Graduate Students Mini Symposium VIII - 2023

13:15 h Shunsuke Nomura - AG Shima

Transition of the electron-donating systems of heterodisulfide reductase under nickel-limiting conditions

In the methanogenic pathway from CO₂ and H₂, low-potential electrons for the CO₂ reduction are formed by an electron-bifurcation reaction catalysed by heterodisulfide reductase (Hdr) in complex with associating [NiFe]-hydrogenase (Mvh). In addition, F₄₂₀-reducing [NiFe]-hydrogenase (Frh) provides electrons to the methanogenic pathway. Here, we report that under strictly nickel-limiting conditions mimicking the natural habitats, both [NiFe]-hydrogenases disappear, where Frh is substituted by a coupled reaction with [Fe]-hydrogenase (Hmd), and Mvh is exchanged with F₄₂₀-dependent electron-donating proteins (Elp). We characterized the Elp-Hdr complexes. These results suggest that the nickel-dependent transition and the electron-donating system of Hdr generally occur in nature.

13:45 h Johannes Schwabe - AG Sogaard-Andersen

Evidence for a widespread third system for bacterial polysaccharide export across the outer membrane comprising a composite OPX/β-barrel translocon

Bacteria secrete various polysaccharides that have critical functions in, e.g., beneficial and pathogenic human-microbe interactions. In Gram-negative bacteria, export of polysaccharides across the outer membrane depends on two translocons, i.e., OPX proteins in Wzx/Wzy- and ABC transporter-pathways and 16- to 18-stranded β-barrels in synthase-pathways. Using a combination of experiments in Myxococcus xanthus, phylogenomics, and computational structural biology, we provide evidence supporting that a third type of translocon can export polysaccharides across the OM. In this translocon, an OM-spanning β-barrel functions together with a periplasmic OPX protein lacking the OM-spanning domain. Computational genomics support that similar composite systems are widespread in Gram-negative bacteria.

14:15 h Nadiia Pozhydaieva - MPRG Höfer

Exploring molecular mechanisms of T4 Phage Infection of E. coli

Phages offer promising alternatives to antibiotics for treating drug-resistant infections due to their high specificity and efficacy in targeting bacteria. For this reason, understanding the fundamental mechanisms of phage infection is crucial for their practical implementation. Our research focuses on unraveling the molecular foundation of T4 phage infection of Escherichia coli. To achieve this, we performed a time-resolved multi-omics study, revealing both the temporal and functional regulation of infection. In order to identify the key players of infection, we developed a strategy to engineer phages by introducing SNPs, which deactivate target proteins without gene deletion. Our findings provide foundation for gaining deeper insights into the molecular aspects of T4 bacteriophage infection.