Respiratory Electron Transport Chain Research Articles

Effects of Five Dietary Carbohydrate Sources on Growth, Glucose Metabolism, Antioxidant Capacity and Immunity of Largemouth Bass (Micropterus salmoides).

This study investigated the effects of glucose (GLU), tapioca starch (TS), gelatinized tapioca starch (GTS), potato starch (PS) and gelatinized potato starch (GPS) on growth and physiological responses in juvenile largemouth bass Micropterus salmoides. After 8 weeks, fish fed with starch diets had better weight gain and growth rates. Counts of red blood cells and monocytes were increased in the PS and GPS groups, compared to GLU group. Contents of serum triglyceride and total cholesterol were markedly elevated in the TS, PS and GPS groups. There were lower levels of serum glucose, insulin and cholecystokinin, and higher agouti-related peptide contents in the PS group compared to GLU group. PS and GPS could enhance glycolysis and TCA cycle by increasing their enzyme activities and transcriptional levels. Additionally, starch sources markedly heightened mRNA levels of key genes involved in the respiratory electron transport chain. Additionally, elevated mRNA levels of key antioxidant genes were shown in the TS and GTS groups. Moreover, TS and PS could promote immunity by upregulating transcriptional levels of the complement system, lysozyme and hepcidin. Taken together, starch exhibited better growth via increasing glycolysis and TCA cycle compared with GLU, and PS could improve antioxidant and immune capacities in largemouth bass.

Functional Differentiation of the Succinate Dehydrogenase Subunit SdhC Governs the Sensitivity to SDHI Fungicides, ROS Homeostasis, and Pathogenicity in Fusarium asiaticum.

Succinate dehydrogenase (SDH) is an integral component of the tricarboxylic acid cycle (TCA) and respiratory electron transport chain (ETC), targeted by succinate dehydrogenase inhibitors (SDHIs). Fusarium asiaticum is a prominent phytopathogen causing Fusarium head blight (FHB) on wheat. Here, we characterized the functions of the FaSdhA, FaSdhB, FaSdhC1, FaSdhC2, and FaSdhD subunits. Deletion of FaSdhA, FaSdhB, or FaSdhD resulted in significant growth defects in F. asiaticum. The FaSdhC1 or FaSdhC2 deletion mutants exhibited substantial reductions in fungal growth, conidiation, virulence, and reactive oxygen species (ROS). The FaSdhC1 expression was significantly induced by pydiflumetofen (PYD). The ΔFaSdhC1 mutant displayed hypersensitivity to SDHIs, whereas the ΔFaSdhC2 mutant exhibited resistance against most SDHIs. The transmembrane domains of FaSdhC1 are essential for regulating mycelial growth, virulence, and sensitivity to SDHIs. These findings provided valuable insights into how the two SdhC paralogues regulated the functional integrity of SDH, ROS homeostasis, and the sensitivity to SDHIs in phytopathogenic fungi.

Co-exposure of polystyrene nanoplastics and copper induces development toxicity and intestinal mitochondrial dysfunction in vivo and in vitro

Nanoplastics (NPs) have raised concerns about the combined toxicity to living organisms due to their ability to adsorb heavy metals. There is still uncertainty, however, whether NPs combined with heavy metals exert adverse effects on intestinal microenvironment, especially the intestinal cells and microbiota. Herein, the combined effects of 500 nm spherical-shaped polystyrene nanoplastics (PSNPs) and copper ions (Cu2+) on intestinal cells and gut microbiota were assessed using HCT-116 cells and zebrafish models. The combined exposure of PSNPs (10 mg/L) and Cu2+ (0.5 mg/L) induced more severer hatching interference of zebrafish embryos, deformation, and mortality. In larval stage, PSNPs (10 mg/L) accumulated and carried more Cu2+ in the gastrointestinal tract (GIT) of zebrafish after co-exposure for 5 days. Excessive neutrophil recruitment and oxidative stress in GIT of zebrafish larvae were observed. The mechanism of the combined toxicity was revealed by transmission electron microscopy (TEM) showing the injuries of GIT, transcriptome and 16S rDNA gene sequencing showing the toxicity pathways, including oxidative phosphorylation and respiratory electron transport chain, as well as microbial community analysis showing the induced microbiota dysbiosis. In vitro tests using HCT-116 cells showed that PSNPs (10 mg/L) and Cu2+ (0.5 mg/L) increased cell death while decreasing ATP concentration and mitochondrial membrane potential after 48 h exposure. These findings may provide new insights into the combined toxicity of nanoplastics and heavy metals in the intestinal microenvironment.

