FIG 3 .

Purine de novo biosynthesis is required for curli production. (A) Purine de novo biosynthesis pathway in E. coli, adapted from BioCyc. Genes identified by TraDIS that, when mutated, abrogated curli production are indicated by an asterisk. (B) CR staining of wt MS7163, MS7163csgA, defined pur mutants, and their complemented strains following growth on YESCA-CR agar. Strains were grown by spotting 5 µl of an overnight culture on YESCA-CR agar and incubating the culture for 24 h at 37°C. Mutation of genes in the purine de novo biosynthesis abolished CR binding, while complementation restored this phenotype. (C) Western blot analysis of CsgA performed using whole-cell lysates prepared from MS7163 or MS7163csgA and pur mutants and their complemented strains. Bacteria were grown on YESCA agar for 24 h to induce curli production and treated with formic acid to dissolve polymerized CsgA. Anti-OmpA antibody was used as a loading control. (D) CR staining of wt MS7163, MS7163csgA, MS7163purM, and MS7163purK following growth on YESCA-CR agar with (+) and without (−) IMP supplementation.