A study examined the photochemical reaction center complex of a green filamentous bacterium called Roseiflexus castenholzii. They isolated and studied the complex, finding it composed of L, M, and cytochrome subunits. The cytochrome subunit contained hemes c and transferred electrons to special bacteriochlorophylls. The complex also contained three bacteriochlorophyll and bacteriopheophytin molecules. Genetic analysis showed R. castenholzii diverged early from other green bacteria. Its genes for light-harvesting proteins and RC subunits are arranged differently from other bacteria, resembling purple bacteria. This suggests R. castenholzii retains characteristics of a common ancestor of purple and green bacteria.