Dissecting the regulation of bile-induced biofilm formation in Staphylococcus aureus.
Aspiration of bile into the cystic fibrosis (CF) lung has emerged as a prognostic factor for reduced microbial lung biodiversity and the establishment of often fatal, chronic pathogen infections. Staphylococcus aureus is one of the earliest pathogens detected in the lungs of children with CF, and once established as a chronic infection, strategies for its eradication become limited. Several lung pathogens are stimulated to produce biofilms in vitro in the presence of bile. In this study, we further investigated the effects of bile on S. aureus biofilm formation. Most clinical S. aureus strains and the laboratory strain RN4220 were stimulated to form biofilms with sub-inhibitory concentrations of bovine bile. Additionally, we observed bile-induced sensitivity to aminoglycosides, which we exploited in a bursa aurealis transposon screen to isolate mutants reduced in aminoglycoside sensitivity and augmented in bile-induced biofilm formation. We identified five mutants that exhibited hypersensitivity to bile with respect to bile-induced biofilm formation, three of which carried transposon insertions within gene clusters involved in wall teichoic acid (WTA) biosynthesis or transport. Strain TM4 carried an insertion between the divergently oriented tagH and tagG genes, which encode the putative WTA membrane translocation apparatus. Ectopic expression of tagG in TM4 restored a wild-type bile-induced biofilm response, suggesting that reduced translocation of WTA in TM4 induced sensitivity to bile and enhanced the bile-induced biofilm formation response. We propose that WTA may be important for protecting S. aureus against exposure to bile and that bile-induced biofilm formation may be an evolved response to protect cells from bile-induced cell lysis.
School of Biomedical Sciences, CHIRI Research Institute, Curtin University, Perth, Australia.
Dulantha
D
Ulluwishewa
School of Biomedical Sciences, CHIRI Research Institute, Curtin University, Perth, Australia.
Liang
L
Wang
School of Biomedical Sciences, CHIRI Research Institute, Curtin University, Perth, Australia.
Callen
C
Pereira
BIOMERIT Research Centre, School of Microbiology, University College Cork, Cork, Ireland.
Stephanie
S
Flynn
School of Biomedical Sciences, CHIRI Research Institute, Curtin University, Perth, Australia.
Elizabeth
E
Cain
Telethon Kids Institute, School of Paediatric and Child Health, University of Western Australia, Perth, Australia.|Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth, Western Australia, Australia.
Stephen
S
Stick
BIOMERIT Research Centre, School of Microbiology, University College Cork, Cork, Ireland.
F Jerry
FJ
Reen
School of Biomedical Sciences, CHIRI Research Institute, Curtin University, Perth, Australia.
Joshua P
JP
Ramsay
School of Biomedical Sciences, CHIRI Research Institute, Curtin University, Perth, Australia.|BIOMERIT Research Centre, School of Microbiology, University College Cork, Cork, Ireland.
Fergal
F
O'Gara
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000617:Aminoglycosides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001646:Bile / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D002473:Cell Wall / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000382:microbiology* / Q000473:pathology; D004251:DNA Transposable Elements / Q000235:genetics; D006801:Humans; D008168:Lung / Q000382:microbiology / Q000473:pathology; D008826:Microbial Sensitivity Tests; D021381:Protein Transport / Q000235:genetics; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development*; D013682:Teichoic Acids / Q000096:biosynthesis / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D013682:Teichoic Acids