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PubMed1965

Electron microscopy of chromatophores of Rhodopseudomonas spheroides.

Gibson, K. D. (St. Mary's Hospital Medical School, London, England). Electron microscopy of Rhodopseudomonas spheroides. J. Bacteriol. 90:1059-1072. 1965.-Fixed and stained chromatophores and whole cells of anaerobically grown Rhodopseudomonas spheroides were examined in thin sections in the electron microscope. Both purified chromatophores and intracellular membrane-bound vesicles had exactly the same appearance, namely that of spheres or ellipsoids with a thin electron-dense shell surrounding an electron-lucent interior. The distribution of diameters in the two types of structure was also found to be the same, and was compatible with a normal distribution, with a mean of 570 A and a standard deviation 40 A. Negatively stained chromatophores appeared like discs or collapsed spheres. The presence of invaginations of the cytoplasmic membrane in this species was confirmed, and a new structure resembling a twin chromatophore was observed. The bearing of these results on theories of the origin of chromatophores is discussed, and it is concluded that they offer some support for each one of the three main theories about the origin of particulate organelles.

Bacterial Chromatophores↗

PubMed2000

[Phenotypic features and genetic diversity of strains of Rhodopseudomonas].

14 strains of purple non-sulfur bacteria and 3 type strains of Rhodopseudomonas were investigated by phenotypic characterizing, DNA-DNA hybridizing and DGGE analyzing. The characteristics of their morphology, structure and physiology show that 14 strains of isolates have the features of the genus Rhodopseudomonas: dividing asymmetrically by budding, lamellar intracytoplasmic membranes, presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series. On the base of their differences in morphology, growth, carbon sources 14 strains can be divided into 2 groups: g-c group, T group. Parts of 16S rRNA gene were amplified by using a pair of primers: 341f-906r. Denaturing gradient gel electrophoresis(DGGE) of PCR-amplified fragment of rDNA indicated that they have 3 genetic types: 1 of them, including 6 of 8 strains of T groups is similar to that of Rps. rutila R1, the other 2 types, represented separately by 2 of T group or all the g-c group, were different from that of either of 3 type strains The Data of the DNA-DNA hybridization of 8 representative strains indicated that the differences between different types were enough to separate them into different species including 2 possible new species.

DNA, Bacterial↗

PubMed1998

[Isolation and identification of Rhodopseudomonas acidophila from Fujian province, China].

A strain P301 of Gram negative purple nonsulfur bacterium was isolated from the ditch's mud collected in Fuzhou, Fujian. The cells are rod-shaped. Multiplication occur by budding without stalk formation. Growth optimum pH is 5.0-5.7. No growth factors required. The cells contain bacteriochlorophyll a. The photosynthetic membrane system consists of parallel lamellae. According to Bergery's Manual of Determinative Bacteriology, 8th ed. (1974) and 9th ed. (1994), the strain was identified to be Rhodopseudomonas acidophila. But on the side of enzyme activity, utilization of organic substrates and others the strain some differ from the type strain described by N Pfennig (1969). Therefore the strain P301 was identified to be Rhodopseudomonas acidophila var. fujianensis n. var.

China↗

PubMed1978

[Comparative study of B890 pigment-lipoprotein complexes from sulfur (Chromatium minutissimum) and non-sulfur (Rhodopseudomonas palustris) purple photosynthesizing bacteria].

Pigment-lipoprotein B890 complexes containing reaction center and "light-focusing" bacteriochlorophyll a were isolated from photosynthetic membranes of sulfur (Chromatium minutissimum) and non-sulfur (Rhodopseudomonas palustris) purple bacteria after the treatment with Triton X-100. The molecular weights of complexes were evaluated using several methods (200 000-300 000). By means of electron microscopy the sizes of complexes were found to be about 80 A. On the air-water interface hexagonal packing of complexes was observed. The chemical compositions of complexes are very similar except bacteriochlorophyll a whose specific content is somewhat higher in Chromatium minutissimum. The protein composition of complexes was studied and the molecular weights of proteins were estimated by SDS-gel electrophoresis. The results obtained show significant similarities in molecular organization of B890 complexes isolated from sulfur (Chromatium minutissimum) and non-sulfur (Rhodopseudomonas palustris) purple bacteria.

