Synthesis Of Flavins Research Articles

Mechanism underlying the sustained stimulatory effects of energization on biomethane recovery from food waste post-energization cessation

Microbial electrolysis cell-assisted anaerobic digestion represents a promising approach for enhancing methanogenesis. This study investigated the impact of varying energy levels followed by long-term open circuit on biogas recovery from food waste.The results demonstrated that a mild voltage of 0.4 V resulted in 61.7% increase in methane yield, with a methane composition reaching 78.89% vol and a remarkable reduction in digestion time by 8 days. Additionally, the facilitated effects remained after prolonged periods of open-circuit. In-depth study revealed that energization significantly enhanced organic hydrolysis, redox proteins secretion and sludge electro-activity. Microbial communities showed that the ever-present energization enriched the hydrolytic bacterium and electrophiles. Subsequent investigations also revealed the upgradation of enzyme-encoding genes associated with hydrolysis and the synthesis of flavin and its homologs (i.e. ribE, ssuE and nfrA2). These findings collectively demonstrated the enduring benefits of energization were linked to the enhanced hydrolysis and regulated mediator-mediated electron transfer pathway.

Mechanism of Cr(VI) bioreduction by Clostridium sp. LQ25 under Fe(III) reducing conditions

The Cr(VI) bioreduction has attracted widespread attention in the field of Cr(VI) pollution remediation due to its environmental friendliness. Further in-depth research on the reduction mechanisms is necessary to enhance the efficiency of Cr(VI) bioreduction. However, the limited research on Cr(VI) bioreduction mechanisms remains a bottleneck for the practical application of Cr(VI) reduction. In this study, The Cr(VI) reduction of strain LQ25 was significantly improved when Fe(III) was used as an electron acceptor, which increased by 1.6-fold maximum within the set Cr(VI) concentration range. Based on this, the electron transfer process of Cr(VI) reduction was analyzed using strain LQ25. Based on genomic data, flavin proteins were found to interact closely with electron transfer-related proteins using protein–protein interaction (PPi) analysis. Transcriptome analysis revealed that flavin synthesis genes (ribE, ribBA, and ribH) and electron transfer flavoprotein genes (fixA, etfA, fixB, and etfB) were significantly upregulated when Fe(III) was used as the electron acceptor. These results indicate that the fermentative dissimilatory Fe(III)-reducing bacterial strain LQ25 mainly uses flavin as an electron shuttle for electron transfer, which differs from the common use of cytochrome c in respiratory bacteria. These findings on the mechanism of Cr(VI) bioreduction provide technical support for improving the efficiency of Cr(VI) reduction which promote the practical application of Cr(VI) bioreduction in the field of Cr(VI) pollution remediation.

Engineering extracellular electron transfer to promote simultaneous brewing wastewater treatment and chromium reduction

Microbial fuel cell (MFC) technology has been developed for wastewater treatment in the anodic chamber, and heavy metal reduction in the cathodic chamber. However, the limited extracellular electron transfer (EET) rate of exoelectrogens remained a constraint for practical applications of MFCs. Here, a MFC system that used the electricity derived from anodic wastewater treatment to drive cathodic Cr6+ reduction was developed, which enabled an energy self-sustained approach to efficiently address Cr6+ contamination. This MFC system was achieved by screening exoelectrogens with a superior EET rate, promoting the exoelectrogenic EET rate, and constructing a conductive bio-anode. Firstly, Shewanella algae-L3 was screened from brewing wastewater acclimatized sludge, which generated power density of 566.83 mW m−2. Secondly, to facilitate EET rate, flavin synthesis gene operon ribADEHC was overexpressed in engineered S. algae-L3F to increase flavins biosynthesis, which promoted the power density to 1233.21 mW m−2. Thirdly, to facilitate interface electron transfer, carbon nanotube (CNT) was employed to construct a S. algae-L3F-CNT bio-anode, which further enhanced power density to 3112.98 mW m−2. Lastly, S. algae-L3F-CNT bio-anode was used to harvest electrical energy from brewing wastewater to drive cathodic Cr6+ reduction in MFC, realizing 71.43% anodic COD removal and 98.14% cathodic Cr6+ reduction. This study demonstrated that enhanced exoelectrogenic EET could facilitate cathodic Cr6+ reduction in MFC.

Genetic engineering biofilms insitu using ultrasound-mediated DNA delivery.

