Display of the peroxiredoxin Bcp1 of Sulfolobus solfataricus on probiotic spores of Bacillus megaterium

Bacterial spores displaying heterologous proteins have been proposed as a safe and efficient method for delivery of antigens and enzymes to animal mucosal surfaces. Initial studies have been performed using Bacillus subtilis spores, but other spore forming organisms have also been considered. B. megaterium spores have been shown capable of displaying large amounts of a model heterologous protein (Discosoma red fluorescent protein mRFP) that in part crossed the exosporium to localize in the space between the outer coat layer and the exosporium. Here, B. megaterium spores have been used to adsorb Bcp1 (bacterioferritin comigratory protein 1), a peroxiredoxin of the archaeon Sulfolobus solfataricus, known to have an antioxidant activity. The spores were highly efficient in adsorbing the heterologous enzyme which, once adsorbed, retained its activity. The adsorbed Bcp1 localized beneath the exosporium, filling the space between the outer coat and the exosporium. This unusual localization contributed to the stability of the enzyme-spore interaction and to the protection of the adsorbed enzyme in simulated intestinal or gastric conditions.