Bacterial Proteins↗

PubMed1983

Chemical cross-linking studies of the light-harvesting pigment-protein complex B800-850 of Rhodopseudomonas capsulata.

The spatial relationship of the three polypeptides contained in the B800-850 light-harvesting complex of Rhodopseudomonas capsulata has been studied with chemical cross-linking of crude membrane preparations of the phototrophic negative mutant strain Y5. Samples were cross-linked with the cleavable reagent dithiobis (succinimidyl propionate) (1.1 nm chain length) and analyzed by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. Membranes labelled with 14C-amino acids were used to determine the compositional stoichiometry of cross-linked products. It was found that the two polypeptides with an apparent Mr of 8000 and 10 000, respectively, that are associated with the pigments bacteriochlorophyll a and carotenoid form homooligomers as well as heterooligomers. The data support the idea that these polypeptides are closely arranged in clusters probably containing at least four of each species. The third subunit with an Mr of 14 000, which is not associated with pigments, was found to be most susceptible to cross-linking and formed homooligomers but no heterooligomers with the other two subunits, and is thus likely to be loosely attached to these clusters. Comparative studies with the phototrophic positive wild type strain indicated that the results found with the phototrophic negative mutant strain Y5 reflect the organization of the B800-850 complex in the membrane of Rhodopseudomonas capsulata. Studies with the isolated B800-850 complex revealed that the sterical arrangement of the three constituent polypeptides in dodecyl dimethylamine-N-oxide containing solutions must be very similar to that in the membrane.

Bacterial Proteins↗

PubMedDate not supplied

[Generic interrelations of purple bacteria in the genus Rhodopseudomonas].

The technique of DNA--DNA hybridization was used to study relations offween purple nonsulfur bacteria (the family Rhodospirillaceae). The level of homologies with Rhodopseudomonas sphaeroides 8259 was nearly the same for different species (8-17%) in the genus Rhodopseudomonas under the conditions optimal for hybridization. The same level of homologies was found for the DNA of Rhodospirillum rubrum, a species belonging to another genus of purple nonsulfur bacteria (13%). Rhodomicrobium vannielli was most remote from R. sphaeroides 8259 (3%). Similar results were obtained under other conditions of hybridization. The intraspecial heterogeneity of R. sphaeroides was studied in this work. The thermal stability of hybrid duplexes was analysed. The results are indicative of a considerable divergence of different R. sphaeroides strains (delta T50 = 2.1-11.6).

Base Sequence↗

PubMed1976

Photochemical activities of reaction centers from Rhodopseudomonas sphaeroides at low temperature and in the presence of chaotropic agents.

Light-induced absorbance changes were measured at low temperatures in reaction center preparations from Rhodopseudomonas sphaeroides. Absorbance difference spectra measured at 100 degrees K show that ubiquinone is photoreduced at this temperature, both by continuous light and by a short actinic flash. The reduction occurred with relatively high efficiency. These results give support to the idea that ubiquinone is involved in the primary photochemical reaction in Rhodopseudomonas sphaeroides. Reduction of ubiquinone was accompanied by a shift of the infrared absorption band of bacteriopheophytin. The rate of decay of the primary photoproducts (P+870 and ubisemiquinone) appeared to be approximately independent of temperature below 180 degrees K and above 270 degrees K; in the region between 180 and 270 degrees K it increased with decreasing temperature. The rate of decay was not affected by 0-phenanthroline. Secondary reactions were inhibited by lowering the temperature. The light-induced absorbance changes were inhibited by chaotropic agents, like thiocyanate and perchlorate. It was concluded that these agents lower the efficiency of the primary photoconversion. The kinetics indicated that the degree of inhibition was not the same for all reaction centers. The absorption spectrum of the photoconverted reaction centers appeared to be somewhat modified by thiocyanate.

Acetates↗

PubMed1985

Soluble cytochrome composition of the purple phototrophic bacterium, Rhodopseudomonas sphaeroides ATCC 17023.

