The phylogenetic potential of the 23S ribosomal RNA marker has previously been exploited for Legionella and Coxiella (Afseth et al., 1995; Grattard et al., 2006), but has not yet been explored for Rickettsiella bacteria. Moreover, in attempts to go beyond ribosomal phylogenies,

several protein-encoding genes have been investigated as possible phylogenetic markers within the Coxiellaceae (Sekeyová et al., 1999; Leclerque & Kleespies, 2008a, b; Mediannikov et al., 2010), but often with rather limited success. The systematic taxonomic analysis of the first Rickettsiella genome sequence (Leclerque, 2008a) has revealed a set of protein-encoding markers that operate reasonably well above the genus

level; however, the suitability of these markers for generic and infra-generic taxonomic assignments has not been studied ATM/ATR assay previously. Independently, the ftsY gene, which encodes the bacterial homolog of the eukaryotic signal BTK inhibitor recognition particle receptor subunit alpha involved in protein translocation and has previously been identified as the most appropriate single gene marker for the estimation of the G+C content in prokaryotic genomes (Fournier et al., 2006), has recently been introduced as a phylogenetic marker for the characterization of Rickettsiella-like bacteria (Mediannikov et al., 2010; Kleespies et al., 2011). In the study presented here, a partial sequence of the 23S rRNA-encoding gene, an MLST marker set consisting

of six protein-encoding genes selected on the basis of previous data-mining of the R. grylli genome, and the ftsY gene together with the virtually complete 16S rRNA-encoding sequence as a reference were compared for their phylogenetic potential with respect to the generic and infra-generic classification of Rickettsiella bacteria. For this purpose, the orthologous sequences from the R. popilliae-synonymized pathotypes ‘R. melolonthae’ and ‘R. tipulae’ were determined and analyzed together Baf-A1 order with the corresponding R. grylli sequences by a methodological approach combining phylogenetic reconstruction with likelihood-based significance testing. Genomic DNA of Rickettsiella strains BBA1806 (pathotype ‘R. melolonthae’) and BBA296 (pathotype ‘R. tipulae’) was extracted by a standard protocol (Walsh et al., 1991) based on the Chelex 100 resin (Bio-Rad) from, respectively, infected fat body tissue of diseased Melolontha grubs collected in the Lorsch area, Germany, and L3–L4 larvae of the crane fly, T. paludosa, collected near Burscheid, Germany.