The prognostic and antitumor roles of key genes of ferroptosis in liver hepatocellular cancer and stomach adenocarcinoma.

Liver hepatocellular cancer (LIHC) and stomach adenocarcinoma (STAD) are common malignancies with high lethal ratios worldwide. Great progress has been achieved by using diverse therapeutic strategies; however, these diseases still have an unfavourable prognosis. Ferroptosis inducer drugs, unlike apoptosis-related drugs, can overcome the resistance to cancer therapy caused by traditional chemicals. However, the relationship between overall survival (OS) and ferroptosis-related genes, as well as the mechanisms involved, are largely unclear. The expression levels of AIFM2, GPX4, ACSL4, FTH1, NOS1, and PTGS2 in LIHC and STAD were obtained from UALCAN. The correlations of OS with these gene expression levels were obtained using the Kaplan-Meier Plotter database. The OS associated with genetic mutations of those genes compared to that of unchanged genes was analysed using the TIMER website. GO and KEGG enrichment analyses of ferroptosis-related genes and their coexpressed genes in LIHC and STAD were conducted using the STRING and DAVID databases. The relationship of PTGS2 and ACSL4 to immune cell infiltration was analysed using the TIMER website. The viability and GPX5 expression levels in LIHC cells treated with RSL3 and As2O3 were detected by MTT methods and western blotting, respectively. Our results showed that GPX4, FTH1 and AIFM2 were overexpressed in LIHC and STAD. High levels of GPX4, FTH1 and AIFM2 were prominently correlated with better prognosis in LIHC. However, GPX and FTH1 in STAD did not show significant correlations with OS. AIFM2 in STAD had the opposite trend with OS compared with that in LIHC. Moreover, a high mutation rate of these genes (35.74%) was also observed in LIHC patients, and genetic mutation of these genes was correlated with shorter OS. In contrast, the genetic mutation of these genes did not change OS in STAD. Enrichment analysis showed that the respiratory electron transport chain, cell chemotaxis and T-cell migration were related to ferroptosis. ASCL4 and PTGS2 coexpressed with cytokines associated with immune cell infiltration. Compared to RSL3 or As2O3 alone, As2O3 plus RSL3 significantly inhibited the growth of Huh7 cells. GPX4 was downregulated to an undetectable level when in combination with RSL3. Our results indicated that ferroptosis-related genes might play an important role in LIHC and STAD and might be risk factors for overall survival in LIHC and STAD.

Enhancing citric acid tolerance of Acetobacter tropicalis using chemical and physical mutagenesis and adaptive evolution to improve the quality of lemon fruit vinegar.

The high concentration of citric acid in lemons limits the production of lemon fruit vinegar because it inhibits the metabolism of acetic acid bacteria and reduces the utilization of raw materials. This study aimed to enhance the citric acid tolerance of Acetobacter tropicalis by using complex mutagenesis and adaptive laboratory evolution (ALE) and improving the quality of lemon fruit vinegar. After mutagenesis and ALE, A. tropicalis JY-135 grew well under 40g/L citric acid, and it showed high physiological activity and excellent fermentation performance under high concentrations of citric acid. The survival rate and ATP content of JY-135 were 15.27 and 9.30 times higher than that of the original strain J-2736. In the fermentation of lemon fruit vinegar, the acid production and the number of aroma-active compounds were 1.61-fold and 2.17-fold than J-2736. In addition, we found that citric acid tolerance of JY-135 is related to the respiratory electron-transport chain and the tricarboxylic acid (TCA) cycle. This work is of great significance for the production of high-quality lemon fruit vinegar and the enrichment of seed resources of acetic acid bacteria.

Aberrant activated Notch1 promotes prostate enlargement driven by androgen signaling via disrupting mitochondrial function in mouse

