Photosynthetic bacteria Rhodobacter sphaeroides

Zysmilich MG, McDermott A (1994) Photochemically induced dynamic nuclear polarization in the solid-state 15N spectra of reaction centers from photosynthetic bacteria Rhodobacter sphaeroides R-26. J Am Chem Soc 116 8362-8363... 

There are three very well studied DMSO reductase enzymes. The enzymes isolated from the purple photosynthetic bacteria Rhodobacter capsulatus and Rhodobacter sphaeroides (DorA) are periplasmic and share a high sequence identity. They are also the structurally simplest of all Mo enzymes ca. 85 kDa enzymes bearing a single redox active cofactor (the Mo active site). DMSO reductase from E. coli is a more complex membrane bound 140 kDa hetero-trimeric enzyme (DmsABC) bearing five Fe-S clusters in addition to the Mo active site. 

The larger part of research on light-driven eleetron transfer in purple photosynthetic bacteria has involved three speeies, Rhodopseudomonas (Rps.) viridis, Rhodobacter (Rb.) sphaeroides and Rb. capsulatus. The bulk of this article is written in reference to the Rb. sphaeroides reaetion eentre, the subject of the majority of spectroscopic and mutagenesis work earried out to date. However, much of the research described below has involved the reaction centre from Rb. capsulatus or Rps. viridis, or reaetion eentres from other species of purple bacteria. 

Figure 2 H2 production from the lactic acid fermentate of the C. reinhardtii biomass by various photosynthetic bacteria. The fermentate of C. reinhardtii biomass was diluted to give a lactic acid concentration of 30 mmol/1, inoculated with one of the five strain of photosynthetic bacteria (O, Rhodobacter sphaeroides A, Rhodobacter capsulata , Rhodospirillum rubrum 9, Rhodovulum sulfidophilus , Rhodobium marinum), and incubated under illumination of 330 W/m2 at 30°C.

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. 

Fritzsch G, Ermler U, Merckel M and Michel H (1996) Crystallization and structure of the photo synthetic reaction centres from Rhodobacter sphaeroides—wild type and mutants. In Michel-Beyerle M-E (ed) Reaction Centers of Photosynthetic Bacteria. Structure and Dynamics, pp 3-13. Springer-Verlag, Berlin... 

Mathis P (1994) Electron transfer between cytochromeC2 and the isolated reaction center of purple bacterium Rhodobacter sphaeroides. Biochim Biophys Acta 1187 177-180 McDermott G, Prince SM, Freer AA, Hawthornwaite-Lawless AM, Papiz MZ, Cogdelt RJ and Isaacs NW (1995) Crystal structure of an integral membrane light-harvesting complex from photosynthetic bacteria. Nature 374 517-521 Michel H (1982) Three-dimensional crystals of a membrane protein complex. J Mol Biol 158 567-572 Michel H (1983) Crystallization of membrane proteins. Trends Biochem Sci 8 56-59... 

Triplet energy transfer between the primary donorand carotenoids in Rhodobacter sphaeroides R-26.1 reaction centers incorporated with spheroidene analogs havi ng different extents of ff-electron conjugation. Photochem Photobiol 66 97-104 Feher G and Okamura Y (1978) Chemical composition and properties of reaction centers. In Clayton RK and Sistrom WR (eds) The Photosynthetic Bacteria, pp 349-386. Plenum Press, New Y ork... 

Vos M H, Jones M R, Hunter C N, Breton J, Lambry J C and Martin J L 1996 Femtosecond spectroscopy and vibrational ooherenoe of membrane-bound RCs of Rhodobacter sphaeroides genetically modified at positions M210 and LI 81 The Reaction Center of Photosynthetic Bacteria—Structure and Dynamics ed M E Michel-Beyerle (Berlin Springer) pp 271-80... 

Two types of the photosynthetic reaction center (RC) complexes are known in pxirple bacteria, the distribution of which depends on bacterial species (1). In one type, the RC complexes have a cytochrome subunit with four c-type hemes. The other type of RC does not have the cytochrome subunit (Fig. 1). Three demensional structures of both types of RCs have been revealed in Rhodopseudomonas viridis (2) and Rhodobacter sphaeroides (3) the former has the bound cytochrome subunit. The major difference between the two types of RC is only in the presence or absence of the cytochrome subunit and the structure of the other three peptides with pigments and quinones is similar to each other. Evolutionary relationships between the two types of RC and the role of the bound cytochrome subunit are interesting subjects in the photosynthetic electron transfer system in purple bacteria. 

The acceptor side of the PS II reaction center is structurally and functionally homologous to the reducing side of reaction centers from a number of photosynthetic bacteria, including Rhodopseudomonas viridis. Rhodobacter sphaeroides and capsulatus. and Chloroflexus aurantiacus. The reaction center complexes of viridis and sphaeroides have been crystallized, and the three-dimensional structure of these has been determined at high resolution [3-7]. With the exception of (a) the His residues in the bacterial reaction center that serve as ligands to the Mg of the accessory bacteriochlorophylls, and (b) the Glu residue that serves as a ligand to the non-heme iron between and Q0, all of the amino acid residues that function as important... 

The fast transfer and trapping of excitation energy in photosynthetic bacteria have been intensively studied in recent years. For reviews we refer to (1). Steady-state (2) and time-resolved fluorescence (3) and time-resolved picosecond absorption recovery measurements have led to the formation of the following scheme for energy transfer in Rhodobacter (Rb.) sphaeroides. (4,5,6)... 

In Rhodobacter sphaeroides and Rhodospirillum rubrum, a new type of antenna Bchl-form whose energy level is lower than that of the special pair Bchl of the reaction center (RC) has been reported (4-6). Such components should be surveyed in other photosynthetic bacteria to account for the functional role and structural basis for the specific energy level. 

Plasmids in photosynthetic bacteria have been isolated from Rhodospiri1lum rubrum. Rhodobacter sphaeroides and Rhodobacter cap-sulatus (1 5). The sizes of their plasmids ranges from 40 to 200 kilobases. Kuhl et al. (3) have isolated the identical plasmids from nine strains of R. rubrum. In addition, they have reported that the plasmid-less mutants show different colors from the wild strain and can not grow photosynthetically in the light (6). In order to elucidate the biological roles of the plasmids in photosynthetic bacteria, it is essential to determine their DNA sequences. The present study reports the restriction map and the partial nucleotide sequences of R. rubrum plasmid. 

Such pigments occur in many photosynthetic membranes, but their use as molecular voltmeters is most easily accomplished in preparations, known as chromatophores, from certain photosynthetic bacteria such as Rhodobacter sphaeroides or Bhodopseudomonas capsulata. Again, studies of oxygen consiunption and delivery in vivo require highly vascularized tissues which contain many mitochondria, for example, brain, liver or cardiac muscle (although in the latter case the myoglobin contribution cannot be resolved from that of haemc obin). 

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