## 3 Results and Discussion
### Biosynthetic Genes
The fact that those thioesterase superfamilies were shared by different taxonomic groups, together with the high similarities of these sequences, reinforces the possibility of finding methylketone synthase homologs in the selected bacterial taxa. From a practical point of view, the presence of a conserved protein family putatively involved in the biosynthesis of methylketones in different bacterial taxa suggests the possibility of using this sequence fragment as a target when aiming at assessing the biosynthetic potential of 2-heptanone in apiarie  
Figure 4: Estimates of the evolutionary divergences between a selection of representative protein sequences from each cluster. UniProt ID, cluster number and bacterial species are reported for each sequence. The number of amino acid substitutions per site from between sequences are shown. The values highlighted in blue indicate the most similar sequences, while those in red the most diverse. In a previous study, putative acyl-CoA thioesterase biosynthetic genes were sequenced from eight _B. Huringiensis_ strains isolated from honey bees [42], among which were the three isolates tested in this study for 2-heptanone production. Therefore, the occurrence of this metabolite in the culture filtrate of only one out of three bacterial isolates suggests that the targeted acyl-CoA thioesterase genes may not always function as methylketone synthase and that the biosynthesis of 2-heptanone may be strain-specific and dependent from environmental factors. Certainly, studies oriented towards fermentation process optimization are needed for practical implications of 2-heptanone-producing strains in pest management in apiaries. Volatile compounds affecting the behavior of Varroa mites have been proposed as control strategies, but these semiochemical-based methods have received no validation in the field [8]. The use of 2-heptanone to control Varroa has been evaluated by the application of the pure compound in hives at mite-attracting and at miticidal concentrations [14], but issues have been encountered to ensure the persistence of this volatile compound at the desired levels. The possibility of using 2-heptanone-producing bacteria in naturally colonizing apiaries has so far never been evaluated. Figure 5: Genome Neighborhood Diagrams (GNDs) showing the 4 HBT Thioesterase superfamily (PF03061) (red) in the genomes of the representative bacterial species from clusters 1, 3, 6, 7 and 8. The production of 2-heptanone by two _A. bacterium_ strains together with a high number of putative methylketone synthase homologs found within this species, as well as in Acetobacteraceae, suggests that active producers of this compound may be found within this family. Since the beneficial role of these bacteria towards honey bees has been frequently reported [26; 43] but never associated with a particular mechanism, it may be hypothesized that this compound has a role in the interactions between Acetobacteraceae and honey bees. These results are in line with previous reports on the mediation of bee alarm pheromones in intra- and interspecies communications [7] and support the idea that microbially produced volatiles have an effect on honey bee physiology and behavior [44].