FIG 2.

Functionality of SlpA and InvA expressed on the surface of B. subtilis spores. (a) Binding of B. subtilis spores to Caco-2 cells. Spores (5 × 10⁹/well) were added to wells with cultured Caco-2 cells (2 × 10⁵) and incubated for 2 h at 37°C. After extensive washings, the numbers of viable spores bound to the Caco-2 cells were determined by plating whole-cell homogenates. The results represent the average of three independent experiments, with each experiment performed in duplicate. (b) Intestinal transit of B. subtilis spores after oral administration to BALB/c mice. Mice (n = 5/group) were inoculated with a single oral dose (10¹¹ spores/animal) of the spores suspended in bicarbonate solution. Fecal samples were collected periodically, diluted in saline, heated to inactivate vegetative cells, and plated on LB medium supplemented with antibiotics. (c, d) Interaction of B. subtilis spores with PPs. Spores (5 × 10⁹) were given orally to BALB/c mice (n = 4). On days 1 (c) and 6 (d) postadministration, the animals were sacrificed. PPs were surgically removed, homogenized, and plated on LB supplemented with antibiotics for the determination of viable spores and vegetative cells. The assay was performed in duplicate and independently repeated at least three times. Values are expressed as means ± SDs, and the results obtained by statistical analyses represent the differences between the tested strains and the LDV702 strain (*, P < 0.05; ***, P < 0.001).