates, as well as phylogenetic and metagenomic data on uncultured Methanosarcina in anaerobic digesters and diverse soils and sediments, further revealed a physiological dichotomy that corresponded with environment of origin. The physiology of Type I Methanosarcina revolves around H2 production and consumption. In contrast, Type II Methanosarcina eschew H2, and have genes for an Rnf complex and the multi-heme, membrane-bound c-type cytochrome MmcA, shown to be essential for extracellular electron transfer. The distribution of Methanosarcina species in diverse environments suggests that the Type I H2-based physiology is well suited for high energy environments, like anaerobic digesters, whereas Type II Rnf/cytochrome-based physiology is an adaption to the slower, steady-state carbon and electron fluxes common in organic-poor anaerobic soils and sediments. Importance Biogenic methane is a significant greenhouse gas and the conversion of organic wastes to methane is an important bioenergy process. Methanosarcina species play an important role in methane production in many methanogenic soils and sediments as well as anaerobic waste digesters. The studies reported here emphasize that the genus Methanosarcina is composed of two physiologically distinct groups. This is important to recognize when interpreting the role of Methanosarcina in methanogenic environments, especially regarding H2 metabolism. Furthermore, the finding that Type I Methanosarcina predominate in environments with high rates of carbon and electron flux and that Type II Methanosarcina predominate in lower energy environments suggests that evaluating the relative abundance of Type I and Type II Methanosarcina may provide further insights into rates of carbon and electron flux in methanogenic environments.

scholarly journals Electron Transfer Initiated Reactions Photoinduced by Pterins

Pteridines ◽  
2011 ◽  
Vol 22 (1) ◽  
pp. 111-119 ◽  
Author(s):  
Carolina Lorente ◽  
Gabriela Petroselli ◽  
M. Laura Dántola ◽  
Esther Oliveros ◽  
Andrés H. Thomas
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Redox Reactions ◽  
Type I ◽  
Biological Processes ◽  
Type Ii ◽  
Triplet Excited State ◽  
Oxygen Production ◽  
Production Type ◽  
Transfer Mechanisms

Abstract Interest in the photochemistry and photophysics of pterins has increased since the participation of this family of compounds in different photobiological processes has been suggested or demonstrated in recent decades. Pterins participate in relevant biological processes, such as metabolic redox reactions, and can photoinduce the oxidation of biomolecules through both electron transfer mechanisms (Type I) and singlet oxygen production (Type II). This article describes recent findings on electron transfer-initiated reactions photoinduced by the triplet excited state of pterins and connects them in the context of photosensitized processes of biological relevance.

Ground- and excited-state interactions of 2,7,12,17-tetraphenylporphycene with model target biomolecules for type-I photodynamic therapy

2009 ◽  
Vol 13 (01) ◽  
pp. 99-106 ◽  
Author(s):  
Noemí Rubio ◽  
Víctor Martínez-Junza ◽  
Jordi Estruga ◽  
José I. Borrell ◽  
Margarita Mora ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photodynamic Therapy ◽  
Excited State ◽  
Singlet Oxygen ◽  
Cell Lines ◽  
Mechanism Of Action ◽  
Photophysical Properties ◽  
Type I ◽  
Type Ii ◽  
Hydrophobic Compound

Biosubstrate-sensitizer binding is one of the factors that enhances the type-I mechanism over the type-II in the whole photodynamic process. 2,7,12,17-Tetraphenylporphycene (TPPo), a second-generation photosensitizer, is a hydrophobic compound with good photophysical properties for photodynamic therapy applications that has proved its ability for the photoinactivation of different cell lines. Nevertheless, little is known about its mechanism of action. This paper focuses on the study of the interaction/binding of TPPo with different model biomolecules that may favor the type-I mechanism in the overall photodynamic process, including nucleosides, proteins, and phospholipids. Compared with more hydrophilic photosensitizers, it is concluded that TPPo is more likely to undergo type-II (singlet oxygen) than type-I (electron transfer) photodynamic processes in biological environments.

scholarly journals Minireview: Regulation of Steroidogenesis by Electron Transfer

Endocrinology ◽  
2005 ◽  
Vol 146 (6) ◽  
pp. 2544-2550 ◽  
Author(s):  
Walter L. Miller
Keyword(s):  
Electron Transfer ◽  
Electron Flow ◽  
Cytochrome B5 ◽  
Serine Phosphorylation ◽  
Molar Ratio ◽  
Type I ◽  
Type Ii ◽  
Cytochrome P450 Enzymes ◽  
Redox Partners ◽  
P450 Enzyme

