Kinetic bacteriochlorophyll fluorometer

Kocsis, Péter Balázs; Asztalos, Emese; Gingl, Zoltán; Maróti, Péter

doi:10.1007/s11120-010-9556-6

Cited by 25 publications

(42 citation statements)

References 42 publications

(48 reference statements)

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“…Induction of BChl fluorescence. The induction kinetics of the bacteriochlorophyll (BChl) a fluorescence of intact cells were measured by a home built fluorometer (Kocsis et al 2010). The light source was a laser diode (808 nm wavelength and 2 W light power) that produced rectangular shape of illumination and matched the 800 nm absorption band of the LH2 peripheral antenna of the cells.…”

Section: Methodsmentioning

confidence: 99%

Stoichiometry and kinetics of mercury uptake by photosynthetic bacteria

2017

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Mercury adsorption on the cell surface and intracellular uptake by bacteria represent the key first step in the production and accumulation of highly toxic mercury in living organisms. In this work, the biophysical characteristics of the mercury bioaccumulation are studied in intact cells of photosynthetic bacteria by use of analytical (dithizone) assay and physiological photosynthetic markers (pigment content, fluorescence induction and membrane potential) to determine the amount of mercury ions bound to the cell surface and taken up by the cell. It is shown that the Hg(II) uptake mechanism 1) has two kinetically distinguishable components, 2) includes co-opted influx through heavy metal transporters since the slow component is inhibited by Ca 2+ channel blockers, 3) shows complex pH-dependence demonstrating the competition of ligand binding of Hg(II) ions with H + ions (low pH) and high tendency of complex formation of Hg(II) with hydroxyl ions (high pH) and 4) is not a passive but an energy-dependent process as evidenced by light-activation and inhibition by protonophore. Photosynthetic bacteria can accumulate Hg(II) in amounts much (about 10 5 ) greater than their own masses by well defined strong and weak binding sites with equilibrium binding constants in the range of 1 (μM) -1 and 1 (mM) -1 , respectively. The strong binding sites are attributed to sulfhydryl groups as the uptake is blocked by use of sulfhydryl modifying agents and their number is much (two orders of magnitude) smaller than the number of weak binding sites. Biofilms developed by some bacteria (e.g. Rvx. gelatinosus) increase the mercury binding capacity further by a factor of about five. Photosynthetic bacteria in the light act as sponge of Hg(II) and can be potentially used for biomonitoring and bioremediation of mercury contaminated aqueous cultures.2

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Section: Methodsmentioning

confidence: 99%

Stoichiometry and kinetics of mercury uptake by photosynthetic bacteria

2017

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“…The uncoupling agent, p-triflouromethoxy carbonilcyanide phenylhydrazone (FCCP), was applied in 20 μM concentration to abolish the linkage between the respiratory chain and the phosphorylation system by dissipating the proton-motive force across the membrane. Induction and relaxation of BChl fluorescence: The induction and relaxation kinetics of the BChl a fluorescence of intact cells were measured by a home-built fluorometer (Kocsis et al 2010). The light source for both excitation and monitoring was a laser diode (wavelength of 808 nm and maximum light power of 2 W) that produced rectangular shape of illumination of variable duration and intensity and matched the 800-nm absorption band of the LH2 peripheral antenna of the cells.…”

Section: Methodsmentioning

confidence: 99%

Fluorescence induction of photosynthetic bacteria

Sipka¹,

Kis²,

Smart³

et al. 2018

Photosynt.

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The kinetics of bacteriochlorophyll fluorescence in intact cells of the purple nonsulfur bacterium Rhodobacter sphaeroides were measured under continuous and pulsed actinic laser diode (808 nm wavelength and maximum 2 W light power) illumination on the micro-and millisecond timescale. The fluorescence induction curve was interpreted in terms of a combination of photochemical and triplet fluorescence quenchers and was demonstrated to be a reflection of redox changes and electron carrier dynamics. By adjustment of the conditions of single and multiple turnovers of the reaction center, we obtained 11 ms -1 and 120 μs -1 for the rate constants of cytochrome c 2 3+ detachment and cyclic electron flow, respectively. The effects of cytochrome c 2 deletion and chemical treatments of the bacteria and the advantages of the fluorescence induction study on the operation of the electron transport chain in vivo were discussed.

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“…A small fraction of the absorbed light is emitted as BChl fluorescence which is quenched not only by photochemistry but by interactions with carotenoid triplets via an excited state annihilation process (singlet-triplet fusion) (Monger and Parson 1977;Breton et al 1979). Therefore, measurements of timeresolved BChl fluorescence provide a powerful analytic tool to investigate processes of excited energy transfer, photoprotection and photochemical trapping in RC (van Grondelle and Duysens 1980;Kocsis et al 2010;Asztalos et al 2015;Maróti et al 2013;Sipka and Maróti 2016). The transfer of triplet energy has so far been understood mainly in general terms and in many cases the identification of the actual pigments and responsible processes is lacking.…”

Section: Figurementioning

confidence: 99%

Photoprotection in intact cells of photosynthetic bacteria: quenching of bacteriochlorophyll fluorescence by carotenoid triplets

Sipka

Maróti

2017

Photosynth Res

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Upon high light excitation in photosynthetic bacteria various triplet states of pigments can accumulate leading to harmful effects. Here, the generation and lifetime of flash-induced carotenoid triplets ( 3 Car) have been studied by observation of the quenching of bacteriochlorophyll (BChl) fluorescence in different strains of photosynthetic bacteria including Rvx. gelatinosus (anaerobic and semianaerobic), Rsp. rubrum, Thio. roseopersicina, Rba. sphaeroides 2.4.1 and carotenoid and cytochrome deficient mutants Rba. sphaeroides Ga, R-26 and cycA, respectively. The following results were obtained: 1) 3 Car quenching is observed during and not exclusively after the photochemical rise of the fluorescence yield of BChl indicating that the charge separation in the reaction center (RC) and the carotenoid triplet formation are not consecutive but parallel processes. 2) The photo-protective function of 3 Car is not limited to the RC only and can be described by a model in which the carotenoids are distributed in the lake of the BChl pigments.3) The observed lifetime of 3 Car in intact cells is the weighted average of the lifetimes of the carotenoids with various numbers of conjugated double bonds in the bacterial strain. 4) The lifetime of 3 Car measured in the light is significantly shorter (1-2 μs) than that measured in the dark (2-10 μs). The difference reveals the importance of the dynamics of 3 Car before relaxation. The results will be discussed not only in terms of energy levels of the 3 Car but also in terms of the kinetics of transitions among different sublevels in the excited triplet state of the carotenoid.

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Kinetic bacteriochlorophyll fluorometer

Cited by 25 publications

References 42 publications

Stoichiometry and kinetics of mercury uptake by photosynthetic bacteria

Stoichiometry and kinetics of mercury uptake by photosynthetic bacteria

Fluorescence induction of photosynthetic bacteria

Photoprotection in intact cells of photosynthetic bacteria: quenching of bacteriochlorophyll fluorescence by carotenoid triplets

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