Charged Higgs production with a WW boson or a top quark

I present theoretical results for charged Higgs production in association with a $W$ boson or a top quark at the LHC. I calculate higher-order threshold corrections and show that they are very significant. I present detailed results for total cross sections as well as transverse-momentum and rapidity distributions for various LHC energies.Comment: 5 pages, 4 figures; presented at the EPS Conference on High Energy Physics (EPS-HEP2017), Venice, Italy, July 5-12, 201

Ein hämbasierter Redoxsensor aus dem methanogenen Archaeon Methanosarcina acetivorans\textit {Methanosarcina acetivorans}

In dieser Arbeit wurde ein hämbasiertes Sensorprotein aus dem methanogenen Archaeon $\textit {Methanosarcina acetivorans}$ charakterisiert. Mit Hilfe verschiedener spektroskopischer Methoden (UV/vis, Resonanz-Raman, MCD) wurden die Eigenschaften des Hämkofaktors des Proteins MsmS erstmalig beschrieben. Die Koordinierung des Häms ist heterogen und ein Histidinrest ist der proximale Ligand. Des Weiteren konnte gezeigt werden, dass der Kofaktor über einen Cysteinrest kovalent mit dem Protein verknüpft ist. Durch $\textit {in vitro}$ Aktivitätsassays der C-terminalen Kinasedomäne konnten Erkenntnisse über eine Funktion als Redoxsensor gewonnen werden. Die Untersuchung einer $\textit {in frame}$-Deletionsmutante des kodierenden Gens $\it ma4561$ lieferte erste Hinweise auf eine direkte oder indirekte Beteiligung an der Wahrnehmung von Dimethylsulfid

Overcoming the energetic limitations of syngas fermentation

The fermentation of synthesis gas (including carbon monoxide, carbon dioxide, and hydrogen) with anaerobic acetogens is an established biotechnological process that has recently been transferred to a commercial scale. The natural product spectrum of acetogens is natively restricted to acetate, ethanol, and 2,3-butanediol but is rapidly expanding to heterologous products. Syngas fermentation can achieve high carbon-efficiencies; however, the underlying metabolism is operating at a thermodynamic limit. This necessitates special enzymatic properties for energy conservation by acetogens. Therefore, the availability of cellular energy is considered to restrain the efficient production of energy-intense products with complex production pathways. The optimization of the feed-gas composition and other process parameters, genetic engineering, and integration with other biotechnologies is required to overcome this limitation

Nitrate Feed Improves Growth and Ethanol Production of Clostridium ljungdahlii With CO2 and H-2, but Results in Stochastic Inhibition Events

The pH-value in fermentation broth is a critical factor for the metabolic flux and growth behavior of acetogens. A decreasing pH level throughout time due to undissociated acetic acid accumulation is anticipated under uncontrolled pH conditions such as in bottle experiments. As a result, the impact of changes in the metabolism (e.g., due to a genetic modification) might remain unclear or even unrevealed. In contrast, pH-controlled conditions can be achieved in bioreactors. Here, we present a self-built, comparatively cheap, and user-friendly multiple-bioreactor system (MBS) consisting of six pH-controlled bioreactors at a 1-L scale. We tested the functionality of the MBS by cultivating the acetogen Clostridium ljungdahlii with CO2 and H2 at steady-state conditions (=chemostat). The experiments (total of 10 bioreactors) were addressing the two questions: (1) does the MBS provide replicable data for gas-fermentation experiments?; and (2) does feeding nitrate influence the product spectrum under controlled pH conditions with CO2 and H2? We applied four different periods in each experiment ranging from pH 6.0 to pH 4.5. On the one hand, our data showed high reproducibility for gas-fermentation experiments with C. ljungdahlii under standard cultivation conditions using the MBS. On the other hand, feeding nitrate as sole N-source improved growth by up to 62% and ethanol production by 2-3-fold. However, we observed differences in growth, and acetate and ethanol production rates between all nitrate bioreactors. We explained the different performances with a pH-buffering effect that resulted from the interplay between undissociated acetic acid production and ammonium production and because of stochastic inhibition events, which led to complete crashes at different operating times

Genetic Evidence Reveals the Indispensable Role of the rseC Gene for Autotrophy and the Importance of a Functional Electron Balance for Nitrate Reduction in Clostridium ljungdahlii

For Clostridium ljungdahlii, the RNF complex plays a key role for energy conversion from gaseous substrates such as hydrogen and carbon dioxide. In a previous study, a disruption of RNF-complex genes led to the loss of autotrophy, while heterotrophy was still possible via glycolysis. Furthermore, it was shown that the energy limitation during autotrophy could be lifted by nitrate supplementation, which resulted in an elevated cellular growth and ATP yield. Here, we used CRISPR-Cas12a to delete: (1) the RNF complex-encoding gene cluster rnfCDGEAB; (2) the putative RNF regulator gene rseC; and (3) a gene cluster that encodes for a putative nitrate reductase. The deletion of either rnfCDGEAB or rseC resulted in a complete loss of autotrophy, which could be restored by plasmid-based complementation of the deleted genes. We observed a transcriptional repression of the RNF-gene cluster in the rseC-deletion strain during autotrophy and investigated the distribution of the rseC gene among acetogenic bacteria. To examine nitrate reduction and its connection to the RNF complex, we compared autotrophic and heterotrophic growth of our three deletion strains with either ammonium or nitrate. The rnfCDGEAB- and rseC-deletion strains failed to reduce nitrate as a metabolic activity in non-growing cultures during autotrophy but not during heterotrophy. In contrast, the nitrate reductase deletion strain was able to grow in all tested conditions but lost the ability to reduce nitrate. Our findings highlight the important role of the rseC gene for autotrophy, and in addition, contribute to understand the connection of nitrate reduction to energy metabolism