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Journal articles on the topic 'Light-Harvesting Antenna (LHA)'

Author: Grafiati

Published: 4 June 2021

Last updated: 17 February 2022

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1

Yeo, Hyeonuk, Kazuo Tanaka, and Yoshiki Chujo. "Construction and properties of a light-harvesting antenna system for phosphorescent materials based on oligofluorene-tethered Pt–porphyrins." RSC Advances 7, no. 18 (2017): 10869–74. http://dx.doi.org/10.1039/c6ra28735b.

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Tetramerous molecular assemblies composed of four oligofluorenes as a light-harvesting antenna (LHA) and a Pt–porphyrin core as a phosphorescent chromophore were designed and synthesized for obtaining efficient phosphorescent materials.

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2

Köhler, J., A. M. van Oijen, M. Ketelaars, et al. "Optical Spectroscopy of Individual Photosynthetic Pigment Protein Complexes." International Journal of Modern Physics B 15, no. 28n30 (2001): 3633–36. http://dx.doi.org/10.1142/s0217979201008317.

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Photosynthesis is the process by which plants, algae and photosynthetic bacteria convert solar energy into a form that can be used to sustain the life process. The light reactions occur in closely coupled pigment systems. The energy is absorbed by a network of antenna pigment proteins and efficiently transferred to the photochemical reaction centre where a charge separation takes place providing the free energy for subsequent chemical reactions. The total conversion process, starting with the absorption of a photon and ending with a stable charge separated state occurs within less than 50 ps and has an overall quantum yield of more than 90%. The success of this natural process is based on both the highly efficient absorption of photons by the light-harvesting antenna system and the rapid and efficient transfer of excitation energy to the reaction centre. It is known that most photosynthetic purple bacteria contain two types of antenna complexes, light-harvesting complex 1 (LH1) and light harvesting complex 2 (LH2) which both have a ring-like structure [1,2]. (Some bacterial species like Rhodopseudomonas acidophila contain a third light-harvesting complex termed B800-820.) The reaction centre (RC) presumably forms the core of the LH1 complex, while LH2 complexes are arranged around the perimeter of the LH1 ring in a two-dimensional structure. However the full three-dimensional structure of the whole photosynthetic unit is as yet unknown. The absorption of a photon (mainly) takes place in the LH2 pigments followed by a fast transfer of the excitation energy to the LH1 complex and subsequently to the reaction centre. It appears that the whole structure is highly optimized for capturing light energy and to funnel it to the reaction centre [3-7].

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3

Pishchalnikov, Roman Y., Denis D. Chesalin, and Andrei P. Razjivin. "The Relationship between the Spatial Arrangement of Pigments and Exciton Transition Moments in Photosynthetic Light-Harvesting Complexes." International Journal of Molecular Sciences 22, no. 18 (2021): 10031. http://dx.doi.org/10.3390/ijms221810031.

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Considering bacteriochlorophyll molecules embedded in the protein matrix of the light-harvesting complexes of purple bacteria (known as LH2 and LH1-RC) as examples of systems of interacting pigment molecules, we investigated the relationship between the spatial arrangement of the pigments and their exciton transition moments. Based on the recently reported crystal structures of LH2 and LH1-RC and the outcomes of previous theoretical studies, as well as adopting the Frenkel exciton Hamiltonian for two-level molecules, we performed visualizations of the LH2 and LH1 exciton transition moments. To make the electron transition moments in the exciton representation invariant with respect to the position of the system in space, a system of pigments must be translated to the center of mass before starting the calculations. As a result, the visualization of the transition moments for LH2 provided the following pattern: two strong transitions were outside of LH2 and the other two were perpendicular and at the center of LH2. The antenna of LH1-RC was characterized as having the same location of the strongest moments in the center of the complex, exactly as in the B850 ring, which actually coincides with the RC. Considering LH2 and LH1 as supermolecules, each of which has excitation energies and corresponding transition moments, we propose that the outer transitions of LH2 can be important for inter-complex energy exchange, while the inner transitions keep the energy in the complex; moreover, in the case of LH1, the inner transitions increased the rate of antenna-to-RC energy transfer.

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4

Cardoso Ramos, Felipe, Michele Nottoli, Lorenzo Cupellini, and Benedetta Mennucci. "The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling." Chemical Science 10, no. 42 (2019): 9650–62. http://dx.doi.org/10.1039/c9sc02886b.

