The Histidine Operon Is Ancient
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Fani et al. (2005) studied the organization of the histidine synthesis genes across the Proteobacteria. They reported that the unified operon hisGDC(NB)HAF(IE) found in Escherichia coli, where hisNB and hisIE are gene fusions, is broken up in many Proteobacteria. They considered that the common ancestor of the Proteobacteria may have had this unified organization and it was then broken up in several lineages, or that the unified operon may have evolved by joining several pieces. They favored the joining model, with the unified operon forming in the ancestor of the ß/γ-Proteobacteria, because they thought it unlikely that the operon would independently break up multiple times. However, they restricted their analysis to the Proteobacteria and considered other genomes as being outside the scope of their study.
As can be seen with the MicrobesOnline comparative genome browser (e.g., http://www.microbesonline.org/hisoperon), bacteria across many phyla have a compact histidine operon,...
KeywordsMycobacterium Tuberculosis Horizontal Transfer Unify Organization Operon Structure Sulfolobus Solfataricus
This work was supported by a grant from the DOE Genomics:GTL program (DE-AC03-76SF00098).