Penetration of 042 and 042aap through mucus. Columns of 10 mg/ml mucin in HBSS were prepared in tuberculin syringes, and the bacterial inocula were applied to the top of the column. The columns were incubated at 37°C for 75 minutes. After this time, the mucin suspension was drained from the column in 0.1-ml fractions, and the number of 042 (black bars) or 042aap (white bars) was determined by quantitative plating in triplicate. Bars represent SD. Fraction 10 represents the bottom of the column, fraction 1 the top. *P < 0.05 by Student’s t test of log-transformed data.