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saeRS and sarA act synergistically to repress protease production and promote biofilm formation in Staphylococcus aureus.

Mrak LN, Zielinska AK, Beenken KE, Mrak IN, Atwood DN, Griffin LM, Lee CY, Smeltzer MS - PLoS ONE (2012)

Bottom Line: The reduced accumulation of Spa was reversed by mutation of the gene encoding aureolysin, while the reduced accumulation of FnbA was reversed by mutation of the sspABC operon.These results demonstrate that saeRS and sarA act synergistically to repress the production of extracellular proteases that would otherwise limit accumulation of critical proteins that contribute to biofilm formation, with constitutive activation of saeRS limiting protease production, even in a sarA mutant, to a degree that can be correlated with increased enhanced capacity to form a biofilm.Although it remains unclear whether these effects are mediated directly or indirectly, studies done with an sspA::lux reporter suggest they are mediated at a transcriptional level.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America.

ABSTRACT
Mutation of the staphylococcal accessory regulator (sarA) limits biofilm formation in diverse strains of Staphylococcus aureus, but there are exceptions. One of these is the commonly studied strain Newman. This strain has two defects of potential relevance, the first being mutations that preclude anchoring of the fibronectin-binding proteins FnbA and FnbB to the cell wall, and the second being a point mutation in saeS that results in constitutive activation of the saePQRS regulatory system. We repaired these defects to determine whether either plays a role in biofilm formation and, if so, whether this could account for the reduced impact of sarA in Newman. Restoration of surface-anchored FnbA enhanced biofilm formation, but mutation of sarA in this fnbA-positive strain increased rather than decreased biofilm formation. Mutation of sarA in an saeS-repaired derivative of Newman (P18L) or a Newman saeRS mutant (ΔsaeRS) resulted in a biofilm-deficient phenotype like that observed in clinical isolates, even in the absence of surface-anchored FnbA. These phenotypes were correlated with increased production of extracellular proteases and decreased accumulation of FnbA and/or Spa in the P18L and ΔsaeRS sarA mutants by comparison to the Newman sarA mutant. The reduced accumulation of Spa was reversed by mutation of the gene encoding aureolysin, while the reduced accumulation of FnbA was reversed by mutation of the sspABC operon. These results demonstrate that saeRS and sarA act synergistically to repress the production of extracellular proteases that would otherwise limit accumulation of critical proteins that contribute to biofilm formation, with constitutive activation of saeRS limiting protease production, even in a sarA mutant, to a degree that can be correlated with increased enhanced capacity to form a biofilm. Although it remains unclear whether these effects are mediated directly or indirectly, studies done with an sspA::lux reporter suggest they are mediated at a transcriptional level.

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Impact of endogenous fibronectin-binding proteins on biofilm formation in Newman.Biofilm formation was assessed using a microtiter plate assay in Newman with and without introduction of surface-anchored FnbA (pFnbA) and/or mutation of its endogenous fnbA and fnbB. Asterisks indicate statistical significance (p<0.05) by comparison to the isogenic parent strain (WT).
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pone-0038453-g002: Impact of endogenous fibronectin-binding proteins on biofilm formation in Newman.Biofilm formation was assessed using a microtiter plate assay in Newman with and without introduction of surface-anchored FnbA (pFnbA) and/or mutation of its endogenous fnbA and fnbB. Asterisks indicate statistical significance (p<0.05) by comparison to the isogenic parent strain (WT).

Mentions: Newman encodes both fnbA and fnbB, with the defect in these genes precluding anchoring of the corresponding proteins to the cell surface but not their production [15]. This raises the possibility that the increased production of extracellular forms of these proteins impact the sarA-dependent biofilm phenotype. This is particularly true since protein A has been shown to promote biofilm formation in both its surface associated and extracellular forms [18]. To investigate this, we generated fnbA/fnbB mutants in Newman, its sarA mutant, and their pFnbA derivatives and assessed the impact on biofilm formation, but this had little impact on biofilm phenotype of the Newman pFnbA sarA mutant (Fig. 2). This provides further support for the hypothesis that these disparate phenotypes are due to something other than the impact of saeRS on the transcription of fnbA.


saeRS and sarA act synergistically to repress protease production and promote biofilm formation in Staphylococcus aureus.

