Ubiquinone 10 formation in Rhodospirillum rubrum under different culture conditions

Abstract

The formation of ubiquinone 10 and bacteriochlorophyll (bchl) was determined in Rhodospirillum rubrum grown under different culture conditions. Transfer of chemotrophically grown cultures to photosynthetic conditions leads to the formation of the pigments until cells reach the stationary phase of growth. Bchl-synthesis initially exceeds quinone synthesis. On a cellular protein basis quinone levels first decrease by about a factor of two and subsequently increase by a factor of four. Bchl levels per protein increase until cells reach the stationary phase of growth. Quinone levels per bchl decrease rather rapidly and become constant in the growing culture. When cells were transferred under continuous phototrophic conditions to new culture medium, both pigments are formed concomitantly. While protein synthesis starts immediately, bchl and ubiquinone formation is slightly delayed. This causes a short time decrease in the amount of both pigments per cellular protein followed by an increase to a constant level. Ratios of ubiquinone per bchl are constant. The transfer of phototrophically grown cultures to chemotrophic conditions results in a complete inhibition of bchl formation while quinone synthesis resumes. Quinone cellular levels decrease slightly and then remain constant. Quinone values increase per bchl which is eventually diluted out of the cells.