scholarly journals Sustained Photoevolution of Molecular Hydrogen in a Mutant of Synechocystis sp. Strain PCC 6803 Deficient in the Type I NADPH-Dehydrogenase Complex

2004 ◽  
Vol 186 (6) ◽  
pp. 1737-1746 ◽  
Author(s):  
Laurent Cournac ◽  
Geneviève Guedeney ◽  
Gilles Peltier ◽  
Paulette M. Vignais
Keyword(s):  
Photosynthetic Electron Transport ◽  
Type I ◽  
Adaptation Period ◽  
Hydrogen Metabolism ◽  
Whole Cells ◽  
Time Period ◽  
Nadph Dehydrogenase ◽  
Dehydrogenase Complex ◽  
Pcc 6803

ABSTRACT The interaction between hydrogen metabolism, respiration, and photosynthesis was studied in vivo in whole cells of Synechocystis sp. strain PCC 6803 by continuously monitoring the changes in gas concentrations (H2, CO2, and O2) with an online mass spectrometer. The in vivo activity of the bidirectional [NiFe]hydrogenase [H2:NAD(P) oxidoreductase], encoded by the hoxEFUYH genes, was also measured independently by the proton-deuterium (H-D) exchange reaction in the presence of D2. This technique allowed us to demonstrate that the hydrogenase was insensitive to light, was reversibly inactivated by O2, and could be quickly reactivated by NADH or NADPH (+H2). H2 was evolved by cells incubated anaerobically in the dark, after an adaptation period. This dark H2 evolution was enhanced by exogenously added glucose and resulted from the oxidation of NAD(P)H produced by fermentation reactions. Upon illumination, a short (less than 30-s) burst of H2 output was observed, followed by rapid H2 uptake and a concomitant decrease in CO2 concentration in the cyanobacterial cell suspension. Uptake of both H2 and CO2 was linked to photosynthetic electron transport in the thylakoids. In the ndhB mutant M55, which is defective in the type I NADPH-dehydrogenase complex (NDH-1) and produces only low amounts of O2 in the light, H2 uptake was negligible during dark-to-light transitions, allowing several minutes of continuous H2 production. A sustained rate of photoevolution of H2 corresponding to 6 μmol of H2 mg of chlorophyll−1 h−1 or 2 ml of H2 liter−1 h−1 was observed over a longer time period in the presence of glucose and was slightly enhanced by the addition of the O2 scavenger glucose oxidase. By the use of the inhibitors DCMU [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and DBMIB (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone), it was shown that two pathways of electron supply for H2 production operate in M55, namely photolysis of water at the level of photosystem II and carbohydrate-mediated reduction of the plastoquinone pool.

On the Mechanism of Benzoquinone Penetration and Photoreduction by Whole Cells

1971 ◽  
Vol 26 (6) ◽  
pp. 585-588 ◽  
Author(s):  
H. Gimmler ◽  
M. Avron
Keyword(s):  
Electron Transport ◽  
Cell Membrane ◽  
Photosynthetic Electron Transport ◽  
Electron Acceptors ◽  
Electron Donors ◽  
Porphyridium Cruentum ◽  
Whole Cells ◽  
Time Treatment ◽  
Short Time

Short time treatment of intact Porphyridium cruentum cells with benzoquinone results in changes of the cell membranes, which lead to a higher permeability. This increased permeability allows the measurements of photosynthetic electron transport reactions with various electron donors, ac. ceptors and mediators, which cannot enter untreated cells. The capacity of benzoquinone to act as a Hill - reagent in vivo is interpreted as due to a double action of this compound: changing the permeability of the cells by reacting with the cell membrane coupled with the ability of the unreacted molecules to serve as electron acceptors.

scholarly journals Topology and Boundaries of the Aerotaxis Receptor Aer in the Membrane of Escherichia coli

2006 ◽  
Vol 188 (3) ◽  
pp. 894-901 ◽  
Author(s):  
Divya N. Amin ◽  
Barry L. Taylor ◽  
Mark S. Johnson
Keyword(s):  
Escherichia Coli ◽  
Lateral Diffusion ◽  
Membrane Vesicles ◽  
Membrane Receptors ◽  
Disulfonic Acid ◽  
Type I ◽  
Membrane Anchor ◽  
Whole Cells ◽  
Membrane Spanning

