Comparative genomic studies have identified several conserved signature indels (CSIs) that are specific for all species belonging to the phylum Aquificota and provide potential molecular markers.

[10][11][12] Several CSIs have also been identified that are specific for the species from the Aquificota and provide potential molecular markers for this phylum.

It is suggested that the network of hydrogen bonds formed between the water molecules, CSI residues and ADP/ATP helps to maintain ATP/ADP binding to the SecA protein at high temperatures, which contributes to the bacteria’s overall thermostability.

[19] In contrast to the very high G+C content of their rRNAs (i.e. more than 62%), which is required for stability of their secondary structures at high growth temperatures,[20] the inference that the Aquificota do not constitute a deep-branch lineage is also independently strongly supported by CSIs in a number of important proteins (viz.

[19] A specific relationship of the Aquificota to the Proteobacteria is supported by a two-amino-acid CSI in the protein inorganic pyrophosphatase, which is uniquely found in species from these two phyla.

[3] The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[23] and National Center for Biotechnology Information (NCBI)[24][25] Thermosulfidibacteraceae Desulfurobacteriaceae Hydrogenothermaceae Aquificaceae [incl.