Definitive assignment by multigenome analysis of the gammaproteobacterial genus Thermithiobacillus to the class Acidithiobacillia.

The class Acidithiobacillia was established using multiprotein phylogenetic analysis of all the available genomes of the genus Acidithiobacillus (comprising Family I, the Acidithiobacillaceae, of the Acidithiobacillales, the order created for Bergey's Manual of Systematic Bacteriology), and for representative genomes of all available bacterial orders. The Acidithiobacillales contain a second family, the Thermithiobacillaceae, represented by Thermithiobacillus tepidarius, and created on the basis of nearest neighbour 16S ribosomal RNA gene sequence similarities. This could not be included in the original multiprotein analysis as no genome sequence for Thermithio bacillus was available. The publication of the genome sequence of Thermithiobacillus tepidarius in 2013 has enabled phylogenetic assessment of this organism by comparative multigenome analysis. This shows definitively that Thermithiobacillus is a member of the class Acidithiobacillia, distinct from the Acidithiobacillus genus, and confirms it to represent a second family within the Acidithiobacillia.