Dark heterotrophic growth conditions result in an increase in the content of photosystem II units in the filamentous cyanobacterium Anabaena variabilis ATCC 29413.
The filamentous nitrogen-fixing cyanobacterium Anabaena variabilis ATCC 29413 is capable of heterotrophic growth in complete darkness. After 6 months of continuous dark growth, both the autotrophic and heterotrophic cultures were found to have the same doubling time of 14 h. On a cellular basis, the chlorophyll content remained the same and the phycobilin content showed an increase in the dark-grown cultures. Fluorescence emission spectra at 77 K of dark-grown cells indicated that the phycobilisomes are functionally associated with photosystem II (PSII). Moreover, upon transfer to light, the dark-grown cells readily evolved oxygen. Although photosystem I (PSI) and whole chain-mediated electron transfer rates were comparable in both types of cultures, the rate of PSII-mediated electron transfer was found to be 20% higher in dark-grown cells. The PSI to PSII ratio changed from 6:1 in autotrophic cultures to 4:1 in the dark-grown cells. These changes in the rate of PSII electron transfer and in the stoichiometry between the two photosystems under dark, heterotrophic growth conditions were brought about by a preferential increase in the number of PSII units while the number of PSI units remained unchanged. The advantages of using this organism in the selection of PSI-deficient mutants are discussed.
Department of Biology, Washington University, St. Louis, Missouri 63130.
R M
RM
Mannan
H B
HB
Pakrasi
D017033:Anabaena / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D002455:Cell Division; D003624:Darkness; D004237:Diuron / Q000378:metabolism; D004579:Electron Transport; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000096:biosynthesis; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000096:biosynthesis*; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D045524:Phycobilisomes; D013696:Temperature
D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D045524:Phycobilisomes; D004237:Diuron