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Mol Microbiol. 2013 Aug;89(4):760-73. doi: 10.1111/mmi.12312. Epub 2013 Jul 17.

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

Author information

1
Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, 68198, USA.

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 aureus Ktr 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 0.1 mM 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. aureus Ktr 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.

PMID:
23815639
PMCID:
PMC3754831
DOI:
10.1111/mmi.12312
[Indexed for MEDLINE]
Free PMC Article

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