Struktūrinė ir funkcinė su atsparumu antibiotikams siejamų taškinių mutacijų analizė Streptococcus pneumoniae topoizomerazės IV ParC subvienete

This Bachelor's thesis is based on a study of point mutations in the topoisomerase IV ParC subunit of Streptococcus pneumoniae leading to resistance to fluoroquinolones. This bacterium is a well-known pathogen causing many diseases like pneumonia, meningitis, otitis or sepsis. Due to immoderate use of antibiotics in medicine, agriculture and farming, S. pneumoniae, as many other bacteria, has gained resistance to various antimicrobial agents. This can happen through several molecular mechanisms. A typical mechanism of resitance is the appearing of point mutations in one or more proteins of the pathogen interfering with the binding to the drug. This mechanism was not comprehensively studied so far in S. pneumoniae, thus making it difficult to understand the molecular reasons of non-susceptibility to antibiotics. Fluoroquinolones are a class of broad-spectrum antibiotics, used for Gram-positive as well as Gram-negative bacteria. With the help of bioinformatics tools and resources, 49 genomes from different strains of S.pneumoniae were aligned and analysed for possible mutations. This thesis focuses on the structural and functional analysis of three point mutations found in the topoisomerase ParC subunit: changes from serine to phenylalanine at position 79, lysine to asparagine at position 137 as well as change from glutamic acid to lysine at position 379. The first two mutations were previously reported in the literature to cause resistance to fluoroquinolones. They are known to entail important structural changes in the interaction of ParC with DNA and the fluoroquinolone, respectively. The third dramatic alteration at position 379 was identified in this study from the multiple sequence alignment of ParC genes from different strains. Therefore, it was analysed for potential structural changes leading to non-susceptibility to the drug. The structural and functional analysis did not highlight important disruption of bonds or interactions were found. This thesis also covers an overview of all the 20 mutations identified during this study, and a description of the biochemical properties of each mutation