PIGMENT INTERACTIONS IN CHLOROSOMES OF VARIOUS GREEN BACTERIA

Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyll c- and bacteriochlorophyll e-synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical in Chlorobium limicola, Chlorobium tepidum, and Chlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophyll e is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes from Chloroflexus auranticus, either isolated or in the whole bacteria.