| Abstract [eng] |
Streptococcus pneumoniae and Streptococcus pyogenes are of the main pathogens causing bacterial respiratory tract infections. They secrete cholesterol-dependent toxins: pneumolysin and streptolysin O, respectively. These toxins cause cell death by forming pores in the cell membrane. Antibiotics are most often prescribed to treat respiratory tract diseases, but they are not always necessary. For this reason, research on toxins produced by pathogens of the respiratory tract could help us not only to understand pore formation mechanism more deeply but also allow us to create faster and more accurate tools for diagnostics, which could reduce unnecessary consumption of antibiotics. Latest studies of cholesterol-dependent cytolysins are concentrated on the influence of membrane composition and environmental factors such as pH, on the activity of these toxins. So the focus of this Master thesis was to evaluate effect of membrane composition and pH on the activity of cholesterol-dependent toxins found in respiratory tract: pneumolysin and streptolysin O. Using electrochemical impedance spectroscopy and surface plasmon resonance we found that activity of pneumolysin is affected by membrane composition. Pneumolysin is most active in tBLMs containing 15 % of sphingomyelin or 20 % of saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipids. Activity of streptolysin O is also affected by tBLM composition. Highest activity is reached in membranes containing 20 % of DPPC. Both toxins: pneumolysin and streptolysin O, are affected by pH. Pneumolysin is most active when pH is 8, while activity of streptolysin O peaks at pH 7. |
