Localization of cytochrome b6f complexes implies an incomplete respiratory chain in cytoplasmic membranes of the cyanobacterium Synechocystis sp. PCC 6803

AbstractThe cytochrome b6f complex is an integral part of the photosynthetic and respiratory electron transfer chain of oxygenic photosynthetic bacteria. The core of this complex is composed of four subunits, cytochrome b, cytochrome f, subunit IV and the Rieske protein (PetC). In this study deletion mutants of all three petC genes of Synechocystis sp. PCC 6803 were constructed to investigate their localization, involvement in electron transfer, respiration and photohydrogen evolution. Immunoblots revealed that PetC1, PetC2, and all other core subunits were exclusively localized in the thylakoids, while the third Rieske protein (PetC3) was the only subunit found in the cytoplasmic membrane. Deletion of petC3 and both of the quinol oxidases failed to elicit a change in respiration rate, when compared to the respective oxidase mutant. This supports a different function of PetC3 other than respiratory electron transfer. We conclude that the cytoplasmic membrane of Synechocystis lacks both a cytochrome c oxidase and the cytochrome b6f complex and present a model for the major electron transfer pathways in the two membranes of Synechocystis. In this model there is no proton pumping electron transfer complex in the cytoplasmic membrane.Cyclic electron transfer was impaired in all petC1 mutants. Nonetheless, hydrogenase activity and photohydrogen evolution of all mutants were similar to wild type cells. A reduced linear electron transfer and an increased quinol oxidase activity seem to counteract an increased hydrogen evolution in this case. This adds further support to the close interplay between the cytochrome bd oxidase and the bidirectional hydrogenase

In Vivo Assembly of Photosystem I-Hydrogenase Chimera for In Vitro PhotoH2 Production

Funding Information: P.W., A.F., and J.A. contributed equally to this work. The authors are grateful to the Bundesministerium für Bildung und Forschung (BMBF) in the framework of the project CyFun (03SF0652A). The authors also thank Prof. Wolfgang Lubitz (Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr) for providing the DvMF[NiFe]-H2ase used for the fabrication of the H2 microsensor. Part of the project was funded by the research training group GRK2341 “Microbial Substrate Conversion (MiCon)” of the German research council (DFG) and the Dietmar Hopp Stiftung. P.W. is grateful for the financial support provided by the China Scholarship Council (CSC). F.C. is grateful to the support provided by FCT–Fundação para a Ciência e a Tecnologia, I.P. through MOSTMICRO-ITQB R&D Unit (UIDB/04612/2020, UIDP/04612/2020) and LS4FUTURE Associated Laboratory (LA/P/0087/2020). Open access funding enabled and organized by Projekt DEAL. Funding Information: P.W., A.F., and J.A. contributed equally to this work. The authors are grateful to the Bundesministerium für Bildung und Forschung (BMBF) in the framework of the project CyFun (03SF0652A). The authors also thank Prof. Wolfgang Lubitz (Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr) for providing the DvMF[NiFe]‐Hase used for the fabrication of the H microsensor. Part of the project was funded by the research training group GRK2341 “Microbial Substrate Conversion (MiCon)” of the German research council (DFG) and the Dietmar Hopp Stiftung. P.W. is grateful for the financial support provided by the China Scholarship Council (CSC). F.C. is grateful to the support provided by FCT–Fundação para a Ciência e a Tecnologia, I.P. through MOSTMICRO‐ITQB R&D Unit (UIDB/04612/2020, UIDP/04612/2020) and LS4FUTURE Associated Laboratory (LA/P/0087/2020). 2 2 Publisher Copyright: © 2023 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH.Photosynthetic hydrogen (photoH2) production is an elegant approach to storing solar energy. The most efficient strategy is to couple the hydrogen-producing enzyme, the hydrogenase (H2ase), directly to photosystem I (PSI), which is a light-driven nanomachine found in photosynthetic organisms. PSI–H2ase fusions have been tested in vivo and in vitro. Both approaches have each their specific advantages and drawbacks. Here, a system to combine both approaches by assembling PSI–H2ase fusions in vivo for in vitro photoH2 production is established. For this, cyanobacterial PSI–H2ase fusion mutants are generated and characterized concerning photoH2 production in vivo. The chimeric protein is purified and embedded in a redox polymer on an electrode where it successfully produces photoH2 in vitro. The combination of in vivo and in vitro processes comes along with reciprocal benefits. The in vivo assembly ensures that the chimeric protein is fully functional and suited for the fabrication of bioelectrodes in vitro. At the same time, the photoelectrochemical in vitro characterization now permits to analyze the assemblies in detail. This will open avenues to optimize in vivo and in vitro approaches for photoH2 production in a target-oriented manner in the future.publishersversionpublishe

