Photosynthesis-independent regulation of bacteriochlorophyll synthesis by light intensity in Rhodobacter capsulatus

The amounts of bacteriochlorophyll a in a Rhodobacter capsulatus mutant strain which lacks the light-harvesting I and reaction center complexes were measured in cultures grown with different light intensities. Light intensity regulation of bacteriochlorophyll synthesis was found, manifested as differences in the amounts of a light harvesting complex II-like absorption peak in vivo, and the amount of organic solvent-extracted bacteriochlorophyll a, in comparisons between low and high light-grown cells. This light regulation was also evaluated by use of puc::lacZ fusions, which indicated that control is exerted independently of puc gene transcription or translation. We suggest that this light regulation might operate at the level of the enzymatic activity of bacteriochlorophyll biosynthetic enzymes.