Figure 1.

Bacterial load increase on the Drosophila body surfaces after eclosion for different times and variations in fly survival and AMP gene expressions

(A and B) Time-dependent increase of the bacterial CFUs on the surfaces of female (A) and male (B) flies. Within each panel, different capital and lower letters labeled above each sample represent the significance of difference at the level of p < 0.01 and p < 0.05, respectively, after one-way ANOVA analysis.

(C and D) Variation or non-variation of the CFU numbers formed on the LB medium with the addition of different antibiotics. Both the 2-DPE (C) and 10-DPE (D) flies were washed for CFU counting. DPE, days post eclosion. The antibiotic nafcillin largely inhibits the G+ bacteria whereas aztreonam inhibits the G- bacteria. The difference level of the two-tailed Student’s t test for significance is at: ∗∗∗, p < 0.001.

(E) No obvious difference in the CFU numbers formed on different media. The 2-DPE flies were washed for CFU counting. Panels A-E: Values are represented as mean ± SD.

(F and G) Survival of the different-age female flies against the topical infection of B. bassiana (F) and M. robertsii (G). Mocks one and two represent the two- and 10-DPE flies treated with 0.05% Tween 20, respectively. Plotted values are represented as mean ± SEM (SE of mean). More than 70 flies were used for each treatment and the experiments were repeated twice.

(H and I) qRT-PCR analysis of the antimicrobial gene expressions after the topical infection of the two- and 10-DPE female flies with B. bassiana (Bb, panel H) and M. robertsii (Mr, panel I) for 48 h. The flies treated with 0.05% Tween 20 were used as mock controls. Values are mean ± SD. There were three replicates each with 10 flies, and the two-tailed Student’s t test was conducted to compare the expression level difference of AMP genes: ∗, p < 0.05; ∗∗, p < 0.01; ∗∗∗, p < 0.001; ∗∗∗∗, p < 0.0001. (See also Figure S1 and Table S1).