D

Vibrio cholerae is a curved, motile Gram-negative bacillus, not a Gram-positive rod; in contrast, it causes profuse sodium- and water-rich diarrhea, produces cholera toxin, and that toxin activates adenylate cyclase in enterocytes—all of which are well-documented features [Wai, 1999, PMID 10556702; Vanden Broeck, 2007, PMID 17716938].