16S rRNA gene sequence analysis is the most commonly used method for identifying bacteria or for constructing bacterial phylogenetic relationship. however,its usefulness is limited because of the high percentage of sequence similarity between closely related species. The use of protein-encoding genes as phylogenetic markers is now a common approach.Detailed investigations have demonstrated that sequences from protein-encoding genes can accurately predict genome relatedness and may replace DNA–DNA hybridization for species identification and delineation in the future