Papers by Andre Vermeglio
Biochimica Et Biophysica Acta - Bioenergetics, Dec 1, 1980
The orientations of high potential cytochromes with respect to photosynthetic membranes was inves... more The orientations of high potential cytochromes with respect to photosynthetic membranes was investigated in spinach chloroplasts and in Rhodopseudomonas viridis. The general approach consists in detection with polarized light of photoinduced absorbance changes related to the oxidation of the cytochromes. The orientation of cytochrome £558 was measured at room temperature in chromatophores and whole cells of 82• viridis, oriented 1981 AUG 26 PM 4: 1 0
Microbiology (Reading, England), 2002
Selenium oxyanions, particularly selenite, can be highly toxic to living organisms. Few bacteria ... more Selenium oxyanions, particularly selenite, can be highly toxic to living organisms. Few bacteria reduce both selenate and selenite into the less toxic elemental selenium. Insights into the mechanisms of the transport and the reduction of selenium oxyanions in Escherichia coli were provided by a genetic analysis based on transposon mutagenesis. Ten mutants impaired in selenate reduction were analysed. Three of them were altered in genes encoding transport proteins including a porin, an inner-membrane protein and a sulfate carrier. Two mutants were altered in genes required for molybdopterin biosynthesis, strongly suggesting that the selenate reductase of E. coli is a molybdoenzyme. However, mutants deleted in various oxomolybdenum enzymes described so far in this species still reduced selenate. Finally, a mutant in the gene ygfK encoding a putative oxidoreductase was obtained. This gene is located upstream of ygfN and ygfM in the ygfKLMN putative operon. YgfN and YgfM code for a moly...
Journal of Biological Chemistry, 2000
Archives of Microbiology, 1993
Light inhibited each step of the denitrification process in whole cells of Rhodobacter sphaeroide... more Light inhibited each step of the denitrification process in whole cells of Rhodobacter sphaeroides forma sp. denitrificans. This inhibition by light was prevented in the presence of exogenous electron donors like N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) plus ascorbate or in the presence of an uncoupler (carbonyl cyanide m-chlorophenylhydrazone). Addition of myxothiazol restored the inhibition by light in uncoupled cells. Measurements of light-induced absorbance changes under these conditions showed that this inhibition is due, for the steps of reduction of nitrite to dinitrogen, to the photooxidation of cytochromes cl plus c2 and not due to the photoinduced membrane potential. Moreover, the presence of oxygen inhibited almost all of the reduction of nitrate and nitrous oxide but only 70% of the reduction of nitrite to nitrous oxide. These inhibitions were overcome in the presence of TMPD plus ascorbate. This implies that the inhibition in presence of oxygen was due to a diversion of the reducing power from the denitrifying chain to the respiratory chain. It was concluded from this series of experiments that the reduction of nitrate to nitrite is inhibited when the ubiquinone pool is partly oxidized and that nitrite and nitrous oxide reductions are inhibited when cytochromes c I plus c 2 are oxidized by photosynthesis or respiration.
Biochimica Et Biophysica Acta - Bioenergetics, Nov 1, 2022
A very high rate for cyclic electron flow (CEF) around PSI (~180 s-1 or 210 s-1 in minimum medium... more A very high rate for cyclic electron flow (CEF) around PSI (~180 s-1 or 210 s-1 in minimum medium or in the presence of a carbon source respectively) is measured in the presence of methyl viologen (MV) in intact cells of Chlamydomonas reinhardtii under anaerobic conditions. The observation of an efficient CEF in the presence of methyl viologen is in agreement with the previous results reports of Asada et al in broken chloroplasts (Plant Cell Physiol. 31(4) (1990) 557-564). From the analysis of the P700 and PC absorbance changes, we propose that a confinement between 2 PC molecules, 1 PSI and 1 cytb6f corresponding to a functional supercomplex is responsible for these high rates of CEF. Supercomplex formation is also observed in the absence of methyl viologen, but with lower maximal CEF rate (about 100 s-1) suggesting that this compound facilitates the mediation of electron transfer from PSI acceptors to the stromal side of cytb6f. Further analysis of CEF in mutants of Chlamydomonas defective in state transitions shows the requirement of a kinase-driven transition to state 2 to establish this functional supercomplex configuration. However, a movement of the LHCII antennae is not involved in this process. We discuss the possible involvement of auxiliary proteins, among which is a small cytb6f-associated polypeptide, the PETO protein, which is one of the targets of the STT7 kinase.
