Figure 3. Experimental co-evolution.

Experimental co-evolution: S. aureus and E. faecalis were co-passaged (co-evolution treatment) and S. aureus was passaged alone (Single evolution treatment) within non-evolving, genetically homogeneous C. elegans host populations. At each generation, the same C. elegans host populations were exposed to mixed bacterial lawns of S. aureus and E. faecalis or single species lawns of S. aureus. After 24 h of exposure, 10 colonies of S. aureus and/or E. faecalis were collected from the pooled guts of 10 dead hosts using selective media and passaged to the next generation. Each treatment had five replicate populations and was conducted for 10 passages. Colours: magenta, pathogen (S. aureus); turquoise, defensive microbe (E. faecalis).