Final answer:
Pathogens like Salmonella and Vibrio cholerae invade the host's intestinal epithelium via effector protein-induced membrane ruffling or surface protein-mediated receptor binding and endocytosis, leading to diseases characterized by severe dehydration and diarrhea.
Step-by-step explanation:
Toxins from pathogens like Salmonella, Shigella, and Vibrio cholerae enter the host's intestinal epithelium primarily by two methods: the trigger mechanism and receptor-mediated endocytosis. In the trigger mechanism, pathogens secrete effector proteins that induce membrane ruffling, which facilitates bacterial cell entry. An example of this trigger mechanism is apparent with Salmonella entering the intestinal epithelial cells. On the other hand, some bacteria, such as Yersinia pseudotuberculosis and L. monocytogenes, produce surface proteins that bind to host cell receptors, inducing endocytosis. For instance, Cholera toxin uses an A-B toxin structure where the B subunit binds to the epithelial cell, and the A subunit enters the cytoplasm causing an increase in cAMP, which disrupts cell function leading to severe dehydration and diarrhea.