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Photosynthetic organisms purple bacteria

A study of photosynthetic organisms other than green plants has revealed that certain bacteria, such as the purple sulfur bacteria, utilize H2S instead of H20 as a reductant in photosynthesis. The product obtained is elemental sulfur instead of oxygen ... [Pg.282]

Fig. 3 Schematic model of light-harvesting compartments in photosynthetic organisms and their position with respect to the membrane and the reaction centers. RC1(2) Photosystem I(II) reaction centre. Peripheral membrane antennas Chlorosome/FMO in green sulfur and nonsulfur bacteria, phycobilisome (PBS) in cyanobacteria and rhodophytes and peridinin-chlorophyll proteins (PCP) in dyno-phytes. Integral membrane accessory antennas LH2 in purple bacteria, LHC family in all eukaryotes. Integral membrane core antennas B808-867 complex in green nonsulfur bacteria, LH1 in purple bacteria, CP43/CP47 (not shown) in cyanobacteria and all eukaryotes. Fig. 3 Schematic model of light-harvesting compartments in photosynthetic organisms and their position with respect to the membrane and the reaction centers. RC1(2) Photosystem I(II) reaction centre. Peripheral membrane antennas Chlorosome/FMO in green sulfur and nonsulfur bacteria, phycobilisome (PBS) in cyanobacteria and rhodophytes and peridinin-chlorophyll proteins (PCP) in dyno-phytes. Integral membrane accessory antennas LH2 in purple bacteria, LHC family in all eukaryotes. Integral membrane core antennas B808-867 complex in green nonsulfur bacteria, LH1 in purple bacteria, CP43/CP47 (not shown) in cyanobacteria and all eukaryotes.
Fig. 2. Spectral range (absorption in nm) of the antenna system of oxygenic (plants, algae, cyanobacteria) and anoxygenic (green and purple bacteria) photosynthetic organisms. The antenna systems (antenna complexes) are located either within (intramembrane) or on the surface (extramembrane) of the photosynthetic membrane. Fig. 2. Spectral range (absorption in nm) of the antenna system of oxygenic (plants, algae, cyanobacteria) and anoxygenic (green and purple bacteria) photosynthetic organisms. The antenna systems (antenna complexes) are located either within (intramembrane) or on the surface (extramembrane) of the photosynthetic membrane.
Interestingly, reaction centers of apparently all photosynthetic organisms may be assigned to one or the other of these two types. For instance, the reaction center of both purple bacteria and the green filamentous bacteria, Chloroflexaceae, and green-plant PS II are of the OQ-type. On the other hand, the green sulfur bacteria, Chlorobiaceae, the Heliobacteria, and photosystem I all have the FeS-type reaction centers. [Pg.41]

Photosynthetic prokaryotes such as cyanobacteria and photosynthetic bacteria lack chloroplasts and in these organisms the light reactions that drive photosynthesis take place in the cell s inner plasma membrane. The photosynthetic apparatus of purple bacteria, for example, is contained in a system of rntra-cytoplasmic membranes. Fig. 1 depicts the morphologies of two such purple bacteria - Rhodobacter (Rb.) sphaeroides [Fig. 1 (A)], formerly called Rhodopseudomonas sphaeroides, and Rhodopseudomonas (Rp.) viridis [Fig. 1 (B)] - species that are commonly used for photosynthesis studies. The former contains bacteriochlorophyll a (BChl a), which absorbs in the 800-880 run region in vivo, while the latter contains BChl b, which absorbs in the 960-1020 run region. [Pg.47]

Fig. 10. Transfer of electronic-excitation energy in the photosynthetic unit of purpie bacteria. The figure shows a funneling of excitation energy from different energy levels (left scale) toward the reaction center. The vertical dashed arrows indicate intracomplex transfers, and the slanted solid arrows indicate intercomplex transfers. Note that LH1 exists in all purple bacteria while LH2 exists in most and LH3 exists only in certain species. Figure source Hu, Ritz, Damjanovic and Schulten (1997) Pigment organization and transfer of electronic excitation in the photosynthetic unit of purple bacteria. J Phys Chem 101 3859. Fig. 10. Transfer of electronic-excitation energy in the photosynthetic unit of purpie bacteria. The figure shows a funneling of excitation energy from different energy levels (left scale) toward the reaction center. The vertical dashed arrows indicate intracomplex transfers, and the slanted solid arrows indicate intercomplex transfers. Note that LH1 exists in all purple bacteria while LH2 exists in most and LH3 exists only in certain species. Figure source Hu, Ritz, Damjanovic and Schulten (1997) Pigment organization and transfer of electronic excitation in the photosynthetic unit of purple bacteria. J Phys Chem 101 3859.
ATP synthesis in photosynthetic organisms, i.e., photophosphorylation, was discovered nearly fifty years ago. In 1954 Albert Frenkel" using membrane vesicles of purple bacteria, and Daniel Arnon and coworkers, using spinach chloroplasts, reported light-induced phosphorylation almost simultaneously and opened up a new era in photosynthesis research. These investigations not only established the conditions necessary for ATP synthesis by photosynthetic membranes, but also established that ATP synthesis is closely related to electron transport. [Pg.668]

One of the bacteria classified into the purple bacteria group has been known to oxidize photosynthetically ferrous carbonate and ferrous sulfide to ferric hydroxide, resulting in the production of organic compounds [reactions (5.10) and (5.11)] (Ehrenreich and Widdel, 1994). Then ferric hydroxide is changed to iron (III) oxide. [Pg.91]


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