Isolation and light-stimulated expression of canthaxanthin and spirilloxanthin biosynthesis genes from the photosynthetic bacterium Bradyrhizobium sp. strain ORS278.

Some aerobic photosynthetic bacteria produce a cocktail of carotenoids, some of them being of a high economic value. A good example is the photosynthetic Bradyrhizobium sp. strain ORS278, which synthesizes, in addition to the photosynthetic carotenoid spirilloxanthin, large amounts of canthaxanthin. Here, we describe the procedures that have been successfully used to isolate the different crt genes involved in the synthesis of both carotenoids in this bacteria. The synthesis of these carotenoids is stimulated under far-red light by a bacteriophytochrome. The procedure we developed to study the effect of the light on carotenoids synthesis is also described. Finally, we describe a procedure to genetically transform photosynthetic Bradyrhizobium strain ORS278 for improvement of canthaxanthin production.