Bacillus subtilis is a naturally competent bacterium capable of taking up extracellular DNA from the environment and integrating it into its chromosome. The efficiency of this process strongly depends on the degree of genetic relatedness between donor DNA and the recipient genome and decreases markedly as genetic similarity declines. In addition, B. subtilis exhibits kin discrimination, forming different interactions with genetically related and less related strains, which is evident at swarm boundaries where antagonistic interactions lead to the formation of clear demarcation lines. The aim of this master’s thesis was to investigate the impact of kin discrimination on DNA transfer between genetically related and less related strains, as well as between different species of the genus Bacillus, in liquid and semi-solid media. We hypothesized that DNA transfer and integration efficiency would decrease with declining genetic similarity between donor and recipient strains. To address this, we generated 43 rifampicin-resistant Bacillus mutant strains as donors for DNA transfer to the recipient strain B. subtilis PS-216, optimized a method for isolating rifampicin-resistant mutants, and identified point mutations in the rpoB gene. Spontaneous rifampicin-resistant mutants arose in liquid medium, preventing reliable assessment of the effect of DNA relatedness on transformation under these conditions. In contrast, experiments on semi-solid medium revealed a trend in decreasing DNA transfer frequency with decreasing donor–recipient relatedness. DNA integration remained detectable at 84,90 % sequence similarity based on rpoB gene comparisons between the recipient strain and donor strain PS-99. Overall, these results indicate that genetic relatedness significantly influences DNA transfer and integration, providing insight into gene flow among different Bacillus strains and species.
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