FIG 2.

Representative STM hybridization reactions. Bacterial DNA was isolated from input and output mutant pools and signature tags amplified, labeled with DIG, and then used to hybridize membranes spotted with a signature tag array. Out of 56 initial signature tags, 3 were found to be cross-reactive (4, 13, and 56) and were subsequently excluded. Each array was composed of 53 signature tags that were shown to be specific. Red circles highlight those mutants that show a reduction in abundance between the input and the output pools. The tag numbers (1 to 56) are indicated.