Der Einfluss der lichtintensität und der sauerstoffspannung auf die differenzierung der membranen von Rhodospirillum rubrum

Abstract

1. 1. Cells of Rhodospirillum rubrum precultured at low light intensity were exposed to moderate (4000 lux) and then to low (400 lux) light intensities for 5 and 4 h, respectively. During culture under moderate light intensity oxygen within the freshly diluted cultured is consumed. Under these conditions growth continues without bacteriochlorophyll synthesis. 2. 2. During exposure to 4000 lux the thylakoids undergo a change from a spherical into a flattened sturcture. This change is reversed after exposure to 400 lux. 3. 3. Within cells precultured at low light intensity the radioactive label of incorporated [2- 14C]acetate is equally distributed between thylakoids and cytoplasmic membrane. Under moderate light intensity the label is preferentially increased in the cytoplasmic membrane fraction. However, equal distribution is again obtained after lowering the light intensity. 4. 4. The specific bacteriochlorophyll content of thylakoids decreases under moderate light intensity from 100 to 45 μg bacteriochlorophyll per mg protein and increases during the period of low light intensity up to 80 μg bacteriochlorophyll per mg protein. 5. 5. During incubation under 4000 lux the different thylakoid proteins approach a pattern which is typical for the cytoplasmic membrane. Radioactive labeled amino acids are preferentially incorporated into proteins which are characteristic of the cytoplasmic membrane. The protein pattern of this modified membrane again becomes typical for thylakoids during the following exposure to 400 lux. This, too, is in agreement with the preferential amino acid incorporation into thylakoid-specific proteins. 6. 6. The results indicate that thylakoids and the cytoplasmic membrane represent reversible modifications of a dynamic membrane system.