FIG. 1.

Characterization of sialidase mutants. (A) Growth of strains in BHI broth supplemented with fetal bovine serum and N-acetyl muramic acid as determined by OD₆₀₀. Wt, wild type. (B) Sialidase activities of bacterial strains measured with the fluorescent substrate 4-methylumbelliferyl-N-acetyl-α-d-neuraminic acid. Sialidase activities associated with total cell extract and membrane and secreted fractions were determined for each strain. Equal amounts of protein fractions (25 to 100 μg) for each strain were assayed. Bars represent fluorescence values (means and standard deviations) from triplicate readings. Data are representative of more than three independent experiments with similar results. WT, wild type.