A detailed study of the soluble cytochrome composition of Rhodopseudomonas sphaeroides (ATCC 17023) indicates that there are five c-type cytochromes and one b-type cytochrome present. The molecular weights, heme contents, amino acid compositions, isoelectric points, and oxidation-reduction potentials were determined and the proteins were compared with those from other bacterial sources. Cytochromes c2 and c' have previously been well characterized. Cytochrome c-551.5 is a diheme protein which has a very low redox potential, similar to certain purple bacterial and algal cytochromes. Cytochrome c-554 is an oligomer, which is spectrally similar to the low-spin isozyme of cytochrome c' found in other purple bacteria (e.g., Rhodopseudomonas palustris cytochrome c-556). An unusual high-spin c-type heme protein has also been isolated. It is spectrally distinguishable from cytochrome c' and binds a variety of heme ligands including oxygen. A large molecular-weight cytochrome b-558 is also present which appears related to a similar protein from Rhodospirillum rubrum, and the bacterioferritin from Escherichia coli. None of the soluble proteins appear to be related to the abundant membrane-bound c-type cytochrome in Rps. sphaeroides which has a larger subunit molecular weight similar to mitochondrial cytochrome c1 and chloroplast cytochrome f.

Bacterial Proteins↗

PubMed1983

Characterization of cytochrome b in the isolated ubiquinol-cytochrome c2 oxidoreductase from Rhodopseudomonas sphaeroides GA.

Extinction coefficients for cytochrome b and c1 in the isolated cytochrome bc1 complex from Rhodopseudomonas sphaeroides GA have been determined. They are 25 mM-1 . cm-1 at 561 nm for cytochrome b and 17.4 mM-1 . cm-1 at 553 nM for cytochrome c1, for the difference between the reduced and the oxidized state. Cytochrome b is present in two forms in the complex. One form has an Em7 of 50 mV, an alpha-peak of 557 nm at liquid N2 temperature and of 561 nm at RT, which is red-shifted by antimycin A. The other form has an Em7 of -90 mV, a double alpha-peak of 555 and 561 nm at liquid N2 temperature corresponding to 559 and 566 nm at RT. The absorption at 566 nm is red-shifted by myxothiazol. The two shifts are independent of each other. Both midpoint potentials of cytochromes b are pH-dependent. The redox center compositions of the cytochrome bc1 complexes from Rhodopseudomonas sphaeroides and from mitochondria are identical.

Antimycin A↗

PubMed1980

Interaction of cytochrome c with reaction centers of Rhodopseudomonas sphaeroides R-26: determination of number of binding sites and dissociation constants by equilibrium dialysis.

The number of binding sites and dissociation constants of cytochrome c (horse heart) and cytochrome c2 (Rhodopseudomonas sphaeroides) to reaction centers of Rhodopseudomonas sphaeroides R-26 was determined by equilibrium dialysis. One binding site was found for both cytochromes. The dissociation constants (10 mM Tris-HCl, pH 8.0) were approximately 0.4 microM and approximately 1.0 microM for cytochrome c and cytochrome C2 respectively. Oxidized and reduced forms of both cytochromes bound to reaction centers with approximately equal affinity.

Bacterial Proteins↗

PubMed2000

Cloning, sequencing and analysis of the pucC genes from Rubrivivax gelatinosus strain 151 and Rhodopseudomonas acidophila strain 10050.

The pucC genes of Rubrivivax gelatinosus strain 151 and Rhodopseudomonas acidophila strain 10050 have been identified, cloned and sequenced. In Rubrivivax gelatinosus the arrangement of the pucC gene with regard to the pucBA genes was shown to differ from that found in other species of photosynthetic bacteria. The Rhodopseudomonas acidophila pucC was found downstream of four new pucBA gene pairs, bringing the sequenced pucBA pairs to a total of eight in this strain. The predicted PucC protein sequences were compared to those of PucC from other species and showed high similarity. Similarity was also seen to more distantly related proteins LhaA and orf428 of Rhodobacter capsulatus, orf G115 of Rhodospirillum rubrum and 'orf428' from Synechocystis sp. PCC6803. An analysis of the predicted secondary structure of these proteins is given, and their structural similarity to proteins in the Major Facilitator Superfamily is discussed with regard to their possible function.

Journal Article↗

PubMed1985

Lipid biosynthesis in synchronized cultures of the photosynthetic bacterium Rhodopseudomonas sphaeroides.