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5

Michalik, Maciej, Mateusz Zbyradowski, Heriyanto, and Leszek Fiedor. "Tuning the Photophysical Features of Self-Assembling Photoactive Polypeptides for Light-Harvesting." Materials 12, no. 21 (2019): 3554. http://dx.doi.org/10.3390/ma12213554.

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The LH1 complex is the major light-harvesting antenna of purple photosynthetic bacteria. Its role is to capture photons, and then store them and transfer the excitation energy to the photosynthetic reaction center. The structure of LH1 is modular and it cooperatively self-assembles from the subunits composed of short transmembrane polypeptides that reversibly bind the photoactive cofactors: bacteriochlorophyll and carotenoid. LH1 assembly, the intra-complex interactions and the light-harvesting features of LH1 can be controlled in micellar media by varying the surfactant concentration and by adding carotenoid and/or a co-solvent. By exploiting this approach, we can manipulate the size of the assembly, the intensity of light absorption, and the energy and lifetime of its first excited singlet state. For instance, via the introduction of Ni-substituted bacteriochlorophyll into LH1, the lifetime of this electronic state of the antenna can be shortened by almost three orders of magnitude. On the other hand, via the exchange of carotenoid, light absorption in the visible range can be tuned. These results show how in a relatively simple self-assembling pigment-polypeptide system a sophisticated functional tuning can be achieved and thus they provide guidelines for the construction of bio-inspired photoactive nanodevices.

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6

Cogdell, Richard J., Andrew Gall, and Jürgen Köhler. "The architecture and function of the light-harvesting apparatus of purple bacteria: from single molecules to in vivo membranes." Quarterly Reviews of Biophysics 39, no. 3 (2006): 227–324. http://dx.doi.org/10.1017/s0033583506004434.

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1. Introduction 2292. Structures 2342.1 The structure of LH2 2342.2 Natural variants of peripheral antenna complexes 2422.3 RC–LH1 complexes 2423. Spectroscopy 2493.1 Steady-state spectroscopy 2493.2 Factors which affect the position of the Qy absorption band of Bchla 2494. Regulation of biosynthesis and assembly 2574.1 Regulation 2574.1.1 Oxygen 2574.1.2 Light 2584.1.2.1 AppA: blue-light-mediated regulation 2594.1.2.2 Bacteriophytochromes 2594.1.3 From the RC to the mature PSU 2614.2 Assembly 2614.2.1 LH1 2624.2.2 LH2 2635. Frenkel excitons 2655.1 General 2655.2 B800 2675.3 B850 2675.4 B850 delocalization 2736. Energy-transfer pathways: experimental results 2746.1 Theoretical background 2746.2 ‘Follow the excitation energy’ 2766.2.1 Bchla→Bchla energy transfer 2776.2.1.1 B800→B800 2776.2.1.2 B800→B850 2786.2.1.3 B850→B850 2796.2.1.4 B850→B875 2806.2.1.5 B875→RC 2806.2.2 Car[harr ]Bchla energy transfer 2817. Single-molecule spectroscopy 2847.1 Introduction to single-molecule spectroscopy 2847.2 Single-molecule spectroscopy on LH2 2857.2.1 Overview 2857.2.2 B800 2867.2.2.1 General 2867.2.2.2 Intra- and intercomplex disorder of site energies 2877.2.2.3 Electron-phonon coupling 2897.2.2.4 B800→B800 energy transfer revisited 2907.2.3 B850 2938. Quantum mechanics and the purple bacteria LH system 2989. Appendix 2999.1 A crash course on quantum mechanics 2999.2 Interacting dimers 30510. Acknowledgements 30611. References 307This review describes the structures of the two major integral membrane pigment complexes, the RC–LH1 ‘core’ and LH2 complexes, which together make up the light-harvesting system present in typical purple photosynthetic bacteria. The antenna complexes serve to absorb incident solar radiation and to transfer it to the reaction centres, where it is used to ‘power’ the photosynthetic redox reaction and ultimately leads to the synthesis of ATP. Our current understanding of the biosynthesis and assembly of the LH and RC complexes is described, with special emphasis on the roles of the newly described bacteriophytochromes. Using both the structural information and that obtained from a wide variety of biophysical techniques, the details of each of the different energy-transfer reactions that occur, between the absorption of a photon and the charge separation in the RC, are described. Special emphasis is given to show how the use of single-molecule spectroscopy has provided a more detailed understanding of the molecular mechanisms involved in the energy-transfer processes. We have tried, with the help of an Appendix, to make the details of the quantum mechanics that are required to appreciate these molecular mechanisms, accessible to mathematically illiterate biologists. The elegance of the purple bacterial light-harvesting system lies in the way in which it has cleverly exploited quantum mechanics.

