Benjamin Bailleul's research while affiliated with Institute of Physical and Chemical Biology and other places

Publications (60)

Preprint
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Organic carbon fixed through the Calvin Cycle can be diverted towards different metabolic fates within and beyond the plastids of photosynthetic eukaryotes. These include export to the cytoplasm and mitochondrial respiration; gluconeogenesis of storage compounds; and the anabolic synthesis of lipids, amino acids and cofactors via the plastidial pyr...
Article
Like all organisms performing oxygenic photosynthesis, diatoms absorb photons to extract electrons from water at photosystem (PS) II and reduce NADPH at PSI. These two photochemical steps are part of the linear electron flow (LEF), which is coupled to proton pumping into the lumen and ATP synthesis. In the Ocean, turbulent waters generate strong li...
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Recurrent blooms of the toxic dinoflagellate Ostreopsis cf. ovata are frequently reported in the Northwestern Mediterranean Sea. The impact of these proliferations on other microalgal species inhabiting the same habitats is of interest from an ecological prospective. In vitro experiments were carried out to investigate the influence of O. cf. ovata...
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Diatoms are successful phytoplankton clades able to acclimate to changing environmental conditions, including e.g. variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum photosynthetic electron transfer (PET) capacity via the Non Photochemical Quenching (NPQ) process. While the molecular effectors of NPQ...
Preprint
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Diatoms are amongst the most successful clades of oceanic phytoplankton, significantly contributing to photosynthesis on Earth. Their ecological success likely stems from their ability to acclimate to changing environmental conditions, including e.g. variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum...
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Among all the chemical and biotechnological strategies implemented to extract energy from oxygenic photosynthesis, several concern the use of intact photosynthetic organisms (algae, cyanobacteria…). This means rerouting (fully or partially) the electron flow from the photosynthetic chain to an outer collecting electrode generating thus a photocurre...
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Diatoms possess an efficient mechanism to dissipate photons as heat in conditions of excess light, which is visualized as the Non-Photochemical Quenching of chlorophyll a fluorescence (NPQ). In most diatom species, NPQ is proportional to the concentration of the xanthophyll cycle pigment diatoxanthin formed from diadinoxanthin by the diadinoxanthin...
Article
Many cyanobacteria species can use both plastocyanin and cytochrome c6 as lumenal electron carriers to shuttle electrons from the cytochrome b6f to either photosystem I or the respiratory cytochrome c oxidase. In Synechocystis sp. PCC6803 placed in darkness, about 60% of the active PSI centres are bound to a reduced electron donor which is responsi...
Article
The chloroplast ATP synthase (CF1Fo) contains a specific feature to the green lineage: a γ-subunit redox domain that contains a cysteine couple which interacts with the torque-transmitting βDELSEED-loop. This thiol modulation equips CF1Fo with an important environmental fine-tuning mechanism. In vitro, disulfide formation in the γ-redox domain slow...
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Allelopathy is an efficient strategy by which some microalgae can outcompete other species. Allelochemicals from the toxic dinoflagellate Alexandrium minutum have deleterious effects on diatoms, inhibiting metabolism and photosynthesis and therefore give a competitive advantage to the dinoflagellate. The precise mechanisms of allelochemical interac...
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Microbial solar cells that mainly rely on the use of photosynthesic organisms are a promising alternative to photovoltaics for solar electricity production. In that way, we propose a new approach involving electrochemistry and fluorescence techniques. The coupled set-up Electro-Pulse-Amplitude-Modulation (“e-PAM”) enables the simultaneous recording...
Preprint
Full-text available
The chloroplast ATP synthase (CF 1 F o ) contains a specific feature to the green lineage: a γ-subunit redox domain which contains a cysteine couple and interacts with the torque-generating βDELSEED-loop. Based on the recently solved structure of this domain, it was proposed to function as a chock. In vitro , γ-disulfide formation slows down the ac...
Preprint
Full-text available
Microbial solar cells that mainly rely on the use of photosynthesic organisms are a promising alternative to photovoltaics for solar electricity production. In that way, we propose a new approach involving electrochemistry and fluorescence techniques. The coupled set-up Electro-Pulse-Amplitude-Modulation ("e-PAM") enables the simultaneous recording...
Article
Full-text available
Diatoms are the most diverse group of algae with at least 100,000 species. Contributing approximately 20% of annual global carbon fixation, they underpin major aquatic food webs and drive global biogeochemical cycles. Over the last two decades, Thalassiosira pseudonana and Phaeodactylum tricornutum have become the most important references for diat...
