## 3 Results
### Volatile Organic Compounds Produced by Bacillus Bacteria and F. oxysporum
#### 3.2.2 Volatile Organic Compounds Produced by _F. oxysporum_  
In the volatile composition emitted by _F. oxysporum_, 36 compounds were found, among which 34 volatiles were identified, and 2 compounds were classified as sesquiterpenes, but their chemical structures were not determined (Table 2). The largest group were the sesquiterpenes, of which 14 were detected in the analysed samples. The total content of sesquiterpenes was 8.49 \(\pm\) 0.62% (Table 2). The emissions from the fungus included five alcohols, five carbonyl compounds, three carboxylic acids and three esters (Table 2). It was particularly rich in benzaldehyde (25.83 \(\pm\) 1.61%), benzyl alcohol (8.18 \(\pm\) 0.27%) and ethanol (4.62 \(\pm\) 0.01%). The total content of carboxylic acids and esters was relatively low (Table 2). The volatile emission of _F. oxysporum_ was characterised by a high content of chlorinated benzene derivatives (1,4-dichloro-2,5-dimethoxybenzene, 2-chloro-1,4-dimethoxybenzene) and chlorinated benzaldehyde derivatives (3,5-dichlor-4-methoxybenzaldehyde, 3-chloro-4-(methyloxy)benzaldehyde), and the total content of these compounds was 48.45 \(\pm\) 1.46% (Table 2). In addition, methyl N-hydroxybenzene carboximidoate and \(\gamma\)-decalactone were identified in the test samples (Table 2). 2.3 Volatile Organic Compounds Produced by the Interaction of _B. amyloliquefaciens_ and _F. oxysporum_  
Table 3 contains information on the chemical compounds emitted by the microorganisms during the interaction of _B. amyloliquefaciens_ and _F. oxysporum_ (I), as well as individual strain of _B. amyloliquefaciens_ (II) and _F. oxysporum_ (III). In the _B. amyloliquefaciens_ + _F. oxysporum_ interaction, 82 compounds were found, of which 76 were identified with specific chemical structures, and the remaining 6 compounds were classified as sesquiterpene hydrocarbons (Table 3, column I). In the interaction between _B. amyloliquefaciens_ and _F. oxysporum_, sesquiterpenes were the most abundant group of compounds, of which 34 were detected (Table 3). The total content of sesquiterpenes was 50.99 \(\pm\) 2.26%, and the largest numbers were found for spiroax-5,7-diene (16.06 \(\pm\) 0.54%), \(\delta\)-cadinene (0.33 \(\pm\) 0.02%) and sesquiterpene C\({}_{15}\)H  
Figure 4: The main compounds found in the volatile emissions of _Bacillus_ bacteria. with \(R\,I_{exp. }\) = 1488 (4.20 \(\pm\) 0.09%). Sixteen sesquiterpenes were identified that occurred exclusively in the microbial interaction of _B. amyloliquefaciens_ and _F. oxysporum_, including bicyclolelemene, \(\alpha\)-cubebene or \(\alpha\)-copaene (Table 3). The tested samples of _B. amyloliquefaciens + F. oxysporum_ contained monoterpenes such as \(\alpha\)-pinene, \(\delta\)-3-carene and linalool, which were only present in the fungal-bacterial interaction (Table 3). The content of alcohols in _B. amyloliquefaciens + F. oxysporum_ (I) and _B. amyloliquefaciens_ (II) was about 4% and was more than three times lower than in the pure _F. oxysporum_ culture (14.53 \(\pm\) 0.42%). In contrast, the content of carbonyl compounds in _B. amyloliquefaciens + F. oxysporum_ (I) and _F. oxysporum_ (III) varied around 27% and was significantly lower than in the pure _B. amyloliquefaciens_ culture (43.96 \(\pm\) 7.85%). A characteristic feature of the chemical composition of the VOCs present in the _B. amyloliquefaciens + F. oxysporum_ interaction was the presence of alcohols such as isopentanol, butane-2,3-diol, 1-octen-3-ol and undecan-2-ol, as well as carbonyl compounds such as 3-methylpentan-2-one, hexan-2-one and decan-2-one (Table 3). The chlorophenol and benzaldehyde content of the _B. amyloliquefaciens + F. oxysporum_ interaction (1.56 \(\pm\) 0.12%) was more than 30 times lower compared to pure _F. oxysporum_ (48.45 \(\pm\) 1.46%); however, 2-chlorophenol was only present in the bacteria-fungus interaction. In contrast, the content of pyrazine derivatives in _B. amyloliquefaciens + F. oxysporum_ (7.85 \(\pm\) 0.49%) was four times lower than in _B. amyloliquefaciens_ (32.76 \(\pm\) 3.82%).