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Spectral properties of LH2 exhibit very similar even when heterologously express LH2 with β-subunit fusion protein in Rhodobacter sphaeroides  [PDF]
Zhiping Zhao, Xin Nie, Zongli Hu, Guoping Chen, Zaixin Li, Zhi Zhang
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.31013

Interactions between the light-harvesting subunits and the non-covalently bound photopigments attribute considerably to the spectral properties of photosynthetic bacteria light-harvesting complexes. In our previous studies, we have constructed a novel Rhodobacter sphaeroides expression system. In the present study, we focus on the spectral properties of LH2 when heterologously express LH2 with β-subunit- GFP fusion protein in Rb. sphaeroides. Near infra-red spectrum of LH2 remained nearly unchanged as measured by spectroscopy. Fluorescence spectrum suggested that the LH2 with β-subunit-GFP fusion protein complexes still possessed normal activity in energy transfer. However, photopigments contents were significantly decreased to a very low level in the LH2 with β-subunit-GFP fusion protein complexes compared to that of LH2. FT-IR spectra indicated that interactions between photopigments and LH2 α/β- subunits appeared not to be changed. It was concluded that the LH2 spectral properties exhibited very similar even when heterologously expressed LH2 b-subunit fusion protein in Rb. sphaeroides. Our present study may supply a new insight into better understand the interactions between light-harvesting subunits and photopigments and bacterial photosynthesis and promote the development of the novel Rb. sphaeroides expression system.

Effect of the mutation of carotenoids on the dynamics of energy transfer in light-harvesting complexes (LH2) from Rhodobacter sphaeroides 601 at room temperature
Effect of the mutation of carotenoids on the dynamics of energy transfer in light-harvesting complexes (LH2) from Rhodobacter sphaeroides 601 at room temperature

Liu Wei-Min,Liu Yuan,Liu Kang-Jun,Yan Yong-Li,Guo Li-Jun,Xu Chun-He,Qian Shi-Xiong,
,刘 源,刘康俊,闫永丽,郭立俊,徐春和,钱士雄

中国物理 B , 2006,
Abstract: Energy transfers in two kinds of peripheral light-harvesting complexes (LH2) of {Rhodobacter sphaeroides} (RS) 601 are studied by using femtosecond pump--probe spectroscopy with tunable laser wavelength at room temperature. These two complexes are native LH2 (RS601) and green carotenoid mutated LH2 (GM309). The obtained results demonstrate that, compared with spheroidenes with ten conjugated double bonds in native RS601, carotenoid in GM309 containing neurosporenes with nine conjugated double bonds can lead to a reduction in energy transfer rate in the B800-to-B850 band and the disturbance in the energy relaxation processes within the excitonic B850 band.
Excited-state dynamics in light-harvesting complex of Rhodobacter sphaeroides
KangJun Liu,WeiMin Liu,YongLi Yan,ZhiWei Dong,ChunHe Xu,ShiXiong Qian
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0187-7
Abstract: Photodynamics of peripheral antenna complexes, light-harvesting complex (LH2) of Rhodobacter (Rb) Sphaeroides 601, was studied using femtosecond pump-probe technique at different laser wavelengths. The obtained results reveal dramatic dynamical evolutions within B800 and B850 absorption bands of antenna complexes LH2. At excitation wavelength around 835 nm, a sharp photobleaching signal was observed which was assigned to the contribution of the two-exciton state, which was further confirmed by the power dependence measurement. Rate equations with eight-level scheme were used to calculate the population evolution in LH2 and the transient dynamics under femtosecond pulse excitation. The research results prove that not only the transition from ground state to one-exciton state but also that from one-exciton state to two-exciton state contribute to the photodynamics of B850.

