Enterococcusis 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 F0F1ATPase and the sodium Na+V0V1type ATPase under acidic or alkaline conditions, respectively, is well established inthese microorganisms. The potassium uptake transporters KtrI and KtrII were described inEnterococcus hirae, which were associated with growth in acidic and alkaline conditions, respectively. InEnterococcus faecalis, 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 inE.faecalisJH2-2 (a Kdp laboratory natural deficient strain) had no effect on the growth parameters. However, in KtrA defective strains (ΔktrA, ΔkupΔktrA) 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 genusEnterococcus, 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 inE.faecalisis strain-dependent, and this transporter is enriched in strains of clinical origin as compared to environmental, commensal, or food isolates.