Proposal for a new class within the phylum Proteobacteria, Acidithiobacillia classis nov., with the type order Acidithiobacillales, and emended description of the class Gammaproteobacteria.

The order Acidithiobacillales was previously assigned to the class Gammaproteobacteria. Recent analyses have indicated that this order actually lies outside all the proteobacterial classes, as a sister group to the combined classes Betaproteobacteria and Gammaproteobacteria. We now confirm this result with multiprotein phylogenetic analysis of all the available genomes of members of the order Acidithiobacillales and representatives of all available bacterial orders, and propose the new proteobacterial class, Acidithiobacillia, with the type order Acidithiobacillales, comprising the families Acidithiobacillaceae and Thermithiobacillaceae with the type genus Acidithiobacillus.