SummaryThe ability to directly modify native and established biofilms has enormous potential in understanding microbial ecology and application of biofilm in 'real‐world' systems. However, efficient genetic transformation of established biofilms at any scale remains challenging. In this study, we applied an ultrasound‐mediated DNA delivery (UDD) technique to introduce plasmid to established non‐competent biofilms in situ. Two different plasmids containing genes coding for superfolder green fluorescent protein (sfGFP) and the flavin synthesis pathway were introduced into established bacterial biofilms in microfluidic flow (transformation efficiency of 3.9 ± 0.3 × 10‐7 cells in biofilm) and microbial fuel cells (MFCs), respectively, both employing UDD. Gene expression and functional effects of genetically modified bacterial biofilms were observed, where some cells in UDD‐treated Pseudomonas putida UWC1 biofilms expressed sfGFP in flow cells and UDD‐treated Shewanella oneidensis MR‐1 biofilms generated significantly (P < 0.05) greater (61%) bioelectricity production (21.9 ± 1.2 µA cm−2) in MFC than a wild‐type control group (~ 13.6 ± 1.6 µA cm−2). The effects of UDD were amplified in subsequent growth under selection pressure due to antibiotic resistance and metabolism enhancement. UDD‐induced gene transfer on biofilms grown in both microbial flow cells and MFC systems was successfully demonstrated, with working volumes of 0.16 cm3 and 300 cm3, respectively, demonstrating a significant scale‐up in operating volume. This is the first study to report on a potentially scalable direct genetic engineering method for established non‐competent biofilms, which can be exploited in enhancing their capability towards environmental, industrial and medical applications.

Iron deficient Medicago scutellata grown in nutrient solution at high pH accumulates and secretes large amounts of flavins

Flavin synthesis and secretion is an integral part of the toolbox of root-borne Fe facilitators used by Strategy I species upon Fe deficiency. The Fe-deficiency responses of the wild legume Medicago scutellata grown in nutrient solution have been studied at two different pH values (5.5 and 7.5). Parameters studied include leaf chlorophyll, nutrient solution pH, concentrations and contents of micronutrients, flavin accumulation in roots, flavin export to the medium, and root ferric chelate reductase and acidification activities. Results show that M. scutellata behaves upon Fe deficiency as a Strategy I species, with a marked capacity for synthesizing flavins (riboflavin and three hydroxylated riboflavin derivatives), which becomes more intense at high pH. Results also show that this species is capable of exporting a large amount of flavins to the external medium, both at pH 5.5 and 7.5. This is the first report of a species having a major flavin secretion at pH 7.5, in contrast with the very low flavin secretion found in other flavin-producing species such as Beta vulgaris and M. truncatula. These results provide further support to the hypothesis that flavin secretion is relevant for Fe acquisition at high pH, and open the possibility to improve the Fe-efficiency responses in legumes of agronomic interest.

Two Modes of Riboflavin-Mediated Extracellular Electron Transfer in Geobacter uraniireducens.

Anaerobes respire extracellular electron acceptors by extracellular electron transfer (EET). It is widely recognized that flavins can act as electron shuttles to facilitate this process. Flavin synthesis genes are widely distributed in Geobacter species. However, the functions of flavins in the EET of Geobacter species are unclear. Here, we demonstrate that G. uraniireducens can secrete abundant riboflavin (up to 270 nM) to facilitate EET. When an electrode was used as the electron acceptor, the quick recovery of anodizing current after anolyte replacement and the electrochemical behavior of the G. uraniireducens biofilm characterized by differential pulse voltammetry suggest that the self-secreted riboflavin promoted EET by serving as bound redox cofactors for cytochromes. On the contrary, when Fe(III) oxide was the electron acceptor, free riboflavin acted as electron shuttle to mediate the reduction of Fe(III) oxide. The results demonstrate the flexibility of flavins in EET, suggesting that the properties of electron acceptors can affect the binding mode of extracellular flavins, and broaden the knowledge of the EET of Geobacter species.

Mutually Exclusive Alterations in Secondary Metabolism Are Critical for the Uptake of Insoluble Iron Compounds by Arabidopsis and Medicago truncatula

