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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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Related in: MedlinePlus

Impact of aureolysin on saeRS and sarA-dependent biofilm formation.Biofilm formation was assessed in Newman, its P18L derivative, and their sarA, sarA/aur and sarA/ssp mutants with (left) and without (right) the introduction of an intact copy of fnbA. A single asterisk indicates statistical significance (p<0.05) by comparison to the isogenic parent strain, while the double asterisk indicates statistical significance (p<0.05) by comparison to the isogenic sarA mutant.
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pone-0038453-g005: Impact of aureolysin on saeRS and sarA-dependent biofilm formation.Biofilm formation was assessed in Newman, its P18L derivative, and their sarA, sarA/aur and sarA/ssp mutants with (left) and without (right) the introduction of an intact copy of fnbA. A single asterisk indicates statistical significance (p<0.05) by comparison to the isogenic parent strain, while the double asterisk indicates statistical significance (p<0.05) by comparison to the isogenic sarA mutant.

Mentions: Mutation of aur enhanced biofilm formation in a P18L sarA mutant, but had no impact on biofilm formation in a Newman sarA mutant, and this was true irrespective of the presence of pFnbA (Fig. 5). However, the lack of a phenotype in the pFnbA Newman sarA/aur mutant must be taken in context in that biofilm formation was already elevated in the isogenic pFnbA Newman sarA mutant, meaning biofilm formation in this strain may be at a maximum defined by this assay. However, the observation that these same disparate sarA/aur phenotypes were apparent in the absence of pFnbA gene (Fig. 5) confirms the existence of an saeRS-dependent biofilm phenotype in S. aureus that cannot be explained by the impact of proteases on the accumulation of surface associated 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 aureolysin on saeRS and sarA-dependent biofilm formation.Biofilm formation was assessed in Newman, its P18L derivative, and their sarA, sarA/aur and sarA/ssp mutants with (left) and without (right) the introduction of an intact copy of fnbA. A single asterisk indicates statistical significance (p<0.05) by comparison to the isogenic parent strain, while the double asterisk indicates statistical significance (p<0.05) by comparison to the isogenic sarA mutant.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0038453-g005: Impact of aureolysin on saeRS and sarA-dependent biofilm formation.Biofilm formation was assessed in Newman, its P18L derivative, and their sarA, sarA/aur and sarA/ssp mutants with (left) and without (right) the introduction of an intact copy of fnbA. A single asterisk indicates statistical significance (p<0.05) by comparison to the isogenic parent strain, while the double asterisk indicates statistical significance (p<0.05) by comparison to the isogenic sarA mutant.
Mentions: Mutation of aur enhanced biofilm formation in a P18L sarA mutant, but had no impact on biofilm formation in a Newman sarA mutant, and this was true irrespective of the presence of pFnbA (Fig. 5). However, the lack of a phenotype in the pFnbA Newman sarA/aur mutant must be taken in context in that biofilm formation was already elevated in the isogenic pFnbA Newman sarA mutant, meaning biofilm formation in this strain may be at a maximum defined by this assay. However, the observation that these same disparate sarA/aur phenotypes were apparent in the absence of pFnbA gene (Fig. 5) confirms the existence of an saeRS-dependent biofilm phenotype in S. aureus that cannot be explained by the impact of proteases on the accumulation of surface associated 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