General Bacteriology Practice Test

Cholera toxin, produced by the bacterium Vibrio cholerae, has a well-documented mechanism of action that involves the activation of a specific signaling pathway within intestinal epithelial cells. When cholera toxin is internalized, it catalyzes ADP-ribosylation of the Gs protein, which is involved in the regulation of adenylate cyclase.

This modification of the Gs protein prevents its inactivation, leading to persistent activation of adenylate cyclase. As a result, there is a significant increase in the conversion of ATP to cyclic AMP (cAMP). Elevated levels of cAMP then activate protein kinase A (PKA), which in turn promotes various cellular effects, including the secretion of chloride ions and water into the intestinal lumen, resulting in the characteristic watery diarrhea associated with cholera.

Therefore, the correct answer reflects the understanding that cholera toxin's primary effect is the increase in cAMP production, which drives the pathophysiology of cholera.