A new conceptual framework for host-microbe symbiosis

Abstract

Host-microbe relationships are studied across biological disciplines, with unique but overlapping conceptual frameworks arising from each of them. Without a unified framework that can be applied across all host-microbe symbioses, we cannot do the interdisciplinary work necessary to understand the underlying rules that govern them. Here I present a new conceptual framework for host-microbe symbiosis, rooted in the original definition of symbiosis, across three axes: fitness effects, partner fidelity and transmission mode. The three axes make a cube where any symbiotic relationship can be placed. The position of a particular symbiosis is fluid and context-dependent, changing through evolution and throughout the lifetime of an organism. The three axes make for a simple and inclusive framework for symbiosis. We can use this framework to examine every known host-microbe symbiosis, which will allow us to understand the rules and patterns that govern them.