Physiological and compositional changes in Pseudomonas aeruginosa (ATCC 9027) were monitored during, growth on various petroleum compounds in a chemically-defined medium. Growth of P. aeruginosa was observed when furnace oil, kerosene, aviation fuel, light crude oil and hexadecane were used as carbon and energy sources. A variable and extended lag period before active growth was achieved was characteristic of petroleum-grown cells as compared to glucose-grown cells. Growth on the petroleum hydrocarbons, compared with that on glucose, resulted in changes in cell lipid composition, outer membrane proteins, cell-surface hydrophobicity, surface-tension, and pH changes in the growth medium during transition from early to late-log phase. Cell composition and physiology of cells grown in the petroleum mixtures varied due to differences in the chemical composition of the material. Production of an exopolymer (characterized as a peptidoglycolipid) was associated with petroleum-grown cells but not with glucose-grown cells. The above differences illustrate some of the dynamic and physiological and biochemical changes the microorganism undergoes to access its hydrophobic carbon and energy source.

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The Gram-negative bacterium Pseudomonas aeruginosa is a notorious opportunistic pathogen of individuals with the genetic disease cystic fibrosis (CF). Pseudomonas aeruginosa establishes a chronic infection within the CF lung, where the sputum accumulation characteristic of CF provides a complex and copious growth substrate. P. aeruginosa can grow to high densities in vivo (>10⁹ cells/ml lung sputum), and exacerbations associated with P. aeruginosa high density in vivo growth are primary contributors to CF morbidity and mortality. Surprisingly little is known about the catabolic processes that underlie P. aeruginosa in vivo growth. Unfortunately, nutritional modeling of the CF lung environment in animal models is difficult, as current animal models fail to mimic the sputum accumulation characteristic of CF. In this dissertation, I describe the use of expectorated CF sputum as a P. aeruginosa in vitro growth medium. Using global expression analysis, I show that P. aeruginosa up-regulates genes important for amino acid and lactate metabolism during growth in CF sputum as compared to a laboratory medium. P. aeruginosa also demonstrates enhanced production of the cell-cell communication signal 2-heptyl-3-hydroxy-4-quinolone (the Pseudomonas quinolone signal, PQS), a critical regulator of virulence factor production, during growth in CF sputum. Further, I use chemical analyses of CF sputum samples to develop a defined, synthetic medium that can be used to nutritionally model in vivo conditions. Using this medium, I show that PQS biosynthesis and aromatic amino acid metabolism are intimately linked and that cell-cell communication mediated by PQS is strikingly dependent upon the growth environment of P. aeruginosa. In addition, I demonstrate that P. aeruginosa preferentially consumes specific carbon sources present in the CF sputum milieu during rapid growth. I also describe the use of in vivo-relevant nutrient concentrations to evaluate the potential for P. aeruginosa anaerobic growth in CF sputum. Finally, I describe the purification and characterization of the aromatic amino acid-responsive transcriptional regulator PhhR and discuss its potential role in regulation of P. aeruginosa in vivo carbon substrate preference. / text