Multifaceted Interactions of Bacterial Toxins With the Gastrointestinal Mucosa

MR Popoff


Future Microbiol. 2011;6(7):763-797. 

In This Article


Among the large diversity of bacteria, that can reside or transit in the digestive tract, some have developed specific interactions with the gastrointestinal mucosa and are responsible for gastrointestinal or food-borne diseases, which are the major cause of infectious diseases. The most striking features of toxins acting on the gastrointestinal mucosa is their broad variety of size (2–300 kDa), structure (single-chain, multicomponent toxins, AB5 structure) and modes of action, including signal transduction through the membrane, pore formation, alteration of a particular mechanism of eukaryotic cells or cell death. It is intriguing to note that bacteria can produce components, apparently not essential for bacterial growth or survival, which interfere specifically with key components of critical functions in eukaryotic cells, such as enzyme or hormone receptors on the cell surface or intracellular regulatory proteins (heterotrimeric G-proteins or small G-proteins). Evolutionary convergence may explain certain toxin mechanisms on eukaryotic cells. For example, ST mimics a natural hormone (guanylin) and both peptides share a high level of identity. Intestine-colonizing bacteria have developed a long-lasting interplay to survive in the intestinal ecosystem and for that they have produced specific compounds permitting an adaptive response counteracting the host's natural defenses. Enterotoxins have been proposed to interfere with the mucosal defenses by increasing fluid secretion and, thus, disrupting the mucus layer, conditions, that permit the access of intestinal colonizing bacteria to enterocyte surface.[222] However, the advantage of producing such potent and highly specific toxins for environmental bacteria remains unclear. For example, C. botulinum can grow in food and secrete potent neurotoxins. Sometimes, these bacteria do not sporulate and do not survive in certain food, while the toxins can persist and kill a consumer.