Abstract Cytochrome P450 enzymes catalyze the degradation of drugs and xenobiotics, but also catalyze a wide variety of biosynthetic processes, including most steps in steroidogenesis. The catalytic rate of a P450 enzyme is determined in large part by the rate of electron transfer from its redox partners. Type I P450 enzymes, found in mitochondria, receive electrons from reduced nicotinamide adenine dinucleotide (NADPH) via the intermediacy of two proteins—ferredoxin reductase (a flavoprotein) and ferredoxin (an iron/sulfur protein). Type I P450 enzymes include the cholesterol side-chain cleavage enzyme (P450scc), the two isozymes of 11-hydroxylase (P450c11β and P450c11AS), and several vitamin D-metabolizing enzymes. Disorders of these enzymes, but not of the two redox partners, have been described. Type II P450 enzymes, found in the endoplasmic reticulum, receive electrons from NADPH via P450 oxidoreductase (POR), which contains two flavin moieties. Steroidogenic Type II P450 enzymes include 17α-hydroxylase/17,20 lyase (P450c17), 21-hydroxylase (P450c21), and aromatase (P450aro). All P450 enzymes catalyze multiple reactions, but P450c17 appears to be unique in that the ratio of its activities is regulated at a posttranslational level. Three factors can increase the degree of 17,20 lyase activity relative to the 17α-hydroxylase activity by increasing electron flow from POR: a high molar ratio of POR to P450c17, serine phosphorylation of P450c17, and the presence of cytochrome b5, acting as an allosteric factor to promote the interaction of POR with P450c17. POR is required for the activity of all 50 human Type II P450 enzymes, and ablation of the Por gene in mice causes embryonic lethality. Nevertheless, mutation of the human POR gene is compatible with life, causing multiple steroidogenic defects and a skeletal dysplasia called Antley-Bixler syndrome.

scholarly journals Crystal structure of the ferredoxin reductase component of carbazole 1,9a-dioxygenase from Janthinobacterium sp. J3

2021 ◽  
Vol 77 (7) ◽  
Author(s):  
Yuji Ashikawa ◽  
Zui Fujimoto ◽  
Kengo Inoue ◽  
Hisakazu Yamane ◽  
Hideaki Nojiri
Keyword(s):  
Crystal Structure ◽  
Electron Transfer ◽  
Conformational Changes ◽  
Docking Simulation ◽  
Type I ◽  
Type Ii ◽  
Class Iii ◽  
Docking Simulations ◽  
Ferredoxin Reductase ◽  
C Terminus

Carbazole 1,9a-dioxygenase (CARDO), which consists of an oxygenase component and the electron-transport components ferredoxin (CARDO-F) and ferredoxin reductase (CARDO-R), is a Rieske nonheme iron oxygenase (RO). ROs are classified into five subclasses (IA, IB, IIA, IIB and III) based on their number of constituents and the nature of their redox centres. In this study, two types of crystal structure (type I and type II) were resolved of the class III CARDO-R from Janthinobacterium sp. J3 (CARDO-RJ3). Superimposition of the type I and type II structures revealed the absence of flavin adenine dinucleotide (FAD) in the type II structure along with significant conformational changes to the FAD-binding domain and the C-terminus, including movements to fill the space in which FAD had been located. Docking simulation of NADH into the FAD-bound form of CARDO-RJ3 suggested that shifts of the residues at the C-terminus caused the nicotinamide moiety to approach the N5 atom of FAD, which might facilitate electron transfer between the redox centres. Differences in domain arrangement were found compared with RO reductases from the ferredoxin–NADP reductase family, suggesting that these differences correspond to differences in the structures of their redox partners ferredoxin and terminal oxygenase. The results of docking simulations with the redox partner class III CARDO-F from Pseudomonas resinovorans CA10 suggested that complex formation suitable for efficient electron transfer is stabilized by electrostatic attraction and complementary shapes of the interacting regions.

