Generalizing game-changing species in microbial communities

Jie Deng and Serguei Saavedra, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, Marco Tulio Angulo, CONACyT - Institute of Mathematics, Universidad Nacional Autonoma de Mexico, Juriquilla, QA, Mexico

Background/Question/Methods

Microbial communities play vital roles in both natural ecosystems and human health. Consequently, there has been a growing interest in regulating the species collection forming a given microbial community. However, the strong context-specificity of microbial dynamics makes this regulation extremely challenging. To tackle this problem, we integrate tractable theoretical systems with tractable experimental systems to find general conditions under which non-resident species can change the collection of resident communities by either promoting or suppressing resident species –– “game-changing species”. We study the generalization of game-changing species under controlled and changing conditions using in vitro (soil) and in vivo (gut) microbial communities. Specifically, we investigate (i) whether the game-changing capacity of species is intrinsic or context-specific, (ii) the extent to which game-changers are more likely to happen among colonizing (species that can become established in a perturbed community) or transient (species that cannot colonize) non-resident species, and (iii) the extent to which heuristic rules based on mutual invasibility theory (species persistence in a multispecies community requires persistence in all sub-communities) and structuralist theory (species persistence requires a match between internal constraints given by the multispecies community and the external changing conditions) can be integrated with the experimental systems to find generalities for game-changers across communities. Results/Conclusions

We confirm that the game-changing capacity of species is community-specific regardless of whether it is in vitro or in vivo. We find that non-resident colonizers have a higher probability to change resident communities than transients, whereas game-changers are more likely to suppress resident species than to promote them. We show that the heuristic rules based on mutual invasibility theory work as a general contextualization for in vitro but not in in vivo communities. Instead, the heuristic rules based on structuralist theory work as a general contextualization for in vivo but not in in vitro communities. This illustrates that the strong persistence requirements imposed by mutual invasibility theory may only be characteristic of highly controlled environments, whereas the premises of separating internal and external factors established by structuralist theory may provide a closer approximation to the dynamics of communities under changing conditions. Despite the strong context-dependency, our work shows that under an appropriate integration of tractable theoretical and experimental systems, it is possible to unveil regularities shaping changes in the species collection of microbial communities.