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Responses to low oxygen and energy taxis by Pseudomonas aeruginosa

Posted on:2008-10-30Degree:Ph.DType:Dissertation
University:The University of IowaCandidate:Alvarez, CarolinaFull Text:PDF
GTID:1444390005961941Subject:Biology
Abstract/Summary:
Pseudomonas aeruginosa is ubiquitously found in nature and is also an important opportunistic pathogen of patients afflicted with the autosomal recessive disorder cystic fibrosis (CF). Crucial to the development of new antimicrobial therapies is understanding the physiology of P. aeruginosa during these infections, particularly the energy generation pathways utilized while colonizing the hypoxic mucus that deposits on the airway epithelia of CF patients. This facultative anaerobe has three terminal oxidases predicted to have a high affinity for oxygen, which suggests that it is well suited for microaerobic respiration. In this study I showed that P. aeruginosa is able to grow with oxygen concentrations as low as 3 muM dissolved oxygen. Since similar concentrations are found in the CF mucus, these results suggest microaerobic respiration as a plausible in vivo energy generation pathway. I also determined that with decreasing oxygen concentrations, overlapping sets of genes were differentially regulated depending on the amount of oxygen available for respiration. Some of these genes might be involved in survival under said conditions. In addition, I showed that all three terminal oxidases predicted to have a high-affinity for oxygen contribute to microaerobic respiration. P. aeruginosa appears to grow as biofilms within the CF mucus. By using high-affinity terminal oxidase mutants that are impaired in growth with low oxygen, I found that microaerobic respiration is necessary for biofilm development and for maintenance of cell viability. In common with the majority of motile bacteria, P. aeruginosa is able to perform energy taxis to find microenvironments that enhance energy production. I demonstrated that Aer is an energy taxis receptor that mediates aerotaxis and taxis to the alternative electron acceptor nitrate. I also determined that the Aer-mediated energy tactic response dominates over the chemotactic response to some organic compounds that P. aeruginosa utilizes as carbon and energy sources.
Keywords/Search Tags:Aeruginosa, Energy, Oxygen, Microaerobic respiration, Low
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