| Enterobacteriaceae, Pseudomonadales, Pseudomonadaceae, Vibrionaceae, Xanthomonadaceae|
Gammaproteobacteria are a class of several medically, ecologically, and scientifically important groups of bacteria. An exceeding number of important pathogens belong to this class. Like all Proteobacteria, the Gammaproteobacteria are Gram-negative.
The Gammaproteobacteria comprise several medically and scientifically important groups of bacteria, such as the Enterobacteriaceae, Vibrionaceae, and Pseudomonadaceae. A number of important pathogens belong to this class, e.g. Salmonella spp. (enteritis and typhoid fever), Yersinia pestis (plague), Vibrio cholerae (cholera), Pseudomonas aeruginosa (lung infections in hospitalized or cystic fibrosis patients), and Escherichia coli (food poisoning). Important plant pathogens such as Xanthomonas axonopodis pv. citri (citrus canker) and Pseudomonas syringae pv. actinidiae (kiwifruit Psa outbreak) are also Gammaproteobacteria. Members of Chromatium are photosynthetic and oxidize hydrogen sulfide instead of water, producing sulfur as a waste product. Some Gammaproteobacteria are methane oxidizers, and many are symbiotic with geothermic ocean vent-dwelling animals.
Due to a single genus, Acidithiobacillus, the Gammaproteobacteria class is paraphyletic to Betaproteobacteria (reviewed in Proteobacteria#Taxonomy).
A number of bacteria have been described as members of Gammaproteobacteria, but have not yet been assigned an order or family. These include bacteria of the genera Alkalimarinus, Alkalimonas, Arenicella, Gallaecimonas, Ignatzschineria, Litorivivens, Marinicella, Methylohalomonas, Methylonatrum, Plasticicumulans, Pseudohongiella, Sedimenticola, Thiohalobacter, Thiohalomonas, Thiohalorhabdus, Thiolapillus, and Wohlfahrtiimonas.