EFFECTS OF ILLUMINATION INTENSITY ON BACTERIOCHLOROPHYLL-C HOMOLOG DISTRIBUTION IN CHLOROFLEXUS-AURANTIACUS GROWN UNDER CONTROLLED CONDITIONS

Green photosynthetic bacteria contain a mixture of stereoisomers and h omologs of their major light harvesting pigment, bacteriochlorophyll ( BChl) c. We have determined the distribution of photosynthetic pigment s in the green filamentous bacterium Chloroflexus aurantiacus grown in turbidostat culture under light-limited conditions at 5 different ill umination intensities. Pigments were extracted from isolated cells, an alyzed by HPLC, and the homologs of BChl c identified by their mass sp ectra. The ratio between BChl c, BChl a and carotenoid remained consta nt at low illumination intensities; at higher intensities BChl a and c arotenoid increased in parallel compared to BChl c. The BChl c homolog distribution changed even under conditions where the ratio of the tot al amount to the other pigments was unchanged, but there were no evide nce for a constant stoichiometric ratio between any pair of homologs.