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7

Brotosudarmo, Tatas H. P., and Richard J. Cogdell. "STUDY ON THE STRUCTURAL BASIS OF PERIPHERAL LIGHT HARVESTING COMPLEXES (LH2) IN PURPLE NON-SULPHUR PHOTOSYNTHETIC BACTERIA." Indonesian Journal of Chemistry 10, no. 3 (2010): 401–8. http://dx.doi.org/10.22146/ijc.21450.

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Photosynthesis provides an example of a natural process that has been optimized during evolution to harness solar energy efficiently and safely, and finally to use it to produce a carbon-based fuel. Initially, solar energy is captured by the light harvesting pigment-protein complexes. In purple bacteria these antenna complexes are constructed on a rather simple modular basis. Light absorbed by these antenna complexes is funnelled downhill to reaction centres, where light drives a trans-membrane redox reaction. The light harvesting proteins not only provide the scaffolding that correctly positions the bacteriochlorophyll a and carotenoid pigments for optimal energy transfer but also creates an environment that can modulate the wavelength at which different bacteriochlorophyll molecules absorb light thereby creating the energy funnel. How these proteins can modulate the absorption spectra of the bacteriochlorophylls will be discussed in this review.

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8

Hunter, C. N., M. K. Ashby, and S. A. Coomber. "Effect of oxygen on levels of mRNA coding for reaction-centre and light-harvesting polypeptides of Rhodobacter sphaeroides." Biochemical Journal 247, no. 2 (1987): 489–92. http://dx.doi.org/10.1042/bj2470489.

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The relative levels of mRNA for the reaction-centre L and M subunits, B875 (LH1) alpha and beta polypeptides and B800-850 (LH2) alpha and beta polypeptides, have been measured during pigment induction of Rhodobacter sphaeroides. Over the 6 h of the experiment, bacteriochlorophyll levels increased by at least 100-fold. No transcripts for photosynthetic components were detectable at the start of induction; after 2 h the levels of transcripts from the puf operon (encoding reaction-centre and B875 subunits) had reached the maximum; these transcripts were 2.7 and 0.5 kb respectively. The transcript for the puc operon (B800-850 complex) was estimated to be 0.55 kb and reached a maximum level after 6 h. These results are consistent with the proposal that, during the assembly of the photosynthetic apparatus, the synthesis of B875 reaction-centre aggregates precedes that of the major antenna, B800-850.

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9

Niedzwiedzki, Dariusz M., David J. K. Swainsbury, Daniel P. Canniffe, C. Neil Hunter, and Andrew Hitchcock. "A photosynthetic antenna complex foregoes unity carotenoid-to-bacteriochlorophyll energy transfer efficiency to ensure photoprotection." Proceedings of the National Academy of Sciences 117, no. 12 (2020): 6502–8. http://dx.doi.org/10.1073/pnas.1920923117.

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Carotenoids play a number of important roles in photosynthesis, primarily providing light-harvesting and photoprotective energy dissipation functions within pigment–protein complexes. The carbon–carbon double bond (C=C) conjugation length of carotenoids (N), generally between 9 and 15, determines the carotenoid-to-(bacterio)chlorophyll [(B)Chl] energy transfer efficiency. Here we purified and spectroscopically characterized light-harvesting complex 2 (LH2) fromRhodobacter sphaeroidescontaining theN= 7 carotenoid zeta (ζ)-carotene, not previously incorporated within a natural antenna complex. Transient absorption and time-resolved fluorescence show that, relative to the lifetime of the S1state of ζ-carotene in solvent, the lifetime decreases ∼250-fold when ζ-carotene is incorporated within LH2, due to transfer of excitation energy to the B800 and B850 BChlsa. These measurements show that energy transfer proceeds with an efficiency of ∼100%, primarily via the S1→ Qxroute because the S1→ S0fluorescence emission of ζ-carotene overlaps almost perfectly with the Qxabsorption band of the BChls. However, transient absorption measurements performed on microsecond timescales reveal that, unlike the nativeN≥ 9 carotenoids normally utilized in light-harvesting complexes, ζ-carotene does not quench excited triplet states of BChla, likely due to elevation of the ζ-carotene triplet energy state above that of BChla. These findings provide insights into the coevolution of photosynthetic pigments and pigment–protein complexes. We propose that theN≥ 9 carotenoids found in light-harvesting antenna complexes represent a vital compromise that retains an acceptable level of energy transfer from carotenoids to (B)Chls while allowing acquisition of a new, essential function, namely, photoprotective quenching of harmful (B)Chl triplets.

