Comparative allostery of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthetase as a molecular basis for classification.

The allosteric pattern of control for 3-deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthetase has previously been shown to be strongly conserved among the member species of a given genus in bacteria. The implications of this finding as a procedural tool of bacterial phylogeny were pursued by a study of two organisms, Sporosarcina ureae and Aeromonas formicans, the taxonomic positions of which have been historically controversial. S. ureae has characteristics of both Bacillaceae and Micrococcaceae, and A. formicans has characteristics of both Enterobacteriaceae and pseudomonads. Since the patterns of control for DAHP synthetase in all four of these microbial groups are different from one another but internally homogeneous within each group, the results obtained from the two test organisms were unambiguous. It was concluded that S. ureae is properly classified within Bacillaceae, probably deserving generic rank, and that A. formicans belongs with the family Enterobacteriaceae.