FIG. 7.

Proposed model of hif evolution. (a) Insertion (dashed lines) of the extended hif cluster within the purE-pepN intergenic region of a class I strain generates genotype VI (hypothetical [Hyp]). The hic ORFs are indicated with unfilled arrows, and hif operon genes are indicated with filled arrows. (b) Deletions (dashed lines) within the extended hif cluster give rise to genotypes IIa and V. (c) Proposed phylogeny of hif genotypes, based on shared rearrangements only. The relationships shown refer only to genotypes of the purE-pepN region and not to strains or groups of organisms. Branch lengths and the order of mutations between nodes are arbitrary. Δ₁, Δ₂, and Δ₃ are as in Fig. 4.