The Ktr potassium transport system in Staphylococcus aureus and its role in cell physiology, antimicrobial resistance and pathogenesis

Casey M. Gries, Jeffrey L. Bose, Austin S. Nuxoll, Paul D. Fey, Kenneth W. Bayles

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

Potassium (K+) plays a vital role in bacterial physiology, including regulation of cytoplasmic pH, turgor pressure and transmembrane electrical potential. Here, we examine the Staphylococcus aureusKtr system uniquely comprised of two ion-conducting proteins (KtrB and KtrD) and only one regulator (KtrA). Growth of Ktr system mutants was severely inhibited under K+ limitation, yet detectable after an extended lag phase, indicating the presence of a secondary K+ transporter. Disruption of both ktrA and the Kdp-ATPase system, important for K+ uptake in other organisms, eliminated regrowth in 0.1mM K+, demonstrating a compensatory role for Kdp to the Ktr system. Consistent with K+ transport mutations, S. aureus devoid of the Ktr system became sensitive to hyperosmotic conditions, exhibited a hyperpolarized plasma membrane, and increased susceptibility to aminoglycoside antibiotics and cationic antimicrobials. In contrast to other organisms, the S. aureusKtr system was shown to be important for low-K+ growth under alkaline conditions, but played only a minor role in neutral and acidic conditions. In a mouse competitive index model of bacteraemia, the ktrA mutant was significantly outcompeted by the parental strain. Combined, these results demonstrate a primary mechanism of K+ uptake in S.aureus and a role for this system in pathogenesis.

Original languageEnglish (US)
Pages (from-to)760-773
Number of pages14
JournalMolecular Microbiology
Volume89
Issue number4
DOIs
StatePublished - Aug 2013

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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