International Journal of Systematic Bacteriology, 1997
The results of investigations on the morphology, physiology, pigment composition, light-harvestin... more The results of investigations on the morphology, physiology, pigment composition, light-harvesting antenna and reaction center organization, and electron carriers of five Brythrornicrobiurn representatives, and on phylogenetic relations among them, are summarized. On the basis of clear phenotypic differences and distinct phylogenetic positions shown by 16s ribosomal DNA analysis, the tentative species "Erythrornicrobium sibiricum" and "Erythromicrobiurn ursincola" are formally described as the type species of two new genera: Sunduracinobacter sibiricus gen. nov., sp. nov., and Erythrornonus ursincola gen. nov., sp. nov., respectively. The genus Erythrornicrobiurn is at present composed of the type species, E. rurnosurn, and two species, <'E. hydrolyticurn" and "E. ezovicurn," whose nomenclature is yet to be validated. All species studied group within the a-4 subclass of Proteobacteria.
Photosynthesis Research, 1998
Reaction centers (RC) from the species Erythrobacter (Eb.) litoralis, Erythromonas (Em.) ursincol... more Reaction centers (RC) from the species Erythrobacter (Eb.) litoralis, Erythromonas (Em.) ursincola and Sandaracinobacter (S.) sibiricus have been purified by LDAO treatment of light-harvesting-reaction center complexes and DEAE chromatography. The content and overall organisation of the RCs' chromophores, determined by linear dichroism (LD) and absorption spectroscopy, are similar to those isolated from anaerobic photosynthetic bacteria. The redox properties of the
Proceedings of the National Academy of Sciences, 2000
Some leguminous species of the genus Aeschynomene are specifically stem-nodulated by photosynthet... more Some leguminous species of the genus Aeschynomene are specifically stem-nodulated by photosynthetic bradyrhizobia. To study the effect of bacterial photosynthesis during symbiosis, we generated a photosynthesis-negative mutant of the Bradyrhizobium sp. strain ORS278 symbiont of Aeschynomene sensitiva . The presence of a functional photosynthetic unit in bacteroids and the high expression of the photosynthetic genes observed in stem nodules demonstrate that the bacteria are photosynthetically active during stem symbiosis. Stem inoculation by the photosynthetic mutant gave a 50% decrease in stem-nodule number, which reduced nitrogen fixation activity and plant growth in the same proportion. These results indicate an important role of bacterial photosynthesis in the efficiency of stem nodulation.
Proceedings of the National Academy of Sciences, 2009
Purple bacteria have thus far been considered to operate light-driven cyclic electron transfer ch... more Purple bacteria have thus far been considered to operate light-driven cyclic electron transfer chains containing ubiquinone (UQ) as liposoluble electron and proton carrier. We show that in the purple γ-proteobacterium Halorhodospira halophila , menaquinone-8 (MK-8) is the dominant quinone component and that it operates in the Q B -site of the photosynthetic reaction center (RC). The redox potentials of the photooxidized pigment in the RC and of the Rieske center of the bc 1 complex are significantly lower ( E m = +270 mV and +110 mV, respectively) than those determined in other purple bacteria but resemble those determined for species containing MK as pool quinone. These results demonstrate that the photosynthetic cycle in H. halophila is based on MK and not on UQ. This finding together with the unusual organization of genes coding for the bc 1 complex in H. halophila suggests a specific scenario for the evolutionary transition of bioenergetic chains from the low-potential menaquino...
