Role of aap in epithelial cell adherence. Assays were performed for 3 hours in DMEM–0.5% glucose with 0.2 mM IPTG at 37°C in atmosphere. (a) 042; (b) 042aap; (c) 042aap(pAap). (d and e) The standard HEp-2 cell adherence assay was performed using strain 042aap, but with pure Aap (d) or pure BSA (e) added concurrently with the bacterial inoculum. Each protein was added to a final concentration of 0.1 mg/ml. (f) Quantitation of HEp-2 cell adherence on confluent monolayers growing in DMEM without IPTG (042 and 042aap) or with indicated IPTG concentration [042aap(pAap)]. Bacteria were removed from glass using 1% Triton X-100 and quantitated by viable count. Assays were performed in triplicate, and means are illustrated in histograms with error bars indicating SE. *P < 0.05 vs. 042 by one-tailed t test of log-transformed data; **P < 0.05 vs. 042aap by one-tailed t test of log-transformed data.