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11.
Three Synechocystis PCC 6803 strains with different levels of phycobilisome antenna-deficiency have been investigated for their impact on photosynthetic
electron transport and response to environmental factors (i.e. light-quality, -quantity and composition of growth media).
Oxygen yield and P700 reduction kinetic measurements showed enhanced linear electron transport rates—especially under photoautotrophic conditions—with
impaired antenna-size, starting from wild type (WT) (full antenna) over ΔapcE- (phycobilisomes functionally dissociated) and
Olive (lacking phycocyanin) up to the PAL mutant (lacking the whole phycobilisome). In contrast to mixotrophic conditions
(up to 80% contribution), cyclic electron transport plays only a minor role (below 10%) under photoautotrophic conditions
for all the strains, while linear electron transport increased up to 5.5-fold from WT to PAL mutant. The minor contribution
of the cyclic electron transport was proportionally increased with the linear one in the ΔapcE and Olive mutant, but was not
altered in the PAL mutant, indicating that upregulation of the linear route does not have to be correlated with downregulation
of the cyclic electron transport. Antenna-deficiency involves higher linear electron transport rates by tuning the PS2/PS1
ratio from 1:5 in WT up to 1:1 in the PAL mutant. While state transitions were observed only in the WT and Olive mutant, a
further ~30% increase in the PS2/PS1 ratio was achieved in all the strains by long-term adaptation to far red light (720 nm).
These results are discussed in the context of using these cells for future H2 production in direct combination with the photosynthetic electron transport and suggest both Olive and PAL as potential candidates
for future manipulations toward this goal. In conclusion, the highest rates can be expected if mutants deficient in phycobilisome
antennas are grown under photoautotrophic conditions in combination with uncoupling of electron transport and an illumination
which excites preferably PS1. 相似文献
12.
Previously, it was clarified that phycobilisome (PBS) mobility and energy spillover were both involved in light-to-dark induced
state transitions of intact Spirulina platensis cells. In this work, by taking advantage of the characteristic fluorescence spectra of photosystem I (PSI) trimers and monomers
as indicators, the relative contributions for the “mobile PBS” and “energy spillover” are quantitatively estimated by separating
the fluorescence contribution of PBS mobility from that of PSI oligomeric change. Above the phase transition temperature (T
PT) of the membrane lipids, the relative proportion of the contributions is invariable with 65% of “mobile PBS” and 35% of “energy
spillover”. Below T
PT, the proportion for the “mobile PBS” becomes larger under lowering temperature even reaching 95% with 5% “energy spillover”
at 0°C. It is known that lower temperature leads to a further light state due to a more reduced or oxidized PQ pool. Based
on the current result, it can be deduced that disequilibrium of the redox state of the PQ pool will trigger PBS movement instead
of change in the PSI oligomeric state. 相似文献
13.
Specific bleaching of phycobiliproteins from cyanobacteria and red algae at high temperature in vivo
Exposure of blue-green or red algal cells to temperatures exceeding 60–65°C for several minutes resulted in bleaching of all phycobilin absorption in the visible range, with virtually no alteration in chlorophyll or carotenoid absorption. Difference spectra of non-bleached vs bleached cells appeared identical to absorption spectra of purified phycobilisomes isolated from the same cell culture in high phosphate medium. All phycobilin chromophores were bleached at approximately the same rate during heating. There were no changes in apparent molecular weights or relative amounts of the phycobilisome apoproteins during chromophore bleaching. Phycobilisomes in cell extracts from Anacystis nidulans resisted bleaching when suspended in medium of high phosphate concentration, but were bleached at 60–65°C within a few minutes when placed in diluted medium. The results indicate that phycobilisomes in vivo are stabilized by a mechanism other than high osmotic and ionic strength. This represents a rapid and quantitative method to characterize the phycobiliprotein content of cyanobacteria and red algae in vivo.Abbreviations Chl
chlorophyll
- APC
allophycocyanin
- PC
phycocyanin
- PE
phycoerythrin
- SPM
medium, 0.2 M sucrose, 15 mM MgCl2, 0.75 M Na/KPO4, pH 7.8 相似文献
14.
