FIG. 2.

Chemical analysis of Neu4,5Ac₂ in spent culture medium. (A) Neu4,5Ac₂ at a 0.1% final concentration was incubated in minimal glycerol medium without cells for 7 h and then subjected to DMB analysis as described in the text. (B) Neu4,5Ac₂ in the spent culture supernatant of wild type was grown for 7 h in the presence of glycerol. (C) Neu4,5Ac₂ in the spent culture supernatant of the nanS mutant was grown in glycerol medium for 7 h. Note that the same profiles were obtained after comparable chemical analyses of 24-h cultures, indicating the stability of Neu4,5Ac₂ and its resistance to metabolism by E. coli K-12. RF, relative fluorescence.