scholarly journals Ferredoxin:NAD+Oxidoreductase of Thermoanaerobacterium saccharolyticum and Its Role in Ethanol Formation

2016 ◽  
Vol 82 (24) ◽  
pp. 7134-7141 ◽  
Author(s):  
Liang Tian ◽  
Jonathan Lo ◽  
Xiongjun Shao ◽  
Tianyong Zheng ◽  
Daniel G. Olson ◽  
...  
Keyword(s):  
Ethanol Production ◽  
Redox Balance ◽  
Wild Type ◽  
Anaerobic Microorganism ◽  
Content Type ◽  
Ethanol Formation ◽  
Thermoanaerobacterium Saccharolyticum ◽  
Different Strains ◽  
Electron Carriers

ABSTRACTFerredoxin:NAD+oxidoreductase (NADH-FNOR) catalyzes the transfer of electrons from reduced ferredoxin to NAD+. This enzyme has been hypothesized to be the main enzyme responsible for ferredoxin oxidization in the NADH-based ethanol pathway inThermoanaerobacterium saccharolyticum; however, the corresponding gene has not yet been identified. Here, we identified the Tsac_1705 protein as a candidate FNOR based on the homology of its functional domains. We then confirmed its activityin vitrowith a ferredoxin-based FNOR assay. To determine its role in metabolism, thetsac_1705gene was deleted in different strains ofT. saccharolyticum. In wild-typeT. saccharolyticum, deletion oftsac_1705resulted in a 75% loss of NADH-FNOR activity, which indicated that Tsac_1705 is the main NADH-FNOR inT.saccharolyticum. When both NADH- and NADPH-linked FNOR genes were deleted, the ethanol titer decreased and the ratio of ethanol to acetate approached unity, indicative of the absence of FNOR activity. Finally, we tested the effect of heterologous expression of Tsac_1705 inClostridium thermocellumand found improvements in both the titer and the yield of ethanol.IMPORTANCERedox balance plays a crucial role in many metabolic engineering strategies. Ferredoxins are widely used as electron carriers for anaerobic microorganism and plants. This study identified the gene responsible for electron transfer from ferredoxin to NAD+, a key reaction in the ethanol production pathway of this organism and many other metabolic pathways. Identification of this gene is an important step in transferring the ethanol production ability of this organism to other organisms.

scholarly journals High Ethanol Titers from Cellulose by Using Metabolically Engineered Thermophilic, Anaerobic Microbes

2011 ◽  
Vol 77 (23) ◽  
pp. 8288-8294 ◽  
Author(s):  
D. Aaron Argyros ◽  
Shital A. Tripathi ◽  
Trisha F. Barrett ◽  
Stephen R. Rogers ◽  
Lawrence F. Feinberg ◽  
...  
Keyword(s):  
Ethanol Production ◽  
Wild Type Strain ◽  
Ethanol Yield ◽  
Fold Increase ◽  
Substantial Improvement ◽  
Wild Type ◽  
Content Type ◽  
Thermoanaerobacterium Saccharolyticum ◽  
Lactic Acids ◽  
High Ethanol

ABSTRACTThis work describes novel genetic tools for use inClostridium thermocellumthat allow creation of unmarked mutations while using a replicating plasmid. The strategy employed counter-selections developed from the nativeC. thermocellum hptgene and theThermoanaerobacterium saccharolyticum tdkgene and was used to delete the genes for both lactate dehydrogenase (Ldh) and phosphotransacetylase (Pta). The ΔldhΔptamutant was evolved for 2,000 h, resulting in a stable strain with 40:1 ethanol selectivity and a 4.2-fold increase in ethanol yield over the wild-type strain. Ethanol production from cellulose was investigated with an engineered coculture of organic acid-deficient engineered strains of bothC. thermocellumandT. saccharolyticum. Fermentation of 92 g/liter Avicel by this coculture resulted in 38 g/liter ethanol, with acetic and lactic acids below detection limits, in 146 h. These results demonstrate that ethanol production by thermophilic, cellulolytic microbes is amenable to substantial improvement by metabolic engineering.

scholarly journals The Bifunctional Alcohol and Aldehyde Dehydrogenase Gene,adhE, Is Necessary for Ethanol Production in Clostridium thermocellum and Thermoanaerobacterium saccharolyticum

