Effects of Sulfate Limitation on Photosynthesis and Cell Composition of Unicellular Marine Microalgae of Different Phylogenies.

Sulfur (S) is an essential macroelement for photosynthetic organisms and is acquired as sulfate and assimilated as sulfide into cysteine through a highly demanding reductive process. S is a key component of proteins, lipids, and various other cellular metabolites and plays a direct role in photosynthesis, both in the electron transport and in carbon fixation reactions. Despite such central functions, most of our knowledge on S metabolism is focused on plant species, while in microalgae it is still fragmented, particularly concerning their huge phylogenetic diversity.

Enhanced growth and photosynthetic efficiency in wild rocket (Diplotaxis tenuifolia L.) following multi-species microalgal biostimulant application.

Foliar spraying is a simple and efficient technique that enables targeted delivery of biostimulants directly onto plant surfaces, minimizing losses and environmental dispersion. Among biostimulant categories, microalgae-based formulations represent an eco-friendly solution to improve crop productivity, thanks to their richness in bioactive compounds and rapid growth in low-input systems. In this study, the crude extract of three green microalgae with high commercial value and broad biotechnological potential-Auxenochlorella protothecoides, Tetradesmus obliquus and Chlamydomonas reinhardtii-along with their consortium, was tested as foliar biostimulants for the first time on wild rocket (Diplotaxis tenuifolia L.

Monocultures vs. polyculture of microalgae: unveiling physiological changes to facilitate growth in ammonium rich-medium.

Due to the increasing production of wastewater from human activities, the use of algal consortia for phytoremediation has become well-established over the past decade. Understanding how interspecific interactions and cultivation modes (monocultures vs. polyculture) influence algal growth and behaviour is a cutting-edge topic in both fundamental and applied science.

Selection of microalgae in artificial digestate: Strategies towards an effective phycoremediation.

Digestate is a complex by-product of anaerobic digestion and its composition depends on the digestor inputs. It can be exploited as a sustainable source of nutrients for microalgae cultivation but its unbalanced composition and toxic elements make the use challenging. Screening algae in a simplified synthetic digestate which mimics the main nutrient constraints of a real digestate is proposed as a reproducible and effective method to select suitable species for real digestate valorisation and remediation.

Integrative effects of morphology, silicification, and light on diatom vertical movements.

Diatoms represent the most abundant and diversified class of primary producers in present oceans; their distinctive trait is the ability to incorporate silicic acid in a silica outer shell called frustule. Numerous adaptative functions are ascribed to frustules, including the control of vertical movements through the water column; this indirectly determines cell access to fundamental resources such as light and nutrients, and favors diatom escape from predators. At the same time, light guides phototroph movements in the water column by affecting cell density (e.

Fermentation of Microalgal Biomass for Innovative Food Production.

Fermentation is an ancient method used worldwide to process and preserve food while enhancing its nutraceutical profile. Alga-based fermented products have recently been developed and tested due to growing interest in healthy sustainable diets, which demands the development of innovative practices in food production, operating for both human health and Earth sustainability. Algae, particularly microalgae such as , , and , are already cultivated as sources of food due to their valuable compounds, including proteins, pigments, lipids, carotenoids, polyunsaturated fatty acids, steroids, and vitamins.

Time lapse synchrotron IR chemical imaging for observing the acclimation of a single algal cell to CO treatment.

Algae are the main primary producers in aquatic environments and therefore of fundamental importance for the global ecosystem. Mid-infrared (IR) microspectroscopy is a non-invasive tool that allows in principle studying chemical composition on a single-cell level. For a long time, however, mid-infrared (IR) imaging of living algal cells in an aqueous environment has been a challenge due to the strong IR absorption of water.

Regulation of Phagotrophy by Prey, Low Nutrients, and Low Light in the Mixotrophic Haptophyte Isochrysis galbana.

Mixotrophy combines autotrophy and phagotrophy in the same cell. However, it is not known to what extent the phagotrophy influences metabolism, cell composition, and growth. In this work, we assess, on the one hand (first test), the role of phagotrophy on the elemental and biochemical composition, cell metabolism, and enzymes related to C, N, and S metabolism of Isochrysis galbana Parke, 1949.

