FIG. 5.

Invasion rates of S. Typhimurium on HeLa cells after 10, 24, and 48 h of culture expressed in the total (T) cell population and in the LD, MD, and HD cell subpopulations obtained using Radioselectan density gradient centrifugation. The invasion rate represents the percentage of invasive cells expressed with respect to the number of culturable cells inoculated (10⁶ for each inoculum). Error bars represent the standard deviation of sextuplicate β-galactosidase assays. Results are representative of three independent experiments.