Graduate Work (M.Sc.)

Heterologous Expression of Secondary Lipid Biosynthesis Pathways

Omega-3 polyunsaturated fatty acids (PUFAs), such as EPA and DHA are likely beneficial to human health and are of increasing interest for commercial production. Current methods rely on extraction and purification from fish, but concerns about heavy metals and other bioaccumulating contaminants suggest the utility of new production methods. Heterologous expression of genes from PUFA-producing microbes represents one such method.

A number of γ-proteobacteria have been shown to produce EPA and DHA using a “Pfa synthase” gene cluster, whose products are encoded in the operon pfaEABCD. This pathway has been successfully cloned into and expressed by E. coli on multiple occasions, as early as 1996. Recently, Pfa-like gene clusters have been found in a diverse range of bacteria and even a Labyrinthulid protist, Schitzochytrium sp. ATCC-20888, suggesting horizontal gene transfer.

Genetic Tools for Eukaryotic Expression of Bacterial Operons

While the expression of bacterial operons in other bacteria is not trivial, heterologous expression of multi-gene biosynthetic pathways in eukaryotic organisms presents an interesting challenge. Yeast have been used for thousands of years in producing materials for human consumption, and continue to be involved in the production of bread, beer, wine, and fuel. Yeast such as Saccharomyces cerevisiae are also widely employed as eukaryotic model organisms in life science research. S. cerevesiae is not, however, known to process bacterial operons without modification, as each gene must have its own unique regulatory machinery for efficient expression. That said, S. cerevisiae is a veritable DNA wizard: its homologous recombination machinery can be used to manipulate and recombine multiple large genetic pieces with relative ease.

I am interested in developing workflows and toolsets that allow for the "translation" of bacterial genetic code into yeast, and the assembly of large, clustered biosynthetic pathways which can be efficiently expressed in yeast and potentially other eukaryotes.