2015 ◽  
Vol 197 (8) ◽  
pp. 1386-1393 ◽  
Author(s):  
Jonathan Lo ◽  
Tianyong Zheng ◽  
Shuen Hon ◽  
Daniel G. Olson ◽  
Lee R. Lynd
Keyword(s):  
Ethanol Production ◽  
Aldehyde Dehydrogenase ◽  
Clostridium Thermocellum ◽  
Deletion Strain ◽  
Aldh Activity ◽  
Content Type ◽  
Ethanol Formation ◽  
Cell Extracts ◽  
Thermoanaerobacterium Saccharolyticum ◽  
Dehydrogenase Gene

ABSTRACTThermoanaerobacterium saccharolyticumandClostridium thermocellumare anaerobic thermophilic bacteria being investigated for their ability to produce biofuels from plant biomass. The bifunctional alcohol and aldehyde dehydrogenase gene,adhE, is present in these bacteria and has been known to be important for ethanol formation in other anaerobic alcohol producers. This study explores the inactivation of theadhEgene inC. thermocellumandT. saccharolyticum. Deletion ofadhEreduced ethanol production by >95% in bothT. saccharolyticumandC. thermocellum, confirming thatadhEis necessary for ethanol formation in both organisms. In bothadhEdeletion strains, fermentation products shifted from ethanol to lactate production and resulted in lower cell density and longer time to reach maximal cell density. InT. saccharolyticum, theadhEdeletion strain lost >85% of alcohol dehydrogenase (ADH) activity. Aldehyde dehydrogenase (ALDH) activity did not appear to be affected, although ALDH activity was low in cell extracts. Adding ubiquinone-0 to the ALDH assay increased activity in theT. saccharolyticumparent strain but did not increase activity in theadhEdeletion strain, suggesting that ALDH activity was inhibited. InC. thermocellum, theadhEdeletion strain lost >90% of ALDH and ADH activity in cell extracts. TheC. thermocellumadhEdeletion strain contained a point mutation in the lactate dehydrogenase gene, which appears to deregulate its activation by fructose 1,6-bisphosphate, leading to constitutive activation of lactate dehydrogenase.IMPORTANCEThermoanaerobacterium saccharolyticumandClostridium thermocellumare bacteria that have been investigated for their ability to produce biofuels from plant biomass. They have been engineered to produce higher yields of ethanol, yet questions remain about the enzymes responsible for ethanol formation in these bacteria. The genomes of these bacteria encode multiple predicted aldehyde and alcohol dehydrogenases which could be responsible for alcohol formation. This study explores the inactivation ofadhE, a gene encoding a bifunctional alcohol and aldehyde dehydrogenase. Deletion ofadhEreduced ethanol production by >95% in bothT. saccharolyticumandC. thermocellum, confirming thatadhEis necessary for ethanol formation in both organisms. In strains withoutadhE, we note changes in biochemical activity, product formation, and growth.

scholarly journals Mutations in fbiD (Rv2983) as a Novel Determinant of Resistance to Pretomanid and Delamanid in Mycobacterium tuberculosis

2020 ◽  
Vol 65 (1) ◽  
pp. e01948-20
Author(s):  
Dalin Rifat ◽  
Si-Yang Li ◽  
Thomas Ioerger ◽  
Keshav Shah ◽  
Jean-Philippe Lanoix ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Evidence ◽  
Clinical Samples ◽  
Loss Of Function ◽  
Wild Type ◽  
Content Type ◽  
Solid Media ◽  
High Level ◽  
Level Resistance

ABSTRACTThe nitroimidazole prodrugs delamanid and pretomanid comprise one of only two new antimicrobial classes approved to treat tuberculosis (TB) in 50 years. Prior in vitro studies suggest a relatively low barrier to nitroimidazole resistance in Mycobacterium tuberculosis, but clinical evidence is limited to date. We selected pretomanid-resistant M. tuberculosis mutants in two mouse models of TB using a range of pretomanid doses. The frequency of spontaneous resistance was approximately 10−5 CFU. Whole-genome sequencing of 161 resistant isolates from 47 mice revealed 99 unique mutations, of which 91% occurred in 1 of 5 genes previously associated with nitroimidazole activation and resistance, namely, fbiC (56%), fbiA (15%), ddn (12%), fgd (4%), and fbiB (4%). Nearly all mutations were unique to a single mouse and not previously identified. The remaining 9% of resistant mutants harbored mutations in Rv2983 (fbiD), a gene not previously associated with nitroimidazole resistance but recently shown to be a guanylyltransferase necessary for cofactor F420 synthesis. Most mutants exhibited high-level resistance to pretomanid and delamanid, although Rv2983 and fbiB mutants exhibited high-level pretomanid resistance but relatively small changes in delamanid susceptibility. Complementing an Rv2983 mutant with wild-type Rv2983 restored susceptibility to pretomanid and delamanid. By quantifying intracellular F420 and its precursor Fo in overexpressing and loss-of-function mutants, we provide further evidence that Rv2983 is necessary for F420 biosynthesis. Finally, Rv2983 mutants and other F420H2-deficient mutants displayed hypersusceptibility to some antibiotics and to concentrations of malachite green found in solid media used to isolate and propagate mycobacteria from clinical samples.

