Part II - Complexes Derived from Green Photosynthetic Bacteria

Abstract

This chapter discusses extraction, purification, and biological significance of chlorophyll–protein complexes derived from green photosynthetic bacteria. Bacteriochlorophyll–protein complexes can be obtained from Chloropseudomonas ethylicum, strain 2K, and Chlorobium thiosulfatophilum, strain L. The spectra of the chlorophyll–protein complexes from green bacteria indicate the presence of Bchl by the characteristic orange band at 603 mμ in addition to the far-red band at 809mμ. There is no chlorobium chlorophyll associated with the complex. When the Bchl is removed from the complex, the absorption spectrum in ether is virtually identical to that of Bchl a from Chromatium. The bacteriochlorophylls from green bacteria have the same Rf values as Bchl a from purple bacteria in paper chromatography. The chemical and physical studies of Holt and co-workers on the Bchl of green bacteria have established its identity as Bchl a beyond any reasonable doubt. The illumination of whole cells of Chloropseudomonas ethylicum or Chlorobium limicola causes an absorbance decrease centered at 840 mμ. The relationship between the bleaching at 840 mμ and the fluorescence yield of Bchl a in vivo led to the inference that the absorbance changes in the 840-mμ region were a result of a reaction center pigment P840, present in very low concentration. Attempts to release soluble complexes from Rhodopseudomonas sp, NHTC 133, Chromatium, and Rhodospirillum rubrum by alkaline extraction have met with little success.