Figure 1. Survival curves and total cholesterol levels for Wolbachia -infected Drosophila melanogaster fed cholesterol-enriched food.

Survival curves for wMelPop- (A), wMelCS- (B), and wMel-infected flies (C) reared on cholesterol-enriched diets then challenged with DCV by injection into the haemocoel. Each curve represents one of three experiments for that strain. There was a clear effect of diet on survival, where Wolbachia-infected flies (dashed lines with rhomboid markers) reared on the Intermediate (red lines) and High (blue lines) cholesterol-enriched diets had a shorter average survival time than those reared on Standard food (black lines). Each line depicts the mean survival over time (± s.e.m.) for the three vials from each fly line x diet combination. Data were compared statistically using Cox Regression. A delay in virus-induced mortality was observed in Wolbachia-infected flies compared with uninfected (solid lines with square markers). This pathogen blocking effect occurred for all strains with the weakest blocking occurring for the wMel infection. PBS-injected flies (dotted lines) experienced a high rate of survival with (circles) and without (triangles) Wolbachia, indicating that the death observed in DCV-infected flies was not due to trauma or buffer contamination. Mean levels (± s.e.m.) of total cholesterol and cholesteryl esters for wMelPop- (D), wMelCS- (E), and wMel-infected flies (F) reared on Standard (black bars), Intermediate (red) and High (blue) cholesterol diets. Cholesterol quantification was performed on flies from the same bottles used in the survival assays. Data were compared statistically using univariate ANOVA followed by student's t-tests. Flies reared on high cholesterol diets typically had higher cholesterol levels, and this was generally associated with lower mean survival after challenge with DCV.