Legionellales

The Legionellales are an order of Pseudomonadota ("Proteobacteria"). Like all Pseudomonadota, they are Gram-negative.^[2] They comprise two families, typified by Legionella and Coxiella, both of which include notable pathogens. For example, Q fever is caused by Coxiella burnetii and Legionella pneumophila causes Legionnaires' disease^[3][4] and Pontiac fever.^[5][6][7]

Legionellales
Legionella sp. under ultraviolet illumination
Scientific classification
Domain:	Bacteria
Kingdom:	Pseudomonadati
Phylum:	Pseudomonadota
Class:	Gammaproteobacteria
Order:	Legionellales
Families and genera
Legionellaceae    Legionella Coxiellaceae    Aquicella    Coxiella    Diplorickettsia    Rickettsiella    "Ca. Berkiella"[1]    "Ca. Fiscibacter"[1]    "Ca. Ovatusbacter"[1]    "Ca. Pokemonas"[1]

Members of the order Legionellales can be molecularly distinguished from other Gammaproteobacteria by the presence of four conserved signature indels (CSIs) in the proteins tRNA-guanine(34) transglycosylase, lipoprotein-releasing system transmembrane protein lolE and tRNA (guanosine(37)-N1)-methyltransferase TrmD.^[8]