The generally low bioavailability of iron in aerobic soil systems forced plants to evolve sophisticated genetic strategies to improve the acquisition of iron from sparingly soluble and immobile iron pools. To distinguish between conserved and species-dependent components of such strategies, we analyzed iron deficiency-induced changes in the transcriptome of two model species, Arabidopsis (Arabidopsis thaliana) and Medicago truncatula. Transcriptional profiling by RNA sequencing revealed a massive up-regulation of genes coding for enzymes involved in riboflavin biosynthesis in M. truncatula and phenylpropanoid synthesis in Arabidopsis upon iron deficiency. Coexpression and promoter analysis indicated that the synthesis of flavins and phenylpropanoids is tightly linked to and putatively coregulated with other genes encoding proteins involved in iron uptake. We further provide evidence that the production and secretion of phenolic compounds is critical for the uptake of iron from sources with low bioavailability but dispensable under conditions where iron is readily available. In Arabidopsis, homozygous mutations in the Fe(II)- and 2-oxoglutarate-dependent dioxygenase family gene F6'H1 and defects in the expression of PLEIOTROPIC DRUG RESISTANCE9, encoding a putative efflux transporter for products from the phenylpropanoid pathway, compromised iron uptake from an iron source of low bioavailability. Both mutants were partially rescued when grown alongside wild-type Arabidopsis or M. truncatula seedlings, presumably by secreted phenolics and flavins. We concluded that production and secretion of compounds that facilitate the uptake of iron is an essential but poorly understood aspect of the reduction-based iron acquisition strategy, which is likely to contribute substantially to the efficiency of iron uptake in natural conditions.

Structure of the first representative of Pfam family PF04016 (DUF364) reveals enolase and Rossmann-like folds that combine to form a unique active site with a possible role in heavy-metal chelation.

The crystal structure of Dhaf4260 from Desulfitobacterium hafniense DCB-2 was determined by single-wavelength anomalous diffraction (SAD) to a resolution of 2.01 Å using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). This protein structure is the first representative of the PF04016 (DUF364) Pfam family and reveals a novel combination of two well known domains (an enolase N-terminal-like fold followed by a Rossmann-like domain). Structural and bioinformatic analyses reveal partial similarities to Rossmann-like methyltransferases, with residues from the enolase-like fold combining to form a unique active site that is likely to be involved in the condensation or hydrolysis of molecules implicated in the synthesis of flavins, pterins or other siderophores. The genome context of Dhaf4260 and homologs additionally supports a role in heavy-metal chelation.

Changes in the proteomic and metabolic profiles of Beta vulgaris root tips in response to iron deficiency and resupply.

BackgroundPlants grown under iron deficiency show different morphological, biochemical and physiological changes. These changes include, among others, the elicitation of different strategies to improve the acquisition of Fe from the rhizosphere, the adjustment of Fe homeostasis processes and a reorganization of carbohydrate metabolism. The application of modern techniques that allow the simultaneous and untargeted analysis of multiple proteins and metabolites can provide insight into multiple processes taking place in plants under Fe deficiency. The objective of this study was to characterize the changes induced in the root tip proteome and metabolome of sugar beet plants in response to Fe deficiency and resupply.ResultsRoot tip extract proteome maps were obtained by 2-D isoelectric focusing polyacrylamide gel electrophoresis, and approximately 140 spots were detected. Iron deficiency resulted in changes in the relative amounts of 61 polypeptides, and 22 of them were identified by mass spectrometry (MS). Metabolites in root tip extracts were analyzed by gas chromatography-MS, and more than 300 metabolites were resolved. Out of 77 identified metabolites, 26 changed significantly with Fe deficiency. Iron deficiency induced increases in the relative amounts of proteins and metabolites associated to glycolysis, tri-carboxylic acid cycle and anaerobic respiration, confirming previous studies. Furthermore, a protein not present in Fe-sufficient roots, dimethyl-8-ribityllumazine (DMRL) synthase, was present in high amounts in root tips from Fe-deficient sugar beet plants and gene transcript levels were higher in Fe-deficient root tips. Also, a marked increase in the relative amounts of the raffinose family of oligosaccharides (RFOs) was observed in Fe-deficient plants, and a further increase in these compounds occurred upon short term Fe resupply.ConclusionsThe increases in DMRL synthase and in RFO sugars were the major changes induced by Fe deficiency and resupply in root tips of sugar beet plants. Flavin synthesis could be involved in Fe uptake, whereas RFO sugars could be involved in the alleviation of oxidative stress, C trafficking or cell signalling. Our data also confirm the increase in proteins and metabolites related to carbohydrate metabolism and TCA cycle pathways.

ChemInform Abstract: Flavin Synthesis and Incorporation into Synthetic Peptides

ChemInform Abstract: Flavin Synthesis and Incorporation into Synthetic Peptides

A key enzyme for flavin synthesis is required for nitric oxide and reactive oxygen species production in disease resistance

A key enzyme for flavin synthesis is required for nitric oxide and reactive oxygen species production in disease resistance

A key enzyme for flavin synthesis is required for nitric oxide and reactive oxygen species production in disease resistance

