Podcasts about rhodopseudomonas

Here's my summary of the third day of ASM2013, wherein I met with neat people and ideas. Download Episode (4.3 MB, 4.6 minutes) Session 1: Microbe-Microbe Interactions - Cell Contact-Dependent Outer Membrane Exchange in Myxobacteria Presented by Dan Wall Myxobacteria are super cool, a fascinating example of complex cooperative behavior in relatively simple single-celled organisms. They swarm around eating other bacteria until they get low on food, at which point they gather together to form reproductive structures called fruiting bodies to spread to new environments. As part of the mechanism they use to coordinate their activity and distinguish between friends and foes, they seem to exchange components of their outer membrane, but only with closely-related strains. Poster: 1485 - Understanding the Syntrophic Metabolism of a Bacterial Co-culture for Hydrogen Production (Combination of Clostridium cellulolyticum and Rhodopseudomonas palustris to convert cellulosic plant material into hydrogen) Y. Jiao, A. Navid, B. Stewart, J. McKinlay, M. Thelen, J. Pett-Ridge Poster: 1702 - Non-Photosynthetic, Deep-Branching Cyanobacteria of the Human Gut and Subsurface Permit Inference of the Cyanobacterial Ancestor S.C. Di Rienzi, I. Sharon, K.C. Wrighton, O. Koren, L.A. Hug, B.C. Thomas, J.K. Goodrich, J.T. Bell, T.D. Spector, J.F. Banfield, R.E. Ley This Week in Microbiology 56: Live at ASM in Denver They started out talking about scientific misconduct with Ferric Fang, then with Andrew Camilli about the virus with a CRISPR system (listen at about 1 hour 2 min in to hear my question!), and also with Suzanne Fleiszig and Michelle Swanson about a gruesome-sounding eye infection and defenses against intracellular bacteria. You should give it a listen (or watch)! Post questions or comments here or email to bacteriofiles at gmail dot com. Thanks for listening! Subscribe at iTunes, check out the show at Twitter or Facebook

This doctoral thesis presents new approaches for the characterisation of ultrafast energy flow in complex systems, based on concepts of coherent control. By initiating a photoreaction with femtosecond pulses whose temporal phase and amplitude are shaped in such a manner that specific molecular vibrations and states are addressed, the energy flow can be steered at will. The comparison between the ensuing energy flow patterns following shaped and unshaped excitation pulses constitutes a differential measurement of the function of the controlled vibrations and states within the photoreaction. Coherent control as a spectroscopic tool is first applied to biological systems, specifically the light harvesting complex LH2 from the photosynthetic purple bacterium Rhodopseudomonas acidophila, and the isolated carotenoid donor of the same complex. The pump-probe method using shaped excitation pulses is shown to be successful for the first time in controlling the natural function of a biological system, namely the flow of excitation energy in the complex network of states in LH2. By means of a closed-loop optimisation of parametrised excitations, a bending mode in the carotenoid donor can be identified as being responsible for steering the energy flow. This bu vibrational mode couples the carotenoid S2-S1 states; its frequency is determined to be 160±25cm-1. Furthermore the deactivation of the carotenoid S2 state in LH2 and in solution is studied with pump-probe and pump-deplete-probe spectroscopy. Here it is shown that there exists an alternative singlet state S*T (1Bu-) involved in the deactivation process, though only in LH2. Its function as a precursor of ultrafast triplet population and as a donor for photosynthetic energy transfer is characterised with a novel evolutionary target analysis of conventional pump-probe spectra. Secondly, coherent control as a measurement technique is applied to another extremely complex system, in this case a material dominated by non-linear interactions with instantaneous dynamics: Propagation of femtosecond pulses in optical fibres that are only a few micrometers in diameter to generate a supercontinuum of optical frequencies. Here shaped pump pulses succeed in resolving for the first time the sequential steps leading to the enormous spectral broadening. Open-loop variations of precompression allows the evolution and fission of optical solitons to be followed, while closed-loop optimisations render observable the coupling of solitons with phase-matched visible frequencies. On atoms, finally, open-loop control of interfering pathways from the ground to the excited state by application of strongly modulated spectra seeks to establish a direct link between coherent control experiments and theory. The novel phenomenon of a Fresnel zone plate in the time domain is first developed in theory and then successfully realised in experiment.

The spectral properties of the excited electronic state of the reaction centers of Rhodopseudomonas (Rps.) viridis are studied by dichroic transient absorption spectroscopy with sub-picosecond time resolution. The theoretical analysis of the experimental results allows the assignment of the transient absorption from two dimer bands of the special pair and show its excitonic coupling to other pigments.

