Figure 1.
Experimental Evolution of L. plantarum with D. melanogaster Improves Its Growth-Promoting Effect
(A) Longitudinal size of larvae (LS) measured 7 days after egg deposition (AED) on poor-nutrient diet. Larvae were kept germ-free (GF) or associated with LpNIZO2877 (ancestor), LpWJL (growth-promoting L. plantarum strain), or LpNIZO2877-evolved strains. The Delta in larval size (ΔLS) shows the difference between the size of larvae associated with the respective condition and the size of larvae associated with LpNIZO2877 from Drosophila generation 2 (G2) to generation 20 (G20). Each bar refers to an LpNIZO2877-evolved strain isolated from the first replicate of experimental evolution from G2 to G20. LpNIZO2877-evolved strains that exhibited a significant difference (improved) at promoting larval growth compared with the ancestor strain (Student's t test: p < 0.05) are shown in red. LpNIZO2877-evolved strains that exhibited a significant difference (improved) at promoting larval growth compared with the beneficial L. plantarum LpWJL strain are shown in purple.
(B) Developmental timing (DT) of individuals that were kept GF or associated with LpNIZO2877, LpWJL, or LpNIZO2877-evolved strains isolated from Drosophila G1 to G20. The minus Delta in developmental timing (−ΔDT) is calculated from the mean time of emergence of 50% of the pupae associated with the respective condition and the mean time of emergence of 50% of the pupae associated with LpNIZO2877, and shown in the graph. LpNIZO2877-evolved strains that exhibited a significant difference at accelerating DT compared with the ancestor strain (Student's t test: p < 0.05) are shown in red. The evolved strains that have been selected for further analyses are labeled on the x axis.
(C) Difference in maturation time of individuals associated with LpNIZO2877-evolved strains along the first replicate of LpNIZO2877 adaptive evolution. The mean pupariation time of the first 15 individuals at each fly generation is shown on the y axis.
(D) Percentage of LpNIZO2877-evolved strains isolated at each fly generation that were found to be significantly better than the LpNIZO2877 at increasing larval size. Ten bacterial isolates were randomly isolated at the end of each fly generation from newly emerged adult Drosophila (see Figure S1A) and reassociated with new GF Drosophila embryos to quantify their ability to promote larval growth (see A).
(E) Mutations identified in LpNIZO2877-evolved strains from Drosophila generation 2 (G2) to generation 20 (G20) represented along the LpNIZO2877 genome. The genome of each evolved strain is represented as a horizontal line. Red triangles indicate deletions and small green bars show SNPs. Mutations occurring in the same gene of different strains and fixed along the experimental evolution are highlighted in yellow (int1, cheY, ackA).