Redundant potassium transporter systems guarantee the survival of under stress conditions.

is able to grow in media at pH from 5.0 to 9.0 and a high concentration of NaCl (8%). The ability to respond to these extreme conditions requires the rapid movement of three critical ions: proton (H), sodium (Na), and potassium (K). The activity of the proton FF ATPase and the sodium Na VV type ATPase under acidic or alkaline conditions, respectively, is well established in . The potassium uptake transporters KtrI and KtrII were described in , which were associated with growth in acidic and alkaline conditions, respectively. In , the presence of the Kdp (potassium ATPase) system was early established. However, the homeostasis of potassium in this microorganism is not completely explored. In this study, we demonstrate that Kup and KimA are high-affinity potassium transporters, and the inactivation of these genes in . JH2-2 (a Kdp laboratory natural deficient strain) had no effect on the growth parameters. However, in KtrA defective strains (Δ, ΔΔ) an impaired growth was observed under stress conditions, which was restored to wild type levels by external addition of K ions. Among the multiplicity of potassium transporters identify in the genus , Ktr channels (KtrAB and KtrAD), and Kup family symporters (Kup and KimA) are present and may contribute to the particular resistance of these microorganisms to different stress conditions. In addition, we found that the presence of the Kdp system in . is strain-dependent, and this transporter is enriched in strains of clinical origin as compared to environmental, commensal, or food isolates.