ABSTRACT Escherichia coli chemoreceptors are type I membrane receptors that have a periplasmic sensing domain, a cytosolic signaling domain, and two transmembrane segments. The aerotaxis receptor, Aer, is different in that both its sensing and signaling regions are proposed to be cytosolic. This receptor has a 38-residue hydrophobic segment that is thought to form a membrane anchor. Most transmembrane prediction programs predict a single transmembrane-spanning segment, but such a topology is inconsistent with recent studies indicating that there is direct communication between the membrane flanking PAS and HAMP domains. We studied the overall topology and membrane boundaries of the Aer membrane anchor by a cysteine-scanning approach. The proximity of 48 cognate cysteine replacements in Aer dimers was determined in vivo by measuring the rate and extent of disulfide cross-linking after adding the oxidant copper phenanthroline, both at room temperature and to decrease lateral diffusion in the membrane, at 4°C. Membrane boundaries were identified in membrane vesicles using 5-iodoacetamidofluorescein and methoxy polyethylene glycol 5000 (mPEG). To map periplasmic residues, accessible cysteines were blocked in whole cells by pretreatment with 4-acetamido-4′-maleimidylstilbene-2, 2′ disulfonic acid before the cells were lysed in the presence of mPEG. The data were consistent with two membrane-spanning segments, separated by a short periplasmic loop. Although the membrane anchor contains a central proline residue that reaches the periplasm, its position was permissive to several amino acid and peptide replacements.

scholarly journals Inactivation of a Predicted Leader Peptidase Prevents Photoautotrophic Growth of Synechocystis sp. Strain PCC 6803

2005 ◽  
Vol 187 (9) ◽  
pp. 3071-3078 ◽  
Author(s):  
Maria Zhbanko ◽  
Vladislav Zinchenko ◽  
Michael Gutensohn ◽  
Angelika Schierhorn ◽  
Ralf Bernd Klösgen
Keyword(s):  
Photosynthetic Electron Transport ◽  
Kanamycin Resistance ◽  
Open Reading Frames ◽  
Type I ◽  
Signal Peptides ◽  
Photosynthetic Oxygen Evolution ◽  
Photoautotrophic Growth ◽  
Photosynthetic Machinery ◽  
Leader Peptidase ◽  
Pcc 6803

ABSTRACT To establish the role of the two putative type I leader peptidases (LepB1 and LepB2) encoded in the genome of the cyanobacterium Synechocystis sp. strain PCC 6803, we generated independent knockout mutants for both genes by introducing kanamycin resistance cassettes into the two open reading frames (sll0716 [lepB1] and slr1377 [lepB2], respectively). Although the insertion was successful in both instances, it was not possible to select homozygous mutant cells for lepB2, suggesting that the function of this gene is essential for cell viability. In contrast, LepB1 is apparently essential only for photoautotrophic growth, because homozygous lepB1::Kmr cells could be propagated under heterotrophic conditions. They were even capable to some extent of photosynthetic oxygen evolution. However, the photosynthetic activity decreased gradually with extended incubation in the light and was particularly affected by high light intensities. Both features were indicative of photooxidative damage, which was probably caused by inefficient replacement of damaged components of the photosynthetic machinery due to the lack of a leader peptidase removing the signal peptides from photosynthetic precursor proteins. Indeed, processing of the PsbO precursor polypeptide to the corresponding mature protein was significantly affected in the mutant, and reduced amounts of other proteins that are synthesized as precursors with signal peptides accumulated in the cells. These results strongly suggest that LepB1 is important for removal of the signal peptides after membrane transport of the components of the photosynthetic machinery, which in turn is a prerequisite for the biogenesis of a functional photosynthetic electron transport chain.

scholarly journals A type I interferon response defines a conserved microglial state required for effective phagocytosis

2021 ◽  
Author(s):  
Leah C Dorman ◽  
Phi T Nguyen ◽  
Caroline C Escoubas ◽  
Ilia D Vainchtein ◽  
Yinghong Xiao ◽  
...  
Keyword(s):  
Type I Interferon ◽  
Meta Analysis ◽  
Transcriptional Profiling ◽  
Innate Immune ◽  
Interferon Response ◽  
Type I ◽  
Whole Cells ◽  
Microglial Phagocytosis ◽  
The Brain