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The mechanisms underlying interactions between diatoms and bacteria are crucial to understand diatom behaviour and proliferation, and can result in far‐reaching ecological consequences. Recently, 2‐alkyl‐4‐quinolones have been isolated from marine bacteria, both of which (the bacterium and isolated chemical) inhibited growth of microalgae, suggesti...
Article
In plants, algae, and some photosynthetic bacteria, the ElectroChromic Shift (ECS) of photosynthetic pigments, which senses the electric field across photosynthetic membranes, is widely used to quantify the activity of the photosynthetic chain. In cyanobacteria, ECS signals have never been used for physiological studies, although they can provide a...
Article
Apart from the canonical light-driven linear electron flow (LEF) from water to CO2, numerous regulatory and alternative electron transfer pathways exist in chloroplasts. One of them is the cyclic electron flow around Photosystem I (CEF), contributing to photoprotection of both Photosystem I and II (PSI, PSII) and supplying extra ATP to fix atmosphe...
Article
Cyclic electron flow (CEF) is defined as a return of the reductants from the acceptor side of Photosystem I (PSI) to the pool of its donors via the cytochrome b 6 f. It is described to be complementary to the linear electron flow and essential for photosynthesis. However, despite many efforts aimed to characterize CEF, its pathway and its regulatio...
Article
Marine bacteria contribute substantially to nutrient cycling in the oceans and can engage in close interactions with microalgae. Many microalgae harbor characteristic satellite bacteria, many of which participate in N-acyl homoserine lactone (AHL) mediated quorum sensing. In the diffusion-controlled phycosphere, AHLs can reach high local concentrat...
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Whereas photosynthetic function under steady-state light conditions has been well characterized, little is known about its changes that occur in response to light fluctuations. Chlororespiration, a simplified respiratory chain, is widespread across all photosynthetic lineages, but its role remains elusive. Here, we show that chlororespiration plays...
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In changing light conditions, photosynthetic organisms develop different strategies to maintain a fine balance between light harvesting, photochemistry, and photoprotection. One of the most widespread photoprotective mechanisms consists in the dissipation of excess light energy in the form of heat in the photosystem II antenna, which participates t...
Article
The chloroplast F1Fo-ATP synthase (CF1Fo) drives ATP synthesis and the reverse reaction of ATP hydrolysis. The enzyme evolved in a cellular environment where electron transfer processes and molecular oxygen are abundant, and thiol modulation in the γ-subunit via thioredoxin is important for its ATPase activity regulation. Especially under high ligh...
Article
The qualitative screening method to select complex I mutants in the microalga Chlamydomonas, based on reduced growth under heterotrophic condition, is not suited for high throughput screening. In order to develop a fast screening method based on measurements of chlorophyll fluorescence, we first demonstrated that complex I mutants displayed decreas...
Preprint
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Cyclic electron flow (CEF), one of the major alternative electron transport pathways to the primary linear electron flow (LEF) in chloroplasts has been discovered in the middle of the last century. It is defined as a return of the reductants from the acceptor side of the Photosystem I (PSI) to the pool of its donors via the cytochrome b 6 f , and h...
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Photosynthesis is a unique process that allows independent colonization of the land by plants and of the oceans by phytoplankton. Although the photosynthesis process is well understood in plants, we are still unlocking the mechanisms evolved by phytoplankton to achieve extremely efficient photosynthesis. Here, we combine biochemical, structural and...
Preprint
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Photosynthesis needs to adjust to dynamically changing light intensities in order to maximize its efficiency, notably by the employment of alternative electron pathways. One of them is chlororespiration - initially described in Chlamydomonas reinhardtii . This electron transfer pathway, found in all photosynthetic lineages, consists of a reduction...
Article
Amundsen Sea polynyas are among the most productive, yet climate-sensitive ecosystems in the Southern Ocean and host massive annual phytoplankton blooms. These blooms are believed to be controlled by iron fluxes from melting ice and icebergs and by intrusion of nutrient-rich Circumpolar Deep Water, however the interplay between iron effects and oth...
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We measured the light dependence of gross photosynthesis and oxygen uptake rates by membrane inlet mass spectrometry in two open ocean regions: the Amundsen Sea (Antarctica), dominated by Phaeocystis antarctica, and the North Atlantic, dominated by Emiliania huxleyi. In the North Atlantic, respiration was independent of irradiance and was higher th...