The prostate is a vital accessory gonad in the mammalian male reproductive system. With the ever-increasing proportion of the population over 60 years of age worldwide, the incidence of prostate diseases, such as benign prostatic hyperplasia (BPH) and prostate cancer (PCa), is on the rise and is gradually becoming a significant medical problem globally. The notch signaling pathway is essential in regulating prostate early development. However, the potential regulatory mechanism of Notch signaling in prostatic enlargement and hyperplasia remains unclear. In this study, we proved that overactivation of Notch1 signaling in mouse prostatic epithelial cells (OEx) led to prostatic enlargement via enhancing proliferation and inhibiting apoptosis of prostatic epithelial cells. Further study showed that N1ICD/RBPJ directly up-regulated the androgen receptor (AR) and enhanced prostatic sensitivity to androgens. Hyper-proliferation was not found in orchidectomized OEx mice without androgen supply but was observed after Dihydrotestosterone (DHT) supplementation. Our data showed that the number of mitochondrion in prostatic epithelial cells of OEx mice was increased, but the mitochondrial function was impaired, and the essential activity of the mitochondrial respiratory electron transport chain was significantly weakened. Disordered mitochondrial number and metabolic function further resulted in excessive accumulation of reactive oxygen species (ROS). Importantly, anti-oxidant N-Acetyl-L-Cysteine (NAC) therapy could alleviate prostatic hyperplasia caused by the over-activation of Notch1 signaling. Furthermore, we observed the incremental Notch signaling activity in progenitor-like club cells in the scRNA-seq data set of human BPH patients. Moreover, the increased number of TROP2+ progenitors and Club cells was also confirmed in our OEx mice. In conclusion, our study revealed that over-activated Notch1 signaling induces prostatic enlargement by increasing androgen receptor sensitivity, disrupting cellular mitochondrial metabolism, increasing ROS, and a higher number of progenitor cells, all of which can be effectively rescued by NAC treatment.

Abstract 7062: CIP2A enhances mitochondrial respiratory electron transport chain complexes and induces lung cancer in vivo

Abstract Identification of oncogenes that can induce cancer in vivo is critical to elucidation of tumorigenesis and development of targeted therapies. Here, we reported for the first time that forced ectopic expression of CIP2A, the cancerous inhibitor of protein phosphatase 2A (PP2A), in lung tissues induced lung adenocarcinoma in mice. CIP2A upregulated the transcription and translation of mitochondrial DNA (mtDNA), and increases the enzymatic activity of mitochondrial electron transport chain (ETC) complex IV and V, thus enhancing the function of mitochondria and promoting the level of oxidative phosphorylation in tumors. CIP2A inhibited the binding of PP2A-B56α to FOXO3a, leading to the enhancement of the phosphorylation level of FOXO3a. The phosphorylated FOXO3a then translocated into the mitochondrion, and acted as a transcription factor to regulate CIP2A-mediated metabolic reprogramming in cancer cells. We found that oxidative phosphorylation inhibitors effectively inhibited CIP2A-induced cell proliferation. In non-small cell lung cancer, CIP2A level in tumor tissues was positively associated with the level of mtDNA. Our results indicated that CIP2A is able to induce lung adenocarcinoma in mice and has a critical role in mitochondrial oxidative phosphorylation, and represents a promising therapeutic target for non-small cell lung cancer. Competing interests: The authors declare no competing interests. Citation Format: Fu-Ying Yang, Di Wang, Li-Jun liang, Gui-Zhen Wang, Guang-Biao Zhou. CIP2A enhances mitochondrial respiratory electron transport chain complexes and induces lung cancer in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7062.

The RsfSR two-component system regulates SigF function by monitoring the state of the respiratory electron transport chain in Mycobacterium smegmatis

In Mycobacterium smegmatis, the transcriptional activity of the alternative sigma factor SigF is post-translationally regulated by the partner switching system consisting of SigF, the anti-SigF RsbW1, and three anti-SigF antagonists (RsfA, RsfB, and RsbW3). We previously demonstrated that expression of the SigF regulon is strongly induced in the Δaa3 mutant of M. smegmatis lacking the aa3 cytochrome c oxidase, the major terminal oxidase in the respiratory electron transport chain (ETC). Here we identified and characterized the RsfSR two-component system involved in regulating the phosphorylation state of the major anti-SigF antagonist RsfB. RsfS (MSMEG_6130) is a histidine kinase with the CHASE3 (Cyclase/Histidine kinase-associated Sensing Extracellular 3) domain at its N-terminus, and RsfR (MSMEG_6131) is a receiver domain-containing PP2C (Protein Phosphatase 2C)-type phosphatase that can dephosphorylate phosphorylated RsfB. We demonstrated that phosphorylation of RsfR on Asp74 by RsfS reduces the phosphatase activity of RsfR toward phosphorylated RsfB and that the cellular abundance of the active unphosphorylated RsfB is increased in the Δaa3 mutant relative to the wild-type strain. We also demonstrated that the RsfSR two-component system is required for induction of the SigF regulon under respiration-inhibitory conditions such as inactivation of the cytochrome bcc1 complex and aa3 cytochrome c oxidase, as well as hypoxia, electron donor-limiting, high ionic strength, and low pH conditions. Collectively, our results reveal a key regulatory element involved in regulating the SigF signaling system by monitoring the state of the respiratory ETC.

