Bacteria are unicellular organisms but nonetheless they engage in multicellular behaviours like swarming motility and biofilm formation. Essential for their survival in such communities are mechanisms responsible for cooperation and competition. Moreover, bacteria are able to discriminate between strains based on the relatedness and treat less related strains differently than those that are genetically identical (clones) or highly related. This behaviour, referred to as kin discrimination, has been recently described for environmental strains of Bacillus subtilis and the tRNase toxin WapA has been identified as a potential kin discrimination locus. However, the mechanisms behind this process are not sufficiently known. Here, we characterize a role of the WapAI toxin-immunity system in competition between isogenic or non-kin strains. We studied their interactions in pellicles and swarming communities by determining their fitness by colony forming units. We also documented spatial distribution of two types of cells in pellicles by confocal microscopy. Our results show that the fitness of the toxin sensitive strain is significantly reduced compared to the toxin producing strain, regardless whether it is competed against parental or non-kin strain during swarming. In pellicles, parental strain did not outcompete the isogenic wapAI mutant, but the fitness of the non-kin mutant was reduced. Interestingly, mutant and parental cells co-aggregated into larger patches while two differentially labelled but otherwise isogenic strains mixed very well. Patchiness was not observed in non-kin combination, where the wild type outcompeted the mutant strain, which was undetectable by fluorescent microscopy. We conclude that competition in swarms is fiercer than in pellicles, probably due to less intense mixing of genotypes in pellicles.