Abstract
Growth and corrinoid production of Rhodospirillum rubrum were studied in media containing various organic acids as carbon source and precursors of corrinoid molecule under the following cultural conditions : (I) anaerobic in the dark; (II) anaerobic in graded intensities of light; (III) aerobic in the dark. The major corrinoid formed in the cells was confirmed as 5'-deoxyadenosylcobalamin, irrespective of the cultural conditions, by its electrophoretic behaviors at varing pHs and by its conversion to aquocobalamin by irradiation. In addition, several corrinoids, including cobinamide or its coenzyme form, were detected on the bioautograms using E. coli 215 as test organism. Addition of 5,6-dimethylbenzimidazole or adenine to the basal medium used enhanced corrinoid production 1.5〜2 times, indicating transformation of the incomplete forms to the complete ones. Under the cultural condition (I), the bacterial growth was very low but the amounts of corrinoids produced per unit weight of cells as well as specific contents of the vitamin in the cells were high as compared with those under other cultural conditions. Under the photosynthetic condition (II), although the growth rate as well as cell yield was enhanced as the intensity of illumination was raised, the production of the vitamin was lowered by increasing the light intensity beyond a certain high level and the specific content in the cells of the maximal growth period was diminished in inverse proportion to the light intensity. The aerobic-dark cultivation (condition (III) resulted in a similar growth to and a higher vitamin production than those under the anaerobic conditions with a moderate illumination . In each cultural condition, the productivity of corrinoids was high in the cells of earlier growth phases and diminished markedly after the middle exponential period. Glutamate or mesaconate used as a sole carbon source permitted the bacterial growth and enhanced the cellular content of corrinoid. In relation to the demonstration of a B_<12>-dependent glutamate mutase and methylmalonyl CoA mutase in Rsp. rubrum (published elsewhere), functions of B_<12>-participating pathways in the photosynthetic bacteria were discussed with special reference to the biogeneses of the cellular components including bacteriochlorophyll and corrinoid itself.
