Acquisition, reorganization, and merger of genes: Novel management of the beta-ketoadipate pathway in Agrobacterium tumefaciens

Widely distributed among members of the Rhizobiaceae, the protocatechuate branch of the beta-ketoadipate pathway is central to the catabolism of 4-hydroxybenzoate and certain other phenolic compounds. Genetic elements underlying 4-hydroxybenzoate dissimilation in Agrobacterium tumefaciens have been characterized. Eleven pob and pea genes are organized in a compact supraoperon. Evolutionary divergence of A. tumefaciens from Pseudomonas putida and Acinetobacter calcoaceticus, members of a different subdivision of proteobacteria, is reflected in the layout of the pob-pca supraoperon as well as in novel regulatory motifs that govern expression of the genes. At least some of these distinctive features are shared with rhizobial relatives of Agrobacterium.