Antagonistic interactions between soil isolates of Bacillus subtilis are essential for understanding microbial communities in soil. For the study of antagonistic interactions, we used the soft agar overlay method and the measurement of YFP and RFP fluorescence of labeled strain mixtures with fluorescentlz labeled PS-216 in three different growing environments – overlay agar (0,7 % agar in LB), static liquid culture and shaken liquid culture. Antagonism between strains was found to be a prevalent interaction between strains and associated with strain kinship, with some strains exhibiting higher antagonism intensity than the others. The results obtained show that the tested growth conditions do not significantly affect the expression of antagonism, while the combination of strains is the key to its intensity. We also examined the impact of gene mutations associated with kin discrimination on antagonism expression and found that the wapAI operon was crucial for the expression of antagonism, while the operon epsA-O mutation had no significant impact in tested conditions. The findings of this master's thesis point to the complex nature of antagonism expression among the bacteria B. subtilis soil isolates and emphasize the importance of further research in this field, which would better explain the influence of genes and signaling pathways on the expression and the mechanisms of intra-species antagonism.
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