Figure 1
Graphical summary of the origin of different symbionts exposed to C. elegans. (Top panel) E. faecalis derived from a single ancestor clone, E. faecalis OG1RF, was used for an experimental evolution in C. elegans over 15 generations. In the experiment done by King et al.19, C. elegans was exposed to E. faecalis in the absence (green panel) or presence (pink panel) of a fixed, non-evolving pathogen S. aureus. Then, bacteria-killed nematodes were picked and crushed to release the pathogens from inside the carcass and the suspension was streaked on selective media to isolate populations of E. faecalis. Subsequently, 15 colonies were selected to make a lawn for the next exposure generation. From the single evolution, a non-protective E. faecalis was obtained while from the co-colonisation evolution, the protective E. faecalis strain was obtained. (Middle panel) The different strains of E. faecalis were then used for the exposition to C. elegans, in an independent experiment done by Dahan et al.10, alongside with P. mendocina, known to be protective against P. aeruginosa. E. coli OP50 was used as food control. (Bottom panel) 16s rRNA gene sequencing from C. elegans exposed to different symbionts were used for network analysis, keystone taxa identification and metagenomic prediction in the present study.
