Richness and density jointly determine context dependence in bacterial interactions

Keven D Dooley; Joy Bergelson

doi:10.1016/j.isci.2023.108654

Richness and density jointly determine context dependence in bacterial interactions

iScience. 2023 Dec 7;27(1):108654. doi: 10.1016/j.isci.2023.108654. eCollection 2024 Jan 19.

Authors

Keven D Dooley¹, Joy Bergelson²

Affiliations

¹ Committee on Microbiology, University of Chicago, Chicago, IL 60637, USA.
² Center for Genomics and System Biology, Department of Biology, New York University, New York, NY 10003, USA.

Abstract

Pairwise interactions are often used to predict features of complex microbial communities due to the challenge of measuring multi-species interactions in high dimensional contexts. This assumes that interactions are unaffected by community context. Here, we used synthetic bacterial communities to investigate that assumption by observing how interactions varied across contexts. Interactions were most often weakly negative and showed a phylogenetic signal among genera. Community richness and total density emerged as strong predictors of interaction strength and contributed to an attenuation of interactions as richness increased. Population level and per-capita measures of interactions both displayed such attenuation, suggesting factors beyond systematic changes in population size were involved; namely, changes to the interactions themselves. Nevertheless, pairwise interactions retained some explanatory power across contexts, provided those contexts were not substantially divergent in richness. These results suggest that understanding the emergent properties of microbial interactions can improve our ability to predict the features of microbial communities.

Keywords: Bacteriology; Microbiology; Synthetic biology.