Figure 1. Adsorption of the p24 protein to spores of the B. subtilis WW02 strain.

(A) Evaluation of protein adsorption to spores at different pHs. Spores (2×10⁹) were suspended in PBS buffer at pH 4, pH 7 or pH 10, mixed with purified p24 protein (2 µg) and kept for 1 h at room temperature. The samples were centrifuged, washed twice with PBS and the spore coat proteins were extracted and submitted to electrophoresis in SDS-PAGE at 15%. The control lane (Con) represents spore samples without incubation with the protein and the control lane (Pr) shows 2 µg of purified p24. Image is representative of four independent experiments. (B) Detection of protein released from spores after adsorption. Spores adsorbed with p24 (PBS at pH 4) were resuspended in PBS at pH 4, pH 7 or pH 10 and incubated for different times. At indicated time points (15, 30, 45, and 60 min) samples were centrifuged and the supernatants and pellet (spores) were loaded onto 15% SDS-PAGE gel. (C) Determination of the saturation curve of p24 protein adsorption to B. subtilis spores. Increasing amounts of protein (0.5 to 4 µg) were added to B. subtilis spores (2×10⁹) following the procedure described before. The amount of protein adsorbed to the spores coat was quantified by dot-blot assay.