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10

Trinkunas, G., J. L. Herek, T. Polívka, V. Sundström, and T. Pullerits. "Exciton Delocalization Probed by Excitation Annihilation in the Light-Harvesting Antenna LH2." Physical Review Letters 86, no. 18 (2001): 4167–70. http://dx.doi.org/10.1103/physrevlett.86.4167.

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11

Joo, Taiha, Yiwei Jia, Jae-Young Yu, David M. Jonas, and Graham R. Fleming. "Dynamics in Isolated Bacterial Light Harvesting Antenna (LH2) ofRhodobacter sphaeroidesat Room Temperature." Journal of Physical Chemistry 100, no. 6 (1996): 2399–409. http://dx.doi.org/10.1021/jp951652q.

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12

Beekman, Lucas M. P., Martin Steffen, Ivo H. M. van Stokkum, et al. "Characterization of the Light-Harvesting Antennas of Photosynthetic Purple Bacteria by Stark Spectroscopy. 1. LH1 Antenna Complex and the B820 Subunit fromRhodospirillum rubrum." Journal of Physical Chemistry B 101, no. 37 (1997): 7284–92. http://dx.doi.org/10.1021/jp963445b.

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13

Harris, Michelle A., Tuba Sahin, Jianbing Jiang, et al. "Enhanced Light-Harvesting Capacity by Micellar Assembly of Free Accessory Chromophores and LH1-like Antennas." Photochemistry and Photobiology 90, no. 6 (2014): 1264–76. http://dx.doi.org/10.1111/php.12319.

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14

Kwa, Stefan L. S., Herbert van Amerongen, Su Lin, Jan P. Dekker, Rienk van Grondelle, and Walter S. Struve. "Ultrafast energy transfer in LHC-II trimers from the Chl a/b light-harvesting antenna of Photosystem II." Biochimica et Biophysica Acta (BBA) - Bioenergetics 1102, no. 2 (1992): 202–12. http://dx.doi.org/10.1016/0005-2728(92)90101-7.

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15

TAKEDA, Kazuki, Satomi NIWA, and Kunio MIKI. "Crystal Structure of the Complex between the Light Harvesting Core Antenna and the Photosynthetic Reaction Center (LH1-RC Complex)." Nihon Kessho Gakkaishi 57, no. 2 (2015): 104–9. http://dx.doi.org/10.5940/jcrsj.57.104.

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16

Savikhin, S., H. van Amerongen, S. L. Kwa, R. van Grondelle, and W. S. Struve. "Low-temperature energy transfer in LHC-II trimers from the Chl a/b light-harvesting antenna of photosystem II." Biophysical Journal 66, no. 5 (1994): 1597–603. http://dx.doi.org/10.1016/s0006-3495(94)80951-8.

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17

Steunou, Anne-Soisig, Soufian Ouchane, Françoise Reiss-Husson та Chantal Astier. "Involvement of the C-Terminal Extension of the α Polypeptide and of the PucC Protein in LH2 Complex Biosynthesis in Rubrivivax gelatinosus". Journal of Bacteriology 186, № 10 (2004): 3143–52. http://dx.doi.org/10.1128/jb.186.10.3143-3152.2004.

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ABSTRACT The facultative phototrophic nonsulfur bacterium Rubrivivax gelatinosus exhibits several differences from other species of purple bacteria in the organization of its photosynthetic genes. In particular, the puc operon contains only the pucB and pucA genes encoding the β and α polypeptides of the light-harvesting 2 (LH2) complex. Downstream of the pucBA operon is the pucC gene in the opposite transcriptional orientation. The transcription of pucBA and pucC has been studied. No pucC transcript was detected either by Northern blotting or by reverse transcription-PCR analysis. The initiation site of pucBA transcription was determined by primer extension, and Northern blot analysis revealed the presence of two transcripts of 0.8 and 0.65 kb. The half-lives of both transcripts are longer in cells grown semiaerobically than in photosynthetically grown cells, and the small transcript is the less stable. It was reported that the α polypeptide, encoded by the pucA gene, presents a C-terminal extension which is not essential for LH2 function in vitro. The biological role of this alanine- and proline-rich C-terminal extension in vivo has been investigated. Two mutants with C-terminal deletions of 13 and 18 residues have been constructed. Both present the two pucBA transcripts, while their phenotypes are, respectively, LH2+ and LH2−, suggesting that a minimal length of the C-terminal extension is required for LH2 biogenesis. Another important factor involved in the LH2 biogenesis is the PucC protein. To gain insight into the function of this protein in R. gelatinosus, we constructed and characterized a PucC mutant. The mutant is devoid of LH2 complex under semiaerobiosis but still produces a small amount of these antennae under photosynthetic growth conditions. This conditional phenotype suggests the involvement of another factor in LH2 biogenesis.