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Cyanobacteria are important contributors to primary production in the open oceans. Over the past decade, various photosynthesis-related genes have been found in viruses that infect cyanobacteria (cyanophages). Although photosystem II (PSII) genes are common in both cultured cyanophages and environmental samples 1–4 , viral photosystem I (vPSI) gene...
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Diatoms are phytoplanktonic organisms that grow successfully in the ocean where light conditions are highly variable. Studies of the molecular mechanisms of light acclimation in the marine diatom Phaeodactylum tricornutum show that carotenoid de-epoxidation enzymes and LHCX1, a member of the light-harvesting protein family, both contribute to dissi...
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Diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. Over the past 30 million years, they have helped to moderate Earth’s climate by absorbing carbon dioxide from the atmosphere, sequestering it via the biological carbon pump and ultimately burying organic carbon in the lithosph...
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The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF),...
Article
* Photosynthetic organisms have developed various photoprotective mechanisms to cope with exposure to high light intensities. In photosynthetic dinoflagellates that live in symbiosis with cnidarians, the nature and relative amplitude of these regulatory mechanisms are a matter of debate. In our study, the amplitude of photosynthetic alternative ele...
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In Chlamydomonas, unlike in flowering plants, genes coding for Nd7 (NAD7/49kDa) and Nd9 (NAD9/30kDa) core subunits of mitochondrial respiratory-chain complex I are nucleus-encoded. Both genes possess all the features that facilitate their expression and proper import of the polypeptides in mitochondria. By inactivating their expression by RNA inter...
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Diatoms, unicellular phytoplankton that account for ∼40% of marine primary productivity, often dominate coastal and open-ocean upwelling zones. Limitation of growth and productivity by iron at low light is attributed to an elevated cellular Fe requirement for the synthesis of Fe-rich photosynthetic proteins. In the dynamic coastal environment, Fe c...
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Light-induced electron transfer reactions in the chlorophyll a/d-binding Photosystem I reaction centre of Acaryochloris marina were investigated in whole cells by pump-probe optical spectroscopy with a temporal resolution of ~5ns at room temperature. It is shown that phyllosemiquinone, the secondary electron transfer acceptor anion, is oxidised wit...
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In photosynthesis, electron transfer along the photosynthetic chain results in a vectorial transfer of protons from the stroma to the lumenal space of the thylakoids. This promotes the generation of an electrochemical proton gradient (Δμ H+), which comprises a gradient of electric potential (ΔΨ) and of proton concentration (ΔpH). The Δμ H+ has a ce...
Article
Full-text available
Diatoms are prominent phytoplanktonic organisms that contribute around 40% of carbon assimilation in the oceans. They grow and perform optimally in variable environments, being able to cope with unpredictable changes in the amount and quality of light. The molecular mechanisms regulating diatom light responses are, however, still obscure. Using kno...
Article
Full-text available
We have investigated the photosynthetic properties of Acaryochloris marina, a cyanobacterium distinguished by having a high level of chlorophyll d, which has its absorption bands shifted to the red when compared with chlorophyll a. Despite this unusual pigment content, the overall rate and thermodynamics of the photosynthetic electron flow are simi...
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Adaptation of photosynthesis in marine environment has been examined in two strains of the green, picoeukaryote Ostreococcus: OTH95, a surface/high-light strain, and RCC809, a deep-sea/low-light strain. Differences between the two strains include changes in the light-harvesting capacity, which is lower in OTH95, and in the photoprotection capacity,...
Article
Full-text available
Adaptation of photosynthesis in marine environment has been examined in two strains of the green, picoeukaryote Ostreococcus: OTH95, a surface/high-light strain, and RCC809, a deep-sea/low-light strain. Differences between the two strains include changes in the light-harvesting capacity, which is lower in OTH95, and in the photoprotection capacity,...

Citations

... In C. reinhardtii a different protein, LHCSR3, also plays a dual role: it is involved in pH sensing but also binds pigments (including Zeaxanthin), even though the direct role of Zeaxanthin is still not clear [23]. Considering microalgae arising from secondary endosymbiosis, NPQ is mostly studied in diatoms, especially P. tricornutum [24]. Contrary to plants and green algae, diatoms possess a diadinoxanthinin-diatoxanthin (Dd/Dt) xanthophyll cycle. ...
