## 5 Conclusions  
By using two different headspace collection methods, we were able to show that the composition of MVOCs produced by bacteria varies according to the bacterial species, the type of media (artificial TSB vs. natural fruit), the pH, and incubation time. Here, we highlighted that the modulation of QFF electrophysiology (EAG) and behavior (cage assay) resulted from a complex interplay between changes in the relative proportions of MVOCs associated with pH, media, and incubation time. Through our results from GC/EAD and Y-tube olfactometer assays, we identified 2-nonanone and D-limonene, and phenol, isoamyl alcohol, and nonanal as candidate compounds for future \"attractive\" and \"repulsive\" lures, respectively, for virgin QFF. The elaboration of new female synthetic lures based on these MVOCs will be further tested in the field with natural QFF populations. Our work provides a better understanding of the chemical ecology of fruit flies, which is key to designing novel behaviorally disruptive tools to control QFF. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/microorganisms11071643/s1](https://www.mdpi.com/article/10.3390/microorganisms11071643/s1)]([https://www.mdpi.com/article/10.3390/microorganisms11071643/s1](https://www.mdpi.com/article/10.3390/microorganisms11071643/s1)), Table S1. Raw EAG response measurements (mV) from sexually immature female _Bactrocera tryoni_ to Tenax(r) extracts from each bacterium (Control tryptone soya broth (TSB) media; CF: _Citrobacter freundii_; EC: _Enterobacter cloace_; KO: _Klebsiella axytoca_; PA: _Enterobacter_ (syn. _Pantoa) agglomerans_); Table S2. Mean relative proportions of microbial volatile organic compounds (MVOCs) identified for each bacterium grown at pH3, pH5, PH7, pH9, and pH12, and collected via 24 h headspace collection with solid phase micro-extraction (SPME) fiber. The MVOCs highlighted in grey were used in dual choice behavioral assays with individual compounds. (CF: _Citrobacter freundii_; EC: _Enterobacter cloace_; KO: _Klebsiella axytoca_; PA: _Enterobacter_ (syn. _Pantoa) agglomerans_ and tryptone soya broth (TSB) media). * KI: Kovats retention index; ** RT: retention time (in min); Table S3. Mean relative proportions (peak area) of microbial volatile organic compounds (MVOCs) identified for each bacterium grown on tryptone soya broth (TSB) and inoculated on three types of fruits: apple, kiwifruit, and orange. Volatiles were collected via Tenax(r) for 24 h, 3 days, and 5 days, and thermally desorbed. (CF: _Citrobacter freundii_; EC: _Enterobacter cloace_; KO: _Klebsiella axytoca_; PA: _Enterobacter_ (syn. _Pantoa) agglomerans_; TSB media). Figure S1. Representative chromatograph profiles of four bacterial species grown on tryptone soya broth (TSB), collected on Tenax(r)for 24 h and solvent-extracted. From top to bottom: CF-Citrobacter freundii; EC-Enterobacter cloace; KO-Klebsiella axytoca; PA- Enterobacteriaceae (sy. Pantoea) agglomerans and TSB media. Figure S2. Representative chromatograph profiles of four bacterial species grown on tryptone soya broth (TSB), collected with solid phase micro-extraction (SPME) fibre for 1 h and thermally desorbed. From top to bottom: CF-Citrobacter freundii; EC-Enterobacter cloace; KO-Klebsiella oxytoca; PA- Enterobacter (syn. Pantoea) agglomerans and TSB media. Figure S3. Olfactory responses from solid phase micro-extraction (SPME) - Gas-chromatograph coupled with electroantenographic detection (SPME-GC/EAD) of virgin females to microbial volatile organic compounds produced by a mix of four Enterobacteriaceae bacteria adjusted to pH 3,5,7,9 and 12. Conceptualization, A.K.T. and F.M. ; methodology, A.K.T. and F.M. ; validation, A.K.T., L.-A.M. and F.M. ; formal analysis, A.K.T. and F.M. ; investigation, A.K.T., L.-A.M. and F.M. ; resources, A.K.T., L.-A.M. and F.M. ; data curation, A.K.T. and F.M. ; writing, A.K.T. and F.M.--original draft preparation, A.K.T. ; writing--review and editing, A.K.T., L.-A.M. and F.M. ; visualization, A.K.T., L.-A.M. and F.M.