As anticipated, mutants lacking the sphingolipid biosynthesis factors A4GALT, UGCG, and SPTLC2 (all of which contribute to Gb3 production) were far less susceptible to ΔescN mutant infection than wt HT-29 cells; at 5 days postinfection, the abundance of these mutants did not differ from that of mock-infected controls (Fig. 4A). This evidence concerns the gene UGCG and infection.