... The cultures were maintained for ten days at 23 • C under a 14:10 light/dark cycle with a light intensity of 250 µmol/m 2 /s, at which time the cells were harvested by centrifugation at 1800 rpm for 12 min and the supernatant was discarded. Ten days of growth was previously identified as the peak for toxin production in this strain [9,28]. ...
... Because of its potential benefit in utilizing solar energy, this photocurrent has attracted wide interest in various engineering fields as a component of "biophotovoltaic" technology (Rosenbaum et al. 2010;McCormick et al. 2015;Ng et al. 2017;Tschörtner et al. 2019;Liu and Choi 2021). Various studies have successfully improved the photocurrent yield through the modification of the access of photosynthetic cells to electrodes and the screening of the electrochemical mediators (Sawa et al. 2017;Bombelli et al. 2015;Lemaître et al. 2021;Çevik et al. 2018;Wenzel et al. 2018). According to the literature, the electrons are possibly transferred from photosynthetic cells to an electrode via reduced nicotinamide adenine dinucleotide phosphate (NADPH) and/or other electron mediator(s) (Zhang et al. 2018;Thirumurthy et al. 2020;Shlosberg et al. 2021). ...
... 2.5). Dt is converted back to Dd in the absence of a pronounced ΔpH, that is, under low light and to some extent also dark conditions, catalyzed via an epoxidase, which then operates faster than the de-epoxidase (Blommaert et al. 2021). Interestingly, after a switch from high light, the epoxidation reaction in diatoms is faster under low light conditions than in darkness Blommaert et al. 2017). ...
... Recently, however, an in vivo P700 reduction kinetic study on the PSI from Synechocystis sp. PCC6803 showed similar kinetic features to those of green algae and higher plants 51 PsaF may make the Cyt c 6 -binding specific but flexible, which could provide further explanation for the limited resolution of Cyt c 6 in our density map. This proposal is consistent with the low local resolution of bound Pc at the non-productive site of Chlamydomonas PSI 48 . ...
... However, the apparent generation during the b-phase is underestimated especially when a fast ECS decay is produced by a highly active ATP synthase that deenergizes the membrane simultaneously [reviewed in 52]. High ATP synthase activity in such flash experiments occur when the cysteine pair in its -subunit is reduced (as a result of PSI electron flow) and when the available energy source (pmf) is above a critical threshold [53,54]. Both parameters are limited in PSII-inhibited samples, thus slowing down ATP synthase activity. ...
... marina, M. polykrikoides and G. impudicum caused similar changes in G. catenatum, such as a decrease in growth and morphological changes [17,19]. Cell lysis caused by filtrates is a consequence of a continuous disarrangement of the cell membrane during the interaction with cell filtrates, as the first structure with which the allelochemicals have contact is the cell membrane [65,66]. Damage in the cell membrane can lead to osmotic changes, which can disrupt the life cycle of alveolates [67,68]. ...
... However, neither of them seems to fulfil entirely the criteria to support CEF by itself. NDH (2.5 e −1 s −1 PSI −1 in plants, 4 e −1 s −1 PSI −1 in Chlamydomonas) seems to be too slow to account for the CEF rates measured in vivo (~100 and ~60 e −1 s −1 PSI −1 in plants and green algae respectively) (Joliot et al., 2004) (Nawrocki et al., 2017). On the other hand, a Chlamydomonas mutant strain lacking PGRL1 is still able of high rates of CEF (Nandha et al., 2007), similarly to what was previously reported in plants. ...
... All chronoamperometry experiments were given 90 s of equilibrium period in the dark prior to initial light irradiation. It should be noted that in the presence of DCBQ, the mediated photocurrents drop rapidly, possibly due to diffusional limitations of the mediator in the unstirred electrolyte and partial cytotoxicity effects 40,41 . As such, only the initial (first light cycle) mediated photocurrents were analysed. ...
... atpA, atpB, and atpE encode the α, β, and ε subunits of plastid ATPase, respectively. ATPase is the critical enzyme in energy metabolism and plays a central role in photosynthesis(Felix et al., 2020). The divergence of Dn is proof that genes go through different degrees of selective constraints, but it is still challenging to discern what degree of selective constraints caused this difference.Numerous studies of angiosperm plastomes have found that most variation occurred in noncoding sequences, and occasionally in the protein-coding sequences which evolve more rapidly. ...