scholarly journals Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

2014 ◽  
Vol 80 (8) ◽  
pp. 2410-2416 ◽  
Author(s):  
Areen Banerjee ◽  
Ching Leang ◽  
Toshiyuki Ueki ◽  
Kelly P. Nevin ◽  
Derek R. Lovley
Keyword(s):  
Ethanol Production ◽  
Genetic Manipulation ◽  
Electron Flow ◽  
Model Organism ◽  
Inducible Expression ◽  
Carbon Flow ◽  
Wild Type ◽  
Content Type ◽  
Microbial Electrosynthesis ◽  
Clostridium Ljungdahlii

ABSTRACTThe development of tools for genetic manipulation ofClostridium ljungdahliihas increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox forC. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported forClostridium perfringens, was investigated. The plasmid pAH2, originally developed forC. perfringenswith agusAreporter gene, functioned as an effective lactose-inducible system inC. ljungdahlii. Lactose induction ofC. ljungdahliicontaining pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression ofadhE130-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression ofadhE1in a strain in whichadhE1and theadhE1homologadhE2had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression ofadhE2similarly failed to restore ethanol production, suggesting thatadhE1is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.

scholarly journals Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

2012 ◽  
Vol 56 (8) ◽  
pp. 4146-4153 ◽  
Author(s):  
Zaid Al-Nakeeb ◽  
Ajay Sudan ◽  
Adam R. Jeans ◽  
Lea Gregson ◽  
Joanne Goodwin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Therapeutic Strategies ◽  
Wild Type ◽  
Content Type ◽  
Exposure Response ◽  
Prevention And Treatment ◽  
Resistant Infection ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

scholarly journals Abrogation of Neuraminidase Reduces Biofilm Formation, Capsule Biosynthesis, and Virulence of Porphyromonas gingivalis

2011 ◽  
Vol 80 (1) ◽  
pp. 3-13 ◽  
Author(s):  
Chen Li ◽  
Kurniyati ◽  
Bo Hu ◽  
Jiang Bian ◽  
Jianlan Sun ◽  
...  
Keyword(s):  
Porphyromonas Gingivalis ◽  
Biofilm Formation ◽  
Adult Population ◽  
Transcriptional Analysis ◽  
Wild Type ◽  
Content Type ◽  
Multiple Organs ◽  
Biochemical Analyses

ABSTRACTThe oral bacteriumPorphyromonas gingivalisis a key etiological agent of human periodontitis, a prevalent chronic disease that affects up to 80% of the adult population worldwide.P. gingivalisexhibits neuraminidase activity. However, the enzyme responsible for this activity, its biochemical features, and its role in the physiology and virulence ofP. gingivalisremain elusive. In this report, we found thatP. gingivalisencodes a neuraminidase, PG0352 (SiaPg). Transcriptional analysis showed thatPG0352is monocistronic and is regulated by a sigma70-like promoter. Biochemical analyses demonstrated that SiaPgis an exo-α-neuraminidase that cleaves glycosidic-linked sialic acids. Cryoelectron microscopy and tomography analyses revealed that thePG0352deletion mutant (ΔPG352) failed to produce an intact capsule layer. Compared to the wild type,in vitrostudies showed that ΔPG352 formed less biofilm and was less resistant to killing by the host complement.In vivostudies showed that while the wild type caused a spreading type of infection that affected multiple organs and all infected mice were killed, ΔPG352 only caused localized infection and all animals survived. Taken together, these results demonstrate that SiaPgis an important virulence factor that contributes to the biofilm formation, capsule biosynthesis, and pathogenicity ofP. gingivalis, and it can potentially serve as a new target for developing therapeutic agents againstP. gingivalisinfection.

scholarly journals Antifungal Activity of SCY-078 and Standard Antifungal Agents against 178 Clinical Isolates of Resistant and Susceptible Candida Species

