Phylogenetic tree highlighting the position of H. thermophilus TK-6T relative to the type strains of the other species within the genus and to the type strains of the other genera within the family Aquificaceae. The trees were inferred from 1,423 aligned characters [14,15] of the 16S rRNA gene sequence under the maximum likelihood criterion  and rooted in accordance with the current taxonomy . The branches are scaled in terms of the expected number of substitutions per site. Numbers above branches are support values from 1,000 bootstrap replicates  if larger than 60%. Lineages with type strain genome sequencing projects registered in GOLD  are shown in blue, published genomes in bold [12,20,21].