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Beekman, Lucas M. P., Raoul N. Frese, Greg J. S. Fowler, et al. "Characterization of the Light-Harvesting Antennas of Photosynthetic Purple Bacteria by Stark Spectroscopy. 2. LH2 Complexes: Influence of the Protein Environment." Journal of Physical Chemistry B 101, no. 37 (1997): 7293–301. http://dx.doi.org/10.1021/jp963447w.

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19

Ho, Junming, Elizabeth Kish, Dalvin D. Méndez-Hernández, et al. "Triplet–triplet energy transfer in artificial and natural photosynthetic antennas." Proceedings of the National Academy of Sciences 114, no. 28 (2017): E5513—E5521. http://dx.doi.org/10.1073/pnas.1614857114.

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In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet–triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.

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20

Morishige, Daryl T., Shivanthi Anandan, James T. Jaing, and J. Philip Thornber. "Amino-terminal sequence of the 21 kDa apoprotein of a minor light- harvesting pigment-protein complex of the Photosystem II antenna (LHC IId/CP24)." FEBS Letters 264, no. 2 (1990): 239–42. http://dx.doi.org/10.1016/0014-5793(90)80257-j.

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21

McGlynn, Peter, Willem H. J. Westerhuis, Michael R. Jones, and C. Neil Hunter. "Consequences for the Organization of Reaction Center-Light Harvesting Antenna 1 (LH1) Core Complexes ofRhodobacter sphaeroidesArising from Deletion of Amino Acid Residues from the C Terminus of the LH1 Polypeptide." Journal of Biological Chemistry 271, no. 6 (1996): 3285–92. http://dx.doi.org/10.1074/jbc.271.6.3285.

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22

Morishige, Daryl T., and J. Philip Thornber. "Identification and Analysis of a Barley cDNA Clone Encoding the 31-Kilodalton LHC IIa (CP29) Apoprotein of the Light-Harvesting Antenna Complex of Photosystem II." Plant Physiology 98, no. 1 (1992): 238–45. http://dx.doi.org/10.1104/pp.98.1.238.

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23

Fixen, Kathryn R., Yasuhiro Oda, and Caroline S. Harwood. "Redox Regulation of a Light-Harvesting Antenna Complex in an Anoxygenic Phototroph." mBio 10, no. 6 (2019). http://dx.doi.org/10.1128/mbio.02838-19.

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ABSTRACT The purple nonsulfur bacterium Rhodopseudomonas palustris is a model for understanding how a phototrophic organism adapts to changes in light intensity because it produces different light-harvesting (LH) complexes under high light (LH2) and low light intensities (LH3 and LH4). Outside of this change in the composition of the photosystem, little is understood about how R. palustris senses and responds to low light intensity. On the basis of the results of transcription analysis of 17 R. palustris strains grown in low light, we found that R. palustris strains downregulate many genes involved in iron transport and homeostasis. The only operon upregulated in the majority of R. palustris exposed to low light intensity was pucBAd, which encodes LH4. In previous work, pucBAd expression was shown to be modulated in response to light quality by bacteriophytochromes that are part of a low-light signal transduction system. Here we found that this signal transduction system also includes a redox-sensitive protein, LhfE, and that its redox sensitivity is required for LH4 synthesis in response to low light. Our results suggest that R. palustris upregulates its LH4 system when the cellular redox state is relatively oxidized. Consistent with this, we found that LH4 synthesis was upregulated under high light intensity when R. palustris was grown semiaerobically or under nitrogen-fixing conditions. Thus, changes in the LH4 system in R. palustris are not dependent on light intensity per se but rather on cellular redox changes that occur as a consequence of changes in light intensity. IMPORTANCE An essential aspect of the physiology of phototrophic bacteria is their ability to adjust the amount and composition of their light-harvesting apparatus in response to changing environmental conditions. The phototrophic purple bacterium R. palustris adapts its photosystem to a range of light intensities by altering the amount and composition of its peripheral LH complexes. Here we found that R. palustris regulates its LH4 complex in response to the cellular redox state rather than in response to light intensity per se. Relatively oxidizing conditions, including low light, semiaerobic growth, and growth under nitrogen-fixing conditions, all stimulated a signal transduction system to activate LH4 expression. By understanding how LH composition is regulated in R. palustris, we will gain insight into how and why a photosynthetic organism senses and adapts its photosystem to multiple environmental cues.

