Skip to main content
Dryad

Host associated transmission favors transition of a commensal toward antagonism

Data files

Jun 06, 2023 version files 50.43 KB

Abstract

The impacts of host-associated microbes for their hosts varies along a continuum of antagonistic, neutral, and beneficial interactions. Transmission mode is predicted to contribute to transitions along the continuum by altering opportunities for the alignment of host and microbe fitness interests.  Under vertical transmission, microbial evolution is tightly coupled to the host environment, which may facilitate fitness alignment. In contrast, environmentally transmitted microbes spend time in the external environment, outside of hosts, partially decoupling their evolution from the host. This decoupling may misalign host and microbe fitness interests, potentially favoring antagonistic microbial traits. Here, we tested whether transmission environment alters microbial evolution by manipulating the interaction between a commensal Serratia marcescens bacteria and their insect host Anasa tristis, which are the primary vector of these bacteria into plants, where they cause disease. We experimentally evolved S. marcescens through several selection environments. The bacteria were passaged between A. tristis hosts, between A. tristis hosts and soil, through soil, or through standard culture media. We observed rapid evolution of virulence toward hosts across treatments when bacterial evolution occurred within the host environment, indicating that direct host-to-host transmission can increase opportunities for microbes to adapt to hosts and evolve antagonistic traits.