Bacteriochlorophyll cs, a new bacteriochlorophyll from Chloroflexus aurantiacus

From four strains of the gliding phototrophic bacterium Chloroflexus aurantiacus, the as yet unknown bacteriochlorophyll cs was isolated in addition to small amounts of the known bacteriochlorophyll ap. The new bacteriochlorophyll cs is the main photosynthetic pigment of these organisms under the growth conditions used. It is different from the known bacteriochlorophylls c, as could be shown unequivocally by chromatographic examinations. Evidence for the structure of the new bacteriochlorophyll cs was obtained from mass spectra. The u.v./vis.-spectra and the chromatographic behavior are in accord with the suggested structure. The result includes two particularly interesting aspects: 1. Unlike the bacteriochlorophylls c, d, and e of the Chlorobiaceae, bacteriochlorophyll cs of Chloroflexus is not a mixture of isomeric and homologous molecules; 2. the esterifying alcohol of the propionic acid side chain is neither farnesol nor another isoprenoid alcohol, but is the straight chain aliphatic (C-18) stearylalcohol.