CAROTENOID PIGMENTS AND THE IN VIVO SPECTRUM OF BACTERIOCHLOROPHYLL

Abstract

Abstract— The isolation of a mutant, strain PM‐9, of Rhodopseudonionus spheroides with an abnormal complement of carotenoid pigments is described. PM‐9 accumulates phytoene, phytofluene, ζ‐carotene and neurosporene. Semi‐aerobic cultures form more ζ‐carotene and neurosporene relative to total carotenoids than do photo‐synthetic cultures. PM‐9 is killed on exposure to light and oxygen. By making use of the effect of oxygen on the nature of the carotenoids in PM‐9, we have shown that these pigments do not directly influence the in vivo spectrum of bacteriochlorophyll. Diphenylamine inhibits the synthesis of coloured carotenoids in Rhodopseudonionos gelatinosa but does not change the bacteriochlorophyll spectrum.

Identification of the pigment pool responsible for the flash‐induced carotenoid band shift in Rhodopseudomonas sphaeroides chromatophores

“…If the observed differences in absorbance spectra attributabIe to carotenoids in the isolated light harvesting complexes ([8], table 1) are a reflection of their in vivo spectra, then a shift of carotenoid a B850 and B875 levels were calculated from the approximations in [20] which assume a similar extinction coefficient and symmetri~l absorbance bands for bath antenna complexes, In these analyses, it should be noted that a single absorbance maximum is observed in the isolated B875 complex near 875 nm [ 81.…”

Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum

“…UV-C-UV-B light must have acted as a selective force (Sagan, 1973;Mulkidjanian et al, 2003;Serrano-Andrés and Merchán, 2009), not only for stability but also for photon dissipation characteristics, and this was probably the onset of an evolution through a thermodynamic natural selection. Among the contemporary, more universal biological molecules, aromatic amino acids (phenylalanine, tyrosine, tryptophan, histidine), cystine (Pace et al, 1995;Edelhoch, 1967); pteridine (pterin and flavin), pyridine, quinone, porphyrin, and corrin cofactors; and different isoprenoids (Crounse et al, 1963) all absorb in the UV-C-UV-B, and some of them in the visible as well (see Table 1). …”

“…Phytoene, a 40-carbon intermediate in the biosynthesis of carotenoids, whose synthesis from two molecules of geranylgeranyl pyrophosphate (GGPP) marks the first committed step in the biosynthesis of carotenoids, has an UV-vis absorption spectrum typical for a triply conjugated system with its main absorption maximum in the UV-B range at 285 nm (Crounse et al, 1963). Phytofluene, the second product of carotenoid biosynthesis formed from phytoene in a desaturation reaction leading to the formation of five conjugated double bonds, has an absorption spectra in the UV-A region, with maximal absorption at 348 nm (Crounse et al, 1963).…”

THE SPECTRUM OF BACTERIOCHLOROPHYLL IN VIVO: OBSERVATIONS ON MUTANTS OF RHODOPSEUDOMONAS SPHEROIDES UNABLE TO GROW PHOTOSYNTHETICALLY

“…Phenocopies of strain u.v.-33, produced by growth in the presence of diphenylamine, which inhibits formation of colored carotenoids, have unaltered spectra in the region of BChl absorption. (10) We previously reported(l) that the spectrum of BChl in strain PM-8 :bg-58, a derivative of strain PM-8 which is unable to form colored carotenoid pigments, was different from the u.v.-33 spectrum. The position of the single major absorption band in strain PM-8: bg-58 is at 863 mp rather than at 870 mp; furthermore, the small band at 805 mp in the u.v.-33 spectrum is completely absent in PM-8:bg-58.…”