Lu Tao Wu Yongqiang Song Hongyu,

微生物学报 , 1997,
Abstract: The complete nucleotide sequence of a 5.4-kb chromosomal EcoRI-Sall fragment was determined, which contains the structural gene (gltE) for the large subunit of Rhodobacter sphaeroides glutamate synthase, as well as the 5' - and 3'-flanking regions. A open reading frame of 4636 base pairs was identified as R. sphaeroides gltB gene- The MW of the large subunit, as deduced from the nucleotide sequence, was estimated as 164 kD. Comparision of the nucleotide sequences revealed a high similarity among gltB genes of R. sphaeroides, Azospirillum brasilense and Escherichia coll The deduced amino acid sequence of R. sphaeroides GltB showed a high similarity with that of A. brasilense GltB.
Acquirement and characterization of a carotenoid mutant (GM309) of Rhodobacter sphaeroides 601
Yuan Liu,Wei Zhang,Yongqiang Wu,Chunhe Xu
Science China Life Sciences , 2004, DOI: 10.1360/02yc0254
Abstract: A green mutant was obtained among the chemically induced mutants of Rhodobacter sphaeroides 601 (RS601) and named GM309. A blue shift of 20 nm of the carotenoid absorption spectrum was found in the light-harvesting complex II (LH2) of GM309. Different from LH2 of RS601, it was found that the carotenoids in GM309-LH2 changed to be neurosporene by mutation. Neurosporene lacks a conjugate double bond, compared with the spheroidene in RS601-LH2 which has ten conjugate double bonds. As shown by absorption and circular dichroism spectroscopy, the overall structure of GM309-LH2 is little affected by this change. From fluorescence emission spectra, it is found that GM309-LH2 can transfer energy from carotenoids to Bchl-B850 without any change in efficiency. But the efficiency of energy transfer from B800 to B850 in GM309-LH2 is decreased to be 42% of that of the native. This work would provide a novel method to investigate the mechanism of excitation energy transfer in LH2.
The Effect of Aeration, Agitation and Light on Biohydrogen Production by Rhodobacter sphaeroides NCIMB 8253  [PDF]
S. Za`imah Syed Jaapar,M.S. Kalil,N. Anuar
Pakistan Journal of Biological Sciences , 2009,
Abstract: Photo fermentation is a biological process that can be applied for hydrogen production. The process is environmental friendly which is operated under mild conditions using renewable resources. In order to increase yield of H2 produced by Rhodobacter sphaeroides, some experimental factors that may enhance H2 production were studied. The effect of operating parameters including agitation, aeration and light on hydrogen production using R. sphaeroides NCIMB 8253 was investigated. Rhodobacter sphaeroides NCIMB 8253 was grown in 100 mL serum bottle containing growth medium with maliec acid as the sole organic carbon source. The cultures were incubated anaerobically at 30°C with tungsten lamp (100 W) as the light source (3.8 klux) and argon gas was purged for maintaining anaerobic condition. The results show that maximum hydrogen produced was higher (54.37 mL) in static culture with 69.98% of H2 in the total gas compared with shake culture (11.57 mL) with 57.86% of H2. By using static culture, H2 produced was five times higher compared with non-static in both aerobic and anaerobic condition. It was found that growth and H2 production with fluorescent lamp showed better results than growth and H2 production with tungsten light.
The Effects of Different Carbon Sources on the Growth of Rhodobacter sphaeroides  [PDF]
Noah Zavala, Lorenzo Baeza, Santos Gonzalez, Madhusudan Choudhary
Advances in Microbiology (AiM) , 2019, DOI: 10.4236/aim.2019.98045
Abstract: Rhodobacter sphaeroides is a purple non-sulfur bacterium that belongs to the α-3 subdivision of Proteobacteria. R. sphaeroides is a model bacterial species because of its complex genome structure and expanded metabolic capabilities. The genome of R. sphaeroides consists of two circular chromosomes and five endogenous plasmids. It has the ability to grow under a wide variety of environmental conditions. It grows aerobically (~20% O2), semi-aerobically (~2% O2), and photosynthetically (under anaerobic condition plus light). It has been previously shown that many bacterial species utilize a number of alternate carbon sources for their optimal growth under a variety of growth conditions. We hypothesize that different or an additional carbon source in the minimal medium differentially affects the bacterial growth under dark-aerobic conditions. The bacterial growth kinetics and the number of cells in the bacterial culture were analyzed by measuring the optical density (OD at 600 nm) and the colony forming units (CFUs) at regular intervals of bacterial cultures. Results reveal that sodium succinate is the preferred sole carbon source for the optimal growth of R. sphaeroides. The results of growth kinetics and CFUs together concluded that from the tested carbon sources, sodium succinate is the best single carbon source in the minimal media for the optimal growth of R. sphaeroides. Interestingly, cell culture grown in SIS supplemented with sodium acetate exhibits a prolonged lag phase with the lowest ODs and CFUs that later switches to the growth-burst phase support previously discovered similar phenomenon of the growth-rate switch in the presence of acetate metabolism. Future work will utilize the aerobically grown R. sphaeroides’ cells as a biocatalyst to deplete the oxygen levels from natural gas streams and industrial gas pipelines.
The prevalence of gene duplications and their ancient origin in Rhodobacter sphaeroides 2.4.1