Cryo-EM structure of HQNO-bound Alternative Complex III from the anoxygenic phototrophic bacterium Chloroflexus aurantiacus.

Alternative complex III (ACIII) couples quinol oxidation and electron acceptor reduction with potential transmembrane proton translocation. It is compositionally and structurally different from the cytochrome bc1/b6f complexes, but functionally replaces these enzymes in the photosynthetic and/or respiratory electron transport chains (ETCs) of many bacteria. However, the true compositions and architectures of ACIIIs remain unclear, as do their structural and functional relevance in mediating the ETCs. We here determined cryogenic electron microscopy structures of photosynthetic ACIII isolated from Chloroflexus aurantiacus (CaACIIIp), in apo-form and in complexed form bound to a menadiol analog 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Besides six canonical subunits (ActABCDEF), the structures revealed conformations of two previously unresolved subunits, ActG and I, which contributed to the complex stability. We also elucidated the structural basis of menaquinol oxidation and subsequent electron transfer along the [3Fe-4S]-6 hemes wire to its periplasmic electron acceptors, using electron paramagnetic resonance (EPR), spectroelectrochemistry, enzymatic analyses and molecular dynamics (MD) simulations. A unique insertion loop in ActE was shown to function in determining the binding specificity of CaACIIIp for downstream electron acceptors. This study broadens our understanding of the structural diversity and molecular evolution of ACIIIs, enabling further investigation of the (mena)quinol oxidoreductases evolved coupling mechanism in bacterial energy conservation.

Evaluation of SYP-34773's resistance risk and its impact on the activity of mitochondrial respiratory electron transport chain complex I in Phytophthora litchii.

SYP-34773 is a low-toxicity pyrimidine amine compound, which was synthesized by modifying the lead compound diflumetorim. Previous literature has shown that it can strongly inhibit the mycelial growth of several important plant pathogens, including Phytophthora litchii. However, the resistance risk of SYP-34773 has not been reported for P. litchii. The mean effective concentration (EC50 ) value of SYP-34773 against the mycelial growth of 111 P. litchii isolates was 0.108 ± 0.008 μg mL-1 , which can be used as the baseline sensitivity for SYP-34773 resistance detection in the future. Six mutants were obtained from two parental strain through fungicide induction, whose resistance factors fell between 194- and 687-fold, with stability. Results regarding mycelial growth, sporangial production, sporangial germination, zoospore release, cystspore germination, and pathogenicity showed that the mutants' compound fitness index values were significantly lower than those of their parental isolate. Furthermore, there was no cross-resistance between SYP-34773 and diflumetorim in P. litchii. Significant inhibition of the mitochondrial complex I enzyme activity in two wild-type P. litchii isolates, but not in mutants, was observed upon treatment with SYP-34773. The resistance risk of SYP-34773 in P. litchii is moderate, and resistance management strategies should be adopted in field use. SYP-34773 is a mitochondrial complex I inhibitor, and SYP-34773-resistant P. litchii isolates did not show cross-resistance against diflumetorim. © 2023 Society of Chemical Industry.

Structural determinants of mitochondrial STAT3 targeting and function

Signal transducer and activator of transcription (STAT) 3 has been found within mitochondria in addition to its canonical role of shuttling between cytoplasm and nucleus during cytokine signaling. Mitochondrial STAT3 has been implicated in modulation of cellular metabolism, largely through effects on the respiratory electron transport chain. However, the structural requirements underlying mitochondrial targeting and function have remained unclear. Here, we show that mitochondrial STAT3 partitions between mitochondrial compartments defined by differential detergent solubility, suggesting that mitochondrial STAT3 is membrane associated. The majority of STAT3 was found in an SDS soluble fraction copurifying with respiratory chain proteins, including numerous components of the complex I NADH dehydrogenase, while a minor component was found with proteins of the mitochondrial translation machinery. Mitochondrial targeting of STAT3 required the amino-terminal domain, and an internal linker domain motif also directed mitochondrial translocation. However, neither the phosphorylation of serine 727 nor the presence of mitochondrial DNA was required for the mitochondrial localization of STAT3. Two cysteine residues in the STAT3 SH2 domain, which have been previously suggested to be targets for protein palmitoylation, were also not required for mitochondrial translocation, but were required for its function as an enhancer of complex I activity. These structural determinants of STAT3 mitochondrial targeting and function provide potential therapeutic targets for disrupting the activity of mitochondrial STAT3 in diseases such as cancer.

Physiological and transcriptomic analyses provide preliminary insights into the autotoxicity of Lilium brownii.

