Identification of the Carotenoid Pigment Canthaxanthin from Photosynthetic Bradyrhizobium Strains

Canthaxanthin (4,4(prm1)-diketo-(beta)-carotene) is produced as the major carotenoid pigment by orange- and dark-pink-pigmented bacteriochlorophyll-containing Bradyrhizobium strains isolated from stem nodules of Aeschynomene species. These two new pigmentation groups differ from the well-studied strain BTAi1, which accumulates spirilloxanthin as the sole carotenoid.