The sloABCR operon of Streptococcus mutans encodes an Mn and Fe transport system required for endocarditis virulence and its Mn-dependent repressor

Sehmi Paik, Arunsri Brown, Cindy L. Munro, Cynthia Nau Cornelissen, Todd Kitten

Research output: Contribution to journalArticlepeer-review

73 Scopus citations

Abstract

Streptococcus mutans belongs to the viridans group of oral streptococci, which is the leading cause of endocarditis in humans. The LraI family of lipoproteins in viridans group streptococci and other bacteria have been shown to function as virulence factors, adhesins, or ABC-type metal transporters. We previously reported the identification of the S. mutans LraI operon, sloABCR, which encodes components of a putative metal uptake system composed of SloA, an ATP-binding protein, SloB, an integral membrane protein, and SloC, a solute-binding lipoprotein, as well as a metal-dependent regulator, SloR. We report here the functional analysis of this operon. By Western blotting, addition of Mn to the growth medium repressed SloC expression in a wild-type strain but not in a sloR mutant. Other metals tested had little effect. Cells were also tested for aerobic growth in media stripped of metals then reconstituted with Mg and either Mn or Fe. Fe at 10 μM supported growth of the wild-type strain but not of a sloA or sloC mutant. Mn at 0.1 μM supported growth of the wild-type strain and sloR mutant but not of sloA or sloC mutants. The combined results suggest that the SloABC proteins transport both metals, although the SloR protein represses this system only in response to Mn. These conclusions are supported by 55Fe uptake studies with Mn as a competitor. Finally, a SloA mutant demonstrated loss of virulence in a rat model of endocarditis, suggesting that metal transport is required for endocarditis pathogenesis.

Original languageEnglish (US)
Pages (from-to)5967-5975
Number of pages9
JournalJournal of bacteriology
Volume185
Issue number20
DOIs
StatePublished - Oct 2003
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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