Zero field absorption detected magnetic resonance hole burning measurements were performed on photosynthetic reaction centers of the bacteria Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis. Extrapolation to zero microwave power yielded pseudohomogeneous linewidths of 2.0 MHz for Rhodopseudomonas viridis, 1.0 and 0.9 MHz for the protonated forms of Rhodobacter sphaeroides R26 with and without monomer bacteriochlorophyll exchanged, and 0.25 MHz as an upper limit for fully deuterated reaction centers of Rhodobacter sphaeroides R26. The measured linewidths were interpreted as being due to unresolved hyperfine interaction between the nuclear spins and the triplet electron spin, the line shape being determined by spectral diffusion among the nuclei. The difference in linewidths between Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis is then explained by triplet delocalization on the special pair in the former, and localization on one dimer half on the latter. In the fully deuterated sample, four quadrupole satellites were observed in the hole spectra arising from the eight 14N nitrogens in the special pair. The quadrupole parameters seem to be very similar for all nitrogens and were determined to =1.25±0.1 MHz and =0.9±0.1 MHz. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

The primary, light-induced charge separation in reaction centers of Rhodopseudomonas viridis is investigated with femtosecond time resolution. The absorption changes after direct excitation of the primary donor P at 955 nm are investigated in the time range from 100 fs to 600 ps. The experimental data, taken at various probing wavelengths, reveal one subpicosecond and two picosecond time constants: 0.65 ± 0.2 ps, 3.5 ± 0.4 ps, and 200 ± 20 ps. The previously undetected 0.65 ps kinetics can be observed clearly in the spectral range of the Qx and Qy transitions of the monomeric bacteriochlorophylls. The experimental data support the idea that the accessory bacteriochlorophyll B A participates in the electron-transfer process. References

Pigments of borohydride-treated reaction centers of Rhodobacter sphaeroides R 26 and Rhodopseudomonas viridis were analyzed by HPLC with polychromatic detection. In both species, pigment composition and contents were unchanged. Reaction centers from Rhodobacter sphaeroides R26 were prepared in which bacteriochlorophylls (BA,B) and bacteriopheophytins (HA,B) were exchanged with their potential borohydride products reduced at C-31. [3-Hydroxyethyl]-BChl a exchanges selectively into the BA,B pockets, and 31-OH-BPh a to the HA,B pockets. Stable reaction centers are obtained in both cases. A comparison of the absorption and circular dichroism spectra of reaction centers after exchange with 31-OH pigments, and of borohydride-modified reaction centers, reveal distinct differences. It is concluded that during borohydride reduction none of the pigments is chemically modified or extracted from the reaction centers.

Mon, 1 Jan 1990 12:00:00 +0100 https://epub.ub.uni-muenchen.de/3758/1/3758.pdf Zinth, Wolfgang; Stilz, Hans Ulrich; Scheer, Hugo; Oesterhelt, Dieter; Michel, H.; Kaiser, Wolfgang; Buchanan, S.; Holzapfel, Wolfgang; Hamm, P.; Lauterwasser, Christoph; Finkele, Ulrich; Dressler, K.

The light-induced radical cation of the primary electron donor P960+• in photosynthetic reaction centers from Rhodopseudomonas viridis has been investigated by ESR, ENDOR and TRIPLE techniques. Both the comparison with the cation radical of monomeric bacteriochlorophyll b (BChl b) and with molecular-orbital calculations performed on P960+• using the results of an X-ray structure analysis, consistently show an asymmetric distribution of the unpaired electron over the two BChl b molecules which constitute P960+•. The possible relevance of this result for the primary electron transfer step in the reaction center is briefly discussed.

Absorption spectra and light-induced absorbance changes of crystals from Rhodopseudomonas viridis reaction centers are recorded. A theoretical analysis of the absorption and circular dichroism spectra is presented, yielding a consistent picture of spectroscopic and structural information.

Polarized spectra of absorption and light-induced absorbance changes are presented for the crystallized reaction centers of Rhodopseudomonas viridis. We find that a model based on extended dipole interaction between all six pigments is capable of interpreting detailed features such as the contributions from the individual pigments to the various absorption peaks. Even though the pigments are arranged in approximate C2 symmetry, the optical spectra together with the calculations reflect deviations from this symmetry, which may be important in understanding the electron pathway.

