Actinobacteria is the phylum that has the biggest genome in the Bacteria domain and includes many colored species. Their pigment analysis revealed that structurally diverse carotenoids are responsible for their pigmentation. This chapter reviews the biosynthesis of the diverse carotenoids of Actinobacteria. Its carotenoids belong to three different types: 1) carotenoid of C50 chain length, 2) carotenoids with aromatic end groups, and 3) keto carotenoid like canthaxanthin (β,β-carotene-4,4'-dione) or monocyclic keto-γ-carotene derivatives. Species from the genus Rhodococcus are the only known Actinobacteria with a simultaneous pathway to aromatic and to keto carotenoids.
Keywords: Actinobacteria; Aromatic carotenoids; Carotenoid biosynthesis; CrtO; Rhodococcus.