Expanding the scope of the enzymatic synthesis of DNA for (i) expansion of the genetic alphabet and (ii) next generation sequencing

DNA polymerases synthesize DNA, the essential biomolecule responsible for encoding the complex information necessary for life, with remarkable efficiency and fidelity. Chemists and biologists have exploited this extraordinary enzyme to develop a wide range of biotechnological tools, including but certainly not limited to PCR and Sanger sequencing. While these landmark applications continue to be relied upon to this day, they represent only a small fraction of the possible uses of these enzymes. Here, I detail my work to expand the scope of the enzymatic synthesis of DNA in two distinct fields. Chapters 2--5 detail efforts to identify replicable candidate unnatural base pairs to expand the genetic alphabet from the natural four base code to an expanded six base code. Using a wide range of techniques, including chemical synthesis, directed evolution of DNA polymerases, and screening based methodologies, the d 5SICS:dMMO2 base pair is identified, resulting in our strongest candidate base pair identified to date. Chapter 6 details the use of an activity based phage display system to identify a DNA polymerase that possesses improved recognition of substrates applicable in next generation sequencing applications.