What is "legionellales"

The Legionellales are an order of Proteobacteria. Like all Proteobacteria, they are Gram-negative. 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.