## 4 Discussion
### Chemical Compounds Detected by GC-Ms
Our results confirm the presence of the three aforementioned alcohols in the volatile compositions of _Bacillus_ (Table 1). In addition, [PERSON] et al. [55] found that 2-ethylhexan-1-ol and butane-2,3-diol produced by _B. majorensis_, a bacterial species closely related to _B. subtilis_[36], were effective in reducing the growth of the fungus _Colletotrichum cococodes_. [PERSON] et al. [45] showed that n-hexadecane, which was also found in our analyses in the pure _B. subtilis_ culture (Table 1), did not inhibit the growth of _F. oxysporum_. In contrast, n-heptadecane, whose presence in _B. amyloliquefaciens_ and _B. subtilis_ (Table 1) was confirmed by our analyses, inhibited the growth of the fungus _F. oxysporum_ by only 1.29 \(\pm\) 0.85% [45]. [PERSON] et al. [49] found, that 2,3,5-tri-methylpyrazine completely inhibited the growth of _F. soloni_. Our studies confirmed the presence of this compound in the cultures of all bacterial species tested, namely, _B. amyloliquefaciens_, _B. subtilis_ and _B. thuringiensis_ (Table 1). In addition, [PERSON] et al. [49] found that di-methyltrisulphide caused the complete growth inhibition of _F. solani_, while our analyses showed the presence of this sulphide in the volatile emissions of _B. subtilis_ and _B. thuringiensis_ (Table 1). In contrast, [PERSON] et al. [31] showed that styrene and phenol, which were present in the volatile emission of _B. amyloliquefaciens_ NJN-6, reduced the growth of _F. oxysporum_ f. sp. _cubense_. In our study, styrene and phenol were identified only for the interactions of _B. amyloliquefaciens_ and _F. oxysporum_, while these compounds were not present in both pure _B. amyloliquefaciens_ and _F. oxysporum_ strains (Table 2). Research by other authors also confirmed that short-chain fatty acids, which have between two and five carbon atoms in their backbone, effectively inhibited the growth of _F. oxysporum_[23; 30; 45]. Pentanoic acid and isopentanoic acid inhibited the growth of the fungus by 50%-70% [23; 30]. For carboxylic acids with a shorter carbon chain, such as acetic acid, propanoic acid and butanoic acid, the inhibitory effect was lower at 20%-30% [30; 45]. [PERSON] et al. [7] also demonstrated the antifungal properties of volatile carboxylic acids. They also demonstrated that acetic acid, propanoic acid, butanoic acid, pentanoic acid and isopentanoic acid had a synergistic effect [7]. To summarise, both our results and the data from the literature clearly indicate that volatile organic compounds released by bacteria of the genus _Bacillus_ can be successfully used to control pathogenic fungi of _F. oxysporum_. Relevant information can be obtained by analysing the chemical composition of the volatile mixtures produced by both pure bacterial and fungal cultures, as well as those emitted during the interaction of the two microorganisms. Comparing the results of such analyses can provide valuable information on which chemical compounds are most effective against _F. oxysporum_. Both mixtures of VOCs produced by bacteria and individual compounds contained in these mixtures can have antifungal properties.