Limitation by a shared mutualist promotes coexistence of multiple competing partners

Sarah P. Hammarlund, Tomáš Gedeon, Ross P. Carlson, William R. Harcombe

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Although mutualisms are often studied as simple pairwise interactions, they typically involve complex networks of interacting species. How multiple mutualistic partners that provide the same service and compete for resources are maintained in mutualistic networks is an open question. We use a model bacterial community in which multiple ‘partner strains’ of Escherichia coli compete for a carbon source and exchange resources with a ‘shared mutualist’ strain of Salmonella enterica. In laboratory experiments, competing E. coli strains readily coexist in the presence of S. enterica, despite differences in their competitive abilities. We use ecological modeling to demonstrate that a shared mutualist can create temporary resource niche partitioning by limiting growth rates, even if yield is set by a resource external to a mutualism. This mechanism can extend to maintain multiple competing partner species. Our results improve our understanding of complex mutualistic communities and aid efforts to design stable microbial communities.

Original languageEnglish (US)
Article number619
JournalNature communications
Issue number1
StatePublished - Dec 2021

Bibliographical note

Funding Information:
We thank Lisa Fazzino, Ben Holte, and Alejandro Behling for assistance with preliminary experiments, Jeremy Chacón for help with modeling, and Brian Smith, Leno Smith, and Jonathan Martinson for providing comments on the manuscript. This work was supported by the National Institutes of Health (1R01-GM121498 to W.R.H. and U01EB019416 to R.P.C.), and by a National Science Foundation Graduate Research Fellowship for S.P.H.

Publisher Copyright:
© 2021, The Author(s).


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