Photosynthesis Research - PHOTOSYNTH RES, 1998
We have studied the electron transfer reactions from the tetraheme cytochrome of Rhodopseudomonas... more We have studied the electron transfer reactions from the tetraheme cytochrome of Rhodopseudomonas viridis to the oxidized primary donor in whole cells with a new high sensitivity spectrophotometer. In this apparatus the monochromatic detecting flashes are provided by a YAG pumped Optical Parametric Oscillator, allowing a 10 ns time resolution. When four hemes are reduced the observed electron transfer reaction sequence is the following: first the low-potential c552 heme (the number refers to the maximum absorption wavelength in the alpha-band region) is oxidized with a half time of 130 ns, in agreement with previous reports of measurements performed with purified reaction centers. Then, the electron hole is transferred to the low potential c554 heme with a half time of 2.6 µs. When only the two high potential hemes are reduced the observed electron transfer sequence is the following: oxidation of the high potential c559 heme in the hundreds of ns time range (410 ns), reduction of th...
Photosynthesis Research, 2012
Photosynthetic electron transfer has been examined in whole cells, isolated membranes and in part... more Photosynthetic electron transfer has been examined in whole cells, isolated membranes and in partially purified reaction centers (RCs) of Roseicyclus mahoneyensis, strain ML6 and Porphyrobacter meromictius, strain ML31, two species of obligate aerobic anoxygenic phototrophic bacteria. Photochemical activity in strain ML31 was observed aerobically, but the photosynthetic apparatus was not functional under anaerobic conditions. In strain ML6 low levels of photochemistry were measured anaerobically, possibly due to incomplete reduction of the primary electron acceptor (Q A) prior to light excitation, however, electron transfer occurred optimally under low oxygen conditions. Photoinduced electron transfer involves a soluble cytochrome c in both strains, and an additional reaction center (RC)-bound cytochrome c in ML6. The redox properties of the primary electron donor (P) and Q A of ML31 are similar to those previously determined for other aerobic phototrophs, with midpoint redox potentials of ?463 mV and-25 mV, respectively. Strain ML6 showed a very narrow range of ambient redox potentials appropriate for photosynthesis, with midpoint redox potentials of ?415 mV for P and ?94 mV for Q A. Cytoplasm soluble and photosynthetic complex bound cytochromes were characterized in terms of apparent molecular mass. Fluorescence excitation spectra revealed that abundant carotenoids not intimately associated with the RC are not involved in photosynthetic energy conservation.
Photosynthesis Research, 2008
The vertical distribution of culturable anoxygenic phototrophic bacteria was investigated at five... more The vertical distribution of culturable anoxygenic phototrophic bacteria was investigated at five sites at or near the Juan de Fuca Ridge in the Pacific Ocean. Twelve similar strains of obligately aerobic phototrophic bacteria were isolated in pure culture, from depths ranging from 500 to 2,379 m below the surface. These strains appear morphologically, physiologically, biochemically, and phylogenetically similar to Citromicrobium bathyomarinum strain JF-1, a bacterium previously isolated from hydrothermal vent plume waters. Only one aerobic phototrophic strain was isolated from surface waters. This strain is morphologically and physiologically distinct from the strains isolated at deeper sampling locations, and phylogenetic analysis indicates that it is most closely related to the genus Erythrobacter. Phototrophs were cultivated from three water casts taken above vents but not from two casts taken away from active vent sites. No culturable anaerobic anoxygenic phototrophs were detected. The photosynthetic apparatus was investigated in strain JF-1 and contains light-harvesting I and reaction center complexes, which are functional under aerobic conditions. Keywords Aerobic phototrophic bacteria Á Anoxygenic photosynthesis Á Bacteriochlorophyll Á Erythrobacter Á Citromicrobium Á Juan de Fuca Ridge
Journal of the American Chemical Society, 2006
In many electron-transfer proteins, the arrangement of cofactors implies a succession of uphill a... more In many electron-transfer proteins, the arrangement of cofactors implies a succession of uphill and downhill steps. The kinetic implications of such arrangements are examined in the present work, based on a study of chimeric photosynthetic reaction centers obtained by expressing the tetraheme subunit from Blastochloris viridis in another purple bacterium, Rubrivivax gelatinosus. Site-directed mutations of the environment of heme c559, which is the immediate electron donor to the primary donor P, induced modifications of this heme's midpoint potential over a range of 400 mV. This resulted in shifts of the apparent midpoint potentials of the neighboring carriers, yielding estimates of the interactions between redox centers. At both extremities of the explored range, the energy profile of the electron-transfer chain presented an additional uphill step, either downstream or upstream from c559. These modifications caused conspicuous changes of the electron-transfer rate across the tetraheme subunit, which became ∼100-fold slower in the mutants where the midpoint potential of c559 was lowest. A theoretical analysis of the kinetics is presented, predicting a displacement of the rate-limiting step when lowering the potential of c559. A reasonable agreement with the data was obtained when combining this treatment with the rates predicted by electron transfer theory for the individual rate constants.