Operation Everest II: adaptations in human skeletal muscle

1989 ◽  
Vol 66 (5) ◽  
pp. 2454-2461 ◽  
Author(s):  
H. J. Green ◽  
J. R. Sutton ◽  
A. Cymerman ◽  
P. M. Young ◽  
C. S. Houston
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Succinic Dehydrogenase ◽  
High Energy ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Type Ii ◽  
Cross Sectional ◽  
Distribution Type

Adaptations in skeletal muscle in response to progressive hypobaria were investigated in eight male subjects [maximal O2 uptake = 51.2 +/- 3.0 (SE) ml.kg-1.min-1] over 40 days of progressive decompression to the stimulated altitude of the summit of Mt. Everest. Samples of the vastus lateralis muscle extracted before decompression (SL-1), at 380 and 282 Torr, and on return to sea level (SL-2) indicated that maximal activities of enzymes representative of the citric acid cycle, beta-oxidation, glycogenolysis, glycolysis, glucose phosphorylation, and high-energy phosphate transfer were unchanged (P greater than 0.05) at 380 and 282 Torr over initial SL-1 values. After exposure to 282 Torr, however, representing an additional period of approximately 7 days, reductions (P less than 0.05) were noted in succinic dehydrogenase (21%), citrate synthetase (37%), and hexokinase (53%) between SL-2 and 380 Torr. No changes were found in the other enzymes. Capillarization as measured by the number of capillaries per cross-sectional area (CC/FA) was increased (P less than 0.05) in both type I (0.94 +/- 0.8 vs. 1.16 +/- 0.05) and type II (0.84 +/- 0.07 vs. 1.05 +/- 0.08) fibers between SL-1 and SL-2. This increase was mediated by a reduction in fiber area. No changes were found in fiber-type distribution (type I vs. type II). These findings do not support the hypothesis, at least in humans, that, at the level of the muscle cell, extreme hypobaric hypoxia elicits adaptations directed toward maximizing oxidative function.

scholarly journals Generation of High Current Densities in Geobacter sulfurreducens Lacking the Putative Gene for the PilB Pilus Assembly Motor

2021 ◽  
Author(s):  
Toshiyuki Ueki ◽  
David J. F. Walker ◽  
Kelly P. Nevin ◽  
Joy E. Ward ◽  
Trevor L. Woodard ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Geobacter Sulfurreducens ◽  
Metal Corrosion ◽  
Extracellular Electron Transfer ◽  
Renewable Electricity ◽  
Gene Deletions ◽  
Putative Gene ◽  
Content Type ◽  
Soils And Sediments ◽  
Current Densities

Geobacter sulfurreducens is a model microbe for the study of biogeochemically and technologically significant processes, such as the reduction of Fe(III) oxides in soils and sediments, bioelectrochemical applications that produce electric current from waste organic matter or drive useful processes with the consumption of renewable electricity, direct interspecies electron transfer in anaerobic digestors and methanogenic soils and sediments, and metal corrosion. Elucidating the phenotypes associated with gene deletions is an important strategy for determining the mechanisms for extracellular electron transfer in G. sulfurreducens .

scholarly journals Cytochromes in extracellular electron transfer in Geobacter

2021 ◽  
Author(s):  
Toshiyuki Ueki
Keyword(s):  
Electron Transfer ◽  
Critical Role ◽  
Geobacter Sulfurreducens ◽  
Electron Donors ◽  
Metal Corrosion ◽  
Extracellular Electron Transfer ◽  
Natural Environments ◽  
Anaerobic Digesters ◽  
Oxidation Reduction ◽  
Cellular Components

Extracellular electron transfer (EET) is an important biological process in microbial physiology as found in dissimilatory metal oxidation/reduction and interspecies electron transfer in syntrophy in natural environments. EET also plays a critical role in microorganisms relevant to environmental biotechnology in metal-contaminated areas, metal corrosion, bioelectrochemical systems, and anaerobic digesters. Geobacter species exist in a diversity of natural and artificial environments. One of the outstanding features of Geobacter species is the capability of direct EET with solid electron donors and acceptors including metals, electrodes, and other cells. Therefore, Geobacter species are pivotal in environmental biogeochemical cycles and biotechnology applications. Geobacter sulfurreducens, a representative Geobacter species, has been studied for the direct EET as a model microorganism. G. sulfurreducens employs electrically conductive pili (e-pili) and c-type cytochromes for the direct EET. The biological function and electronics applications of the e-pili have been reviewed recently and this review focuses on the cytochromes. Geobacter species have an unusually large number of cytochromes encoded in their genomes. Unlike most other microorganisms, Geobacter species localize multiple cytochromes in each subcellular fraction: outer membrane, periplasm, and inner membrane, as well as in the extracellular space, and differentially utilize these cytochromes for the EET with various electron donors and acceptors. Some of the cytochromes are functionally redundant. Thus, the EET in Geobacter is complicated. Geobacter coordinates the cytochromes with other cellular components in the elaborate EET system to flourish in the environment.

