Vibrio and related genera
A few other genera, including Vibrio and Aeromonas, are also facultative anaerobes able to carry out the fermentative reactions described above, but are differentiated from the enteric bacteria by being oxidase-positive (Table 7.4). Vibrio and Photobacteriumboth include examples of marine bioluminescentspecies; these are widely found both in seawater and associated with fish and other marine life. The lumi-nescence, which requires the presence of oxygen, is due to an oxidation reaction carried out by the enzyme luciferase.
Vibrio cholerae is the causative agent of cholera, a debilitating and often fatal formof acute diarrhoea transmitted in faecally contaminated water. It remains a major killer in many third world countries. Several species of Vibrio, including V. cholerae, have been shown to possess two circular chromosomes instead of the usual one.
Representative genera: Vibrio, Aeromonas