PMID:18375547

Citation	O'Neill, E, Pozzi, C, Houston, P, Humphreys, H, Robinson, DA, Loughman, A, Foster, TJ and O'Gara, JP (2008) A novel Staphylococcus aureus biofilm phenotype mediated by the fibronectin-binding proteins, FnBPA and FnBPB. J. Bacteriol. 190:3835-50
Abstract	Device-associated infections involving biofilm remain a persistent clinical problem. We recently reported that four methicillin-resistant Staphylococcus aureus (MRSA) strains formed biofilm independently of the icaADBC-encoded exopolysaccharide. Here, we report that MRSA biofilm development was promoted under mildly acidic growth conditions triggered by the addition of glucose to the growth medium. Loss of sortase, which anchors LPXTG-containing proteins to peptidoglycan, reduced the MRSA biofilm phenotype. Furthermore introduction of mutations in fnbA and fnbB, which encode the LPXTG-anchored multifunctional fibrinogen and fibronectin-binding proteins, FnBPA and FnBPB, reduced biofilm formation by several MRSA strains. However, these mutations had no effect on biofilm formation by methicillin-sensitive S. aureus strains. FnBP-promoted biofilm occurred at the level of intercellular accumulation and not primary attachment. Mutation of fnbA or fnbB alone did not substantially affect biofilm, and expression of either gene alone from a complementing plasmid in fnbA fnbB mutants restored biofilm formation. FnBP-promoted biofilm was dependent on the integrity of SarA but not through effects on fnbA or fnbB transcription. Using plasmid constructs lacking regions of FnBPA to complement an fnbAB mutant revealed that the A domain alone and not the domain required for fibronectin binding could promote biofilm. Additionally, an A-domain N304A substitution that abolished fibrinogen binding did not affect biofilm. These data identify a novel S. aureus biofilm phenotype promoted by FnBPA and FnBPB which is apparently independent of the known ligand-binding activities of these multifunctional surface proteins.
Links	PubMed PMC2395027 Online version:10.1128/JB.00167-08
Keywords	Adhesins, Bacterial/chemistry; Adhesins, Bacterial/genetics; Adhesins, Bacterial/physiology; Anti-Bacterial Agents/pharmacology; Biofilms/growth & development; Gene Expression Regulation, Bacterial/physiology; Hydrogen-Ion Concentration; Methicillin Resistance; Phenotype; Protein Structure, Tertiary; Staphylococcus aureus/drug effects; Staphylococcus aureus/genetics; Staphylococcus aureus/physiology; Time Factors
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STAA8:FNBA		GO:0007155: cell adhesion	ECO:0000315:		P		Fig. 4 fnbpA contributes to glucose induced biofilm development of S. aureus.	complete CACAO 9592
STAAR:FNBA		GO:0042710: biofilm formation	ECO:0000315:		P		Fig. 4 shows fnbpA contributes to glucose induced biofilm development of S. aureus	complete CACAO 9618
STAAU:Q9AEP9		GO:0044011: single-species biofilm formation on inanimate substrate	ECO:0000315:		P		Fig. 4 A mutation in both fnbpA and fnbpB leads to a dramatic decrease in the amount of biofilm that is formed by the bacteria.	complete CACAO 9988

References

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