Determination of PNAG production by immunological assay. Crude extracts were prepared from overnight cultures grown in M9Glu/sup at 37°C. PNAG detection was carried out with polyclonal PNAG specific antibodies as detailed in Materials and Methods. PNAG determination was repeated four times (twice on each of two independent EPS extractions) with very similar results: data shown are from a typical experiment. Upper panel (pnp+): E. coli C-1a (wt), C-5936 (ΔpgaC), C-5930 (ΔcsgA), C-5928 (ΔbcsA), C-5934 (ΔwcaD); lower panel (Δpnp): E. coli C-5691 (wt), C-5937 (ΔpgaC), C-5931 (ΔcsgA), C-5929 (ΔbcsA), C-5935 (ΔwcaD).