Identification of Point Mutations in Clinical Staphylococcus aureus Strains That Produce Small-Colony Variants Auxotrophic for Menadione

Dean, Melissa A.; Olsen, Randall J.; Long, S. Wesley; Rosato, Adriana E.; Musser, James M.

doi:10.1128/iai.01487-13

Cited by 58 publications

(71 citation statements)

References 37 publications

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“…The profile of metabolic genes we have identified and indeed the induction of surface proteins, such as Ebh, have not previously been seen in SCVs and are different from those of previous reports (46)(47)(48). It is reasonable to postulate that Ebh is indeed a core factor in the SCV lifestyle (perhaps, in particular the stable SCV cell type) but was missed in previous studies.…”

Section: Figcontrasting

confidence: 48%

“…8; see Tables S2 to S5 in the supplemental material), we determined there was an induction in stable SCV cells of pathways associated with metabolism (especially amino acid transport, biosynthesis, and catabolism) and surface proteins. Importantly, there was no induction of any of the previously reported adhesive proteins for biofilm cells, as mentioned above, or indeed those proteins previously reported in S. aureus SCVs (46)(47)(48). Recently a large, 1.1-MDa, (10,000 amino acids [aa]) surface protein known as the host-extracellular matrix binding protein, EmbP or Ebh, was identified as expressed in biofilm of Staphylococcus epidermidis (49), and although not shown in S. aureus biofilm, it is involved in S. aureus virulence (50).…”

Section: Figmentioning

confidence: 76%

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Prolonged Growth of a Clinical Staphylococcus aureus Strain Selects for a Stable Small-Colony-Variant Cell Type

et al. 2015

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dAn undetermined feature of Staphylococcus aureus pathogenesis is its persistence and then relapse of disease. This has been explained by its switch to alternative lifestyles, mainly as biofilm or small-colony variants (SCVs). Studying the native characteristics of SCVs has been problematic due to their reversion to the parental lifestyle. We have observed that for a number of S. aureus strains as they switch to an SCV lifestyle, there is the formation of an extracellular matrix. We focused our analysis on one strain, WCH-SK2. For bacterial survival in the host, the combination of low nutrients and the prolonged time frame forms a stress that selects for a specific cell type from the population. In this context, we used steady-state growth conditions with low nutrients and a controlled low growth rate for a prolonged time and with methylglyoxal. These conditions induced S. aureus WCH-SK2 into a stable SCV cell type; the cells did not revert after subculturing. Analysis revealed these cells possessed a metabolic and surface profile that was different from those of previously described SCVs or biofilm cells. The extracellular matrix was protein and extracellular DNA but not polysaccharide. The SCV cells induced expression of certain surface proteins (such as Ebh) and synthesis of lantibiotics while downregulating factors that stimulate the immune response (leucocidin, capsule, and carotenoid). Our data reveal cell heterogeneity within an S. aureus population and under conditions that resemble long-term survival in the host have identified a previously unnoticed S. aureus cell type with a distinctive metabolic and molecular profile. Staphylococcus aureus has an incredible ability to survive, either by adapting to environmental conditions or defending against exogenous stress. In part, this ability is provided by the breadth of lifestyles or modes of growth S. aureus can adopt. Key to an understanding of chronic, persistent, and relapsing S. aureus infections is determining the basis for their switch to quasi-dormant lifestyles. Across different bacterial species, these alternative lifestyles form a population known as persister cells (1). It has been proposed that while within their host, a subpopulation of S. aureus survives host-generated and therapeutic antimicrobial stresses by inducing biofilm growth on host tissue or by growing as smallcolony variants (SCVs). It is likely this is not an on-off switch, from planktonically growing cells to a biofilm or likewise to SCVs, but a continuum of cell types; the bacterial population will have the potential for a diverse range of lifestyles defined by different metabolic pathways and surface structures. In a multicellular biofilm, the metabolically quiescent bacterial community produces a highly protective extracellular polymeric substance (EPS). The EPS is variously composed of polysaccharides (mainly the ica operon-encoded polysaccharide intercellular adhesin [PIA]), extracellular DNA (eDNA), and protein, and its protection results in persistent bacterial infections (...

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Section: Figcontrasting

confidence: 48%

Section: Figmentioning

confidence: 76%

Prolonged Growth of a Clinical Staphylococcus aureus Strain Selects for a Stable Small-Colony-Variant Cell Type

et al. 2015

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“…Mutations were confirmed by DNA sequencing. Both the hemB and menD mutants displayed a typical SCV appearance, as described previously (27,29,48,49) (see Fig. S1 in the supplemental material).…”

Section: Methodsmentioning

confidence: 99%

“…However, the mechanisms by which these mutations influence the expression of specific virulence factors are not always clear. This is particularly true for small-colony variants, where mutations in biosynthetic-pathway genes result in disruption of the electron transport chain and loss of Agr activity (25)(26)(27)(28)(29).…”

Section: Discussionmentioning

confidence: 99%

“…SCVs typically arise from wild-type bacteria via mutations in genes associated with biosynthetic pathways, including those of menaquinone, heme, and thymidine, and are a normal part of the S. aureus life cycle (25)(26)(27)(28)(29). The loss of menaquinone or heme production results in loss of the electron transport chain, leading to decreased membrane potential and reduced ATP production and growth rate (20,30,31).…”

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The Agr Quorum-Sensing System Regulates Fibronectin Binding but Not Hemolysis in the Absence of a Functional Electron Transport Chain

et al. 2014

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Staphylococcus aureus is responsible for numerous chronic and recurrent infections, which are frequently associated with the emergence of small-colony variants (SCVs) that lack a functional electron transport chain. SCVs exhibit enhanced expression of fibronectin-binding protein (FnBP) and greatly reduced hemolysin production, although the basis for this is unclear. One hypothesis is that these phenotypes are a consequence of the reduced Agr activity of SCVs, while an alternative is that the lack of a functional electron transport chain and the resulting reduction in ATP production are responsible. Disruption of the electron transport chain of S. aureus genetically (hemB and menD) or chemically, using 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), inhibited both growth and Agr activity and conferred an SCV phenotype. Supplementation of the culture medium with synthetic autoinducing peptide (sAIP) significantly increased Agr expression in both hemB mutant strains and S. aureus grown with HQNO and significantly reduced staphylococcal adhesion to fibronectin. However, sAIP did not promote hemolysin expression in hemB mutant strains or S. aureus grown with HQNO. Therefore, while Agr regulates fibronectin binding in SCVs, it cannot promote hemolysin production in the absence of a functional electron transport chain.

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Colonization and Persistence Strategies of Staphylococcus aureus

Becker

2024

Staphylococcus Aureus

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Identification of Point Mutations in Clinical Staphylococcus aureus Strains That Produce Small-Colony Variants Auxotrophic for Menadione

Cited by 58 publications

References 37 publications

Prolonged Growth of a Clinical Staphylococcus aureus Strain Selects for a Stable Small-Colony-Variant Cell Type

Prolonged Growth of a Clinical Staphylococcus aureus Strain Selects for a Stable Small-Colony-Variant Cell Type

The Agr Quorum-Sensing System Regulates Fibronectin Binding but Not Hemolysis in the Absence of a Functional Electron Transport Chain

Colonization and Persistence Strategies of Staphylococcus aureus

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