Photosynthesis, bacterial

The discovery that certain bacteria could carry out photosynthesis opened up a new field of photosynthetic research. It was found that certain green-, red-, purple-, and brown-colored bacteria could produce organic matter from carbon dioxide upon illumination. The formation of organic matter was not accompanied by oxygen evolution. As a result of work with the green sulfur bacteria, van Niel (21) showed that their CO2 assimilation process was in close agreement with the following equation  

The similarity of this process to photosynthesis in green plants is obvious  

In this equation, H2A represents a hydrogen donor which reduces carbon dioxide with the aid of absorbed radiation, and A is the dehydrogenated donor. 

Reaction (4) is a hydrogenation-dehydrogenation reaction which conforms to the principles of comparative biochemistry set forth by the Dutch microbiologist Kluyver. This concept, as stated by van Niel 21), postulates as a fruitful central idea that all metabolic activities are intrinsically similar, and that each consists of a more or less extended series of inter- or intramolecular hydrogenation-dehydrogenation reactions. The comparative biochemistry principle has been extremely valuable in developing theoretical approaches to the photosynthetic reaction. 

In addition to the pigmented bacteria, some colorless bacteria are able to fix carbon dioxide in the absence of light. These colorless bacteria, known as chemosynthetic or chemoautotrophic organisms, obtain energy for assimilating and reducing CO2 by oxidizing NH3, H2S, and H2. 

A simpler and better-understood process of the primary photosynthetic reaction and charge separation occurs in bacterial photosynthesis, which has only one photosystem instead of the two photosystems of green-plant photosynthesis. 

After reduction of the oxidised special pair by a c-type cytochrome, the energy of a second photon is used to transfer a second electron to QB  

For the BChl fe-containing bacterium Rhodopseudomonas viridis the observed reduction in line width of P was not a factor of 1.4 but of 1.2. This is remarkable. 

Other photosynthetic bacteria show grosso modo the same EPR signal of P as Rb. sphaeroides, and presumably their primary donor also consists of a dimeric BChl complex. 

The primary donor of plant photosytem I (P-700 in the oxidized state) gives rise to a Gaussian EPR line, with = 2.0025 0.0001 and AH = 1.2 0.1 G [13], i.e. the line width is about v 2 smaller than that of the Chi radical in vitro. (Chi a in CH3OH/50% glycerol, Fe oxidized AH = 9.7 0.1 G I2 oxidized 9.5 0.1 G A.J. Hoff, unpublished results.) The suggestion that the primary donor is a dimer (see Section 4.1) is corroborated by some [14,15] but not all [16,17] proton ENDOR experiments. 

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WW Parson, Z-T Chu, A Warshel. Electrostatic control of charge separation in bacterial photosynthesis. Biochim Biophys Acta 1017 251-272, 1990. 

Bacterial Photosynthesis A light-dependent, anaerobic mode of metabolism. Carbon dioxide is reduced to glucose, which is used for both biosynthesis and energy production. Depending on the hydrogen source used to reduce COj, both photolithotrophic and photoorganotrophic reactions exist in bacteria. 

Porphyrin derivatives as models in bacterial photosynthesis imitation 98PAC2189. 

Sulfate reducing bacteria were not antecedents of photosynthetic bacteria, but rather evolved from ancestral types which were photosynthetic bacteria. Although initially surprising, this evolntionary relationship is consistent with the idea that the accumulation of sulfate, the obligatory terminal electron acceptor for the sulfate reducing bacteria, was the resnlt of bacterial photosynthesis. 

Gest H. 1972. Energy conversion and generation of reducing power in bacterial photosynthesis. Adv Microb Physiol 7 243-82. 

Gest, H., Blankenship, R.E. 2004. Time line of discoveries anoxygenic bacterial photosynthesis. Photosynthesis Res 80 59-70. 

Analogies of Rare Earth Porphyrin Doubledeckers with the Special Pair of Bacteriochlorophylls in Bacterial Photosynthesis... 

