Evolutionary tree of integron integrase (intI) genes. This figure is modeled after Figure two in , in which bacteria are classified into two categories: "Marine environment" and "Soil and freshwater environment." We added two more categories, including "Human or animal bodies" to refer to the Treponema sps., and “A variety of environments” category, bounded by red dashed box, to represent species with intI genes closely-related with the Treponema category, but originated from a variety of environments.
Wu et al. BMC Evolutionary Biology 2013 13:16 doi:10.1186/1471-2148-13-16