Single acquisition of protelomerase gave rise to speciation of a large and diverse clade within the Agrobacterium/Rhizobium supercluster characterized by the presence of a linear chromid

- Genome architecture may solve the controversial taxonomic status of Agrobacterium.
- Linear secondary chromosome characterizes a large single clade within Rhizobiaceae.
- Protelomerase gene acquisition is the founding event of this lineage.
- The Agrobacterium genus could be redefined as a linear-chromid-bearing lineage.
- Protelomerase-related linearization occurred at least 6 times in the tree of life.