Bacteria-Phage Antagonistic Coevolution in Soil

TLDR

Bacteria and phages coevolve rapidly in laboratory settings, but their dynamics in natural environments remain uncertain. In soil, bacteria and phages coevolve rapidly through fluctuating selection dynamics, with hosts becoming more resistant to contemporary parasites due to fitness costs, a process that likely shapes natural microbial communities.

Abstract

Bacteria and their viruses (phages) undergo rapid coevolution in test tubes, but the relevance to natural environments is unclear. By using a "mark-recapture" approach, we showed rapid coevolution of bacteria and phages in a soil community. Unlike coevolution in vitro, which is characterized by increases in infectivity and resistance through time (arms race dynamics), coevolution in soil resulted in hosts more resistant to their contemporary than past and future parasites (fluctuating selection dynamics). Fluctuating selection dynamics, which can potentially continue indefinitely, can be explained by fitness costs constraining the evolution of high levels of resistance in soil. These results suggest that rapid coevolution between bacteria and phage is likely to play a key role in structuring natural microbial communities.