AUTHOR=Acciarri Giuliana , Gizzi Fernán O. , Torres Manno Mariano A. , Stülke Jörg , Espariz Martín , Blancato Víctor S. , Magni Christian 

TITLE=Redundant potassium transporter systems guarantee the survival of Enterococcus faecalis under stress conditions

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1117684

DOI=10.3389/fmicb.2023.1117684

ISSN=1664-302X

ABSTRACT=<p><italic>Enterococcus</italic> 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<sup>+</sup>), sodium (Na<sup>+</sup>), and potassium (K<sup>+</sup>). The activity of the proton F<sub>0</sub>F<sub>1</sub> ATPase and the sodium Na<sup>+</sup> V<sub>0</sub>V<sub>1</sub> type ATPase under acidic or alkaline conditions, respectively, is well established in <italic>these microorganisms</italic>. The potassium uptake transporters KtrI and KtrII were described in <italic>Enterococcus hirae</italic>, which were associated with growth in acidic and alkaline conditions, respectively. In <italic>Enterococcus faecalis</italic>, 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 <italic>E</italic>. <italic>faecalis</italic> JH2-2 (a Kdp laboratory natural deficient strain) had no effect on the growth parameters. However, in KtrA defective strains (Δ<italic>ktrA</italic>, Δ<italic>kup</italic>Δ<italic>ktrA</italic>) an impaired growth was observed under stress conditions, which was restored to wild type levels by external addition of K<sup>+</sup> ions. Among the multiplicity of potassium transporters identify in the genus <italic>Enterococcus</italic>, 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 <italic>E</italic>. <italic>faecalis</italic> is strain-dependent, and this transporter is enriched in strains of clinical origin as compared to environmental, commensal, or food isolates.</p>