Phototrophic bacteria structure

The results of this study demonstrate that the antenna and the reaction center of R rubrum differ in then-specificities of carotenoid binding. Thus, the microorganism follows in this respect the pattern of other related phototrophic bacteria (Cogdell and Thomber, 1979 Cogdell et al., 1976). Such difference suggests strongly that the functional role of the carotenoid in each type of photosynthetic complex has differential aspects of importance sufficient to impose distinctive structural requirements. The available information on... 

Isoprenoids represent the largest family of natural products, with an exceptional structural diversity. Isoprenoids are present in all living organisms. This group includes essential metabolites, such as sterols 27 (Fig. 6) of the eukaryotic plasma membranes, prenyl chains of the quinones 22 and 23 from electron transport chains, and carotenoids 25 from the photosynthetic apparatus in the plant chloroplasts, or in the phototrophic bacteria. Isoprenoids also include secondary metabolites of a more restricted distribution and with a less obvious physiologic significance. Their carbon skeleton can be derived from the combination of C5 subunits with the branched skeleton of isoprene. 

Stolz J. F. (1991) The ecology of phototrophic bacteria. In Structure of Phototrophic Prokaryotes (ed. J. F. Stolz). CRC Press, Boca Raton, FL, pp. 105-123. 

Also procedures for the isolation of inside-out membranes, by French Press treatment of intact bacteria, have been described. In phototrophic organisms, these membranes are derived from the invaginations of the plasma membrane and are called chromatophores. These preparations have been extensively used for studies on light-dependent cyclic electron transfer and photophosphorylation. In non-phototrophic bacteria the resulting structures are often called inverted membranes or membrane particles, in analogy with sub-mitochondrial particles. Amongst others, these preparations have been isolated from Azotobacter vinelandii and E. coli. These inverted membranes can be used for the study of oxidative phosphorylation and the determination of H /e stoicheiometries since the enzymatic machinery for these processes is located on the external surface of these membranes. Also excretion of ions (like ) from intact cells can be studied conveniently in these preparations because these ions are accumulated in inverted membranes. 

The term consortium describes such a temporary symbiotic association of two or more different bacteria in a physical and structured way. Consortia comprise a colorless central bacterium, and attached to its surface (hence epibionts) are up to 20 phototrophic bacteria [48, 62]. 

Main pigments of phototrophic bacteria of the orders Chlorobinea (green bacteria) and Rhodospirillinea (purple bacteria). B. a and b have the actual bacte-riochlorin skeleton while B. c-ehave the chlorin skeleton on which the chlorophylls of higher plants and cyanobacteria are based they are also very similar to chlorophylls in other respects. Elucidation of the detailed spatial constmction of the crystallized bacterial photosynthesis system from membranes of Rhodo-pseudomonas viridis was realized in 1984 by Deisen-hofer, Huber, and Michel by X-ray structural analysis for which they received the Nobel Prize for Chemistry in 1988. ... 

Drews, G. (1985) Structure and functional organization of light-harvesting complexes and photochemical reaction centers in membranes of phototrophic bacteria. Microbial. Rev. 49,59-70. 

Reaction Centers (RC s) from phototrophic bacteria catalyze light-driven transmembrane electron transfer as a first step in the (cyclic) electron transfer chain of such bacteria (for a review see Okamura et al., 1983 and Dutton et al., 1982). Many of the structural and functional features of RC s have already been elucidated the remaining questions mainly focus on (i) the effects of transmembrane gradients (of redox potential and electrochemical potential of protons) on the reactions catalyzed by the RC s and (ii) the interactions between RC s and physiological and artificial electron donors and acceptors. Many of the unsolved aspects can be optimally investigated under conditions, in which the RC s have been reconstituted into artificial membranes either in planar (Schonfeld et al., 1979) or vesicular form (Crofts et al., 1977 Pachence et al., 1979). Here I report on the structure of reconstituted RC vesicles and light-dependent unidirectional proton translocation catalyzed by these vesicles. 

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