Mannan-Binding Lectin in Diabetic Kidney Disease: The Impact of Mouse Genetics in a Type 1 Diabetes Model

Background. Mannan-binding lectin (MBL) is involved in the development of diabetic nephropathy. MBL is a part of the innate immune system where it can activate the complement system. Serum MBL level predicts later renal impairment in diabetes patients. Direct involvement of MBL in the development of diabetic kidney disease is observed in one animal strain. However, this involvement may differ among the animal strains. We thus examined the impact of the genetic background on the role of MBL in diabetic nephropathy. Materials/Methods. C57BL/6JBomTac and 129S6/SvEvTac mice were compared. In both strains, experimental type 1 diabetes was induced in wild-type (WT) and MBL-knockout (MBL-KO) mice by streptozotocin. Nondiabetic WT and MBL-KO mice were used as controls. We tested if MBL modified the diabetes-induced kidney changes by two-way ANOVA allowing for interaction. Results. MBL aggravated diabetes-induced kidney growth and glomerulus enlargement in C57BL/6JBomTac mice. MBL did not modify diabetes effects on glomerular basement membrane thickness or mesangial volume in any strain. Diabetes-induced changes in renal gene transcription of growth factors and matrix components were unaffected by MBL. Conclusions. Strain-specific MBL effects were found on downstream diabetic kidney changes. This emphasizes the importance of genetic background in this model of diabetic complications

Synechocystis sp. PCC 6803 Requires the Bidirectional Hydrogenase to Metabolize Glucose and Arginine Under Oxic Conditions

The cyanobacterium Synechocystis sp.PCC 6803 possesses a bidirectional NiFe-hydrogenase, HoxEFUYH. It functions to produce hydrogen under dark, fermentative conditions and photoproduces hydrogen when dark-adapted cells are illuminated. Unexpectedly, we found that the deletion of the large subunit of the hydrogenase (HoxH) in Synechocystis leads to an inability to grow on arginine and glucose under continuous light in the presence of oxygen. This is surprising, as the hydrogenase is an oxygen-sensitive enzyme. In wild-type (WT) cells, thylakoid membranes largely disappeared, cyanophycin accumulated, and the plastoquinone (PQ) pool was highly reduced, whereas ΔhoxH cells entered a dormant-like state and neither consumed glucose nor arginine at comparable rates to the WT. Hydrogen production was not traceable in the WT under these conditions. We tested and could show that the hydrogenase does not work as an oxidase on arginine and glucose but has an impact on the redox states of photosynthetic complexes in the presence of oxygen. It acts as an electron valve as an immediate response to the supply of arginine and glucose but supports the input of electrons from arginine and glucose oxidation into the photosynthetic electron chain in the long run, possibly via the NDH-1 complex. Despite the data presented in this study, the latter scenario requires further proof. The exact role of the hydrogenase in the presence of arginine and glucose remains unresolved. In addition, a unique feature of the hydrogenase is its ability to shift electrons between NAD(H), NADP(H), ferredoxin, and flavodoxin, which was recently shown in vitro and might be required for fine-tuning. Taken together, our data show that Synechocystis depends on the hydrogenase to metabolize organic carbon and nitrogen in the presence of oxygen, which might be an explanation for its prevalence in aerobic cyanobacteria

Evidence for Electron Transfer from the Bidirectional Hydrogenase to the Photosynthetic Complex I (NDH-1) in the Cyanobacterium Synechocystis sp. PCC 6803

The cyanobacterial bidirectional [NiFe]-hydrogenase is a pentameric enzyme. Apart from the small and large hydrogenase subunits (HoxYH) it contains a diaphorase module (HoxEFU) that interacts with NAD(P)+ and ferredoxin. HoxEFU shows strong similarity to the outermost subunits (NuoEFG) of canonical respiratory complexes I. Photosynthetic complex I (NDH-1) lacks these three subunits. This led to the idea that HoxEFU might interact with NDH-1 instead. HoxEFUYH utilizes excited electrons from PSI for photohydrogen production and it catalyzes the reverse reaction and feeds electrons into the photosynthetic electron transport. We analyzed hydrogenase activity, photohydrogen evolution and hydrogen uptake, the respiration and photosynthetic electron transport of ΔhoxEFUYH, and a knock-out strain with dysfunctional NDH-1 (ΔndhD1/ΔndhD2) of the cyanobacterium Synechocystis sp. PCC 6803. Photohydrogen production was prolonged in ΔndhD1/ΔndhD2 due to diminished hydrogen uptake. Electrons from hydrogen oxidation must follow a different route into the photosynthetic electron transport in this mutant compared to wild type cells. Furthermore, respiration was reduced in ΔhoxEFUYH and the ΔndhD1/ΔndhD2 localization of the hydrogenase to the membrane was impaired. These data indicate that electron transfer from the hydrogenase to the NDH-1 complex is either direct, by the binding of the hydrogenase to the complex, or indirect, via an additional mediator