Lilium brownii F. E. Brown ex Miellez var. viridulum Baker (Longya lily) is a variety of Lilium brownii F.E. Br. ex Miellez. We used HS-SPME and GC-MS to screened the tissues of L. brownii roots, stems, bulbs, and leaves and obtained 2,4-DTBP as an autotoxic substance for subsequent analysis. 2,4-DTBP was highly autotoxic in some treatment groups. Based on changes in physiological indicators, we carried out transcriptomic analysis to investigate the mechanisms of autotoxicity of substances on L. brownii and obtained 188,505 Unigenes. GO and KEGG enrichment analyses showed that L. brownii responded differently to different concentrations and treatment times of 2,4-DTBP. We observed significant changes in genes associated with ROS, phytohormones, and MAPK signaling cascades. 2,4-DTBP affects chloroplasts, the integrity of the respiratory electron transport chain, and ribosomes, causing L. brownii autotoxicity. Our findings provide a practical genomic resource for future research on L. brownii autotoxicity and evidence for the mechanism of action of autotoxic substances.

High expression of NADH Ubiquinone Oxidoreductase Subunit B11 induces catheter-associated venous thrombosis on continuous blood purification.

Venous thromboembolism (VTE) is a common vascular disease of venous return disorders, including deep venous thrombosis and pulmonary embolism (PE), with high morbidity and high mortality. However, the relationship between oxidative phosphorylation and NDUFB11 and venous thromboembolism is still unclear. The venous thromboembolism datasets GSE48000 and GSE19151 were downloaded, and the differentially expressed Genes (DEGs) were screened. The protein-protein interaction (PPI) network was constructed. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used for functional enrichment analysis. The comparative toxicogenomics database (CTD) was used to identify the diseases most associated with the core genes. TargetScan was used to screen miRNA regulating central DEGs. Western blotting (WB) experiment and real-time quantitative PCR (RT-qPCR) experiment were performed. A total of 500 DEGs were identified. GO analysis showed that the DEGs were mainly enriched in ATP synthesis coupled electron transport, respiratory electron transport chain, cytoplasm, enzyme binding, nonalcoholic fatty liver disease, oxidative phosphorylation, and Alzheimer disease. Enrichment items were similar to GO and KEGG enrichment items of DEGs. The result of CTD showed that 12 genes (RPS24, FAU, RPLP0, RPS15A, RPS29, RPL9, RPL31, RPL27, NDUFB11, RPL34, COX7B, RPS27L) were associated with chemical and drug-induced liver injury, inflammation, kidney disease, and congenital pure red cell aplasia. WB and RT-qPCR results showed that the expression levels of 12 genes in venous thromboembolism were higher than normal whole blood tissue samples. NDUFB11 is highly expressed in catheter-related venous thromboembolism during continuous blood purification, which may lead to the formation of venous thrombosis through oxidative phosphorylation pathway.

A Novel Variant of the CYCS Gene Alters Apoptosis of Megakaryocytes in a Family with Thrombocytopenia

