Person: Foulston, Lucy
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Foulston
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Lucy
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Foulston, Lucy
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Publication Alternative modes of biofilm formation by plant-associated Bacillus cereus(BlackWell Publishing Ltd, 2015) Gao, Tantan; Foulston, Lucy; Chai, Yunrong; Wang, Qi; Losick, RichardThe ability to form multicellular communities known as biofilms is a widespread adaptive behavior of bacteria. Members of the Bacillus group of bacteria have been found to form biofilms on plant roots, where they protect against pathogens and promote growth. In the case of the model bacterium Bacillus subtilis the genetic pathway controlling biofilm formation and the production of an extracellular matrix is relatively well understood. However, it is unclear whether other members of this genus utilize similar mechanisms. We determined that a plant-associated strain of Bacillus cereus (905) can form biofilms by two seemingly independent pathways. In one mode involving the formation of floating biofilms (pellicles) B. cereus 905 appears to rely on orthologs of many of the genes known to be important for B. subtilis biofilm formation. We report that B. cereus 905 also forms submerged, surface-associated biofilms and in a manner that resembles biofilm formation by the pathogen Staphylococcus aureus. This alternative mode, which does not rely on B. subtilis-like genes for pellicle formation, takes place under conditions of glucose fermentation and depends on a drop in the pH of the medium.Publication The Extracellular Matrix of Staphylococcus aureus Biofilms Comprises Cytoplasmic Proteins That Associate with the Cell Surface in Response to Decreasing pH(American Society of Microbiology, 2014) Foulston, Lucy; Elsholz, Alexander K. W.; Defrancesco, Alicia; Losick, RichardABSTRACT Biofilm formation by Staphylococcus aureus involves the formation of an extracellular matrix, but the composition of this matrix has been uncertain. Here we report that the matrix is largely composed of cytoplasmic proteins that reversibly associate with the cell surface in a manner that depends on pH. We propose a model for biofilm formation in which cytoplasmic proteins are released from cells in stationary phase. These proteins associate with the cell surface in response to decreasing pH during biofilm formation. Rather than utilizing a dedicated matrix protein, S. aureus appears to recycle cytoplasmic proteins that moonlight as components of the extracellular matrix.Publication Genes Contributing to Staphylococcus aureus Fitness in Abscess- and Infection-Related Ecologies(American Society of Microbiology, 2014) Valentino, Michael D.; Foulston, Lucy; Sadaka, Ama; Kos, Veronica N.; Villet, Regis A.; Santa Maria, John; Lazinski, David W.; Camilli, Andrew; Walker, Suzanne; Hooper, David; Gilmore, Michael S.ABSTRACT Staphylococcus aureus is a leading cause of both community- and hospital-acquired infections that are increasingly antibiotic resistant. The emergence of S. aureus resistance to even last-line antibiotics heightens the need for the development of new drugs with novel targets. We generated a highly saturated transposon insertion mutant library in the genome of S. aureus and used Tn-seq analysis to probe the entire genome, with unprecedented resolution and sensitivity, for genes of importance in infection. We further identified genes contributing to fitness in various infected compartments (blood and ocular fluids) and compared them to genes required for growth in rich medium. This resulted in the identification of 426 genes that were important for S. aureus fitness during growth in infection models, including 71 genes that could be considered essential for survival specifically during infection. These findings highlight novel as well as previously known genes encoding virulence traits and metabolic pathways important for S. aureus proliferation at sites of infection, which may represent new therapeutic targets.