FIG 6.

Sialic acid release from Caco-2 cells after treatment with 16-h TH culture supernatants containing NanI, NanJ, or NanH. Supernatants were removed from five independent cultures (wild-type CN3718 expresses all three sialidase genes; BMC205 has null mutations in all three sialidase genes [17]; ENanJ expresses only the nanJ gene, ENanI expresses only the nanI gene, and ENanH expresses only the nanH gene) that had been grown for 16 h at 37°C in TH broth. The supernatants were then incubated with Caco-2 cells (see Materials and Methods) for 16 h at 37°C, and the concentration of sialic acid released from the Caco-2 cells was then detected using the EnzyChrom neuraminidase assay kit. All experiments were repeated three times, and mean values are shown. The error bars indicate standard deviations.