Browsing by Author "Shen, Gaozhong"

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Breaking the Red Limit: Efficient Trapping of Long-Wavelength Excitations in Chlorophyll-f-Containing Photosystem I
(Elsevier BV, 2021-01) Tros, Martijn; Mascoli, Vincenzo; Shen, Gaozhong; Ho, Ming-Yang; Bersanini, Luca; Gisriel, Christopher J.; Bryant, Donald A.; Croce, Roberta
Background: Food insecurity (FI) is an important public health issue for US veterans. For many veterans, civilian life is fraught with service-incurred health issues and socioeconomic challenges, each risk factors for FI. The FI literature on veterans is limited due to insufficient coverage of the topic’s complexity and the methods used to study it in this population. No published analysis has evaluated how FI has been examined in US veterans. Objectives: We assessed how FI has been examined in US military veterans by identifying (1) the major content areas, or domains, studied in association with FI and (2) the existing research gaps. Methods: A scoping literature review was conducted to map the main research domains of the FI literature and identify knowledge gaps. Electronic database and hand searches identified potentially relevant studies (n = 61). Data extraction, utilizing a standardized set of design parameters, was completed. Duplicate removal and application of inclusion/exclusion criteria resulted in the studies (n = 21) selected for critical review. Results: Eight research domains were determined: FI prevalence, health status, dietary practices, health care utilization, economic instability, homelessness/housing instability, food program participation, and community/emergency preparedness—the most dominant was health status and the least dominant were social determinants (ie, homelessness/housing instability, food program participation). Research on validity and usability of FI assessment methods in veterans was virtually absent. Military service factors, longitudinal effects, FI among women, intervention effectiveness, and other areas lacked sufficient inquiry. Conclusion: Research is required on lesser examined content areas and methodology to optimize surveillance and policy for veteran FI.
Effect of mono-and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002
(Frontiers Research Foundation (OA), 2014) Bernstein, Hans C.; Konopka, Allan; Melnicki, Matthew R.; Hill, Eric A.; Kucek, Leo A.; Zhang, Shuyi; Shen, Gaozhong; Bryant, Donald A.; Beliaev, Alexander S.
Synechococcus sp. PCC 7002 was grown to steady state in optically thin turbidostat cultures under conditions for which light quantity and quality was systematically varied by modulating the output of narrow-band LEDs. Cells were provided photons absorbed primarily by chlorophyll (680 nm) or phycocyanin (630 nm) as the organism was subjected to four distinct mono- and dichromatic regimes. During cultivation with dichromatic light, growth rates were generally proportional to the total incident irradiance at values <275 2 μmol photons m− · s−1 and were not affected by the ratio of 630:680 nm wavelengths. Notably, under monochromatic light conditions, cultures exhibited similar growth rates only when they were irradiated with 630 nm light; cultures irradiated with only 680 nm light grew at rates that were 60–70% of those under other light quality regimes at equivalent irradiances. The functionality of photosystem II and associated processes such as maximum rate of photosynthetic electron transport, rate of cyclic electron flow, and rate of dark respiration generally increased as a function of growth rate. Nonetheless, some of the photophysiological parameters measured here displayed distinct patterns with respect to growth rate of cultures adapted to a single wavelength including phycobiliprotein content, which increased under severely light-limited growth conditions. Additionally, the ratio of photosystem II to photosystem I increased ∼40% over the range of growth rates, although cells grown with 680 nm light only had the highest ratios. These results suggest the presence of effective mechanisms which allow acclimation of Synechococcus sp. PCC 7002 acclimation to different irradiance conditions.
Harvesting far-red light: Functional integration of chlorophyll f into Photosystem I complexes of Synechococcus sp. PCC 7002
(2020-08) Tros, Martijn; Bersanini, Luca; Shen, Gaozhong; Ho, Ming-Yang; van Stokkum, Ivo H. M.; Bryant, Donald A.; Croce, Roberta
The heterologous expression of the far-red absorbing chlorophyll (Chl) f in organisms that do not synthesize this pigment has been suggested as a viable solution to expand the solar spectrum that drives oxygenic photosynthesis. In this study, we investigate the functional binding of Chl f to the Photosystem I (PSI) of the cyanobacterium Synechococcus 7002, which has been engineered to express the Chl f synthase gene. By optimizing growth light conditions, one-to-four Chl f pigments were found in the complexes. By using a range of spectroscopic techniques, isolated PSI trimeric complexes were investigated to determine how the insertion of Chl f affects excitation energy transfer and trapping efficiency. The results show that the Chls f are functionally connected to the reaction center of the PSI complex and their presence does not change the overall pigment organization of the complex. Chl f substitutes Chl a (but not the Chl a red forms) while maintaining efficient energy transfer within the PSI complex. At the same time, the introduction of Chl f extends the photosynthetically active radiation of the new hybrid PSI complexes up to 750 nm, which is advantageous in far-red light enriched environments. These conclusions provide insights to engineer the photosynthetic machinery of crops to include Chl f and therefore increase the light-harvesting capability of photosynthesis.
