Membrane differentiation in phototrophically growing Rhodospirillum rubrum during transition from low to high light intensity

Abstract

1. 1. The effects of the transference of cells cultivated at low light intensities to high light intensity (8000 lux) on membranes of phototrophically growing Rhodospirillum rubrum were investigated. 2. 2. For at least two generations no bacteriochlorophyll is formed. Thus the pigment contents of whole cells and intracytoplasmic membranes as well as the cellular contents of intracytoplasmic membranes decrease. 3. 3. Radioactive label incorporated into intracytoplasmic membranes is not transferred into the cytoplasmic membrane fraction during pulse chase. However, there is a direct incorporation of label into both types of membranes under high light intensity. 4. 4. Protein patterns of crude fractions composed of cytoplasmic and intracytoplasmic membranes reveal an increase of a protein (Zone B) typical for cytoplasmic membranes. Within purified intracytoplasmic membranes there is no such increase. Incorporation of labeled amino acids demonstrates a synthesis of all of the membrane proteins except those associated with bacteriochlorophyll synthesis (Zone G). 5. 5. KCN-sensitive NADH oxidase increases in crude membrane fractions on a bacteriochlorophyll basis, it stays constant on a cellular protein basis. In purified intracytoplasmic membranes there is only a very slight increase on a bacteriochlorophyll basis and a decrease of the oxidase activity on a membrane protein basis. 6. 6. Photophosphorylation activity increases slightly on a bacteriochlorophyll basis within crude membranes and purified intracytoplasmic membranes. 7. 7. The results are compared with results obtained previously under aerobic conditions. Unlike aerobiosis, high light intensity and anaerobiosis result obviously in a conservation of the intracytoplasmic membranes and their function. Cytoplasmic membranes are formed independent from intracytoplasmic membranes. Intracytoplasmic membranes are differentiated, structurally and functionally, but are not converted to cytoplasmic membranes.