EFFECT OF CO2 ON BIOSYNTHESIS OF CAROTENOIDS IN RHODOPSEUDOMONAS SPHEROIDES

In anaerobic photosynthetic cultures of Rhodopseudomonas spheroides, the light-induced induced synthesis of carotenoid pigments is greatly affected by the presence or absence of CO2. Cultures gassed with N2 alone synthesize predominantly the yellow carotenoid(s). Gassing with a mixture of N2CO2 results in the preferential synthesis of red carotenoids. CO2 exerts similar effects in cultures maintained at consultant light intensity. The pigments formed in the presence of CO2 are similar in their spectra to those normally found in Rhodopseudomonas spheroides. The addition of chloramphenicol to growing cultures prevents the CO2-induced preferential synthesis of red carotenoid, as well as general pigment formation. The results indicate that the effect of CO2 is not mediated through a conversion of preformed yellow carotenoid to red carotenoid. © 1969.