Cells Of Photosynthetic Bacteria Research Articles

Respiratory control and the basis of light-induced inhibition of respiration in chromatophores from Rhodopseudomonas capsulata

A preparation of chromatophores from Rhodopseudomonas capsulata is described in which NADH oxidase activity is stimulated by uncouplers and during ATP synthesis, and is strongly inhibited upon illumination. The inhibition is completely reversed by addition of a protonophore or the combination of valinomycin, nigericin and K + , thus demonstrating that the proton electro-chemical gradient generated by light-driven cyclic electron flow is responsible for the inhibition of respiration. By analogy it is suggested that light-induced inhibition of respiration in intact cells of photosynthetic bacteria is also controlled by the proton electrochemical gradient. The results show that all chromatophores that possess oxidase activity must also have light-driven cyclic electron flow pathways. This has implications for experiments in which carotenoid band shifts and distributions of permeant anions have been compared as indicators of membrane potentials in chromatophores.

The kinetics of carotenoid absorption changes in intact cells of photosynthetic bacteria

The kinetics of carotenoid absorption changes have been measured in intact cells of Rhodopseudomonas capsulata after short flash excitation. The observed changes were consistent with the thesis that they indicate the development and dissipation of membrane potential. In the generation of the absorption changes in anaerobic cells, fast (complete in 0.5 ms) and slow (half-time 3 ms) components can be distinguished. The slow component corresponds kinetically to the rate of cytochrome c re-reduction and is similarly antimycin sensitive. These data are similar to those observed in isolated chromatophores which have been artifically poised with redox mediators. In aerobic intact cells the kinetic profile is altered, mainly because the decay of the carotenoid change is much faster. Inhibition of respiration with KCN leads to flash-induced changes similar to those in anaerobic cells. At least two components can be distinguished in the decay of the carotenoid absorption changes in anaerobic intact cells. Only the faster decay component was inhibited by venturicidin which suggests that it corresponds to H + flux through the F 0F 1-ATPase during ATP synthesis. The contribution of the venturicidin-sensitive decay to the total decay was dependent upon the initial amplitude of the carotenoid absorption change produced by the flash group. This suggests that there is an apparent threshold of membrane potential for ATP synthesis. Supporting evidence was provided by the finding that venturicidin stimulated the steady-state light-induced carotenoid absorption change at high but not at low light intensities. The entire decay of the carotenoid absorption changes was stimulated by carbonyl cyanide p-trifluoromethoxyphenylhydrazone in a manner that can be interpreted as an ionophore catalysing the dissipation of membrane potential.

A bioreactor for continuous treatment of waste waters with immobilized cells of photosynthetic bacteria

A bioreactor for assaying immobilized cells of photosynthetic bacteria for hydrogen production under optimal operating conditions was made. High and lasting H2-photoevolutions were obtained using waste waters as substrates.

A new approach to the theory of linear dichroism in partially ordered systems. Application to reaction centers and whole cells of photosynthetic bacteria

We have developed a new approach to the theory of linear dichroism in partially ordered systems. The description of the partially ordered ensemble uses a density of states function, D(theta, phi, approximately delta), which gives the probability that the direction of polarization for incident polarized light has spherical angles theta and phi in an axis system fixed with respect to the molecule; approximately delta = (delta 1, delta 2...delta n) is a set of parameters that describes the partial ordering. We derive new formulas for linear dichroism using the density of states function and then apply these formulas to the analysis of linear dichroism in reaction centers and whole cells of photosynthetic bacteria. One advantage of our approach is that the order parameter, approximately delta, provides a more complete description of the distribution function than the traditional order parameters used by other authors. Knowledge of approximately delta gives a good physical description of the partial ordering and allows one to calculate accurate limits for the range of possible orientations of the transition moments.

Electron paramagnetic resonance detection of carotenoid triplet states

Triplet states of carotenoids have been detected by X-band electron paramagnetic resonance (EPR) and are reported here for the first time. The systems in which carotenoid triplets are observed include cells of photosynthetic bacteria, isolated bacteriochlorophyll-protein complexes, and detergent micelles which contain ..beta..-carotene. It is well known that if electron transfer is blocked following the initial acceptor in the bacterial photochemical reaction center, back reaction of the primary radical pair produces a bacteriochlorophyll dimer triplet. Previous optical studies have shown that in reaction centers containing carotenoids the bacteriochlorophyll dimer triplet sensitizes the carotenoid triplet. We have observed this carotenoid triplet state by EPR in reaction centers of Rhodopseudomonas sphaeroides, strain 2.4.1 (wild type), which contain the carotenoid spheroidene. The zero-field splitting parameters of the triplet spectrum are /D/ = 0.0290 +- 0.0005 cm/sup -1/ and /E/ = 0.0044 +-0.0006 cm/sup -1/, in contrast with the parameters of the bacteriochlorophyll dimer triplet, which are /D/ = 0.0189 +- 0.0004 cm/sup -1/ and /E/ = 0.0032 +- 0.004 cm/sup -1/. Bacteriochlorophyll in a light harvesting protein complex from Rps. sphaeroides, wild type, also sensitizes carotenoid triplet formation. In whole cells the EPR spectra vary with temperature between 100 and 10 K. Carotenoidmore » triplets also have been observed by EPR in whole cells of Rps. sphaeroides and cells of Rhodospirillum rubrum which contain the carotenoid spirilloxanthin. Attempts to observe the triplet state EPR spectrum of ..beta..-carotene in numerous organic solvents failed. However, in nonionic detergent micelles and in phospholipid bilayer vesicles ..beta..-carotene gives a triplet state spectrum with /D/ = 0.0333 +- 0.0010 cm/sup -1/ and /E/ = 0.0037 +- 0.0010 cm/sup -1/. 6 figures, 1 table.« less

