Application of the numerical characteristic of formal order analysis of the prokaryotic genomes for reclassification within the genus Rickettsia

Genomes representing Rickettsiaceae family were analyzed using formal order analysis (FOA) of information chain in order to develop a new approach for the classification of prokaryotes. Average remoteness — the numerical characteristic of order was used to compare the genomes. FOA allows one to directly take into account arrangement of nucleotides in each sequence. The obtained results clarified the previously known classification. In addition Rickettsia felis group was discovered between the ancestral group and spotted fever group (SFG) and R. akari group located between the SFG and genus Orientia. Software used for the analysis of nucleotide sequences with FOA is freely available at http://foarlab.org.