What happens when a bacterium gets into a fungus and stays — for generations

Bacteria living inside other cells can form stable, mutually beneficial partnerships with their hosts, but it is rare that two organisms are sufficiently compatible on their first encounter. Injecting bacteria into potential fungal hosts provides insights into the early evolutionary dynamics of the formation of such partnerships, and the associated costs and opportunities. Implanting bacteria into a fungus gives rise to a partnership that evolves over time.