Bacteriochlorophyll c _S, a new bacteriochlorophyll from Chloroflexus aurantiacus

Abstract

From four strains of the gliding phototrophic bacterium Chloroflexus aurantiacus, the as yet un-known bacteriochlorophyll c _S was isolated in addition to small amounts of the know bacteriochlorophyll a _P. The new bacteriochlorophyll c _S 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 c _S 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 c _S 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.