ABSTRACT
Abstract Clostridia are the bacteria, which produce the highest number of toxins, and are involved in severe diseases in man and animals. Most of the clostridial toxins are pore forming toxins responsible for gangrenes and gastro intestinal diseases. Among them, perfringolysin has been largely studied and it is the paradigm of the cholesterol binding cytotoxins, whereas Clostridium septicum alpha toxin, which is related to aerolysin, is the prototype of several clostridial toxins forming small pores. Other toxins active on the cell surface possess an enzymatic activity such as phospholipase C and collagenase and are involved in the degradation of specific cell membrane or extracellular matrix components. Three groups of clostridial toxins have the ability to enter cells: large clostridial toxins, binary toxins, and neurotoxins. The binary and large clostridial toxins alter the actin cytoskeleton by enzymatically modifying the actin monomers and the regulatory proteins from the Rho family, respectively. Clostridial neurotoxins proteolyse key components of the neuroexocytosis system. Botulinum neurotoxins inhibit neurotransmission at the neuromuscular junctions, whereas tetanus toxin targets the inhibitory intemeurons of the central nervous system. The high potency of clostridial toxins result from their specific targets, which have an essential cellular function, and from the type of modification that they induce.
