The goal of the Phage Team is to modify the capsid sizes of enterobacteriophages T4 (a large phage) and T7 (a smaller phage). Bacteriophages are subjected to random mutagenesis by growing them in liquid culture with 5'-bromodeoxyuridine (BrdU), a nucleotide analog that causes mutation. Phages are then separated from the bacteria and purified in a CsCl gradient. The gradient is separated into fractions and each fraction is tested for the presence of phage. The plaque sizes in phage-containing fractions are analyzed and compared with the plaques produced by wild-type phage. Plaque-size variants are then purified, tested for phenotypic stability, and are imaged and measured using transmission electron microscopy (TEM). Stable mutants showing varying capsid sizes are added to the library and their mutations are characterized by PCR and sequencing. Mutants are then subjected to further mutagenesis.
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