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Functional amyloids composed of phenol soluble modulins stabilize Staphylococcus aureus biofilms.

Schwartz K, Syed AK, Stephenson RE, Rickard AH, Boles BR - PLoS Pathog. (2012)

Bottom Line: Mutants unable to produce PSMs were susceptible to biofilm disassembly by matrix degrading enzymes and mechanical stress.Previous work has associated PSMs with biofilm disassembly, and we present data showing that soluble PSM peptides disperse biofilms while polymerized peptides do not.This work suggests the PSMs' aggregation into amyloid fibers modulates their biological activity and role in biofilms.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America.

ABSTRACT
Staphylococcus aureus is an opportunistic pathogen that colonizes the skin and mucosal surfaces of mammals. Persistent staphylococcal infections often involve surface-associated communities called biofilms. Here we report the discovery of a novel extracellular fibril structure that promotes S. aureus biofilm integrity. Biochemical and genetic analysis has revealed that these fibers have amyloid-like properties and consist of small peptides called phenol soluble modulins (PSMs). Mutants unable to produce PSMs were susceptible to biofilm disassembly by matrix degrading enzymes and mechanical stress. Previous work has associated PSMs with biofilm disassembly, and we present data showing that soluble PSM peptides disperse biofilms while polymerized peptides do not. This work suggests the PSMs' aggregation into amyloid fibers modulates their biological activity and role in biofilms.

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Phenol soluble modulins are small peptides expressed from three discrete regions of the S. aureus genome.(A) Phenol soluble modulins (PSMs) are encoded in two operons, the alpha (αPSM1–4) and beta (βPSM1–2) operons, and δ-toxin is encoded within the Agr regulatory RNA, RNAIII (hld). (B) PSMs are small hydrophobic peptides with highly similar amino acid content.
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ppat-1002744-g004: Phenol soluble modulins are small peptides expressed from three discrete regions of the S. aureus genome.(A) Phenol soluble modulins (PSMs) are encoded in two operons, the alpha (αPSM1–4) and beta (βPSM1–2) operons, and δ-toxin is encoded within the Agr regulatory RNA, RNAIII (hld). (B) PSMs are small hydrophobic peptides with highly similar amino acid content.

Mentions: Amyloid fibrils from bacterial biofilms were previously shown to be poorly soluble in sodium dodecyl sulfate (SDS) and do not migrate through polyacrylamide gels [33]. We therefore employed SDS-PAGE to isolate large insoluble structures. S. aureus biofilm samples were grown in drip bioreactors for five days with PNG media or TSBg. These biofilms were harvested, homogenized, and lysed, and the lysates were run into a 12% SDS-polyacrylamide gel. Lysates from biofilms grown in PNG media retained insoluble material in the wells of the stacking gel while TSBg-grown lysates did not (Fig. 3A). The insoluble material retained within the wells of the stacking gel was recovered, treated with 100% formic acid (FA), then separated once more by SDS-PAGE alongside an untreated control (Fig. 3B). We observed protein enrichment in the FA-treated sample, and the four dominant bands were excised and analyzed via mass spectrometry (MS). Surprisingly, MS analysis identified the same peptides as being abundant in each sample, regardless of the band's migration through the gel matrix (Fig. 3B & 3D). These proteins were the alpha (αPSM) phenol soluble modulins and the S. aureus delta hemolysin (δ-toxin) (Fig. 4A & 4B).


Functional amyloids composed of phenol soluble modulins stabilize Staphylococcus aureus biofilms.

Schwartz K, Syed AK, Stephenson RE, Rickard AH, Boles BR - PLoS Pathog. (2012)

Phenol soluble modulins are small peptides expressed from three discrete regions of the S. aureus genome.(A) Phenol soluble modulins (PSMs) are encoded in two operons, the alpha (αPSM1–4) and beta (βPSM1–2) operons, and δ-toxin is encoded within the Agr regulatory RNA, RNAIII (hld). (B) PSMs are small hydrophobic peptides with highly similar amino acid content.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369951&req=5

ppat-1002744-g004: Phenol soluble modulins are small peptides expressed from three discrete regions of the S. aureus genome.(A) Phenol soluble modulins (PSMs) are encoded in two operons, the alpha (αPSM1–4) and beta (βPSM1–2) operons, and δ-toxin is encoded within the Agr regulatory RNA, RNAIII (hld). (B) PSMs are small hydrophobic peptides with highly similar amino acid content.
Mentions: Amyloid fibrils from bacterial biofilms were previously shown to be poorly soluble in sodium dodecyl sulfate (SDS) and do not migrate through polyacrylamide gels [33]. We therefore employed SDS-PAGE to isolate large insoluble structures. S. aureus biofilm samples were grown in drip bioreactors for five days with PNG media or TSBg. These biofilms were harvested, homogenized, and lysed, and the lysates were run into a 12% SDS-polyacrylamide gel. Lysates from biofilms grown in PNG media retained insoluble material in the wells of the stacking gel while TSBg-grown lysates did not (Fig. 3A). The insoluble material retained within the wells of the stacking gel was recovered, treated with 100% formic acid (FA), then separated once more by SDS-PAGE alongside an untreated control (Fig. 3B). We observed protein enrichment in the FA-treated sample, and the four dominant bands were excised and analyzed via mass spectrometry (MS). Surprisingly, MS analysis identified the same peptides as being abundant in each sample, regardless of the band's migration through the gel matrix (Fig. 3B & 3D). These proteins were the alpha (αPSM) phenol soluble modulins and the S. aureus delta hemolysin (δ-toxin) (Fig. 4A & 4B).

Bottom Line: Mutants unable to produce PSMs were susceptible to biofilm disassembly by matrix degrading enzymes and mechanical stress.Previous work has associated PSMs with biofilm disassembly, and we present data showing that soluble PSM peptides disperse biofilms while polymerized peptides do not.This work suggests the PSMs' aggregation into amyloid fibers modulates their biological activity and role in biofilms.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America.

ABSTRACT
Staphylococcus aureus is an opportunistic pathogen that colonizes the skin and mucosal surfaces of mammals. Persistent staphylococcal infections often involve surface-associated communities called biofilms. Here we report the discovery of a novel extracellular fibril structure that promotes S. aureus biofilm integrity. Biochemical and genetic analysis has revealed that these fibers have amyloid-like properties and consist of small peptides called phenol soluble modulins (PSMs). Mutants unable to produce PSMs were susceptible to biofilm disassembly by matrix degrading enzymes and mechanical stress. Previous work has associated PSMs with biofilm disassembly, and we present data showing that soluble PSM peptides disperse biofilms while polymerized peptides do not. This work suggests the PSMs' aggregation into amyloid fibers modulates their biological activity and role in biofilms.

Show MeSH
Related in: MedlinePlus