PMID:19188357

Citation	Lauderdale, KJ, Boles, BR, Cheung, AL and Horswill, AR (2009) Interconnections between Sigma B, agr, and proteolytic activity in Staphylococcus aureus biofilm maturation. Infect. Immun. 77:1623-35
Abstract	Staphylococcus aureus is a proficient biofilm former on host tissues and medical implants. We mutagenized S. aureus strain SH1000 to identify loci essential for ica-independent mechanisms of biofilm maturation and identified multiple insertions in the rsbUVW-sigB operon. Following construction and characterization of a sigB deletion, we determined that the biofilm phenotype was due to a lack of sigma factor B (SigB) activity. The phenotype was conserved in a sigB mutant of USA300 strain LAC, a well-studied community-associated methicillin-resistant S. aureus isolate. We determined that agr RNAIII levels were elevated in the sigB mutants, and high levels of RNAIII expression are known to have antibiofilm effects. By introducing an agr mutation into the SH1000 or LAC sigB deletion strain, S. aureus regained biofilm capacity, indicating that the biofilm phenotype was agr dependent. Protease activity is linked to agr activity and ica-independent biofilm formation, and we observed that the protease inhibitors phenylmethylsulfonyl fluoride and alpha-macroglobulin could reverse the sigB biofilm defect. Similarly, inactivating genes encoding both the aureolysin and Spl extracellular proteases in the sigB mutant restored biofilm capacity. Due to the growing link between murein hydrolase activity and biofilm maturation, autolysin zymography was performed, which revealed an altered profile in the sigB mutant; again, the phenotype could be repaired through protease inactivation. These findings indicate that the lack of SigB activity results in increased RNAIII expression, thus elevating extracellular protease levels and altering the murein hydrolase activity profile. Altogether, our observations demonstrate that SigB is an essential regulator of S. aureus biofilm maturation.
Links	PubMed PMC2663138 Online version:10.1128/IAI.01036-08
Keywords	Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Biofilms/growth & development; DNA Transposable Elements; Gene Expression Regulation, Bacterial; Humans; Methicillin-Resistant Staphylococcus aureus/enzymology; Methicillin-Resistant Staphylococcus aureus/genetics; Methicillin-Resistant Staphylococcus aureus/growth & development; Methicillin-Resistant Staphylococcus aureus/metabolism; Mutagenesis, Insertional; Mutation; N-Acetylmuramoyl-L-alanine Amidase/genetics; N-Acetylmuramoyl-L-alanine Amidase/metabolism; Peptide Hydrolases/genetics; Peptide Hydrolases/metabolism; RNA, Bacterial/genetics; RNA, Bacterial/metabolism; Sigma Factor/genetics; Sigma Factor/metabolism; Staphylococcus aureus/enzymology; Staphylococcus aureus/genetics; Staphylococcus aureus/growth & development; Staphylococcus aureus/metabolism; Trans-Activators/genetics; Trans-Activators/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STAA3:Q2FF57		GO:0003824: catalytic activity	ECO:0000315:		F		Figure 3 (C&D): Sigma factor B is needed for biofilm formation in S aureus.	complete CACAO 9623
STAA8:Q2FWJ1	involved_in	GO:0044011: single-species biofilm formation on inanimate substrate	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
STAA8:Q2FWJ1		GO:0044011: single-species biofilm formation on inanimate substrate	ECO:0000315:		P		Figure 3 (C&D): Sigma factor B is needed for biofilm formation in S aureus.	complete CACAO 9839

References

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