There is a need for easy, practical, reliable and robust techniques for the identification and classification of bacterial isolates to the species level as alternatives to 16S rRNA gene sequence analysis and DNA-DNA hybridization. Here, we demonstrate that multilocus sequence analysis (MLSA) of housekeeping genes is a valuable alternative technique. An MLSA study of 10 housekeeping genes (atpD, dnaK, gap, glnA, gltA, gyrB, pnp, recA, rpoB and thrC) was performed on 34 representatives of the

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... ntatives of the genus Ensifer. Genetic analysis and comparison with 16S and 23S rRNA gene sequences demonstrated clear species boundaries and a higher discrimination potential for all housekeeping genes. Comparison of housekeeping gene sequence data with DNA-DNA reassociation data revealed good correlation at the intraspecies level, but indicated that housekeeping gene sequencing is superior to DNA-DNA hybridization for the assessment of genetic relatedness between Ensifer species. Our MLSA data, confirmed by DNA-DNA hybridizations, support the suggestion that Ensifer xinjiangensis is a later heterotypic synonym of Ensifer fredii.