## 3 Results
### Identification of VOCs Using HS-SPME-GC-Ms  
Based on the bacterial growth curve registered on tryptic soy broth medium and the reduction in soft rot symptoms revealed by _K. cowanii_ Cp1, we used the characterization of VOCs during the lag phase as an approximation of which biomolecules are present during the early stages of competitive colonization, and those during log-stationary phases were used to assess the differences in VOCs between physiological growth phases. Together, this reveals the true nature of these important metabolic activities that are enacted during colony establishment. The results obtained by means of HS-SPME-GC-MS were highly significant (Figure 10 and Supplementary Tables S2-S4 and Figure S5. The VOCs characterized at 2 h of bacterial growth (lag phase) included chemical classes of ketones (10.38%), esters (9.84%), pyrazines (9.84%), and hydrocarbons (9.29%), but of particular relevance were three major compounds identified with the highest relative peak-area percentages, which were 2,5-dimethyl-pyrazine (RT 31.12), benzaldehyde (RT 40.59), and cyclodotdecane (RT 70.55) (Figure 11). When the VOCs were analyzed at 4 h of bacterial growth (lag phase), the chemical compounds identified included ketones (12.85%), pyrazines (10.06%), and alcohols (8.94%). Interestingly, we detected new major compounds with the highest relative peak-area percentages: isopropyl alcohol (RT 9.63), ethanol (RT 9.89), and acetoin (RT 29.63). The percentages of 2,5-dimethyl-pyrazine (RT 31.12) and cyclodotdecane (RT 70.53) were maintained (Figure 11). Finally, the VOCs identified at 6 h of bacterial growth (stationary  
Figure 7: Evaluation of bacterial growth inhibition essays. (**A**) _K. cowanii_ Cp1 and _P. aroidarum_ SM2 in confrontation and (**B**) cell-free filtrate tests performed at 2, 4, 6, 8, and 10 h of growth of _K. cowanii_ Cp1, evaluated directly on _P. aroidearum_ SM2 in duplicate (R1 and R2). phase) included chemical classes of alcohols (13.07%), ketones (9.15%), and esters (7.84%). The major compounds detected with the highest relative peak-area percentages were ethanol (RT 9.90), acetoin (RT 29.62), and 2,5-dimethyl-pyrazine (TR 31.10), while the new major compounds detected at the highest relative peak-area percentages were 2,3-butanediol (RT 42.56) and 4,6-dichloro-5-cyanopyrimidine (RT 76.15) (Figure 11). Our results reveal that these VOCs produced during bacterial growth phases may be essential given their effect on _P. aroidearum_ SM2 colonization and their capacity to reduce soft rot symptoms. Therefore, we decided to assess whether commercially available 2,5-dimethyl-pyrazine and acetoin impact _P. aroidearum_ SM2 colonization on serrano chili fruits and reduce the presence of soft rot symptoms. Figure 8: Inhibition of bacterial growth colonies of _P. aroidearum_ SM2 through VOCs produced by _K. cowanii_ Cpl. (**A**) Bacterial growth colonies produced using the double culture method and (**B**) measurement  
of colony diameter at 2, 4, and 6 h of experimental growth. The data were analyzed using [PERSON]'s mean adjustment test (\(p\) = 0.05), which was performed in the Minitab Statistical Software. Values by different letters show statistical differences. Figure 9: Pathogenic inhibition assays using cell-free filtrates obtained from bacterial growth of \(K\). _cowanii_ Cp1. Cell-free filtrates were obtained at 0 (T1), 1 (T2), 2 (T3), 3 (T4), 4 (T5), 6 (T6), 8 (T7), and 10 h (T8). _P. aroidearum_ SM2 was inoculated in 1 mL of each cell-free filtrate, and serrano chili fruit was immersed directly using a 50 mL Falcon tube in order to evaluate the reduction in soft rot symptoms over 24 h. For negative and positive controls, we used 1 mL of 0.1% peptone. Experiments were performed in triplicate. Figure 11: VOCs with highest relative peak-area percentages produced by _K. cowanii_ Cp1 during growth phases.