title: Induction of attachment-independent biofilm formation and repression of Hfq expression by low-fluid-shear culture of Staphylococcus aureus.
abstract: The opportunistic pathogen Staphylococcus aureus encounters a wide variety of fluid shear levels within the human host, and they may play a key role in dictating whether this organism adopts a commensal interaction with the host or transitions to cause disease. By using rotating-wall vessel bioreactors to create a physiologically relevant, low-fluid-shear environment, S. aureus was evaluated for cellular responses that could impact its colonization and virulence. S. aureus cells grown in a low-fluid-shear environment initiated a novel attachment-independent biofilm phenotype and were completely encased in extracellular polymeric substances. Compared to controls, low-shear-cultured cells displayed slower growth and repressed virulence characteristics, including decreased carotenoid production, increased susceptibility to oxidative stress, and reduced survival in whole blood. Transcriptional whole-genome microarray profiling suggested alterations in metabolic pathways. Further genetic expression analysis revealed downregulation of the RNA chaperone Hfq, which parallels low-fluid-shear responses of certain Gram-negative organisms. This is the first study to report an Hfq association with fluid shear in a Gram-positive organism, suggesting an evolutionarily conserved response to fluid shear among structurally diverse prokaryotes. Collectively, our results suggest S. aureus responds to a low-fluid-shear environment by initiating a biofilm/colonization phenotype with diminished virulence characteristics, which could lead to insight into key factors influencing the divergence between infection and colonization during the initial host-pathogen interaction.
authors.affiliation: Department of Microbiology & Immunology, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Castro
authors.forename: Mayra
authors.initials: M
authors.lastname: Nelman-Gonzalez
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Nickerson
authors.forename: C Mark
authors.initials: CM
authors.lastname: Ott
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein / Q000096:biosynthesis*; D046228:Microarray Analysis; D013211:Staphylococcus aureus / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D013312:Stress, Physiological; D037521:Virulence Factors / Q000096:biosynthesis
chemical_list: D035001:Host Factor 1 Protein; D037521:Virulence Factors