pro·te·o·bac·te·ri·um 
(pr
ō′t
ē-
ō-b
ăk-tîr
ē-
əm)
n. pl. pro·te·o·bac·te·ri·a (-tîr
ē-
ə)
Any of numerous gram-negative bacteria of the phylum Proteobacteria, including E. coli, the agrobacteria, many nitrogen-fixing bacteria, and many pathogens, such as salmonella.
[New Latin prōteobactērium, back-formed singular of Prōteobactēria, phylum name : Greek Prōteus, Proteus (the great morphological, metabolic, and ecological diversity of the phylum being likened to the god's shape-shifting powers) + New Latin bactērium, bacterium; see BACTERIUM.]