Phycobilisomes are protein complexes that harvest light and transfer energy to the photo system. Here, the three dimensional structure of intact phycobilisomes from Nostoc flagelliforme is studied by a combination of negative stain electron microscopy and cryo-electron microscopy. Results show that the intact phycobilisomes are composed of a tricylindrical core and six rods. Each allophycocyanin cylinder presents a double-layered structure when viewed from the side and a triangular shape when viewed from the top. These characteristics indicate that allophycocyanin trimers in the intact phycobilisomes are arranged into hexameric oligomers in a parallel manner. 相似文献
15.
Disc-shaped phycobilisomes were purified from Triton X100 treated cell homogenates of the unicellular marine red alga, Rhodella violacea. Their absorption spectrum had principal maxima at 544 and 568 nm (B-phycoerythrin), 624 nm (C-phycocyanin) and a distinct shoulder at 652 nm (allophycocyanin). Intermolecular energy transfer within the phycobilisomes was clearly demonstrated by fluorescence data. Excited at 546 nm intact phycobilisomes showed a main fluorescence emission maximum at 665 nm, a minor one at 577 nm and a shoulder at 730 nm.Dissociated phycobilisomes revealed a composition of 58% B-phycoerythrin, 25% C-phycocyanin and 17% allophycocyanin under the cultural conditions used. Analytical methods resolved no other components than phycobiliproteins. In addition to the defined C-phycocyanin and two isoproteins of B-phycoerythrin a stable heterogeneous aggregate of B-phycoerythrin/C-phycocyanin was separated in considerable amounts.In the electron microscope negatively stained phycobilisomes appeared as elliptical aggregates having dimensions slightly above the values found in ultrathin sections and a detailed subunit structure. All observations and data suggest a new rhodophytan phycobilisome type in Rhodella violacea.Abbreviations PBS
phycobilisome(s)
- PE
B-phycoerythrin
- PC
C-phycocyanin
- APC
allophycocyanin
- C
concentration (mg/ml)
- E
extinction 相似文献
16.
Kirilovsky D 《Photosynthesis research》2007,93(1-3):7-16
Plants and algae have developed multiple protective mechanisms to survive under high light conditions. Thermal dissipation
of excitation energy in the membrane-bound chlorophyll-antenna of photosystem II (PSII) decreases the energy arriving at the
reaction center and thus reduces the generation of toxic photo-oxidative species. This process results in a decrease of PSII-related
fluorescence emission, known as non-photochemical quenching (NPQ). It has always been assumed that cyanobacteria, the progenitor
of the chloroplast, lacked an equivalent photoprotective mechanism. Recently, however, evidence has been presented for the
existence of at least three distinct mechanisms for dissipating excess absorbed energy in cyanobacteria. One of these mechanisms,
characterized by a blue-light-induced fluorescence quenching, is related to the phycobilisomes, the extramembranal antenna
of cyanobacterial PSII. In this photoprotective mechanism the soluble carotenoid-binding protein (OCP) encoded by the slr1963 gene in Synechocystis sp. PCC 6803, of previously unknown function, plays an essential role. The amount of energy transferred from the phycobilisomes
to the photosystems is reduced and the OCP acts as the photoreceptor and as the mediator of this antenna-related process.
These are novel roles for a soluble carotenoid protein. 相似文献
17.
Erhard Mörschel 《Planta》1982,154(3):251-258
Phycobilisomes of red algae and cyanobacteria contain small amounts of nonpigmented polypeptides in addition to the major constituent biliprotein pigments. The localization of these polypeptides is analyzed by gel electrophoresis of phycobilisome fragments obtained by selective dissociation and subsequent separation. Five groups of biliprotein aggregates are determined, belonging to the 6, 11, 16, 18 and 23 S categories. Accessory nonpigmented high molecular weight proteins (80,000 MW) are exclusively bound to phycobilisome core fractions and thylakoids, thus apparently serving as links between the phycobilisomes and the photosynthetic units of the thylakoids. In contrast, smaller nonpigmented accessory polypeptides of 20,000 to 60,000 MW are preferably found in the peripheral biliprotein stacks. They may either form a compatible link between the phycobilisome core and periphery or bind and co-polymerize with hexameric biliproteins in the peripheral stacks to enhance or effect binding of the aggregates. Furthermore, they may determine the arrangement and composition of the phycobilisomes during development and chromatic adaptation.Abbreviations PE
phycoerythrin
- PEC
phycoerythrocyanin
- PC
phycocyanin
- APC
allophycocyanin 相似文献
18.