Nitric oxide (NO) and reactive oxygen species (ROS) play key roles in plant immunity. However, the regulatory mechanisms of the production of these radicals are not fully understood. Hypersensitive response (HR) cell death requires the simultaneous and balanced production of NO and ROS. In this study we indentified NbRibAencoding a bifunctional enzyme, guanosine triphosphate cyclohydrolase II/3,4-dihydroxy-2-butanone-4-phosphate synthase, which participates in the biosynthesis of flavin, by screening genes related to mitogen-activated protein kinase-mediated cell death, using virus-induced gene silencing. Levels of endogenous riboflavin and its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are important prosthetic groups for several enzymes participating in redox reactions, decreased in NbRibA-silenced Nicotiana benthamiana. Silencing NbRibA compromised not only HR cell death, but also the NO and ROS production induced by INF1 elicitin and a constitutively active form of NbMEK2 (NbMEK2DD), and also induced high susceptibility to oomycete Phytophthora infestans and ascomycete Colletotrichum orbiculare. Compromised radical production and HR cell death induced by INF1 in NbRibA-silenced leaves were rescued by adding riboflavin, FMN or FAD. These results indicate that flavin biosynthesis participates in regulating NO and ROS production, and HR cell death.

Flavin synthesis and incorporation into synthetic peptides.

AbstractThere exists a hierarchical approach to the study of flavoprotein function in biology: investigation in natural systems (by far the most common) (1); using semisynthetic systems, pioneered by Kaiser (2,3), where the flavin is attached near to the active site of a natural enzyme and the flavin chemistry modifies the catalytic behavior of the enzyme; and in fully synthetic systems where the flavin is attached to novel chemical frameworks (4) or synthetic peptides (5–7). The focus of our research falls into the last category, as studies aimed at understanding the molecular basis of catalytic fitness in enzymes are often confounded by the sheer complexity of natural proteins. Using insights drawn from natural systems, we design and synthesize minimalistic structures that assemble the component peptides and prosthetic groups into a functional array. We term these working structures molecular maquettes. The peptide framework of choice is the well-characterized, robust, and structurally defined tetra α-helix bundle, which is a dimer of helix-loop-helix secondary structure motifs, that pack together to form a well defined hydrophobic core (8). To date, there has been much success with this approach, notably the incorporation of heme into tetra α-helix bundle proteins, via bis-histidine axial coordination to the porphyrin iron (9).KeywordsPotassium CyanidePorphyrin IronReactive ThiolLaser Desorption Mass SpectrometrySecondary Structure MotifThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

ChemInform Abstract: Synthesis of Flavins Bearing a Sulfur Functional Group and Their Catalytic Activities for Reduction of Disulfides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of flavins bearing a sulfur functional group and their catalytic activities for reduction of disulfides

AbstractBis‐flavins, each of which bears a disulfide linkage in the molecule, have been synthesized as model compounds for dihydronicotinamide dependent disulfide reductase. These flavins were found to be much better catalysts to promote the reduction of dibenzyl disulfide to α‐toluenethiol than 3‐methyllumiflavin.

ChemInform Abstract: Evidence for a Competing Condensation Reaction in the Alloxan Synthesis of Flavins: Synthesis and Crystal and Molecular Structures of 7‐Chloro‐8‐methylalloxazine and 7,10‐Dimethyl‐8‐[(2‐hydroxyethyl)thio]isoalloxazine.

AbstractThe reaction of the diamines obtained from (I) with alloxan (II) yields the isoalloxazines (III) accompanied by a minor product.

Evidence for a competing condensation reaction in the alloxan synthesis of flavins: synthesis and crystal and molecular structures of 7-chloro-8-methylalloxazine and 7,10-dimethyl-8-[(2-hydroxyethyl)thio]isoalloxazine

Evidence for a competing condensation reaction in the alloxan synthesis of flavins: synthesis and crystal and molecular structures of 7-chloro-8-methylalloxazine and 7,10-dimethyl-8-[(2-hydroxyethyl)thio]isoalloxazine

Importance of a competing condensation reaction in the alloxan synthesis of flavins

Importance of a competing condensation reaction in the alloxan synthesis of flavins

ChemInform Abstract: A SYNTHESIS OF FLAVINS BY NITROSATIVE CYCLIZATION OF 6‐(N‐ALKYLANILINO)URACILS WITH N‐NITROSODIMETHYLAMINEPHOSPHORUS OXYCHLORIDE MIXTURE

AbstractA Synthesis of Flavins by Nitrosative Cyclization of ö‐(N‐Alkylanilinomracils with N‐Nitrosodimethylamine‐Phosphorus Oxychloride Mixtures.

A Synthesis of Flavins by the Reaction of 6-(N-Alkylanilino)-5-nitrouracils with Diethyl Azodicarboxylate in the Presence of Base

A Synthesis of Flavins by the Reaction of 6-(N-Alkylanilino)-5-nitrouracils with Diethyl Azodicarboxylate in the Presence of Base