Journal of Biological Chemistry, 2004
Aerobic photosynthetic bacteria possess the unusual characteristic of producing different classes... more Aerobic photosynthetic bacteria possess the unusual characteristic of producing different classes of carotenoids. In this study, we demonstrate the presence of two distinct crt gene clusters involved in the synthesis of spirilloxanthin and canthaxanthin in a Bradyrhizobium strain. Each cluster contains the genes crtE, crtB, and crtI leading to the common precursor lycopene. We show that spirilloxanthin is associated with the photosynthetic complexes, while canthaxanthin protects the bacteria from oxidative stress. Only the spirilloxanthin crt genes are regulated by light via the control of a bacteriophytochrome. Despite this difference in regulation, the biosyntheses of both carotenoids are strongly interconnected at the level of the common precursors. Phylogenetic analysis suggests that the canthaxanthin crt gene cluster has been acquired by a lateral gene transfer. This acquisition may constitute a major selective advantage for this class of bacteria, which photosynthesize only under conditions where harmful reactive oxygen species are generated. Carotenoids comprise a large class of pigments that are widely distributed in living organisms. They are synthesized by all photosynthetic organisms from bacteria to plants where they play at least three essential functions (1). First, they act as accessory light-harvesting pigments by absorbing light in the 450-570 nm region. Second, they are important for the assembly and stability of some of these light-harvesting complexes. Finally they operate as photoprotectors by directly quenching both triplet excited (bacterio)chlorophylls and singlet oxygen. Carotenoids are also synthesized by a wide variety of nonphotosynthetic bacteria (2). Less is known about their precise function in these bacteria, but it is well accepted that their strong antioxidant character may protect the organisms against (photo)oxidative damage. A remarkable feature of aerobic phototrophic bacteria, besides their ability to photosynthesize only under aerobic condi-* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The nucleotide sequence(s) reported in this paper has been submitted to the GenBank TM /EBI Data Bank with accession number(s) AF182374.
Journal of Biological Chemistry, 2004
Journal of Biological Chemistry, 2000
The orientation of the chromophores in the cytochrome bc 1 of Rhodospirillum rubrum, Rhodobacter ... more The orientation of the chromophores in the cytochrome bc 1 of Rhodospirillum rubrum, Rhodobacter sphaeroides, and beef heart mitochondria is reported. The combination of redox-resolved absorption spectrophotometry and linear dichroism experiments at low temperature allows the determination of the orientation of the three hemes with respect to the membrane plane. The orientations of the b Hand b L-hemes of the R. sphaeroides and beef heart mitochondrial complexes are similar to those determined by crystallographic studies of the mitochondrial cytochrome bc 1. On the other hand the orientations of the b-hemes of the R. rubrum complex lead to the conclusion that the b H-heme is more perpendicular to the membrane plane than the b L-heme. This could be explained by a specific organization of the b-hemes due to subunit composition of the complex or, alternatively, to a different spatial position of the heme transitions with respect to the porphyrin macrocycle compared with the other complexes. Moreover, our results demonstrate a different orientation of the heme c 1 of the three studied complexes in comparison to crystallographic studies. This difference may arise from the above hypothesis on the transitions of the heme or from flexibility of this subunit in function of its redox state.