A study on the membrane potential and pH gradient in chromatophores and intact cells of photosynthetic bacteria

Generation of membrane potential (delta psi) and transmembrane pH difference (delta pH) was studied in PPi-energized chromatophores of Rhodospirillum rubrum by means of measurements of carotenoid and bacteriochlorophyll absorption changes, atebrin and 8-anilinonaphthalene-1-sulphonate fluorescence responses, and phenyldicarbaundecaborane transport. The data obtained are consistent with the suggestion that carotenoid, bacteriochlorophyll and phenyldicarbaundecaborane responses are indicators of delta psi, while an atebrin response is an indicator of delta pH. The fluorescence of 8-anilinonaphthalene-1-sulphonate is affected both by delta psi and delta pH.

Studies on ion transport in cells of photosynthetic bacteria. I. The key role of anions in determining the direction and magnitude of hydrogen ion flux.

Studies on ion transport in cells of photosynthetic bacteria. I. The key role of anions in determining the direction and magnitude of hydrogen ion flux.

Studies on ion transport in cells of photosynthetic bacteria. II. Analysis of reversed hydrogen ion change.

Studies on ion transport in cells of photosynthetic bacteria. II. Analysis of reversed hydrogen ion change.

Studies on ion transport in cells of photosynthetic bacteria. 3. The influence of uncouplers on hydrogen ion change.

Studies on ion transport in cells of photosynthetic bacteria. 3. The influence of uncouplers on hydrogen ion change.

The absolute yield of bacteriochlorophyll fluorescence in vivo.

Abstract— –The method of Weber and Teale for determining absolute fluorescence quantum yield of dyes in solution was modified for determination of the yield of bacteriochlorophyll fluorescence from chromatophores and whole cells of photosynthetic bacteria. Measured yields ranged from about 1–6 per cent. The yield depended on intensity and wavelength of the exciting light. The higher yield at higher light intensity was interpreted as due to saturation of photosynthesis. The lower yield in some strains when excited at 810 nm was attributed to preferential excitation of the reaction center pigment P800.From this study and the lifetime measurements of others, the relation τ=Q.τ0 was substantiated for the fluorescence of bacteriochlorophyll in vivo, τ being the actual lifetime, τ0 the intrinsic lifetime as estimated from the absorption band area, and Q the quantum yield of fluorescence.

THE ACCELERATING ACTION OF 5–METHYLPHENAZINIUM METHYL SULFATE ON LIGHT INDUCED ABSORBANCY AND ESR CHANGES IN RHODOSPIRILLUM CHROMATOPHORES*

THE DYE 5-methylphenazinium methyl sulfate (PMS) has been used either as an electron donor or as an electron acceptor in the respiratory This dye has also been used in the study of photosynthetic systems, acting as a by-pass for the antimycin-A sensitive locus and as an agent which is capable of increasing rates of light induced phosphorylation under certain conditions.(3) Light induced reversible absorbancy and electron spin resonance (ESR) changes in both cell-free preparations and intact cells of photosynthetic bacteria have been observed and studied by several investigator~.(4-~~) We wish to report here some of our observations regarding the effect of oxidized PMS upon light induced absorbancy and ESR changes in isolated chromatophores. Illumination of chromatophores produces a distinct ESR signal and distinct absorbancy changes; the decay of these light induced changes at 433 and 790 mp is represented in Figs. 1-3. It was observed that upon addition of oxidized PMS the rates of the slow dark decay of both the ESR signal and the absorbancy changes could be markedly accelerated (Figs. 1-3). A quantitative evaluation of these observations is given in Table 1 which lists the calculated values of the time constants ( T ) for a series of experiments covering a wide concentration range of added PMS. The evaluation of these data shows that the 7 values for the slow decay components at 433 and 790 mp are identical within experimental error, while the values for the slow dark decay of the ESR signal differ significantly from those calculated for the absorbancy changes. It is apparent that the values of the slow decay components seen at 433 and at 790 mp behave similarly upon the addition of varying amounts of PMS and differ significantly from the 7 values of the ESR decays.