Single Algal Cells Research Articles

Promoting effects of ferric ions on Microcystis aeruginosa growth and arsenate accumulation and reduction at different phosphorus environments

The effects of different dissolved organic phosphorus (DOP) associated with distinct iron conditions (iron deficient (dFe), ferric ions (Fe3+), and colloidal iron (CFe)) on algal growth and arsenate (As(V)) metabolism were systematically evaluated and compared in Microcystis aeruginosa. Two chemical forms of DOP (D-glucose-6-phosphate (GP) and phytic acid (PA)), as well as dissolved inorganic phosphorus (DIP), were employed as distinct phosphorus environments. The results revealed that As(V) metabolism of M. aeruginosa was more influenced by different phosphorus forms than by different iron conditions. Conversely, the release of microcystins in the media was found to be significantly more affected by the different phosphorus forms than by the iron conditions. Moreover, DOP was observed to promote arsenic (As) biotransformation, particularly the efflux of methylated As from a single algal cell, whereas DIP was found to primarily facilitate As(V) accumulation in algae. The total As metabolism amount per algal cell under PA was observed to be five times that observed under DIP and GP. The influence of iron conditions on the synthesis of algal metabolites was notable, as evidenced by the metabolites identified in algae of aliphatic (δ 1.28–1.68), humic acid-like and aromatic protein-like substances through 1H-NMR spectra and three-dimensional excitation-emission matrix fluorescence spectroscopy analysis. This impact was particularly notable at Fe3+ conditions, due to the role of Fe3+ as a micronutrient with highly bioavailable forms, which enhanced the synthesis of organic compounds in algae and promoted algal growth. Consequently, Fe3+ could inhibit As accumulation under DIP but promote it under DOP. The obtained results facilitate a more comprehensive understanding of the combined role of different phosphorus forms and iron conditions in algal bloom outbreaks and As(V) metabolism.

Daily turnover of active giant virus infection during algal blooms revealed by single-cell transcriptomics.

Giant viruses infect many unicellular eukaryotes, including algae that form massive oceanic blooms. Despite the major impact of viruses on the marine ecosystem, the ability to quantify and assess active viral infection in nature remains a major challenge. We applied single-cell RNA sequencing, to profile virus and host transcriptomes of 12,000 single algal cells from a coccolithophore bloom. Viral infection was detected already at early exponential bloom phase, negatively correlating with the bloom intensity. A consistent percent of infected coccolithophores displayed the early phase of viral replication for several consecutive days, indicating a daily turnover and continuous virocell-associated metabolite production, potentially affecting the surrounding microbiome. Linking single-cell infection state to host physiology revealed that infected cells remained calcified even in the late infection stage. These findings stress the importance of studying host-virus dynamics in natural populations, at single-cell resolution, to better understand virus life cycle and its impact on microbial food webs.

Optical single-pixel volumetric imaging by three-dimensional light-field illumination

Three-dimensional single-pixel imaging (3D SPI) has become an attractive imaging modality for both biomedical research and optical sensing. 3D-SPI techniques generally depend on time-of-flight or stereovision principle to extract depth information from backscattered light. However, existing implementations for these two optical schemes are limited to surface mapping of 3D objects at depth resolutions, at best, at the millimeter level. Here, we report 3D light-field illumination single-pixel microscopy (3D-LFI-SPM) that enables volumetric imaging of microscopic objects with a near-diffraction-limit 3D optical resolution. Aimed at 3D space reconstruction, 3D-LFI-SPM optically samples the 3D Fourier spectrum by combining 3D structured light-field illumination with single-element intensity detection. We build a 3D-LFI-SPM prototype that provides an imaging volume of ∼390 × 390 × 3,800 μm3 and achieves 2.7-μm lateral resolution and better than 37-μm axial resolution. Its capability of 3D visualization of label-free optical absorption contrast is demonstrated by imaging single algal cells in vivo. Our approach opens broad perspectives for 3D SPI with potential applications in various fields, such as biomedical functional imaging.

Evaluation of Cd2+ stress on Synechocystis sp. PCC6803 based on single-cell elemental accumulation and algal toxicological response

With the development of single cell analysis techniques, the concept of precision toxicology has been proposed in recent years. Due to the heterogeneity of cells, we need to perform toxicological assessments on individual cells. Microalgae, one kind of important primary producers, play as a major pathway by which heavy metals enter the food chain and thus accumulate/transfer to higher trophic levels. Herein, the biosorption of Cd (Ex-Cd) and bioaccumulation of Cd (In-Cd) for Synechocystis sp. PCC 6803 were investigated by online 3D droplet microfluidic device combined with inductively coupled plasma mass spectrometry detection. Meanwhile, the algal toxicological responses of the algae cell to Cd2+ exposure under different concentration (50, 100, and 150 μg L − 1) and time (15 min, 24, 48 and 96 h) were studied. Combining single-cell analysis with toxicological indicators, the toxicity mechanism of Cd2+to algal was discussed. The single cell analysis results revealed heterogeneity in cellular uptake of Cd2+. The proportion of Cd-containing cells and Cd content in single algal cells all reached the maximum at 24 h. The uptake of Cd2+ occurred within 15 min under all tested exposure concentrations and a large part of Cd2+ were adsorbed on the algal cells surface. The Pearson correlation analysis showed that cell density, chlorophyll a and carotenoids were significantly negatively correlated with Cd accumulation, whereas ROS level and SOD activity were significantly positively correlated with Cd accumulation. It suggested that Cd2+accumulated intracellular would show toxic effects on the algal cells and oxidative stress is the main mechanism of Cd toxicity to algal cells. This work promotes our understanding of the toxicological responses of microalgae under Cd stress at single cells level.