Microglia, the innate immune cells of the brain, are exquisitely sensitive to dynamic changes in the brain environment. We used single cell RNA sequencing to define glial responses in the early postnatal somatosensory cortex after partial whisker lesion, revealing transcriptomic shifts in both astrocytes and microglia during the resulting topographic remapping. The most distinct change was the emergence of a type I interferon (IFN-I) responsive microglia population that was rare in the resting cortex but expanded 20-fold after whisker deprivation. The top gene candidate in this cluster, Ifitm3, marked a conserved but transient subset of microglia that were in the process of phagocytosing whole cells. IFITM3 protein identified this subset in vivo, where it was enriched in early microglial phagosomes. Loss of canonical IFN-I signaling in Ifnar1-/- animals resulted in abnormal 'bubble' microglia with deficient phagolysosomal processing. In a meta-analysis of transcriptomes, we identified the IFN-I signature in microglia across a range of pathologies. We identified phagocytic IFITM3+ microglia in two murine disease models: SARS-CoV-2 infection and Alzheimer's Disease. These data reveal the potential of transcriptional profiling after defined perturbation to elicit transient microglial states, and identify a novel role for IFN-I signaling in regulating microglial phagocytosis.

scholarly journals In Vivo Role of Catalase-Peroxidase inSynechocystis sp. Strain PCC 6803

1999 ◽  
Vol 181 (6) ◽  
pp. 1875-1882 ◽  
Author(s):  
Martin Tichy ◽  
Wim Vermaas
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Protective Role ◽  
Scavenging Activity ◽  
Wild Type ◽  
Gene Coding ◽  
In The Wild ◽  
Catalase Peroxidase ◽  
Pcc 6803

ABSTRACT The katG gene coding for the only catalase-peroxidase in the cyanobacterium Synechocystis sp. strain PCC 6803 was deleted in this organism. Although the rate of H2O2 decomposition was about 30 times lower in the ΔkatG mutant than in the wild type, the strain had a normal phenotype and its doubling time as well as its resistance to H2O2 and methyl viologen were indistinguishable from those of the wild type. The residual H2O2-scavenging capacity was more than sufficient to deal with the rate of H2O2production by the cell, estimated to be less than 1% of the maximum rate of photosynthetic electron transport in vivo. We propose that catalase-peroxidase has a protective role against environmental H2O2 generated by algae or bacteria in the ecosystem (for example, in mats). This protective role is most apparent at a high cell density of the cyanobacterium. The residual H2O2-scavenging activity in the ΔkatG mutant was a light-dependent peroxidase activity. However, neither glutathione peroxidase nor ascorbate peroxidase accounted for a significant part of this H2O2-scavenging activity. When a small thiol such as dithiothreitol was added to the medium, the rate of H2O2 decomposition in the ΔkatG mutant increased more than 10-fold, indicating that a thiol-specific peroxidase, for which thioredoxin may be the physiological electron donor, is present. Oxidized thioredoxin is likely to be reduced again by photosynthetic electron transport. Therefore, under laboratory conditions, there are only two enzymatic mechanisms for H2O2 decomposition present inSynechocystis sp. strain PCC 6803. One is catalyzed by a catalase-peroxidase, and the other is catalyzed by thiol-specific peroxidase.

Effects of Preloading of Stannous Compounds on the Distribution of 99mTc-Pertechnetate

1977 ◽  
Vol 16 (01) ◽  
pp. 26-29 ◽  
Author(s):  
D. D. Greenberg ◽  
P. Som ◽  
G. E. Meinken ◽  
D. F. Sacker ◽  
H. L. Atkins ◽  
...  
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Plasma Ratio ◽  
99Mtc Pertechnetate ◽  
Time Period ◽  
Stannous Ion ◽  
Distribution Studies

Summary 99mTc-pertechnetate distribution studies were performed in rabbits and mice following pretreatment between 5—336 hours with various routinely used stannous complexes (HSA, MAA, GHT, DTPA, PYPs) containing different amounts of Sn++ (0.17 —15.0 μ mg/kg). Beyond a concentration of 0.26 mg/kg of Sn++ an alteration in 99mTc-pertechnetate distribution was observed. The red blood cell was found to be the most prominent target. An in-vivo reduction of 99mTc-pertechnetate apparently occurred by the presence of stannous ion within the red blood cell. Preloading time period between 5—24 hours did not alter the uptake of RBC/plasma ratio. Beyond that period it decreased slowly and still persisted up to 2 weeks following pretreatment. RBC/ plasma ratio of 99mTcO4 - increased with increased Sn++ content of various commercially available pharmaceutical kits.