Introduction: In humans, the CYCS gene encodes Cytochrome c, a protein important for the respiratory electron transport chain in mitochondria and for apoptosis. The clinical features of known CYCS pathogenic variants have been reported to be linked with thrombocytopenia. Herein, we present a novel variant of CYCS gene found in a Greek family with thrombocytopenia and its effects in apoptosis. Patients: A 1 year-old patient (Patient 1) with moderate thrombocytopenia (platelets=42×10 3/μl, MCV=76fL) and reported family history of thrombocytopenia has been referred to “Aghia Sophia” Children's Hospital for Whole Exome Sequencing. A 28 year-old female (Patient 2) and her 52 year-old mother (Patient 3) have been referred to the Hematology Unit of Attikon University General Hospital due to chronic grade III thrombocytopenia with no evidence of hemorrhagic diathesis. A thorough hematological examination of these two adult patients, including peripheral blood - bone marrow morphology, functional platelet assays, marrow cytogenetics and NGS, has detected no abnormalities. A trial of gamma globulin and steroids has been performed with no platelet response. Family history revealed more family members with thrombocytopenia on the side of the mother. In total five family members with moderate thrombocytopenia and four members with normal platelet counts have been tested with Sanger sequencing. Methods: Whole Exome Sequencing has been performed on Patient 1 and Sanger sequencing/Segregation analysis in nine members of the family. Florescence Activated Cell Sorting (FACS) has been performed in bone marrow mononuclear cells of Patient 2, Patient 3 and eight healthy controls. The antibody panel used included PE anti-human CD42a, PE/Cyanine7 anti-human CD42b, APC/Cyanine7 anti-human CD31 and APC anti-human CD71 antibodies. The stained cells (immature and mature megakaryocytes) have been sorted on a FACS Aria IIu (BD Biosciences) and subsequently stained with Annexin V FITC/7-AAD, to allow the detection of early-stage and late-stage cell apoptosis. Results: A novel missense variant of unknown significance (VUS) in the CYCS gene ( CYCS(NM_018947.6):c.292T>C (p.Tyr98His)) has been identified using whole exome sequencing in Patient 1. Segregation analysis of the variant in the family showed complete genotype-phenotype correlation (five family members with moderate thrombocytopenia, four members with normal platelet counts) (Figure 1A). The variant has been found to be heterozygous in all family members tested. To investigate the functional role of the novel variant and its potential link to the thrombocytopenic phenotype FACS has been performed to isolate immature and mature megakaryocytes (positive for CD42a, CD42b, CD31 and medium positive for CD71) followed by analysis of apoptosis in Patient 2, Patient 3 and healthy controls. Cells undergoing early apoptosis have stained positive for Annexin V, while late apoptotic cells have been characterized by positive staining for both Annexin V and 7-AAD. Our preliminary results show increased numbers of apoptotic cells in the patients compared to controls (Figure 1B). We are currently validating this finding by inserting the CYCS gene variant in the megakaryocytic cell line DAMI, using the CRISPR-Cas9 system. Conclusions: A novel missense variant in the CYCS gene has been identified in a Greek family with thrombocytopenia, where the phenotype is mild with isolated thrombocytopenia, no hemorrhagic diathesis and no any other organ dysfunction. FACS analysis of two variant carriers has revealed increased apoptosis of immature and mature megakaryocytes compared to controls. This study will delineate the molecular mechanisms underlying thrombocytopenia in the family and it is expected that the findings will be translated in novel therapeutic management strategies for patients with thrombocytopenic related pathologies. Figure 1. A novel missense variant in the CYCS gene increases apoptosis in megakaryocytes. A. Segregation analysis of the family: Thrombocytopenia phenotype is marked with pink and carriers of the variant with dot. B. FACS analysis of megakaryocytes stained with Annexin V/7-AAD: Percentages of total apoptotic cells (early and late) are shown on the chart. Values represent mean ± SE, N=2 for patients and N=8 for controls (three FACS experiments have been performed for patient 2, two for patient 3 and one for each control).

Transforming liquid flow fuel cells to controllable reactors for highly-efficient oxidation of 5-hydroxymethylfurfural to 2, 5-furandicarboxylic acid at low temperature

Highly-efficient oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) at low temperature with air as the oxidant is still challenging. Herein, inspired by the respiratory electron transport chain (ETC) of living cells mediated by electron carriers, we constructed artificial ETCs and transformed liquid flow fuel cells (LFFCs) to flexible reactors for efficient oxidation of HMF to produce FDCA under mild conditions. This LFFC reactor employed an electrodeposition modified nickel foam as an anode to promote HMF oxidation and (VO2)2SO4 as a cathode electron carrier to facilitate the electron transfer to air. The reaction rate could be easily controlled by selecting the anode catalyst, adjusting the external loading and changing the cathodic electron carrier or oxidants. A maximal power density of 44.9 mW cm−2 at room temperature was achieved, while for FDCA production, short-circuit condition was preferred to achieve quick transfer of electrons. For a single batch operation with 0.1 M initial HMF, FDCA yield reached 97.1%. By fed-batch operation, FDCA concentration reached 144.5 g L–1 with a total yield of 96%. Ni2+/Ni3+ redox couple was the active species mediating the electron transfer, while both experimental and DFT calculation results indicated that HMFCA pathway was the preferred reaction mechanism.

Respiration is essential for aerobic growth of Zymomonas mobilis ZM4.