Lipid biosynthesis has been studied in photosynthetic cultures of Rhodopseudomonas sphaeroides that had been synchronized by stationary-phase cycling or by a centrifugation selection procedure. Synchrony index values in the range 0.70-0.80 were obtained for the first cell cycle with both synchronization methods. The major membrane lipids phosphatidylethanolamine and phosphatidylglycerol were accumulated discontinuously during the cell cycle, their mass doubling immediately before cell division. This accumulation of lipid corresponded to peaks in incorporation of radioactivity from either [1-14C]acetate or [2-3H]glycerol into individual acyl lipids as measured in individual portions of bacteria. For phosphatidylglycerol an additional peak of incorporation of radioactivity from [2-3H]glycerol was found midway through the cell cycle. In spite of their rather similar endogenous fatty acid compositions, the individual phosphoacylglycerols showed distinctive patterns of incorporation of radioactivity from [1-14C]acetate into their acyl moieties. The discontinuous synthesis of acyl lipids observed in cultures of Rhodopseudomonas sphaeroides synchronized by either stationary-phase cycling or centrifugation selection procedures contrasted with the accumulation of chlorophyll-protein complexes whose amounts were found to increase throughout the cell cycle. The implications of these findings for the control of lipid synthesis in bacterial photosynthetic membranes are discussed.

Acetates↗

PubMed1966

Photoreduction of Pyridine Nucleotide by Subcellular Preparations from Rhodopseudomonas spheroides.

We have investigated the photoreduction of pyridine nucleotides by crude extracts and chromatophores of Rhodopseudomonas spheroides.Our findings are as follows:NADP is preferentially photoreduced by crude extracts (37,000 x g supernatant fraction) and there is no requirement for the addition of exogenous substrates. Crude extracts also catalyze a nonphotosensitive reduction of NAD.NADP photoreduction is completely inhibited if an NADH trapping system is present and indicates that NADH is required for NADP photoreduction.Washed chromatophores (150,000 x g pellet) do not catalyze NADP photoreduction unless the supernatant fraction is added. The restoring effect of supernatant fraction is lost upon boiling and dialysis. However, supernatant materials can be replaced by an NADH generating system. There is no requirement for anaerobic conditions.Evidence has been presented which suggests that Rhodopseudomonas spheroides contains an energy-linked transhydrogenase that can be driven by a high energy intermediate generated by light or ATP. This intermediate may also be functional in ATP synthesis. The synthesis of ATP and the ATP-supported transhydrogenase is inhibited by oligomycin. This inhibitor does not affect the light-mediated reaction.

Journal Article↗

PubMedDate not supplied

[Study of ferredoxins in membranes of Rhodopseudomonas spheroides by means of Mossbauer spectroscopy].

Mössbauer spectra were investigated in membranes (chromatophores) of Rhodopseudomonas sphaeroides, enriched in 57Fe, over a temperature range from 4.2 to 300 K. The spectrum of isolated chromatophores is a symmetric doublet characterized by an isomeric shift delta=0.60+/-0.03 mm/s, quadrupole splitting delta=0.54+/-0.03 mm/s and a width gamma delta of 1.42+/-0.04 mm/3 at half maximum. These parameters, which are in fact characteristic of the Mössbauer spectra of bacterial ferredoxins, appeared practically invariable over a wide range of temperatures. The spectrum of dithionite-treated chromatophores, measured immediately after dithionite treatment, exhibits, in addition, a doublet having parameters characteristic of high-spin bivalent iron. The doublet linewidth of the Fe2+ (S=2) iron is equal, at room temperature, to the emission spectrum linewidth. At 4K, some broadening of the spectrum is observed, which is of magnetic origin. The intensity of the Fe2+(S=2) doublet from a dithionite-treated sample shows a pronounced drop after several days of storage, with the intensity of the initial doublet rising. The overall area under the spectra, the linewidth and shape are not changed. Based on experimental data obtained, possible models of the active center composed of most frequently encountered membrane-bound ferredoxins of the photosynthetic bacterium Rhodopseudomonas sphaeroides are discussed.

Cell Membrane↗

PubMed1958

Endogenous photosensitization in a carotenoidless mutant of Rhodopseudomonas speroides.

