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About the Authors:
Nicole M. Vega
Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Validation, Visualization, Writing - original draft, Writing - review & editing
* E-mail: [email protected] (NMV); [email protected] (JG)
Affiliation: Physics of Livings Systems, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
Jeff Gore
Roles Conceptualization, Formal analysis, Funding acquisition, Resources, Supervision, Writing - review & editing
* E-mail: [email protected] (NMV); [email protected] (JG)
Affiliation: Physics of Livings Systems, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of AmericaAbstract
Host-associated bacterial communities vary extensively between individuals, but it can be very difficult to determine the sources of this heterogeneity. Here, we demonstrate that stochastic bacterial community assembly in the Caenorhabditis elegans intestine is sufficient to produce strong interworm heterogeneity in community composition. When worms are fed with two neutrally competing, fluorescently labeled bacterial strains, we observe stochastically driven bimodality in community composition, in which approximately half of the worms are dominated by each bacterial strain. A simple model incorporating stochastic colonization suggests that heterogeneity between worms is driven by the low rate at which bacteria successfully establish new intestinal colonies. We can increase this rate experimentally by feeding worms at high bacterial density; in these conditions, the bimodality disappears. These results demonstrate that demographic noise is a potentially important driver of diversity in bacterial community formation and suggest a role for C. elegans as a model system for ecology of host-associated communities.
Author summary
Host-associated bacterial communities-also known as microbiomes-vary extensively between individuals, even among clones exposed to the same environment. The sources of this variation are not entirely understood and can be very difficult to determine. In this manuscript, we demonstrate experimentally how randomness in bacterial colonization can result in large differences in the composition of host-associated bacterial communities, using the nematode worm Caenorhabditis elegans as a tractable host model. We find that the amount of variation between individual communities is a function of two rates relevant to how bacteria colonize the host intestine: the colonization rate and the birth rate. We can manipulate the degree of variation between communities by altering the colonization rate, using the amount of bacteria presented to the worms to control the rate at which migrants enter the...