Figure 5.

Bacterial community dynamics in response to ethanol diets

(A–D) Total CFUs, (B) A. pasteurianus CFUs, (C) L. brevis CFUs, and (D) L. plantarum CFUs. The abundance of Acetobacter decreased with increasing dietary ethanol, while the abundance of Lactobacillus plantarum decreased slightly and Lactobacillus brevis increased. Each point represents an individual fly. All points below the dashed line are 0 CFUs and are jittered for clarity. The black bars represent the mean of the log transformed bacterial load. Number of individual flies per ethanol treatment was: 0% N = 14; 2.5% N = 11; 5% N = 16; 7.5% N = 10; 10% N = 11; 12.5% N = 11; 15% N = 8 from two separate biological replicates. There was no effect of fly age on bacterial composition [multivariate ANOVA (Adonis, package vegan in R; p = 0.159)] and therefore all four timepoints were pooled (see STAR Methods).

(E) In vitro, Acetobacter is more sensitive to ethanol than L. plantarum or L. brevis. Growth was measured using MRS (Lactobacilli) or MYPL (Acetobacter) liquid media containing 0%–15% ethanol in a 96-well plate for 24 h with shaking at 30°C. 12 technical replicates of each strain at each ethanol concentration per plate. Data points are the final normalized OD of two independent biological replicates. A two-parameter Weibull function was fit to the normalized ODs from the aggregate data for each strain (R package drc: Analysis of Dose-Response Curves). The inhibitory concentration for 50% growth (IC50) was calculated as the ethanol percentage that reduced normalized maximum OD by half. See also Figure S8.