Endogenous photosensitization in a carotenoidless mutant of Rhodopseudomonas spheroides has been studied. When this mutant is exposed to visible light and oxygen there is a short lag period followed by exponential killing of the cells. The killing process obeys the Bunsen-Roscoe law of reciprocity and is temperature-independent. The chlorophyll content of the cells does not affect the rate of killing until a certain low threshold has been reached. Exposure of photosynthetically grown cells to air in the dark induces a temporary desensitization to the killing. A certain proportion of the population is invariably resistant to the photokilling. Evidence is presented to show that the resistance of these cells is probably a result of their abnormally low chlorophyll content. One consequence of the irradiation is the appearance of abnormally small colonies upon plating the survivors. This is interpreted in terms of a multi-hit theory. The photosensitizing pigment itself (the intracellular bacteriochlorophyll) is destroyed. The process is zero order, temperature-dependent, and does not follow the reciprocity law. It is suggested that the death of the cell results from a disruption of the cell membrane.

Chlorophyll↗

PubMed1998

Sodium alkyl ether sulfate preparative electrophoresis for the preparation of reaction centers without H-subunit from Rhodopseudomonas viridis.

Sodium alkyl ether sulfate (AES), an analog of sodium dodecyl sulfate (SDS) was used in polyacrylamide gel electrophoresis (PAGE) for the partial decomposition of the photosynthetic reaction center (RC) of Rhodopseudomonas viridis. Unlike SDS, AES did not completely dissociate RC into its subunits but selectively detached H-subunit from RC to give RC(-H) without losing the spectroscopic nature of RC. For the denaturation of RC(-H), AES was found to be as mild as 3-[3-cholamidopropyl)dimethylammonio]-l-propanesulfonate (CHAPS).

Electrophoresis, Polyacrylamide Gel↗

PubMed1985

Cloning and expression of the fbc operon encoding the FeS protein, cytochrome b and cytochrome c1 from the Rhodopseudomonas sphaeroides b/c1 complex.

The gene for the FeS protein of the Rhodopseudomonas sphaeroides b/c1 complex was identified by means of cross-hybridization with a segment of the gene encoding the corresponding FeS protein of Neurospora crassa. Plasmids (pRSF1-14) containing the cross-hybridizing region, covering in total 13.5 kb of chromosomal DNA, were expressed in vitro in a homologous system. One RSF plasmid directed the synthesis of all three main polypeptides of the R. sphaeroides b/c1 complex: the FeS protein, cytochrome b and cytochrome c1. The FeS protein and cytochrome c1 were apparently synthesized as precursor forms. None of the pRSF plasmids directed the synthesis of the 10-kd polypeptide found in b/c1 complex preparations. Partial sequencing of the cloned region was performed. Several sites of strong homology between R. sphaeroides and eukaryotic polypeptides of the b/c1 complex were identified. The genes encode the three b/c1 polypeptides in the order: (5') FeS protein, cytochrome b, cytochrome c1. The three genes are transcribed to give a polycistronic mRNA of 2.9 kb. This transcriptional unit has been designated the fbc operon; its coding capacity corresponds to the size of the polycistronic mRNA assuming that only the genes for the FeS protein (fbcF), cytochrome b (fbcB) and cytochrome c1 (fbcC) are present. This could indicate that these three subunits constitute the minimal catalytic unit of the b/c1 complex from photosynthetic membranes.

Chromosome Mapping↗

PubMed1986

The 'light' and 'medium' subunits of the photosynthetic reaction centre from Rhodopseudomonas viridis: isolation of the genes, nucleotide and amino acid sequence.

The 'light' (L) and the 'medium' (M) subunits of the photosynthetic reaction centre from Rhodopseudomonas viridis were isolated and their amino-terminal sequences, as well as the sequences of several chymotryptic peptides, determined. Rps. viridis DNA was cloned in the Escherichia coli plasmid pBR322. Mixed oligonucleotide probes derived from the amino acid sequences were synthesized and utilised to isolate one clone which contained the genes for the L and M subunits of the reaction centre as well as the alpha and beta subunits of the light-harvesting complex and part of the gene for the reaction centre cytochrome. The nucleotide sequences of the L and M subunit genes and teh derived amino acid sequences are presented. The L subunit consists of 273 amino acids and has a mol. wt of 30 571. The M subunit consists of 323 amino acids and has a mol. wt of 35 902. The primary structure is discussed in the light of the recently published secondary and tertiary structure which has shown that both subunits contain five membrane-spanning helices.

Amino Acid Sequence↗