Date of Award


Document Type




Thesis Advisor

Christopher T. Nomura


Polyhydroxyalkanoates (PHAs) are a common family of biodegradable plastics that are used to create a variety of bulk-­‐commodity plastics. Polyhydroxybutyrate (PHB) belongs to the PHA family of bioplastics and has been the most widely studied PHA member. As presence of biodegradable plastics, such as PHB, become more prevalent in everyday products, it is of increasing interest to understand how these plastics are being degraded in the natural environment. Pseudomonas aeruginosa is a common soil bacterium that exhibits the ability to degrade PHB and use the monomer of this polymer, D-­‐3-­‐ hydroxybutyrate (D-­‐3-­‐HB), as a carbon source. P. aeruginosa converts D-­‐3-­‐HB into acetoacetate through the enzymatic action of the cytosolic protein D-­‐3-­‐hydroxybutyrate dehydrogenase (BdhA). Directly adjacent to the bdhA gene within the P. aeruginosa genome are the PA2004 and PA2005 genes, the three of which are all believed to be the primary genes involved in D-­‐3-­‐HB metabolism. Using mutant strains of P. aeruginosa lacking the function of the bdhA, PA2004, or PA2005 genes, complementation assays were performed to determine the role of these genes in D-­‐3-­‐HB metabolism. The experimental results proved that the PA2004 gene codes for a putative transporter protein responsible for the uptake of D-­‐3-­‐HB into the cell and the PA2005 gene encodes an enhancer binding protein that mediates expression of the bdhA-­‐PA2004 gene operon. Characterization of PA2005 gene function, as well as the putative transporter of D-­‐3-­‐HB, encoded by the PA2004 gene, has provided insight into the genetic and metabolic processes responsible for PHB degradation by P. aeruginosa.

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