A magnesium transporter is involved in the cesium ion resistance of the high-concentration cesium ion-resistant bacterium Microbacterium 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 Microbacterium 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 MTS1_03028 encodes the Mg(2+) transporter MgtE and is a candidate Cs(+) resistance-related gene. We performed a bioinformatic analysis of MTS1_03028 and complementation experiments on Cs(+) resistance in the TS-1 MTS1_03028 mutants Mut5 and Mut7 as well as Escherichia coli expressing MTS1_03028 in the presence of Mg(2+). We established the role of MgtE in Cs(+) resistance through a functional analysis of TS-1. Enhancing Mg(2+) 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.