Abstract
Multiplex automated genome engineering (MAGE) uses short oligonucleotides to scarlessly modify genomes; however, insertions >10 bases are still inefficient but can be improved substantially by selection of highly modified chromosomes. Here we describe 'coselection' MAGE (CoS-MAGE) to optimize biosynthesis of aromatic amino acid derivatives by combinatorially inserting multiple T7 promoters simultaneously into 12 genomic operons. Promoter libraries can be quickly generated to study gain-of-function epistatic interactions in gene networks.