Anish Bavishi, Lin Lin, Kristen Schroeder, Anne Peters, Hyuk Cho, Madhusudan Choudhary
BMC Microbiology , 2010, DOI: 10.1186/1471-2180-10-331
Abstract: A protein similarity search (BLASTP) identified 1247 orfs (~29.4% of the total protein coding orfs) that are present in 2 or more copies, 37.5% (234 gene-pairs) of which exist in duplicate copies. The distribution of the duplicate gene-pairs in all Clusters of Orthologous Groups (COGs) differed significantly when compared to the COG distribution across the whole genome. Location plots revealed clusters of gene duplications that possessed the same COG classification. Phylogenetic analyses were performed to determine a tree topology predicting either a Type-A or Type-B phylogenetic relationship. A Type-A phylogenetic relationship shows that a copy of the protein-pair matches more with an ortholog from a species closely related to R. sphaeroides while a Type-B relationship predicts the highest match between both copies of the R. sphaeroides protein-pair. The results revealed that ~77% of the proteins exhibited a Type-A phylogenetic relationship demonstrating the ancient origin of these gene duplications. Additional analyses on three other strains of R. sphaeroides revealed varying levels of gene loss and retention in these strains. Also, analyses on common gene pairs among the four strains revealed that these genes experience similar functional constraints and undergo purifying selection.Although the results suggest that the level of gene duplication in organisms with complex genome structuring (more than one chromosome) seems to be not markedly different from that in organisms with only a single chromosome, these duplications may have aided in genome reorganization in this group of eubacteria prior to the formation of R. sphaeroides as gene duplications involved in specialized functions might have contributed to complex genomic development.Rhodobacter sphaeroides 2.4.1, a purple nonsulfur photosynthetic eubacterium, belongs to the α-3 subgroup of Proteobacteria [1,2], members of which display an array of metabolic capabilities in the assembly and regulation of metabol
CtrA Is Nonessential for Cell Cycle Regulation in Rhodobacter sphaeroides  [PDF]
Lin Lin, Abha Choudhary, Anish Bavishi, Madhusudan Choudhary
Advances in Microbiology (AiM) , 2018, DOI: 10.4236/aim.2018.87037
Abstract: The bacterial cell cycle consists of a series of genetically coordinated biochemical and biophysical events. In Caulobacter crescentus, CtrA is an essential cell cycle regulator that modulates many cell cycle processes. In the present study, the role of the CtrA was investigated in Rhodobacter sphaeroides 2.4.1 by employing genetic, molecular, and bioinformatic approaches. Examination of the ctrA-null mutant revealed that the loss of CtrA did not affect growth characteristics and cell morphology in R. sphaeroides when grown under aerobic or photosynthetic growth conditions but slower growth was noticed in the anaerobic-dark-DMSO condition. Phylogenetic analyses demonstrated that CtrA has diversified its role in major lineages of α-Proteobacteria and has possibly been involved in adaptation to variable lifestyles. Analysis of the CtrA binding sites in the R. sphaeroides genome suggests that CtrA may regulate 127 genes involving different cellular processes. Protein homology searches revealed that only a small number of ctrA-regulated genes are homologous across C. crescentus, R. capsulatus, and R. sphaeroides. Comparison of the functions of putative ctrA-regulated genes in C. crescentus, R. capsulatus, and R. sphaeroides revealed that all three species possessed broad pathway control across a variety of cluster of orthologous gene functions (COGs). However, interestingly, it seems that the essentiality of CtrA in C. crescentus may depend more on the selective control that it exerts on a few critical cell cycle genes and pathways that are not controlled by CtrA in a similar fashion in R. capsulatus and R. sphaeroides.
Role of the Irr Protein in the Regulation of Iron Metabolism in Rhodobacter sphaeroides  [PDF]
Verena Peuser, Bernhard Remes, Gabriele Klug
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042231
Abstract: In Rhizobia the Irr protein is an important regulator for iron-dependent gene expression. We studied the role of the Irr homolog RSP_3179 in the photosynthetic alpha-proteobacterium Rhodobacter sphaeroides. While Irr had little effect on growth under iron-limiting or non-limiting conditions its deletion resulted in increased resistance to hydrogen peroxide and singlet oxygen. This correlates with an elevated expression of katE for catalase in the Irr mutant compared to the wild type under non-stress conditions. Transcriptome studies revealed that Irr affects the expression of genes for iron metabolism, but also has some influence on genes involved in stress response, citric acid cycle, oxidative phosphorylation, transport, and photosynthesis. Most genes showed higher expression levels in the wild type than in the mutant under normal growth conditions indicating an activator function of Irr. Irr was however not required to activate genes of the iron metabolism in response to iron limitation, which showed even stronger induction in the absence of Irr. This was also true for genes mbfA and ccpA, which were verified as direct targets for Irr. Our results suggest that in R. sphaeroides Irr diminishes the strong induction of genes for iron metabolism under iron starvation.
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