Estimating and correcting interference fringes in infrared spectra in infrared hyperspectral imaging.

Short-term acclimation response of individual cells of Thalassiosira weissflogii was monitored by Synchrotron FTIR imaging over the span of 75 minutes. The cells, collected from batch cultures, were maintained in a constant flow of medium, at an irradiance of 120 μmol m-2 s-1 and at 20 °C. Multiple internal reflections due to the micro fluidic channel were modeled, and showed that fringes are additive sinusoids to the pure absorption of the other components of the system.

A tale of two eras: Phytoplankton composition influenced by oceanic paleochemistry.

We report the results of simple experiments which support the hypothesis that changes in ocean chemistry beginning in the Mesozoic Era resulted in an increase in the nutritional quality per mole of C and per cell of planktonic algal biomass compared to earlier phytoplankton. We cultured a cyanobacterium, a diatom, a dinoflagellate, and a green alga in media mimicking aspects of the chemistry of Palaeozoic and Mesozoic-Cenozoic oceans. Substantial differences emerged in the quality of algal biomass between the Palaeozoic and Mesozoic-Cenozoic growth regimes; these differences were strongly affected by interspecific interactions (i.

The mechanisms whereby the green alga Chlorella ohadii, isolated from desert soil crust, exhibits unparalleled photodamage resistance.

Excess illumination damages the photosynthetic apparatus with severe implications with regard to plant productivity. Unlike model organisms, the growth of Chlorella ohadii, isolated from desert soil crust, remains unchanged and photosynthetic O2 evolution increases, even when exposed to irradiation twice that of maximal sunlight. Spectroscopic, biochemical and molecular approaches were applied to uncover the mechanisms involved.

FTIR spectra of algal species can be used as physiological fingerprints to assess their actual growth potential.

Fourier transform infrared (FTIR) spectra were measured from cells of Microcystis aeruginosa and Protoceratium reticulatum, whose growth rates were manipulated by the availability of nutrients or light. As expected, the macromolecular composition changed in response to the treatments. These changes were species-specific and depended on the type of perturbation applied to the growth regime.

Impact of irradiance on the C allocation in the coastal marine diatom Skeletonema marinoi Sarno and Zingone.

Elemental stoichiometry and organic composition were investigated in an Adriatic strain of Skeletonema marinoi, cultured at 25 [low light (LL)] and 250 [high light (HL)]µmol photon m⁻² s⁻¹. Inorganic carbon acquisition, fixation and allocation, and silicic acid and orthophosphate uptake were also studied. The C:P ratio was below the Redfield ratio, especially at LL.

Sulfur and primary production in aquatic environments: an ecological perspective.

Sulfur is one of the critical elements in living matter, as it participates in several structural, metabolic and catalytic activities. Photosynthesis is an important process that entails the use of sulfur during both the light and carbon reactions. Nearly half of global photosynthetic carbon fixation is carried out by phytoplankton in the aquatic environment.

Sulfur and phytoplankton: acquisition, metabolism and impact on the environment.

Sulfur emission from marine phytoplankton has been recognized as an important factor for global climate and as an entry into the biogeochemical S cycle. Despite this significance, little is known about the cellular S metabolism in algae that forms the basis of this emission. Some biochemical and genetic evidence for regulation of S uptake and assimilation is available for the freshwater model alga Chlamydomonas.

An anaplerotic role for mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii.

Previous studies of the mitochondrial carbonic anhydrase (mtCA) of Chlamydomonas reinhardtii showed that expression of the two genes encoding this enzyme activity required photosynthetically active radiation and a low CO(2) concentration. These studies suggested that the mtCA was involved in the inorganic carbon-concentrating mechanism. We have now shown that the expression of the mtCA at low CO(2) concentrations decreases when the external NH(4)(+) concentration decreases, to the point of being undetectable when NH(4)(+) supply restricts the rate of photoautotrophic growth.

Role of phosphoenolpyruvate carboxylase in anaplerosis in the green microalga Dunaliella salina cultured under different nitrogen regimes.

Anaplerosis plays a very important role in providing C for N assimilation. In green algae and higher plants, phosphoenolpyruvate carboxylase (PEPC, EC 4.1.