Increased expression of clumping factor and fibronectin-binding proteins by hemB mutants of Staphylococcus aureus expressing small colony variant phenotypes.
Small colony variants (SCVs) of Staphylococcus aureus are slow-growing subpopulations that cause persistent and relapsing infections. The altered phenotype of SCV can arise from defects in menadione or hemin biosynthesis, which disrupt the electron transport chain and decrease ATP concentrations. With SCVs, virulence is altered by a decrease in exotoxin production and susceptibility to various antibiotics, allowing their intracellular survival. The expression of bacterial adhesins by SCVs is poorly documented. We tested fibrinogen- and fibronectin-mediated adhesion of a hemB mutant of S. aureus 8325-4 that is defective for hemin biosynthesis and exhibits a complete SCV phenotype. In this strain, adhesion to fibrinogen and fibronectin was significantly higher than that of its isogenic, normally growing parent and correlated with the increased surface display of these adhesins as assessed by flow cytometry. Real-time quantitative reverse transcription-PCR demonstrated increased expression of clfA and fnb genes by the hemB mutant compared to its isogenic parent. The influence of the hemB mutation on altered adhesin expression was confirmed by showing complete restoration of the wild-type adhesive phenotype in the hemB mutant, either by complementing with intact hemB or by supplementing the growth medium with hemin. Increased surface display of fibrinogen and fibronectin adhesins by the hemB mutation occurred independently from agr, a major regulatory locus of virulence factors in S. aureus. Both agr-positive and agr-lacking hemB mutants were also more efficiently internalized by human embryonic kidney cells than were their isogenic controls, presumably because of increased surface display of their fibronectin adhesins.
Vaudaux
Pierre
P
Division of Infectious Diseases, University Hospital, CH-1211 Geneva 14, Switzerland. Pierre.vaudaux@hcuge.ch
Francois
Patrice
P
Bisognano
Carmelo
C
Kelley
William L
WL
Lew
Daniel P
DP
Schrenzel
Jacques
J
Proctor
Richard A
RA
McNamara
Peter J
PJ
Peters
G
G
Von Eiff
Christof
C
D018829:Adhesins, Bacterial / Q000235:genetics; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D003030:Coagulase / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D004705:Endocytosis; D005340:Fibrinogen / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D015870:Gene Expression; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006427:Hemin / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009154:Mutation; D010641:Phenotype; D016372:RNA, Antisense / Q000235:genetics / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013211:Staphylococcus aureus / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
D018829:Adhesins, Bacterial; C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003030:Coagulase; D004269:DNA, Bacterial; D005353:Fibronectins; D016372:RNA, Antisense; D012329:RNA, Bacterial; D012333:RNA, Messenger; C096035:RNAIII, Staphylococcus aureus; D015534:Trans-Activators; C078635:fibronectin-binding proteins, bacterial; D006427:Hemin; D005340:Fibrinogen