A magnesium transporter is involved in the cesium ion resistance of the high-concentration cesium ion-resistant bacterium sp. TS-1.

Cesium ion (Cs) resistance has been reported in bacteria but is poorly understood as reports on Cs-resistant bacteria have been limited. We previously reported a novel Cs/H antiporter CshA implicated in Cs-resistance in sp. TS-1. The present study used the same screening method to isolate novel Cs-sensitive mutants and their revertants from TS-1. A comparative mutation site analysis using whole-genome sequencing revealed that encodes the Mg transporter MgtE and is a candidate Cs resistance-related gene. We performed a bioinformatic analysis of and complementation experiments on Cs resistance in the TS-1 MTS1_03028 mutants Mut5 and Mut7 as well as expressing in the presence of Mg. We established the role of MgtE in Cs resistance through a functional analysis of TS-1. Enhancing Mg transport by expression of MTS_03028 conferred increased Cs resistance. When this strain was exposed to Cs concentrations exceeding 200 mM, CshA consistently lowered the intracellular Cs concentration. To our knowledge, the present study is the first to clarify the mechanism of Cs resistance in certain bacteria. The study findings offer important insights into the mechanism of bacterial resistance to excess Cs in the environment, suggesting the potential for bioremediation in high Cs-contaminated areas.