Laboratory of Bacterial Physiology
Assoc. Prof. RNDr. Radovan Fišer, Ph.D.
Phone: +420 221 951 754, +420 221 951 712
(additional information can be found also here: http://web.natur.cuni.cz/~konop/contact.php)
The Laboratory of Bacterial Physiology investigates: i) the function of bacterial toxins that affect the cytoplasmic membrane of the target cell, ii) the adaptation of the bacterial membrane to various stresses and the interaction of the membrane with membrane-active compounds, iii) the interaction of bacterial cells with nanomaterials. Together with the usual microbiological methods, a wide range of biophysical approaches is used: methods based on fluorescence spectroscopy and microscopy, conductance measurements on lipid bilayers, X-ray crystallography, analytical methods including gas and liquid chromatography and also computational modelling methods for protein structures.
Bacteria are able to export the toxin molecules into extracellular space. The toxins can drastically change the behavior of the target cells and ultimately cause their death. The research of the Laboratory of Bacterial Physiology is focused on protein toxins of pathogenic bacteria and their interactions with the cytoplasmic membrane of their host cells. We are particularly interested in the adenylate cyclase toxin (CyaA) of Bordetella pertusis, the causative agent of the whooping cough. By employing its several activities, this toxin inhibits the immune response of the target cells. In a close collaboration with the Laboratory of Molecolar Biology of Bacterial Pathogens (Institute of Microbiology, Czech Academy of Sciences; head: Peter Šebo) we suggested a model of the interaction between CyaA and the target membrane (Martín et al., 2004, Fišer et Konopásek, 2009). Also, the significance of the influx of Ca2+ ions into - as well as the efflux of K+ ions from the host cell was proven (Fišer et al., 2007, Wald et al., 2014) together with tracking the path of the CyaA into membrane rafts and into the cytoplasm of the phagocytes (Bumba et al., 2010, Fišer et al., 2012). The Laboratory also cooperates in structural studies of the C-terminal RTX domain of the CyaA and other related RTX toxins that have a crucial role in folding into the native conformation. The results from the CyaA toxin research bring practical implications for human medicine. The modified toxin is able to carry viral, bacterial or parasite antigens into the immune cells inducing the immune response against pathogens. The detoxified CyaA toxin deprived of its enzymatic activities will be the component of the new subunit vaccine against whooping cough, the incidence of which is currently on the rise in developed countries.
In contrast with the toxins of the pathogenic bacteria that inhibit the physiological processes of the host, the other protein toxins, colicins of enterobacteria, are targeted at killing the neighbouring, closely related, gut bacteria. In collaboration with the Laboratory of Bacterial Genetics and Genomics (Faculty of Medicine, Masaryk University, Brno; head: David Šmajs) we proved the pore-forming activity of the recently discovered enterobacterial colicins.
Bacteria represent the outstanding model organisms that react immediately and effectively tp environmental changes. The changes in the membrane composition that alter the membrane fluidity, charge and other physical properties are frequently crucial for the adaptation to environmental changes. At the same time, the membrane is an underestimated target for antibiotics action. The research of the Laboratory is traditionally targeted at the stress adaptation of the model soil bacterium Bacillus subtilis, e.g. at the membrane adaptation induced by the production of the lipopeptide antibiotic surfactin (Seydlová et al., 2013) together with the research of the surfactin interaction with membrane. In future, surfactin itself is a promising candidate for clinical application but neither the molecular mechanism of its effect nor the mechanism underlying the resistence of its producer against surfactin are known so far. Besides other stresses (Seydlová et al., 2012), the cold adaptation in Bacillus subtilis mediated by its membrane fatty acid desaturase is investigated (Beranová et al., 2008; Beranová et al., 2010) together with the cold adaptation of the pathogenic Bordetella species that induce their virulence factors after their entry into the host.
Different nanomaterials are increasingly used in various biomedical applications such as the surface modification of implants, drug delivery or as the substrates in tissue engineering. In newly developed nanomaterials, the opposing characteristics are often sought: biocompatibility with eukaryotic cells and, in contrast, an anti-adhesive and antibacterial character that prevents bacterial colonisation. Our Laboratory investigates the carbon nanomaterials functionalized by the covalent modification of carbon atoms that changes their properties. The antibacterial characteristics of carbon nanomaterials and the mechanisms of their effect on model bacteria (Beranová et al., 2014) are studied in close cooperation with the Laboratory of Diamond Thin Films and Carbon Nanostructures (Institute of Physics, Czech Academy of Sciences; head: Alexander Kromka). Also, antibacterial properties of nanocomposite coatings based on nanosilver and plasma polymers are investigated in cooperation with the Group of Physics of Thin Films and Surfaces of the Department of Macromolecular Physics (Faculty of Mathematics and Physics, Charles University in Prague; Ondřej Kylián).