Journal of Biological Chemistry, 2006
A new type of membrane-bound cytochrome c was found in a marine purple photosynthetic bacterium, ... more A new type of membrane-bound cytochrome c was found in a marine purple photosynthetic bacterium, Rhodovulum sulfidophilum. This cytochrome c was significantly accumulated in cells growing under anaerobic photosynthetic conditions and showed an apparent molecular mass of ϳ100 kDa when purified and analyzed by SDS-PAGE. The midpoint potential of this cytochrome c was 369 mV. Flash-induced kinetic measurements showed that this new cytochrome c can work as an electron donor to the photosynthetic reaction center. The gene coding for this cytochrome c was cloned and analyzed. The deduced molecular mass was nearly equal to 50 kDa. Its C-terminal heme-containing region showed the highest sequence identity to the water-soluble cytochrome c 2 , although its predicted secondary structure resembles that of cytochrome c y. Phylogenetic analyses suggested that this new cytochrome c has evolved from cytochrome c 2. We, thus, propose its designation as cytochrome c 2m. Mutants lacking this cytochrome or cytochrome c 2 showed the same growth rate as the wild type. However, a double mutant lacking both cytochrome c 2 and c 2m showed no growth under photosynthetic conditions. It was concluded that either the membrane-bound cytochrome c 2m or the water-soluble cytochrome c 2 work as a physiological electron carrier in the photosynthetic electron transfer pathway of Rvu. sulfidophilum.
Journal of Biological Chemistry, 2004
We suggest that subscribers photocopy these corrections and insert the photocopies at the appropr... more We suggest that subscribers photocopy these corrections and insert the photocopies at the appropriate places where the article to be corrected originally appeared. Authors are urged to introduce these corrections into any reprints they distribute. Secondary (abstract) services are urged to carry notice of these corrections as prominently as they carried the original abstracts.
Journal of Bacteriology, 2008
The recent sequence analysis of the photosynthetic and plant-symbiotic Bradyrhizobium sp. strain ... more The recent sequence analysis of the photosynthetic and plant-symbiotic Bradyrhizobium sp. strain BTAi1 revealed the unexpected presence of a pucBA operon encoding the apoproteins of peripheral light-harvesting (LH) complexes. This pucBA operon is found close to a bacteriophytochrome gene (BphP3 B BTAi1) and a two-component transcriptional regulator gene (TFBTAi1 gene). In this study, we show that BphP3 B BTAi1 acts as a bona fide bacteriophytochrome and controls, according to light conditions, the expression of the pucBA operon found in its vicinity. This light regulatory pathway is very similar to the one previously described for chromo-BphP4 Rp in Rhodopseudomonas palustris and conducts the synthesis of a peripheral LH complex. This LH complex presents a single absorption band at low temperature, centered at 803 nm. Fluorescence emission analysis of intact cells indicates that this peripheral LH complex does not act as an efficient light antenna. One putative function of this LH c...
Biochemistry, 2009
Three periplasmic electron carriers, HiPIP and two cytochromes c 8 with low-and high-midpoint pot... more Three periplasmic electron carriers, HiPIP and two cytochromes c 8 with low-and high-midpoint potentials, are present in the purple photosynthetic bacterium Rubrivivax gelatinosus. Comparison of the growth rates of mutants lacking one, two, or all three electron carrier proteins showed that HiPIP is the main electron donor to the photochemical reaction center and that high-potential cytochrome c 8 plays a subsidiary role in the electron donation in photosynthetically growing cells. However, the triple deletion mutant was still capable of photosynthetic growth, indicating that another electron donor could be present. A new soluble cytochrome c, which can reduce the photooxidized reaction center in vitro, was purified. Based on amino acid sequence comparisons to known cytochromes, this cytochrome was identified as a diheme cytochrome c of the family of cytochromes c 4. The quadruple mutant lacking this cytochrome and three other electron carriers showed about three times slower growth than the triple mutant under photosynthetic growth conditions. In conclusion, cytochrome c 4 can function as a physiological electron carrier in the photosynthetic electron transport chain in R. gelatinosus.
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Papers by Andre Vermeglio