Source: Members of the genera
Rickettsiella and
Diplorickettsia are observed to form a reliable clade in phylogenetic trees constructed from various datasets of concatenated protein sequences and 16S rRNA sequences, suggesting that they might belong to a single genus. Genomic analyses identified 12
conserved signature indels (CSIs) that are specific for this clade in the proteins
inositol monophosphatase, lysyl-tRNA synthetase, elongation factor P-(R)-beta-lysine ligase, tol-Pal system beta propeller repeat protein TolB, FKBP-type peptidyl-prolyl cis-trans isomerase, response regulator transcription factor, 30S ribosomal protein S2, glycine cleavage system aminomethyltransferase GcvT, M3 family metallopeptidase, lysm peptidoglycan-binding domain-containing protein and oligopeptide transporter. The presence of these CSIs reliably distinguishes this clade from other Legionellales species in molecular terms, further supporting the combination of the genera
Rickettsiella and
Diplorickettsia. Additionally, three CSIs were identified as uniquely shared between
Diplorickettsia, Rickettsiella and
Coxiella, another genus belonging to the family
Coxiellaceae. The absence of
Aquicella species (the remaining genus within the family
Coxiellaceae) from the shared CSIs suggests that the genera
Coxiella, Diplorickettsia and
Rickettsiella share a common ancestor exclusive of
Aquicella. ==References==