Monomerization and trimerization of photosystem I (PSI) in cyanobacteria are reversible to response to light switched off
and on, which leads to “energy spillover” to regulate excitation of the two photosystems in balance. Considering that PSI
is a trans-membrane protein embedded in thylakoid membranes, the monomerization or trimerization must involve a movement of
PSI in the membranes. In this work, the mobility of PSI was demonstrated by dependence of the monomerization and trimerization
on temperature for intact Spirulina platensis cells undergoing a light-to-dark or a dark-to-light transition. Based on the characteristic absorbance of monomers and trimmers,
it confirms that both monomerization and trimerization are temperature-sensitive. The relative populations of the monomers
and trimmers are invariable above the phase transition temperature (T
PT) while directly proportional to temperature below T
PT. On the other hand, the rate to reach the equilibrium population is proportional to temperature above T
PT but invariable below T
PT. The PSI mobility and the temperature-dependent population are contrary to those of plastoquinone (PQ) molecules because
PSI is a trans-membrane protein while PQ molecules are small diffusive electron carriers in thylakoid membranes as well as
their distinctive sizes and environments. The less monomerization of PSI but the invariable time constant at lower temperature
below T
PT may be due to that accumulation of the reduced PQ molecules results in decrease of the stromal-side H+ concentration which is a driving force of PSI monomerization. 相似文献
19.
螺旋藻(Spirulina platensis)藻胆体在解离过程中荧光发射光谱和光能传递的研究 总被引:1,自引:0,他引:1
对螺旋藻(Spirulinaplatensis)藻胆体在室温和77K处于不同浓度磷缓冲溶液和不同解离时间的荧光发射光谱进行了研究。藻胆体在0.9mol/L磷酸缓冲溶液中,由于没有发生解离,光能传递效率高,在77K荧光发射光谱中只有一个峰,位于687nm,属于别藻蓝蛋白-B。当藻胆体悬浮在0.3mol/L磷酸缓冲溶液中1分钟,77K荧光光谱的主峰出现在684nm.又出现655nm和666nm荧光峰,它们依次属子C-藻蓝蛋白和别藻蓝蛋白。在2小时;655nm荧先峰成为主峰,684nm荧光峰为次峰,666nm荧光肩消失。这表明C-藻蓝蛋白所捕获的先能已不能传递给别藻蓝蛋白,但能传给别藻蓝蛋白-B。我们提出在螺旋藻藻胆体中存在两类C-藻蓝蛋白,一是与别藻蓝蛋白相连接,另一是与别藻蓝蛋白-B相连接。 相似文献
20.
螺旋藻(Spirulina platensis)藻胆体在解离过程中荧光发射光谱和光能传递的研究 总被引:1,自引:0,他引:1
对螺旋藻(Spirulinaplatensis)藻胆体在室温和77K处于不同浓度磷缓冲溶液和不同解离时间的荧光发射光谱进行了研究。藻胆体在0.9mol/L磷酸缓冲溶液中,由于没有发生解离,光能传递效率高,在77K荧光发射光谱中只有一个峰,位于687nm,属于别藻蓝蛋白-B。当藻胆体悬浮在0.3mol/L磷酸缓冲溶液中1分钟,77K荧光光谱的主峰出现在684nm.又出现655nm和666nm荧光峰,它们依次属子C-藻蓝蛋白和别藻蓝蛋白。在2小时;655nm荧先峰成为主峰,684nm荧光峰为次峰,666nm荧光肩消失。这表明C-藻蓝蛋白所捕获的先能已不能传递给别藻蓝蛋白,但能传给别藻蓝蛋白-B。我们提出在螺旋藻藻胆体中存在两类C-藻蓝蛋白,一是与别藻蓝蛋白相连接,另一是与别藻蓝蛋白-B相连接。 相似文献