Abstract:Metals like iron, copper, zinc, and manganese are trace elements essential for the survival and growth of diverse organisms. They influence the protease activity, immune response, physiological processes, and anti-infection mechanism in organisms. During bacterial infection, the host can limit or increase the availability of metal ions in the internal environment to inhibit bacterial proliferation. Meanwhile, bacteria have evolved various transport systems to adapt to the changes in metal ion levels in the host. The metal ion efflux systems exhibit distinctive efflux patterns due to variations in the structural and biochemical properties. We reviewed the available articles and our own research findings about the bacterial efflux systems of iron, copper, zinc, and manganese ions, aiming to provide an overview of the progress in the research on the regulatory mechanisms governing bacterial metal homeostasis. This review of metal ion efflux systems across different bacteria highlights the adaptation that enables bacterial survival in diverse host environments.