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Environmental and Forest Biology


Pseudomonas aeruginosa PAO1 is an opportunistic pathogen known to have an arsenal of virulence factors that can affect immunocompromised patients. One of these virulence factors is the redox-active phenazine compound, pyocyanin. The production of pyocyanin is regulated by multiple mechanisms, which include stress response and quorum sensing (QS). In a previous study, we found that the PA2449 gene was required for the biosynthesis of QS homoserine lactones and pyocyanin. This study focused on a particular strain of P. aeruginosa that lacked the ability to produce pyocyanin. We restored the production of pyocyanin in this strain by inserting a vector encoding a gene responsible for pyocyanin biosynthesis, rhlI. We then did various studies to determine the levels at which the toxin was produced compared to the wild type strain. We found that in smaller volumes of medium, the mutant strain production levels were similar to the wild type, 219 μM. In larger volumes of media the two strains produced a similar amount of pyocyanin although the timing of the production between the two strains was different, 4.5 hours for the wild type and 9 hours for the mutant strain containing the vector. We also analyzed other strains with knockouts relevant to the PA2449 gene. This led us to discover the potential role for PA2449 in pyocyanin production, in repressing the expression of MexEF- OprN allowing the intracellular accumulation of PQS. This study will allow us to further understand the mechanisms that Pseudomonas, as well as other bacteria, use when producing toxins.

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