FIG. 2.

Essentiality of genes controlling amino acid biosynthesis in E. coli. (A) Functional overview of amino acid biosynthesis. Each block represents one or more pathways leading to production of a particular amino acid or its key intermediates (shown in smaller boxes). Within each block, stacked bars represent the gene products involved in the pathway (according to SWISS-PROT release of June 2002). Bars are colored according to gene essentiality (green, nonessential; red, essential; gray, undefined). (B) Detailed representation of the lysine biosynthetic pathway. Genes predicted in the ERGO database to be paralogs in this pathway are shown, in addition to genes whose roles in the biosynthesis of lysine have been experimentally verified (in bold).