The Xanthomonadales are early divergents of bacteria within the Gammaproteobacteria, and are often used to root phylogenetic trees created for the class. Until recently, the Xanthomonodales order was inclusive of the families Xanthomonadaceae, Algiphilaceae, Solimonadaceae, Nevskiaceae and Sinobacteraceae. However, no molecular signatures were found that were inclusive of all families. The organisms were taxonomically rearranged such that Xanthomonadales included Xanthomonadaceae, which was later divided into two families. The division was in accordance with CSIs that were found specifically for all members of the emended Xanthomonadales order, providing support for the currently accepted taxonomy. All other species were transferred to Nevskiales, which did not share CSIs with Xanthomonadales, but remain close relatives within the Gammaproteobacteria. Cardiobacteriales, Chromatiales, Methylococcales, Legionellales and Thiotrichales are also deep branching orders that are phylogenetic neighbours of Xanthomonadales and Nevskiales members. The order Nevskiales harbors a single family (Salinisphaeraceae) and six genera: Alkanibacter, Fontimonas, Hydrocarboniphaga, Nevskia, Solimonas and Steroidobacter.
