A systems-wide understanding of photosynthetic acclimation in algae and higher plants

The ability of phototrophs to colonise different environments relied on the robust protection against oxidative stress in phototrophs, a critical requirement for the successful evolutionary transition from water to land. Photosynthetic organisms have developed numerous strategies to adapt their photosynthetic apparatus to changing light conditions in order to optimise their photosynthetic yield, crucial for life to exist on Earth. Photosynthetic acclimation is an excellent example of the complexity of biological systems, in which highly diverse processes, ranging from electron excitation over protein protonation to enzymatic processes coupling ion gradients with biosynthetic activity interact on drastically different timescales, ranging from picoseconds to hours. An efficient functioning of the photosynthetic apparatus and its protection is paramount for efficient downstream processes including metabolism and growth. Modern experimental techniques can be successfully integrated with theoretical and mathematical models to promote our understanding of underlying mechanisms and principles. This Review aims to provide a retrospective analysis of multidisciplinary photosynthetic acclimation research carried out by members of the Marie Curie Initial Training Project “AccliPhot”, placing the results in a wider context. The Review also highlights the applicability of photosynthetic organisms for industry, particularly with regards to the cultivation of microalgae. It aims to demonstrate how theoretical concepts can successfully complement experimental studies broadening our knowledge of common principles in acclimation processes in photosynthetic organisms, as well as in the field of applied microalgal biotechnology

Boosting Biomass Quantity and Quality by Improved Mixotrophic Culture of the Diatom Phaeodactylum tricornutum

International audienceDiatoms are photoautotrophic unicellular algae and are among the most abundant, adaptable, and diverse marine phytoplankton. They are extremely interesting not only for their ecological role but also as potential feedstocks for sustainable biofuels and high-value commodities such as omega fatty acids, because of their capacity to accumulate lipids. However, the cultivation of microalgae on an industrial scale requires higher cell densities and lipid accumulation than those found in nature to make the process economically viable. One of the known ways to induce lipid accumulation in Phaeodactylum tricornutum is nitrogen deprivation, which comes at the expense of growth inhibition and lower cell density. Thus, alternative ways need to be explored to enhance the lipid production as well as biomass density to make them sustainable at industrial scale. In this study, we have used experimental and metabolic modeling approaches to optimize the media composition, in terms of elemental composition, organic and inorganic carbon sources, and light intensity, that boost both biomass quality and quantity of P. tricornutum . Eventually, the optimized conditions were scaled-up to 2 L photobioreactors, where a better system control (temperature, pH, light, aeration/mixing) allowed a further improvement of the biomass capacity of P. tricornutum to 12 g/L

Supplementary Fig. 4 A Respiration and photosynthesis in P. tricornutum cells from Investigating mixotrophic metabolism in the model diatom <i>Phaeodactylum tricornutum</i>

Direct assessment of oxygen consumption by a polarographic approach in both phototrophy (black bar) and mix-otrophy (red bar). B. Fluorescent based-assay to monitoring the changes in respiration using the Redox Dye A in presence of the selected compounds (see methods)

Supplementary Fig. 3 Quantification of intracellular pyruvate by a fluorescence-based method from Investigating mixotrophic metabolism in the model diatom <i>Phaeodactylum tricornutum</i>

A. Pyruvate standard curve. B. Quantification of intracellular pyruvate in cells grown in phototrophy (PHOT) and mixotrophy (MIX)

Supplementary Fig. 5 Screening of mixotrophic efficiency by biolog and redox dye assay in P. tricornutum from Investigating mixotrophic metabolism in the model diatom <i>Phaeodactylum tricornutum</i>

A. OD750 nm changes (relative to phototrophic growth) of P. tricornutum cells grown for 6 days in BiologTM plates P1 and PM2A that contains 190 carbon compounds (see methods). Each data point represents a different com-pound. B. Growth profile of P. tricornutum on few selected compounds (at 20 mM) and a phototrophic control in 100 mL flasks. C. Areas under the growth curves of Supplementary Fig. 5B normalized to the area of the curve of phototrophic growth

Supplementary Fig. 2 Membrane lipid composition in P. tricornutum from Investigating mixotrophic metabolism in the model diatom <i>Phaeodactylum tricornutum</i>

Lipid analysis of cells grow in N-replete conditions and N-deplete conditions in both mixotrophic and phototrophic mode. Each result is the average of two biological replicates ± SD. SQDG, sulfoquinovosyldiacylglycerol; DGDG, digalactosyldiacylglycerol; MGDG, monogalactosyldiacylglycerol; PC, phosphatidylcholine; PHOT: light in N-replete condition; PHOTO-N: light in N-deplete condition; MIX: light+glycerol in N-replete condition; MIX-N: light+glycerol in N-deplete condition

Supplementary Fig. 1 Quantitative analysis of P. tricornutum glycerolipids from Investigating mixotrophic metabolism in the model diatom <i>Phaeodactylum tricornutum</i>

TAG profile in a total lipid extract from cells grown in replete conditions (A) and deplete conditions (B) in both mixotrophic and phototrophic mode. Glycerolipids are expressed in nmol / mg of dry cells. Each result is the average of two biological replicates ± SD. PHOT: light in N-replete condition; PHOTO-N: light in N-deplete condi-tion; MIX: light+glycerol in N-replete condition; MIX-N: light+glycerol in N-deplete condition

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed

Effect of Antiplatelet Therapy on Survival and Organ Support–Free Days in Critically Ill Patients With COVID-19

International audienc