The development of the photosynthetic apparatus and energy transduction in malate-limited phototrophic cultures of Rhodobacter capsulatus

Oelze, J.

doi:10.1007/bf00423139

Cited by 7 publications

(1 citation statement)

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“…Cultures were illuminated with incandescent light, as detailed in the Results section. Continuous chemostat cultures of the wild type were grown anaerobically in a thermostated culture vessel (15). All of the results are based on at least four independent growth experiments.…”

Section: Methodsmentioning

confidence: 99%

Regulation of tetrapyrrole synthesis by light in chemostat cultures of Rhodobacter sphaeroides

Oelze

1988

J Bacteriol

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Control of bacteriochlorophyll (Bchl), magnesium protoporp}yrin monomethyl ester (MgPME), cytochromes, and coproporphyrin by light was studied with chemostat cultures of Rhodobacter sphaeroides growing at a constant dilution rate. By increasing the growth-limiting light energy flux from 10 to 55 W/m2, specific Bchl contents decreased from 19.3 to 7.9 nmol/mg of protein. This was strictly proportional to a decrease in the ratio of B800-850 to B875 light-harvesting complexes. MgPME levels increased from 1.5 to 5.3 nmol/mg of protein, while cytochrome as well as coproporphyrin levels stayed constant at 0.46 and 1.95 nmol/mg of protein, respectively. Since in chemostat cultures steady-state levels of a product represent the rate of synthesis, these results infer only slight control of the rate-limiting step of total tetrapyrrol formation by light. In substrate-limited cultures MgPME was accumulated when growth and Bchl formation approached substrate saturation. This suggests that light controls a second step, i.e., MgPME conversion, whenever too much precursor is available, owing to the low sensitivity of the initial step of control. MgPME was preferentially localized in a subcellular fraction with high contents of B875 complexes. A second fraction exhibiting increased contents of B800-850 complexes lacked significant levels of MgPME. These results are discussed in terms of localization of Bchl synthesis in the membrane system of R. sphaeroides.

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Section: Methodsmentioning

confidence: 99%