Citrulline ureidase gene diversity in the genus <Emphasis Type="Italic">Francisella</Emphasis>

This work describes the results of analysis in silico of the genetic diversity of the citrulline ureidase gene (ctu) in two species of bacteria of the genus Francisella: tularensis (ssp. tularensis, holarctica, mediasiatica, novicida) and philomiragia. The strains of the Central Asiatic subspecies possessing citrulline ureidase activity differ in the ctu gene from ssp. tularensis Schu by three nucleotide substitutions leading to two insignificant amino acid substitutions in the encoded polypeptide. In the strain of F. tularensis ssp. holarctica, the ctu gene encodes an inactive enzyme, which is probably due to amino acid substitutions 151Gly → Asp, 183Pro → Leu, and 222Asp → Asn. Except for the Japan biovar bacteria, all strains of the Holarctic subspecies contain two stop codons in the ctu gene. The bacteria of the novicida subspecies contain the ctu gene only in the strain 3523, whereas the other strains contain the FTN_0827 gene encoding the CN hydrolase, which probably provides the citrulline ureidase activity.