Bacterial photosynthesis. What is the relationship of the Z scheme of Fig. 23-17 to bacterial photosyntheses In photoheterotrophs, such as the purple Rhodospirillum, organic compounds, e.g., succinate, serve as electron donors in Eq. 23-30. Because they can utilize organic compounds for growth, these bacteria have a relatively low requirement for NADPH or other photochemically generated reductants and a larger need for ATP. Their photosynthetic reaction centers receive electrons via cytochrome c from succinate (E° ... 

As pointed out by Van Valen (1971), photosynthesis does not produce a net change in oxidation. Except in bacterial photosynthesis, oxygen production is accompanied by a stoichiometrically equal quantity of reduced carbon. Thus, almost all of the oxygen is eventually used to oxidize reduced carbon. Predominantly, this oxidation occurs as the result of respiration in animals and plants. Further oxidation occurs as the result of forest fires. As observed by Borchert (1951), the only net gain in... 

Research on the electron transfer processes during bacterial photosynthesis is usually performed on chromatophores, i.e. extracts from photosyn-thesizing bacteria. These extracts are free from the cell walls but retain virtually all the contents of the cell membranes. These entities are convenient for research in that they scatter light much less than the bacteria themselves and, in addition, some portions of the electron transfer chain they contain can be acted upon chemically. 

A depending on the size of the lanthanide metals. Delocalization of electron density on four equivalent nitrogen atoms causes elongation of the Ln-N bonds at about 0.10-0.15 A compared to silylamides. The close proximity of the macrocyclic 7i-systems in sandwich complexes proved to be useful as structural and spectroscopic models for the bacteriochlorophyll [Mg(Bchl)]2, the special pair in the reaction center of bacterial photosynthesis [211,212]. The distance between the pyrrole rings in [Mg(Bchl)]2 is about 3 A. 

Natural photosynthesis provides the most dramatic demonstration of the potential hidden in this basic photoreaction. In (bacterial) photosynthesis a chlorophyll-dimer (BC)2—the special pair —receives the radiation energy and thereby gains the energy required to enable it to transfer an electron to a pheophytin moiety (BP), an act occurring within 2-3 picoseconds (Martin et al. 1986) even at very low temperatures. Subsequently the electron is transferred to a quinone acceptor (MQ), which once again occurs (Holten et al. 1978) on a very short time scale of about 230 ps. 

Bartsch, R. G. Nonheme iron proteins and Chromatium iron protein. In Bacterial Photosynthesis, H. Gest, A. San Pietro, and L. P. Vernon, eds., Antioch Press, Yellow Springs, Ohio, pp. 315—326 (1963). 

N. Rigopoulos, and R. C. Fuller The pyruvate phosphoclastic reaction and light-dependent nitrogen fixation in bacterial photosynthesis. Proc. Nat. Acad. Sci. (U. S.) 52, 762-768 (1964). 

Examples of well-known photochemical reactions which involve electron transfer include the primary step in plant and bacterial photosynthesis [2], the photoreduction of ketones by amines [3], a series of sensitized isomerizations of olefins and small ring compounds such as cyclopropanes or of strained polycyclics such as quadricyclane to norbornadiene or Dewar benzenes to benzenes [4], and the reactions of electron-rich substrates in the presence of oxygen which proceed via superoxide [5]. These reactions and others have proved valuable for synthetic applications in addition to their fundamental interest to photochemists. 

Bixon, M., Michel Beyerle, M. E., and Jortner, J., 1988, Formation dynamics, decay kinetics and singlet-triplet splitting of the (bacteriochlorophyll dimer)-positive (bacteriopheophytin)-negative radical pair in bacterial photosynthesis. Isr. J. Chem., 28 1559168. 

Creighton, S., Hwang, J. K., Warshel, A., Parson, W. W., and Norris, J., 1988, Simulating the dynamics of the primary charge separation process in bacterial photosynthesis. Biochemistry, 27 7749781. 

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