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. Author manuscript; available in PMC: 2017 Aug 1.
Published in final edited form as: Evolution. 2016 Jun 24;70(8):1871–1881. doi: 10.1111/evo.12973

Figure 1.

Figure 1

Interactions in the 2 and 3-species systems. S. enterica is the focal strain and the selection for mutualism in each system is determined by tracking the relative frequency of methionine-excreting cooperators (solid red) to non-excreting genotypes (red outline). All S. enterica genotypes require acetate and ammonia. E. coli (blue) consumes lactose, excretes acetate and requires methionine and ammonia. M. extorquens (green) requires acetate. If ammonia is provided in the media then M. extorquens acts as an exploiter with S. enterica for acetate. In contrast, if methylamine is the only nitrogen source then M. extorquens acts as a mutualist providing the other two species with ammonia.