Antagonistic Mobile Genetic Elements Can Counteract Each Other's Effects on Microbial Community Composition

Area of Science:

• Microbial Ecology
• Population Dynamics
• Genetics

Background:

• Bacteriophages (phages) are mobile genetic elements (MGEs) hypothesized to shape bacterial community dynamics.
• Empirical evidence for phages as key drivers of microbial diversity is often mixed.
• Interactions between multiple MGEs and bacteria may influence community structure in complex ways.

Purpose of the Study:

• To investigate how the diversity of MGEs affects bacterial community composition.
• To test the prediction that increasing MGE diversity leads to converging net effects on bacterial taxa.
• To determine if pairwise interactions predict community dynamics in multi-MGE environments.

Main Methods:

• In silico population dynamics simulations were used to model MGE-bacterial interactions.
• Experimental evolution was conducted with three bacterial species, one plasmid, and three phages.
• Community structure was analyzed under different MGE conditions (single vs. multiple).

Main Results:

• While single phages or plasmids altered community structure, their combined presence led to effects that canceled out.
• The net impact of MGEs on bacterial taxa converged as the number of interacting MGEs increased.
• Observed MGE effects were largely indirect and not predictable from simple pairwise interactions.

Conclusions:

• The impact of MGEs, such as phages, on microbial community structure may be overestimated in studies focusing on single MGEs.
• Increasing MGE diversity can lead to a stabilization of bacterial communities, counteracting individual MGE effects.
• Predicting MGE-driven community dynamics from pairwise interactions is challenging due to complex ecological network effects.