2017 ◽  
Vol 61 (11) ◽  
Author(s):  
Wiley A. Schell ◽  
A. M. Jones ◽  
Katyna Borroto-Esoda ◽  
Barbara D. Alexander
Keyword(s):  
Candida Glabrata ◽  
Antifungal Agents ◽  
Candida Parapsilosis ◽  
Candida Krusei ◽  
Wild Type ◽  
Content Type ◽  
Clinical Resistance ◽  
Excellent Activity ◽  
Candida Lusitaniae

ABSTRACT SCY-078 in vitro activity was determined for 178 isolates of resistant or susceptible Candida albicans, Candida dubliniensis, Candida glabrata, Candida krusei, Candida lusitaniae, and Candida parapsilosis, including 44 Candida isolates with known genotypic (FKS1 or FKS2 mutations), phenotypic, or clinical resistance to echinocandins. Results were compared to those for anidulafungin, caspofungin, micafungin, fluconazole, and voriconazole. SCY-078 was shown to have excellent activity against both wild-type isolates and echinocandin- and azole-resistant isolates of Candida species.

scholarly journals Genetic regulation, biochemical properties and physiological importance of arginase from Sinorhizobium meliloti

Microbiology ◽  
2020 ◽  
Vol 166 (5) ◽  
pp. 484-497 ◽  
Author(s):  
Alejandra Arteaga Ide ◽  
Victor M. Hernández ◽  
Liliana Medina-Aparicio ◽  
Edson Carcamo-Noriega ◽  
Lourdes Girard ◽  
...  
Keyword(s):  
Type Species ◽  
Sinorhizobium Meliloti ◽  
Arginase Activity ◽  
Wild Type ◽  
Mobility Shift ◽  
Content Type ◽  
Link Type ◽  
Arginine Catabolism

In bacteria, l-arginine is a precursor of various metabolites and can serve as a source of carbon and/or nitrogen. Arginine catabolism by arginase, which hydrolyzes arginine to l-ornithine and urea, is common in nature but has not been studied in symbiotic nitrogen-fixing rhizobia. The genome of the alfalfa microsymbiont Sinorhizobium meliloti 1021 has two genes annotated as arginases, argI1 (smc03091) and argI2 (sma1711). Biochemical assays with purified ArgI1 and ArgI2 (as 6His-Sumo-tagged proteins) showed that only ArgI1 had detectable arginase activity. A 1021 argI1 null mutant lacked arginase activity and grew at a drastically reduced rate with arginine as sole nitrogen source. Wild-type growth and arginase activity were restored in the argI1 mutant genetically complemented with a genomically integrated argI1 gene. In the wild-type, arginase activity and argI1 transcription were induced several fold by exogenous arginine. ArgI1 purified as a 6His-Sumo-tagged protein had its highest in vitro enzymatic activity at pH 7.5 with Ni2+ as cofactor. The enzyme was also active with Mn2+ and Co2+, both of which gave the enzyme the highest activities at a more alkaline pH. The 6His-Sumo-ArgI1 comprised three identical subunits based on the migration of the urea-dissociated protein in a native polyacrylamide gel. A Lrp-like regulator (smc03092) divergently transcribed from argI1 was required for arginase induction by arginine or ornithine. This regulator was designated ArgIR. Electrophoretic mobility shift assays showed that purified ArgIR bound to the argI1 promoter in a region preceding the predicted argI1 transcriptional start. Our results indicate that ArgI1 is the sole arginase in S. meliloti , that it contributes substantially to arginine catabolism in vivo and that argI1 induction by arginine is dependent on ArgIR.

scholarly journals EUCAST Determination of Olorofim (F901318) Susceptibility of Mold Species, Method Validation, and MICs

2018 ◽  
Vol 62 (8) ◽  
Author(s):  
Karin Meinike Jørgensen ◽  
Karen M. T. Astvad ◽  
Rasmus Krøger Hare ◽  
Maiken Cavling Arendrup
Keyword(s):  
Fusarium Solani ◽  
Susceptibility Testing ◽  
Wild Type ◽  
Preparation Methods ◽  
Content Type ◽  
Microtiter Plates ◽  
Upper Limits ◽  
Limited Variation