Zymomonas mobilis is an alpha-proteobacterium that is a promising platform for industrial scale production of biofuels due to its efficient ethanol fermentation and low biomass generation. Z. mobilis is aerotolerant and encodes a complete respiratory electron transport chain, but the benefit of respiration for growth in oxic conditions has never been confirmed, despite decades of research. Growth and ethanol production of wild-type Z. mobilis is poor in oxic conditions indicating that it does not benefit from oxidative phosphorylation. Additionally, in previous studies, aerobic growth improved significantly when respiratory genes were disrupted (ndh) or acquired point mutations (cydA and cydB), even if respiration was significantly reduced by these changes. Here, we obtained clean deletions of respiratory genes ndh and cydAB, individually and in combination, and showed, for the first time, that deletion of cydAB completely inhibited O2 respiration and dramatically reduced growth in oxic conditions. Both respiration and aerobic growth were restored by expressing a heterologous, water-forming NADH oxidase, noxE. Oxygen can have many negative effects, including formation of reactive oxygen species (ROS) or directly inactivating oxygen sensitive enzymes. Our results suggest that the effect of molecular oxygen on enzymes had a greater negative impact on Z. mobilis than formation of ROS. This result shows that the main role of the electron transport chain in Z. mobilis is reducing the intracellular concentration of molecular oxygen, helping to explain why it is beneficial for Z. mobilis to use electron transport chain complexes that have little capacity to contribute to oxidative phosphorylation. IMPORTANCE A key to producing next-generation biofuels is to engineer microbes that efficiently convert non-food materials into drop-in fuels, and to engineer microbes effectively, we must understand their metabolism thoroughly. Zymomonas mobilis is a bacterium that is a promising candidate biofuel producer, but its metabolism remains poorly understood, especially its metabolism when exposed to oxygen. Although Z. mobilis respires with oxygen, its aerobic growth is poor, and disruption of genes related to respiration counterintuitively improves aerobic growth. This unusual result has sparked decades of research and debate regarding the function of respiration in Z. mobilis. Here, we used a new set of mutants to determine that respiration is essential for aerobic growth and likely protects the cells from damage caused by oxygen. We conclude that the respiratory pathway of Z. mobilis should not be deleted from chassis strains for industrial production because this would yield a strain that is intolerant of oxygen, which is more difficult to manage in industrial settings.

Isopropylthiol emission by bloom-forming Microcystis: Biochemistry, ecophysiology and semiochemistry of a volatile organosulfur compound

Microcystis species not only produce toxic cyanobacterial blooms, but can be a significant source of taste and odour. Previous studies have associated foul-smelling volatile organic sulfur compounds (VOSCs) with Microcystis blooms, but have largely attributed these compounds to bacterial bloom decomposition. However, earlier reports of the production of isopropylthio compounds by several Microcystis strains suggests that these cyanobacteria may themselves be a source of these VOSCs. Sulphur compounds have been shown to play important semiochemical roles in algal cell protection and grazer interactions in marine systems, but little is known about the production and chemical ecology of freshwater cyanobacterial VOSCs. To address this knowledge gap, we undertook the first detailed investigation of the biochemistry, ecophysiology and semiochemistry of these compounds and their production by Microcystis, and tested the hypothesis that they act as multifunctional semiochemicals in processes related to cell protection and grazer defence. Using short-term incubations and an adapted headspace-GC–MS technique, we investigated VOSC production by axenic and non-axenic strains, and verified that isopropylthio compounds are in fact produced by these cyanobacteria, identifying 5 isopropyl moiety-containing VOSCs (isopropylthiol (ISH), isopropylmethyl sulfide, isopropyl methyl disulfide, diisopropyl disulfide (ISSI) and diisopropyl trisulfide) as well as methanethiol in three strains. Further studies with the axenic strain Microcystis PCC 7806 using different light regimes, metabolic inhibitors (sodium azide, DCMU), the antioxidant enzyme catalase and stable labelled precursors (hydrogencarbonate, acetates and sulfate) demonstrated that ISH is a true exo-metabolite, synthesized via the acetate pathway. It is actively produced and continuously excreted by the cyanobacteria during growth, with minimal internal storage or post-lysis catalytic generation. The molar ratios of the redox pair ISH/ISSI are not directly involved in the photosynthetic and respiratory electron transport chains, but dependant on the redox state of the cell - likely mediated by reactive oxygen species (ROS), as shown by a marked effect of catalase. These results, along with toxicological and behavioural assays using the two aquatic invertebrates Thamnocephalus platyurus and Daphnia magna indicate that ISH plays multiple important physiological and ecological roles. It acts as an effective antioxidant against high ROS levels, as often experienced in surface blooms, it elicits avoidance-related behavioural responses in grazer communities and at high levels, it can be toxic to some invertebrates.

