Wiktionary
gammaproteobacteria
n. (plural of gammaproteobacterium English)
Wikipedia
Gammaproteobacteria
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.