Identification and screening of Francisella tularensis indel markers

In silico search for and identification of new types of markers for phylogenic relation studies of Francisella tularensis, the causative agent of tularemia, and PCR screening of twenty-four representative strains of the pathogen, allowed for correct identification of F. tularensis subspecies and groups. The insertion/deletion (indel) markers were able to confirm earlier findings of a phylogenetic relationship between the subspecies of F. tularensis and further extend the phylogeny by positioning F. tularensis ssp. mediasiatica in the phylogenetic tree of F. tularensis. The data also supports previous suspicions that the Japanese strains of F. tularensis ssp. holarctica should be considered a separate subspecies. Some of the markers also suggest possible horizontal gene transfer between the subspcies of F. tularensis. Future developments will consists in screening of additional indel markers in additional strains of F. tularensis and combination with results from other typing methods in the hope of providing the standard future tool for fast and reliable strain identification and phylogenetic analysis. In conclusion, indel markers appear to have suitable discriminatory capabilities for reliable subspecial identification and correct phylogenetic inference within Francisellaceae.