Gammaproteobacteria are a class of several medically, ecologically, and scientifically important groups of bacteria. An exceeding number of important pathogens belongs to this class. Like all Proteobacteria, the Gammaproteobacteria are Gram-negative.
Phylogeny of Gammaproteobacteria after Not all orders are monophyletic, consequently families or genera are shown for Pseudomonadales, Oceanospirillales, and Alteromonadales. In the case of singleton orders, the genus is shown. (In bacterial taxonomy, orders have the suffix -ales, while families have -aceae.)