Factors associated with the occurrence of MRSA CC398 in herds of fattening pigs in Germany

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to investigate the prevalence of MRSA in herds of fattening pigs in different regions of Germany, and to determine factors associated with the occurrence of this pathogen. For this purpose pooled dust samples were collected, and a questionnaire covered information regarding herd characteristics and management practices. Samples were pre-enriched in high-salt medium followed by selective enrichment containing cefoxitin/aztreonam, and culturing. Presumptive colonies were confirmed by multiplex-PCR targeting <it>nuc-</it>, <it>mecA</it>- and 16S rRNA-genes. Isolates were s<it>pa- </it>and SCC<it>mec</it>-, and in selected cases, multilocus sequence-typed. Susceptibilities to 13 antimicrobials were determined by broth microdilution. Statistical analysis was carried out using backward stepwise logistic regression to calculate odds ratios with the MRSA test result as the outcome and herd characteristics as categorical covariates.</p> <p>Results</p> <p>Overall, 152 of 290 (52%) fattening pig farms tested positive for MRSA. The prevalence in the east, north- and south-west of Germany ranged from 39 to 59%.</p> <p>t011 (66%) and t034 (23%) were the most commonly identified s<it>pa</it>-types, and 85% of isolates carried SCC<it>mec </it>Type V. Identified <it>spa</it>-types were all associated with clonal complex CC398. Susceptibility testing revealed that all isolates were resistant to tetracycline. High resistance rates were also found for sulfamethoxazole/trimethoprim (40%), and quinupristin/dalfopristin (32%). In addition, 83% of strains displayed multidrug resistant (> 3 substance classes) phenotypes.</p> <p>Logistic regression revealed herd size (large farms OR: 5.4; CI: 2.7-11.2; p < 0.05), and production type (wean-to-finish OR: 4.0; CI: 1.6-10.4; p < 0.05) as risk factors associated with a positive MRSA finding in fattening pig operations.</p> <p>Conclusions</p> <p>MRSA CC398 is widely distributed among herds of fattening pigs in Germany. Farm management plays a crucial role in the dissemination of MRSA with herd size, and production type representing potential major indicators.</p

A genome-wide association study of thyroid stimulating hormone and free thyroxine in Danish children and adolescents

<div><p>Background</p><p>Hypothyroidism is associated with obesity, and thyroid hormones are involved in the regulation of body composition, including fat mass. Genome-wide association studies (GWAS) in adults have identified 19 and 6 loci associated with plasma concentrations of thyroid stimulating hormone (TSH) and free thyroxine (fT4), respectively.</p><p>Objective</p><p>This study aimed to identify and characterize genetic variants associated with circulating TSH and fT4 in Danish children and adolescents and to examine whether these variants associate with obesity.</p><p>Methods</p><p>Genome-wide association analyses of imputed genotype data with fasting plasma concentrations of TSH and fT4 from a population-based sample of Danish children, adolescents, and young adults, and a group of children, adolescents, and young adults with overweight and obesity were performed (N = 1,764, mean age = 12.0 years [range 2.5−24.7]). Replication was performed in additional comparable samples (N = 2,097, mean age = 11.8 years [1.2−22.8]). Meta-analyses, using linear additive fixed-effect models, were performed on the results of the discovery and replication analyses.</p><p>Results</p><p>No novel loci associated with TSH or fT4 were identified. Four loci previously associated with TSH in adults were confirmed in this study population (<i>PDE10A</i> (rs2983511: <i>β</i> = 0.112<i>SD</i>, <i>p</i> = 4.8 ∙ 10⁻¹⁶), <i>FOXE1</i> (rs7847663: <i>β</i> = 0.223<i>SD</i>, <i>p</i> = 1.5 ∙ 10⁻²⁰), <i>NR3C2</i> (rs9968300: <i>β</i> = 0.194<i>SD</i>), <i>p</i> = 2.4 ∙ 10⁻¹¹), <i>VEGFA (</i>rs2396083: <i>β</i> = 0.088<i>SD</i>, <i>p</i> = 2.2 ∙ 10⁻¹⁰)). Effect sizes of variants known to associate with TSH or fT4 in adults showed a similar direction of effect in our cohort of children and adolescents, 11 of which were associated with TSH or fT4 in our study (<i>p</i><0.0002). None of the TSH or fT4 associated SNPs were associated with obesity in our cohort, indicating no pleiotropic effects of these variants on obesity.</p><p>Conclusion</p><p>In a group of Danish children and adolescents, four loci previously associated with plasma TSH concentrations in adults, were associated with plasma TSH concentrations in children, suggesting comparable genetic determinants of thyroid function in adults and children.</p></div