ABSTRACT Olorofim is a novel antifungal agent with in vitro activity against Aspergillus and some other molds. Here, we addressed technical aspects for EUCAST olorofim testing and generated contemporary MIC data. EUCAST E.Def 9.3.1 testing was performed comparing two plate preparation methods (serial dilution in medium [serial plates] versus predilution in DMSO [ISO plates]), two lots of olorofim, visual (visual-MIC) versus spectrophotometer (spec-MIC) reading, and four polystyrene plates using 34 to 53 Aspergillus isolates from five genera. Subsequently, olorofim MICs were compared to itraconazole, voriconazole, posaconazole, and amphotericin B MICs for 298 clinical mold isolates (2016 to 2017). Wild-type upper limits (WT-UL) were determined following EUCAST principles for epidemiologic cutoff value (ECOFF) setting. Olorofim median MICs comparing serial plates and ISO plates were identical (25/36 [69%]) or one dilution apart (11/36 [31%]). Interperson agreement for visual-MICs was 92% to 94%/100% for ≤1/≤2 dilutions, respectively. The visual-MIC values across tested microtiter plates and olorofim lots revealed only discrete differences (≤1 dilution lower for treated plates). No single spec-MIC criterion was applicable to all species. Olorofim MICs were low against 275 Aspergillus species isolates (modal MIC, 0.06 mg/liter; MIC range, < 0.004 to 0.25 mg/liter) and three dermatophytes (MICs 0.03 to 0.06 mg/liter). MICs against Fusarium were diverse, with full inhibition of F. proliferatum (MIC, 0.016), 50% growth inhibition of Fusarium solani at 1 to 2 mg/liter, and no inhibition of F. dimerum. Olorofim displayed potent in vitro activity against most mold isolates and was associated with limited variation in EUCAST susceptibility testing.

A novel bifunctional aldehyde/alcohol dehydrogenase mediating ethanol formation from acetyl-CoA in hyperthermophiles

2020 ◽  
Author(s):  
Qiang Wang ◽  
Chong Sha ◽  
Hongcheng Wang ◽  
Kesen Ma ◽  
Juergen Wiegel ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Alcohol Dehydrogenase ◽  
Ethanol Production ◽  
Ethanol Fermentation ◽  
Cellulosic Ethanol ◽  
Decarboxylase Activity ◽  
Aldh Activity ◽  
Acetyl Coa ◽  
Ethanol Formation

Abstract Background: Hyperthermophilic fermentation at temperatures above 80 °C allows in situ product removal to mitigate the ethanol toxicity, and reduces microbial contamination without autoclaving/cooling of feedstock. Many species of Thermotoga grow at temperatures up to 90 °C, and have enzymes to degrade and utilize lignocelluloses, which provide advantages for achieving consolidated processes of cellulosic ethanol production. However, no CoA-dependent aldehyde dehydrogenase (CoA-Aldh) from any hyperthermophiles has been documented in literature so far. The pyruvate ferredoxin oxidoreductases from hyperthermophiles have pyruvate decarboxylase activity, which convert about 2% and 98% of pyruvate to acetaldehyde and acetyl-CoA (ac-CoA), respectively. Acetyl-CoA can be converted to acetic acid, if there is no CoA-Aldh to convert ac-CoA to acetaldehyde and further to ethanol. Therefore, the current study aimed to identify and characterize a CoA-Aldh activity that mediates ethanol fermentation in hyperthermophiles.Results: In Thermotoga neapolitana (Tne), a hyperthermophilic iron-acetaldehyde/alcohol dehydrogenase (Fe-AAdh) was, for the first time, revealed to catalyze the ac-CoA reduction to form ethanol via an acetaldehyde intermediate, while the annotated aldh gene in Tne genome only encodes a CoA-independent Aldh that oxidizes aldehyde to acetic acid. Three other Tne alcohol dehydrogenases (Adh) exhibited specific physiological roles in ethanol formation and consumption: Fe-Adh2 mainly catalyzed the reduction of acetaldehyde to produce ethanol, and Fe-Adh1 showed significant activities only under extreme conditions, while Zn-Adh showed special activity in ethanol oxidation. In the in vitro formation of ethanol from ac-CoA, a strong synergy was observed between Fe-Adh1 and Fe-AAdh. The Fe-AAdh gene is highly conserved in Thermotoga spp. and in Pyrococus sp., which is probably responsible for ethanol metabolism in hyperthermophiles.Conclusions: Hyperthermophilic Thermotoga spp. are excellent candidates for biosynthesis of cellulosic ethanol fermentation strains. The finding of a novel hyperthermophilic CoA-Aldh activity of Tne Fe-AAdh revealed the existence of a hyperthermophilic fermentation pathway from ac-CoA to ethanol, which offers a basic frame for in vitro synthesis of a highly active AAdh for effective ethanol fermentation pathway in hyperthermophiles, which is a key element for the approach to the consolidated processes of cellulosic ethanol production.

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