Γ-X-Γ electron transfer in mixed type I-type II GaAs/AlAs quantum well structures

1992 ◽  
Vol 83 (3) ◽  
pp. 245-248 ◽  
Author(s):  
J. Feldmann ◽  
M. Preis ◽  
E.O. Göbel ◽  
P. Dawson ◽  
C.T. Foxon ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Quantum Well ◽  
Mixed Type ◽  
Type I ◽  
Type Ii ◽  
Quantum Well Structures

scholarly journals Inorganic Salts and Antimicrobial Photodynamic Therapy: Mechanistic Conundrums?

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3190 ◽  
Author(s):  
Michael R. Hamblin ◽  
Heidi Abrahamse
Keyword(s):  
Electron Transfer ◽  
Titanium Dioxide ◽  
Singlet Oxygen ◽  
Potassium Thiocyanate ◽  
Molecular Iodine ◽  
Water Soluble ◽  
Inorganic Salts ◽  
Type I ◽  
Bacterial Cells ◽  
Type Ii

We have recently discovered that the photodynamic action of many different photosensitizers (PSs) can be dramatically potentiated by addition of a solution containing a range of different inorganic salts. Most of these studies have centered around antimicrobial photodynamic inactivation that kills Gram-negative and Gram-positive bacteria in suspension. Addition of non-toxic water-soluble salts during illumination can kill up to six additional logs of bacterial cells (one million-fold improvement). The PSs investigated range from those that undergo mainly Type I photochemical mechanisms (electron transfer to produce superoxide, hydrogen peroxide, and hydroxyl radicals), such as phenothiazinium dyes, fullerenes, and titanium dioxide, to those that are mainly Type II (energy transfer to produce singlet oxygen), such as porphyrins, and Rose Bengal. At one extreme of the salts is sodium azide, that quenches singlet oxygen but can produce azide radicals (presumed to be highly reactive) via electron transfer from photoexcited phenothiazinium dyes. Potassium iodide is oxidized to molecular iodine by both Type I and Type II PSs, but may also form reactive iodine species. Potassium bromide is oxidized to hypobromite, but only by titanium dioxide photocatalysis (Type I). Potassium thiocyanate appears to require a mixture of Type I and Type II photochemistry to first produce sulfite, that can then form the sulfur trioxide radical anion. Potassium selenocyanate can react with either Type I or Type II (or indeed with other oxidizing agents) to produce the semi-stable selenocyanogen (SCN)2. Finally, sodium nitrite may react with either Type I or Type II PSs to produce peroxynitrate (again, semi-stable) that can kill bacteria and nitrate tyrosine. Many of these salts (except azide) are non-toxic, and may be clinically applicable.

scholarly journals Radial head fractures in young, active patients

2020 ◽  
Vol 15 (4) ◽  
pp. 251-259
Author(s):  
Christopher G. Larsen ◽  
Michael J. Fitzgerald ◽  
Andrew S. Greenberg
Keyword(s):  
Radial Head ◽  
Young Patients ◽  
Elbow Dislocation ◽  
Early Mobilization ◽  
High Energy ◽  
Type I ◽  
Type Ii ◽  
Radial Head Fractures ◽  
Radial Head Arthroplasty ◽  
Active Patients

AbstractThe radial head is an important stabilizer of the elbow joint. Radial head fractures are commonly associated with additional injuries to the ligamentous structures of the elbow and can significantly compromise elbow stability. Young patients with radial head fractures are more likely to be male and present after a high-energy mechanism of injury. While not perfect, the Mason classification is the most commonly used classification system and can help to guide the management of radial head fractures. Type I fractures are nondisplaced or minimally displaced (less than 2 mm) and are treated nonoperatively with early mobilization. Type II fractures, which are displaced 2–5 mm, can be treated nonoperatively or with open reduction and internal fixation (ORIF). Type III fractures are comminuted and are most often treated with ORIF or with radial head arthroplasty (RHA). Treatment of fractures with an associated elbow dislocation (Mason type IV) is also with ORIF or RHA depending on the degree of comminution. For all of these injuries, assessment and treatment of associated ligamentous injuries are necessary in conjunction with treatment of the bony injury. Despite a significant body of literature available on radial head fractures, there is controversy regarding the optimal management of type II, III, and IV fractures, especially in young, active patients. Common complications following radial head fractures include stiffness, instability, and posttraumatic osteoarthritis; as such, these injuries can lead to significant disability in young, active patients if not managed appropriately.

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