Mrak LN, Zielinska AK, Beenken KE, Mrak IN, Atwood DN, Griffin LM, Lee CY, Smeltzer MS - PLoS ONE (2012)

Impact of endogenous fibronectin-binding proteins on biofilm formation in Newman.Biofilm formation was assessed using a microtiter plate assay in Newman with and without introduction of surface-anchored FnbA (pFnbA) and/or mutation of its endogenous fnbA and fnbB. Asterisks indicate statistical significance (p<0.05) by comparison to the isogenic parent strain (WT).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369899&req=5

pone-0038453-g002: Impact of endogenous fibronectin-binding proteins on biofilm formation in Newman.Biofilm formation was assessed using a microtiter plate assay in Newman with and without introduction of surface-anchored FnbA (pFnbA) and/or mutation of its endogenous fnbA and fnbB. Asterisks indicate statistical significance (p<0.05) by comparison to the isogenic parent strain (WT).
Mentions: Newman encodes both fnbA and fnbB, with the defect in these genes precluding anchoring of the corresponding proteins to the cell surface but not their production [15]. This raises the possibility that the increased production of extracellular forms of these proteins impact the sarA-dependent biofilm phenotype. This is particularly true since protein A has been shown to promote biofilm formation in both its surface associated and extracellular forms [18]. To investigate this, we generated fnbA/fnbB mutants in Newman, its sarA mutant, and their pFnbA derivatives and assessed the impact on biofilm formation, but this had little impact on biofilm phenotype of the Newman pFnbA sarA mutant (Fig. 2). This provides further support for the hypothesis that these disparate phenotypes are due to something other than the impact of saeRS on the transcription of fnbA.

Bottom Line: The reduced accumulation of Spa was reversed by mutation of the gene encoding aureolysin, while the reduced accumulation of FnbA was reversed by mutation of the sspABC operon.These results demonstrate that saeRS and sarA act synergistically to repress the production of extracellular proteases that would otherwise limit accumulation of critical proteins that contribute to biofilm formation, with constitutive activation of saeRS limiting protease production, even in a sarA mutant, to a degree that can be correlated with increased enhanced capacity to form a biofilm.Although it remains unclear whether these effects are mediated directly or indirectly, studies done with an sspA::lux reporter suggest they are mediated at a transcriptional level.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America.

ABSTRACT
Mutation of the staphylococcal accessory regulator (sarA) limits biofilm formation in diverse strains of Staphylococcus aureus, but there are exceptions. One of these is the commonly studied strain Newman. This strain has two defects of potential relevance, the first being mutations that preclude anchoring of the fibronectin-binding proteins FnbA and FnbB to the cell wall, and the second being a point mutation in saeS that results in constitutive activation of the saePQRS regulatory system. We repaired these defects to determine whether either plays a role in biofilm formation and, if so, whether this could account for the reduced impact of sarA in Newman. Restoration of surface-anchored FnbA enhanced biofilm formation, but mutation of sarA in this fnbA-positive strain increased rather than decreased biofilm formation. Mutation of sarA in an saeS-repaired derivative of Newman (P18L) or a Newman saeRS mutant (ΔsaeRS) resulted in a biofilm-deficient phenotype like that observed in clinical isolates, even in the absence of surface-anchored FnbA. These phenotypes were correlated with increased production of extracellular proteases and decreased accumulation of FnbA and/or Spa in the P18L and ΔsaeRS sarA mutants by comparison to the Newman sarA mutant. The reduced accumulation of Spa was reversed by mutation of the gene encoding aureolysin, while the reduced accumulation of FnbA was reversed by mutation of the sspABC operon. These results demonstrate that saeRS and sarA act synergistically to repress the production of extracellular proteases that would otherwise limit accumulation of critical proteins that contribute to biofilm formation, with constitutive activation of saeRS limiting protease production, even in a sarA mutant, to a degree that can be correlated with increased enhanced capacity to form a biofilm. Although it remains unclear whether these effects are mediated directly or indirectly, studies done with an sspA::lux reporter suggest they are mediated at a transcriptional level.

Show MeSH
Related in: MedlinePlus