Streptomyces and particularly Streptomyces scabies the causative agent of common scab in potato tubers are producing different toxins, including thaxtomin A, nigericin, geldanamycin, tuncamycin and bafilomycin. Assay of these toxins in two potato strains from the commercial circuit revealed that thaxtomin A can be detected in significant amounts in scab surface lesions but also in the flesh of the tubers. Other toxins were present under the detection limit of the assay. As thaxtomin A and other Streptomyces toxins are thermostable, potato consumers can be exposed to these molecules. In order to evaluate the potential effect of Streptomyces toxins on the intestinal barrier, their cytotoxicity was studied in-vitro on Caco2/TC7 enterocytes. Except geldanamycin, all other tested toxins showed significant cytotoxicity. Used at sub-lethal concentrations, Streptomyces toxins were without effect on the transepithelial resistance of a model of intestinal epithelium made by fully differentiated Caco2/TC7 cells cultured in inserts. However, measurements of the flow of these toxins through reconstructed intestinal epithelium suggest that thaxtomin A, geldanamycin and tuncamycin could cross the intestinal barrier. These results should deserve in-vivo studies to evaluate the real threat of these toxins in regard of consumers.

Download this article as