Fig. 1

Effects of pharmacological elevation of serotonin on gut microbiome homeostasis and survival of B. dorsalis. a Dose–response curve for 5-HTP (4-day treatment). The error bar represents the standard error, and different letters above each bar indicate significant differences (p < 0.05) according to one-way ANOVA followed by Tukey’s multiple comparison test. b–d 5-HTP treatment increased the gut bacterial load, as determined by b 16S rRNA quantification using real-time PCR and c, d colony-forming unit assay. e, f Relative abundance of the genus Serratia and Providencia in control and 5-HTP-treated B. dorsalis by 16S rDNA sequencing. g 5-HTP treatment increased the load of S. marcescens and h P. alcalifaciens in the gut of B. dorsalis. The housekeeping β-actin gene was used as an endogenous control. i Survival of 5-HTP-treated B. dorsalis and controls. j Survival of B. dorsalis fed S. marcescens or P. alcalifaciens. Bacteria were introduced into fly gut via sugar meals. Flies fed with a diet supplemented with sterile 5% sucrose only served as a control. Surviving flies were counted daily. Two-tailed unpaired t-test was performed in b, c, e, f, g, and h. Error bars indicate ± s.e.m.; *p < 0.05, **p < 0.01