Phylogenetic relationships of Salmonella based on DNA sequence comparison of atpD encoding the beta subunit of ATP synthase.

DNA sequences covering 57% of atpD encoding the beta subunit of ATP synthase were determined for 16 strains of Salmonella enterica, two strains of S. bongori, and one strain each of Citrobacter freundii and Yersinia enterocolitica, and comparison was made with the published Escherichia coli and Enterobacter aerogenes sequences. The phylogenetic tree based on maximum-likelihood analysis showed separation of the subspecies of S. enterica except for two serotypes of subspecies II which were unsupported by a common node. The two serotypes of S. bongori were separated from S. enterica and related to the serotypes of subspecies II. A tight relationship was found between S. enterica subspecies IIIa consisting of monophasic serotypes and subspecies IIIb consisting of diphasic serotypes. This is in conflict with results obtained for most other housekeeping genes and the 23S rRNA gene separating mono- from diphasic subspecies.