Peculiarities of the course of type I allergic reactions in patients with blood diseases

2020 ◽  
pp. 40-50
Author(s):  
A. Nikitina
Keyword(s):  
Search Engines ◽  
Anaphylactic Shock ◽  
Type I ◽  
Allergic Reactions ◽  
Common Cause ◽  
Blood Diseases ◽  
Treatment Regimens ◽  
Modern Methods

Analysis of literature data presented in search engines — Elibrary, PubMed, Cochrane — concerning the risk of developing type I allergic reactions in patients with blood diseases is presented. It is shown that the most common cause of type I allergic reactions is drugs included in the treatment regimens of this category of patients. The article presents statistics on the increase in the number of drug allergies leading to cases of anaphylactic shock in patients with blood diseases. Modern methods for the diagnosis of type I allergic reactions in vivo and in vitro are considered.

scholarly journals Collagen-Based Electrospun Materials for Tissue Engineering: A Systematic Review

2021 ◽  
Vol 8 (3) ◽  
pp. 39
Author(s):  
Britani N. Blackstone ◽  
Summer C. Gallentine ◽  
Heather M. Powell
Keyword(s):  
Systematic Review ◽  
Tissue Engineering ◽  
Collagen Type I ◽  
The Body ◽  
Pool Data ◽  
Type I ◽  
High Concentrations ◽  
Increased Strength

Collagen is a key component of the extracellular matrix (ECM) in organs and tissues throughout the body and is used for many tissue engineering applications. Electrospinning of collagen can produce scaffolds in a wide variety of shapes, fiber diameters and porosities to match that of the native ECM. This systematic review aims to pool data from available manuscripts on electrospun collagen and tissue engineering to provide insight into the connection between source material, solvent, crosslinking method and functional outcomes. D-banding was most often observed in electrospun collagen formed using collagen type I isolated from calfskin, often isolated within the laboratory, with short solution solubilization times. All physical and chemical methods of crosslinking utilized imparted resistance to degradation and increased strength. Cytotoxicity was observed at high concentrations of crosslinking agents and when abbreviated rinsing protocols were utilized. Collagen and collagen-based scaffolds were capable of forming engineered tissues in vitro and in vivo with high similarity to the native structures.

scholarly journals Development of stabilized dual growth factor-loaded hyaluronate collagen dressing matrix

2021 ◽  
Vol 12 ◽  
pp. 204173142199975
Author(s):  
Jihyun Kim ◽  
Kyoung-Mi Lee ◽  
Seung Hwan Han ◽  
Eun Ae Ko ◽  
Dong Suk Yoon ◽  
...  
Keyword(s):  
Wound Healing ◽  
Growth Factor ◽  
Type I ◽  
Diabetic Mice ◽  
Patients With Diabetes ◽  
Diabetic Wound Healing ◽  
Epidermal Growth ◽  
Wound Healing Effect ◽  
Growth Factor Production

Patients with diabetes experience impaired growth factor production such as epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), and they are reportedly involved in wound healing processes. Here, we report dual growth factor-loaded hyaluronate collagen dressing (Dual-HCD) matrix, using different ratios of the concentration of stabilized growth factors—stabilized-EGF (S-EGF) and stabilized-bFGF (S-bFGF). At first, the optimal concentration ratio of S-EGF to S-bFGF in the Dual-HCD matrix is determined to be 1:2 in type I diabetic mice. This Dual-HCD matrix does not cause cytotoxicity and can be used in vivo. The wound-healing effect of this matrix is confirmed in type II diabetic mice. Dual HCD enhances angiogenesis which promotes wound healing and thus, it shows a significantly greater synergistic effect than the HCD matrix loaded with a single growth factor. Overall, we conclude that the Dual-HCD matrix represents an effective therapeutic agent for impaired diabetic wound healing.

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