Strigomonadinae

Strigomonadinae is a subfamily of protists in the order Trypanosomatida. All species in this taxon harbor endodymbiontic bacteria of the Candidatus Kinetoplastibacterium genus.

Use as model organisms
Several species of the Strigomonadinae, notably Strigomonas culicis and Angomonas deanei have been researched as "excellent models for the study of cell evolution because the host protozoan co-evolves with an intracellular bacterium in a mutualistic relationship", and "the origin of new organelles" (i.e. symbiogenesis).