The photoexcited triplet state PT of Rhodopseudomonas sphaeroides R-26 has been investigated by ENDOR measurements performed on frozen photosynthetic reaction centre solutions. For the first time hyperfine data could be obtained for PT. These data indicate a delocalisation of the triplet state over two bacteriochlorophyll a molecules.

An electron spin echo envelope modulation frequency analysis is performed on the triplet state of the primary electron donor (P-860) in 14N reaction centers of the photosynthetic bacterium Rhodopseudomonas sphaeroides R26 and 15N-enriched reaction centers of Rhodopseudomonas sphaeroides 2.4.1, and of the triplet state of 14N or 15N bacteriochlorophyll a in vitro. The hyperfine previous termcouplingnext term constants for 15N 3P-860 are 1.42, 1.74 and 2.04 MHz. The triplet state of the primary donor in bacterial photosynthesis is, on a timescale of a few MHz, delocalized over the two bacteriochlorophyll a molecules making up P-860.

An electron spin echo modulation frequency analysis of P+-860 is performed in 14N chromatophores of Rhodospirillum rubrum, and in 15N substituted reaction centers from Rhodopseudomonas sphaeroides 2.4.1. For the 14N material two sets of nuclear quadrupole parameters are obtained. From the frequencies found for 15N reaction centers the perpendicular, parallel and isotropic hyperfine previous termcouplingnext term constants of three of the four bacteriochlorophyll nitrogen nuclei are inferred.

Tue, 1 Jan 1985 12:00:00 +0100 http://epub.ub.uni-muenchen.de/2161/ http://epub.ub.uni-muenchen.de/2161/1/2161.pdf Heidl, H.; Knödlmayer, K.; Rüdiger, W.; Scheer, Hugo; Schoch, S.; Ullrich, J. Heidl, H.; Knödlmayer, K.; Rüdiger, W.; Scheer, Hugo; Schoch, S. und Ullrich, J. (1985): Degradation of bacteriochlorophyll a in Rhodopseudomonas sphaeroides R26. In: Zeitschrift für Naturforschung C, Vol. 40c: pp. 685-692. Biologi

Tue, 1 Jan 1985 12:00:00 +0100 https://epub.ub.uni-muenchen.de/3250/1/3250.pdf Kaiser, Wolfgang; Franz, M. A.; Nuss, M. C.; Zinth, Wolfgang

Tue, 1 Jan 1985 12:00:00 +0100 https://epub.ub.uni-muenchen.de/3251/1/3251.pdf Kaiser, Wolfgang; Dobler, J.; Sander, M.; Zinth, Wolfgang

Tue, 1 Jan 1985 12:00:00 +0100 https://epub.ub.uni-muenchen.de/3252/1/3252.pdf Zinth, Wolfgang; Dobler, J.; Michel, H.; Lindsay, J. G.; Mackenzie, R. C.; Woolley, K.; Cogdell, Richard J. d

Crystallized reaction centers from Rhodopseudomonas viridis (i) are photochemically active with electron transfer from the special pair to the quinones, (ii) show dichroism giving valuable information on the orientation of the different chromophores and (iii) allow chemical treatment in the crystalline phase.

Thu, 1 Jan 1981 12:00:00 +0100 http://epub.ub.uni-muenchen.de/2835/ http://epub.ub.uni-muenchen.de/2835/1/050.pdf Lendzian, F.; Lubitz, Wolfgang; Scheer, Hugo; Bubenzer, C.; Möbius, K. Lendzian, F.; Lubitz, Wolfgang; Scheer, Hugo; Bubenzer, C. und Möbius, K. (1981): In Vivo Liquid Solution ENDOR and TRIPLE Resonance of Bacterial Photosynthetic Reaction Centers of Rhodopseudomonas sphaeroides R-26. In: Journal of the American Chemical Society, Vol. 103: pp

Mon, 1 Jan 1979 12:00:00 +0100 http://epub.ub.uni-muenchen.de/2582/ http://epub.ub.uni-muenchen.de/2582/1/028.pdf Haberkorn, R.; Michel-Beyerle, Maria E.; Scheer, Hugo; Seydlitz, H.; Tempus, W. Haberkorn, R.; Michel-Beyerle, Maria E.; Scheer, Hugo; Seydlitz, H. und Tempus, W. (1979): Time-resolved magnetic field effect on triplet formation in photosynthetic reaction centers of rhodopseudomonas sphaeroides R-26. In: FEBS Letters, Vol. 100: p