Niche expansion for phototrophic sulfur bacteria at the Proterozoic - Phanerozoic transition
(2020-07) Cui, Xingqian; Liu, Xiao-Lei; Shen, Gaozhong; Ma, Jian; Husain, Fatima; Rocher, Donald; Zumberge, John E.; Bryant, Donald A.; Summons, Roger E.
Fossilized carotenoid hydrocarbons provide a window into the physiology and biochemistry of ancient microbial phototrophic communities for which only a sparse and incomplete fossil record exists. However, accurate interpretation of carotenoid-derived biomarkers requires detailed knowledge of the carotenoid inventories of contemporary phototrophs and their physiologies. Here we report two distinct patterns of fossilized C40 diaromatic carotenoids. Phanerozoic marine settings show distributions of diaromatic hydrocarbons dominated by isorenieratane, a biomarker derived from low-light-adapted phototrophic green sulfur bacteria. In contrast, isorenieratane is only a minor constituent within Neoproterozoic marine sediments and Phanerozoic lacustrine paleoenvironments, for which the major compounds detected are renierapurpurane and renieratane, together with some novel C39 and C38 carotenoid degradation products. This latter pattern can be traced to cyanobacteria as shown by analyses of cultured taxa and laboratory simulations of sedimentary diagenesis. The cyanobacterial carotenoid synechoxanthin, and its immediate biosynthetic precursors, contain thermally labile, aromatic carboxylic-acid functional groups, which upon hydrogenation and mild heating yield mixtures of products that closely resemble those found in the Proterozoic fossil record. The Neoproterozoic–Phanerozoic transition in fossil carotenoid patterns likely reflects a step change in the surface sulfur inventory that afforded opportunities for the expansion of phototropic sulfur bacteria in marine ecosystems. Furthermore, this expansion might have also coincided with a major change in physiology. One possibility is that the green sulfur bacteria developed the capacity to oxidize sulfide fully to sulfate, an innovation which would have significantly increased their capacity for photosynthetic carbon fixation.
Occurrence of Far-Red Light Photoacclimation (FaRLiP) in Diverse Cyanobacteria
(2014-12) Gan, Fei; Shen, Gaozhong; Bryant, Donald A.
Cyanobacteria have evolved a number of acclimation strategies to sense and respond to changing nutrient and light conditions. Leptolyngbya sp. JSC-1 was recently shown to photoacclimate to far-red light by extensively remodeling its photosystem (PS) I, PS II and phycobilisome complexes, thereby gaining the ability to grow in far-red light. A 21-gene photosynthetic gene cluster (rfpA/B/C, apcA2/B2/D2/E2/D3, psbA3/D3/C2/B2/ H2/A4, psaA2/B2/L2/I2/F2/J2) that is specifically expressed in far-red light encodes the core subunits of the three major photosynthetic complexes. The growth responses to far-red light were studied here for five additional cyanobacterial strains, each of which has a gene cluster similar to that in Leptolyngbya sp. JSC-1. After acclimation all five strains could grow continuously in far-red light. Under these growth conditions each strain synthesizes chlorophylls d, f and a after photoacclimation, and each strain produces modified forms of PS I, PS II (and phycobiliproteins) that absorb light between 700 and 800 nm. We conclude that these photosynthetic gene clusters are diagnostic of the capacity to photoacclimate to and grow in far-red light. Given the diversity of terrestrial environments from which these cyanobacteria were isolated, it is likely that FaRLiP plays an important role in optimizing photosynthesis in terrestrial environments.
The structure of Photosystem I acclimated to far-red light illuminates an ecologically important acclimation process in photosynthesis
(2020-02) Gisriel, Christopher; Shen, Gaozhong; Kurashov, Vasily; Ho, Ming-Yang; Zhang, Shangji; Williams, Dewight; Golbeck, John H.; Fromme, Petra; Bryant, Donald A.
Phototrophic organisms are superbly adapted to different light environments but often must acclimate to challenging competition for visible light wavelengths in their niches. Some cyanobacteria overcome this challenge by expressing paralogous photosynthetic proteins and by synthesizing and incorporating ~8% chlorophyll f into their Photosystem I (PSI) complexes, enabling them to grow under far-red light (FRL). We solved the structure of FRL-acclimated PSI from the cyanobacterium Fischerella thermalis PCC 7521 by single-particle, cryo–electron microscopy to understand its structural and functional differences. Four binding sites occupied by chlorophyll f are proposed. Subtle structural changes enable FRL-adapted PSI to extend light utilization for oxygenic photosynthesis to nearly 800 nm. This structure provides a platform for understanding FRL-driven photosynthesis and illustrates the robustness of adaptive and acclimation mechanisms in nature.