Hyphomicrobiales

Hyphomicrobiales, still widely known by its older name Rhizobiales, is an order of Gram-negative Alphaproteobacteria with strikingly varied lifestyles. Some members, the nitrogen-fixing rhizobia spread across families such as Rhizobiaceae, Hyphomicrobiaceae, Phyllobacteriaceae and Nitrobacteraceae, form symbiotic root nodules with plants, while others such as Bartonella and Brucella are pathogens of humans and animals. The order also includes methane- and methanol-oxidizing bacteria and the genus Agrobacterium, long used as a tool in plant genetic engineering.