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Fixen, Kathryn R., Yasuhiro Oda, and Caroline S. Harwood. "Clades of Photosynthetic Bacteria Belonging to the Genus Rhodopseudomonas Show Marked Diversity in Light-Harvesting Antenna Complex Gene Composition and Expression." mSystems 1, no. 1 (2015). http://dx.doi.org/10.1128/msystems.00006-15.

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ABSTRACT Rhodopseudomonas palustris is a phototrophic purple nonsulfur bacterium that adapts its photosystem to allow growth at a range of light intensities. It does this by adjusting the amount and composition of peripheral light-harvesting (LH) antenna complexes that it synthesizes. Rhodopseudomonas strains are notable for containing numerous sets of light-harvesting genes. We determined the diversity of LH complexes and their transcript levels during growth under high and low light intensities in 20 sequenced genomes of strains related to the species Rhodopseudomonas palustris. The data obtained are a resource for investigators with interests as wide-ranging as the biophysics of photosynthesis, the ecology of phototrophic bacteria, and the use of photosynthetic bacteria for biotechnology applications. Many photosynthetic bacteria have peripheral light-harvesting (LH) antenna complexes that increase the efficiency of light energy capture. The purple nonsulfur photosynthetic bacterium Rhodopseudomonas palustris produces different types of LH complexes under high light intensities (LH2 complex) and low light intensities (LH3 and LH4 complexes). There are multiple pucBA operons that encode the α and β peptides that make up these complexes. However, low-resolution structures, amino acid similarities between the complexes, and a lack of transcription analysis have made it difficult to determine the contributions of different pucBA operons to the composition and function of different LH complexes. It was also unclear how much diversity of LH complexes exists in R. palustris and affiliated strains. To address this, we undertook an integrative genomics approach using 20 sequenced strains. Gene content analysis revealed that even closely related strains have differences in their pucBA gene content. Transcriptome analyses of the strains grown under high light and low light revealed that the patterns of expression of the pucBA operons varied among strains grown under the same conditions. We also found that one set of LH2 complex proteins compensated for the lack of an LH4 complex under low light intensities but not under extremely low light intensities, indicating that there is functional redundancy between some of the LH complexes under certain light intensities. The variation observed in LH gene composition and expression in Rhodopseudomonas strains likely reflects how they have evolved to adapt to light conditions in specific soil and water microenvironments. IMPORTANCE Rhodopseudomonas palustris is a phototrophic purple nonsulfur bacterium that adapts its photosystem to allow growth at a range of light intensities. It does this by adjusting the amount and composition of peripheral light-harvesting (LH) antenna complexes that it synthesizes. Rhodopseudomonas strains are notable for containing numerous sets of light-harvesting genes. We determined the diversity of LH complexes and their transcript levels during growth under high and low light intensities in 20 sequenced genomes of strains related to the species Rhodopseudomonas palustris. The data obtained are a resource for investigators with interests as wide-ranging as the biophysics of photosynthesis, the ecology of phototrophic bacteria, and the use of photosynthetic bacteria for biotechnology applications.

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25

Engelken, Johannes, Henner Brinkmann, and Iwona Adamska. "Taxonomic distribution and origins of the extended LHC (light-harvesting complex) antenna protein superfamily." BMC Evolutionary Biology 10, no. 1 (2010). http://dx.doi.org/10.1186/1471-2148-10-233.

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26

Camacho, Rafael, Sumera Tubasum, June Southall, et al. "Fluorescence polarization measures energy funneling in single light-harvesting antennas—LH2 vs conjugated polymers." Scientific Reports 5, no. 1 (2015). http://dx.doi.org/10.1038/srep15080.

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