Design, synthesis, antifungal activity, and molecular docking of novel trifluoromethyl pyrimidine derivatives containing 1,3,4‐oxadiazole and thioether moieties as potential succinate dehydrogenase inhibitors

AbstractSuccinate dehydrogenase (SDH), a pivotal enzyme linking the respiratory electron transport chain and tricarboxylic acid (TCA) cycle, has been identified as an ideal target for developing effective fungicides. In this study, 20 novel trifluoromethyl pyrimidine derivatives containing 1,3,4‐oxadiazole and thioether moieties were prepared and characterized their structures by 1H NMR, 13C NMR, and HRMS. Bioassay results showed that some of the target compounds revealed moderate to good in vitro antifungal activities toward Rhizoctonia solani (R. solani), Botryosphaeria dothidea (B. dothidea), Phomopsis sp., Botrytis cinerea (B. cinerea), Fusarium oxysporum (F. oxysporum), Sclerotinia sclerotiorum (S. sclerotiorum), Phytophthora infestans (P. infestans), and Magnaporthe oryzae (M. oryzae). In particular, compounds 6g and 6i had better in vitro antifungal activity against B. cinerea, with the EC50 values of 19.43 and 28.22 μg/mL, respectively, than that of Pyrimethanil (57.30 μg/mL). As well, compound 6r exhibited good in vitro antifungal activity against F. oxysporum, with the EC50 value of 3.61 μg/mL, which were lower than that of Boscalid (0.40 μg/mL). In addition, the molecular docking simulation revealed that compound 6r interacted with GLN‐150, ASP‐153, LYS‐151, GLY‐154, and GLY‐228 of SDH through hydrogen bond, which could explain the probable mechanism of action between the target compounds and SDH. This is the first report on the antifungal activity of novel trifluoromethyl pyrimidine derivatives containing 1,3,4‐oxadiazole and thioether moieties as potential SDH inhibitors.

The catalytic reaction of cytochrome c oxidase probed by in situ gas titrations and FTIR difference spectroscopy

Cytochrome c oxidase (CcO) is a transmembrane heme‑copper metalloenzyme that catalyzes the reduction of O2 to H2O at the reducing end of the respiratory electron transport chain. To understand this reaction, we followed the conversion of CcO from Rhodobacter sphaeroides between several active-ready and carbon monoxide-inhibited states via attenuated total reflection Fourier-transform infrared (ATR FTIR) difference spectroscopy. Utilizing a novel gas titration setup, we prepared the mixed-valence, CO-inhibited R2CO state as well as the fully-reduced R4 and R4CO states and induced the “active ready” oxidized state OH. These experiments are performed in the dark yielding FTIR difference spectra exclusively triggered by exposure to O2, the natural substrate of CcO. Our data demonstrate that the presence of CO at heme a3 does not impair the catalytic oxidation of CcO when the cycle starts from the fully-reduced states. Interestingly, when starting from the R2CO state, the release of the CO ligand upon purging with inert gas yield a product that is indistinguishable from photolysis-induced states. The observed changes at heme a3 in the catalytic binuclear center (BNC) result from the loss of CO and are unrelated to electronic excitation upon illumination. Based on our experiments, we re-evaluate the assignment of marker bands that appear in time-resolved photolysis and perfusion-induced experiments on CcO.

Transcriptional expression of radiation-induced early cortical morphological alterations and its association with radiation necrosis in patients with nasopharyngeal carcinoma

PurposeTo explore the effects of standard radiotherapy on cortical morphology and its potential transcriptional expression, and to determine the predictive power of cortical morphological measurement at the early stage for radiation necrosis (RN) occurrence within 3 years post-radiotherapy in patients with nasopharyngeal carcinoma (NPC). Methods185 NPC patients participated. Pre-treatment and post-radiotherapy (1–3 months) structural MRI were collected longitudinally and prospectively. Multiple cortical morphological indices were compared between pre-treatment and post-radiotherapy. Brain-wide gene expression was used to assess the transcriptional profiles associated with radiation-induced cortical morphological changes. Machine learning was used to construct predictive models for RN with cortical morphological alterations at the early stage. ResultsRelative to pre-treatment, NPC patients exhibited a widespread reduction in cortical volume (CV) and cortical thickness (CT) post-radiotherapy (p < 0.001). Partial least squares regression analysis revealed that radiotherapy-related cortical atrophy was closely related to transcriptional profiles (p < 0.001), with the most correlated genes enriched in ATPase Na+/K+ transporting alpha-1 and alpha-3 polypeptide and respiratory electron transport chain. Furthermore, models constructed with cortical morphological features at 1–3 months post-radiotherapy had favorable predictive power for RN occurrence in NPC patients within 3-year follow-up, the area under the curve was 0.854 and 0.843 for CV and CT, respectively. ConclusionsNPC patients exhibited widespread cortical atrophy at 1–3 months post-radiotherapy, which was closely correlated with dysfunction of the ATPase Na+/K+ transporting alpha-1 and alpha-3 polypeptide and respiratory electron transport chain. Cortical morphology at 1–3 months post-radiotherapy may serve as an early biomarker for identifying RN.