A s aquaporin acts as peroxiporin for efflux of cellular hydrogen peroxide and alleviation of oxidative stress.

Aquaporins (AQPs) are transmembrane proteins widely distributed in various organisms, and they facilitate bidirectional diffusion of water and uncharged solutes. The catalase-negative bacterium produces the highest HO levels reported to date, which has to be exported to avoid oxidative stress. Here, we report that a aquaporin functions as a peroxiporin facilitating bidirectional transmembrane HO transport. Knockout of this aquaporin homolog, So-AqpA, reduced HO export by ∼50% and increased endogenous HO retention, as indicated by the cellular HO reporter HyPer. Heterologous expression of accelerated exogenous HO influx into and cells, indicating that So-AqpA acts as an HO-transferring aquaporin. Alanine substitution revealed Phe-40 as a key residue for So-AqpA-mediated HO transport. Northern blotting, qPCR, and luciferase reporter assays disclosed that HO induces a >10-fold expression of Super-resolution imaging showed that HO treatment increases So-AqpA protein molecules per cell by 1.6- to 3-fold. Inactivation of two redox-regulatory transcriptional repressors, PerR and MntR, reduced HO-induced expression to 1.8- and 4-fold, respectively. Electrophoretic mobility shift assays determined that MntR, but not PerR, binds to the promoter, indicating that MntR directly regulates HO-induced expression. Importantly, deletion decreased oxic growth and intraspecies competition and diminished the competitive advantages of over the caries pathogen Of note, orthologs with the functionally important Phe-40 are present in all streptococci. Our work has uncovered an intrinsic, HO-inducible bacterial peroxiporin that has a key physiological role in HO detoxification in .