UBC Theses and Dissertations
The regulation and characterization of surfing motility in Pseudomonas aeruginosa Sun, Evelyn
Pseudomonas aeruginosa is an opportunistic pathogen associated with a high incidence of infections in hospitalized and cystic fibrosis (CF) patients. P. aeruginosa is highly adaptable and exhibits diverse lifestyle adaptations depending on its surrounding environment. Here I studied a complex motility lifestyle termed surfing that occurs in the presence of mucin, a glycoprotein that is found in large abundance in the CF lung, and showed that surfing was associated with broad-spectrum antibiotic resistance, conserved in several bacterial species, and regulated by a complex networks of regulators. RNA-Seq revealed ~1,024 genes dysregulated in P. aeruginosa under surfing conditions, while a screen of the PA14 transposon mutant library revealed 192 mutants that exhibited surfing deficiency, 40 of which were regulatory genes, including the putative chemotaxis regulator, PA1463, and two-component regulator, pfeR. Both PA1463 and pfeR were found to be master regulators of P. aeruginosa surfing and mutants in these genes demonstrated dysregulation of the majority of other regulators influencing surfing. Using disk diffusion assays, I investigated the adaptive antibiotic resistance associated with surfing motility. P. aeruginosa surfing cells were significantly more resistant to several antibiotics including all tested aminoglycosides, carbapenems, polymyxins, fluoroquinolones, and trimethoprim, tetracycline, and chloramphenicol. To identify the genes mediating surfing-dependent antibiotic resistance, transposon mutants in antibiotic susceptibility genes that were dysregulated under surfing conditions were screened for altered susceptibility under surfing conditions. This revealed 65 mutants, including mutants in armR, recG, atpB, clpS, nuoB, that exhibited changes in susceptibility to one or more antibiotics, consistent with a contribution to the observed adaptive resistance. It was further demonstrated that other motile bacterial species, including Escherichia coli, Salmonella enterica, Vibrio harveyi, Enterobacter cloacae, Proteus mirabilis, and Bacillus subtilis, exhibited similar characteristics of surfing as observed for P. aeruginosa in the presence of mucin, including rapid surface growth, dependence on flagella, and broad- spectrum adaptive resistance. Therefore, surfing is a conserved motile lifestyle regulated by complex networks of regulators and leads to broad spectrum adaptive antibiotic resistance.
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