Time lapse synchrotron IR chemical imaging for observing the acclimation of a single algal cell to CO2 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. In this study, we employed multi-beam synchrotron radiation to measure time-resolved IR hyperspectral images of individual Thalassiosira weissflogii cells in water in the course of acclimation to an abrupt change of CO2 availability (from 390 to 5000 ppm and vice versa) over 75 min. We used a previously developed algorithm to correct sinusoidal interference fringes from IR hyperspectral imaging data. After preprocessing and fringe correction of the hyperspectral data, principal component analysis (PCA) was performed to assess the spatial distribution of organic pools within the algal cells. Through the analysis of 200,000 spectra, we were able to identify compositional modifications associated with CO2 treatment. PCA revealed changes in the carbohydrate pool (1200–950 cm^{-1}), lipids (1740, 2852, 2922 cm^{-1}), and nucleic acid (1160 and 1201 cm^{-1}) as the major response of exposure to elevated CO2 concentrations. Our results show a local metabolism response to this external perturbation.

Single-cell RNA sequencing of batch Chlamydomonas cultures reveals heterogeneity in their diurnal cycle phase.

The photosynthetic unicellular alga Chlamydomonas (Chlamydomonas reinhardtii) is a versatile reference for algal biology because of its ease of culture in the laboratory. Genomic and systems biology approaches have previously described transcriptome responses to environmental changes using bulk data, thus representing the average behavior from pools of cells. Here, we apply single-cell RNA sequencing (scRNA-seq) to probe the heterogeneity of Chlamydomonas cell populations under three environments and in two genotypes differing by the presence of a cell wall. First, we determined that RNA can be extracted from single algal cells with or without a cell wall, offering the possibility to sample natural algal communities. Second, scRNA-seq successfully separated single cells into nonoverlapping cell clusters according to their growth conditions. Cells exposed to iron or nitrogen deficiency were easily distinguished despite a shared tendency to arrest photosynthesis and cell division to economize resources. Notably, these groups of cells not only recapitulated known patterns observed with bulk RNA-seq but also revealed their inherent heterogeneity. A substantial source of variation between cells originated from their endogenous diurnal phase, although cultures were grown in constant light. We exploited this result to show that circadian iron responses may be conserved from algae to land plants. We document experimentally that bulk RNA-seq data represent an average of typically hidden heterogeneity in the population.

The role of morphological changes in algae adaptation to nutrient stress at the single-cell level

Individual cell heterogeneity within a population can be critical to its peculiar function and fate. Conventional algal cell-based assays mainly analyze the average responses from a population of algal cells. Therefore, the mechanisms through which changes in population characteristics are driven by the behavior of single algal cells are still not well understood. Algal cells may modulate their physiology and metabolism by changing their morphology in response to environmental stress. In this study, an algal single-cell culture and analysis system was developed to investigate the potential role of morphological changes by algal cells during adaptation to nutrient stress based on a microwell array chip. The surface-to-volume ratio of Microcystis aeruginosa (M. aeruginosa) and the volume of Scenedesmus obliquus (S. obliquus) significantly increased with increasing culture time under nutrient stress. The eccentricity of M. aeruginosa and S. obliquus gradually increased and decreased, respectively, with increasing culture time, indicating that the morphology of M. aeruginosa and S. obliquus became increasingly irregular and regular, respectively, under nutrient stress. There were significant correlations between the morphological characteristics and physiological characteristics of M. aeruginosa and S. obliquus under nutrient stress. In M. aeruginosa, an increased surface-to-volume ratio facilitated a high specific fluorescence intensity, specific Raman intensity, and maximum electron transport rate. In S. obliquus, increased cell volume enhanced nutrient absorption, which facilitated a higher specific growth rate. M. aeruginosa and S. obliquus adopted different adaptation strategies in response to nutrient stress based on morphological changes. These findings facilitate the development of management strategies for controlling harmful cyanobacterial blooms.

Interactive Toxicity of Triclosan and Nano-TiO2 to Green Alga Eremosphaera viridis in Lake Erie: A New Perspective Based on Fourier Transform Infrared Spectromicroscopy and Synchrotron-Based X-ray Fluorescence Imaging.

This study explored the toxicity of triclosan in the presence of TiO2 P25 to the green alga Eremosphaera viridis in Lake Erie. Multiple physicochemical end points were conducted to perform a comprehensive analysis of the toxic effects of individual and combined pollutants. Fourier transform infrared spectromicroscopy and synchrotron-based X-ray fluorescence imaging were first documented to be applied to explore the distribution variation of macromolecules and microelements in single algal cells in interactive toxicity studies. The results were different based on different triclosan concentrations and measurement end points. Comparing with individual pollutants, the toxicity intensified in lipids, proteins, and oxidative stress at 1000 and 4000 μg/L triclosan in the presence of P25. There were increases in dry weight, chlorophyll content, lipids, and catalase content when cells were exposed to P25 and 15.625 μg/L triclosan. The toxicity alleviated when P25 interacted with 62.5 and 250 μg/L triclosan compared with triclosan-only exposure. The reasons could be attributed to the combination of adsorption, biodegradation, and photocatalysis of triclosan by algae and P25, triclosan dispersion by increased biomass, triclosan adherency on algal exudates, and triclosan adsorption site reduction on algae surface owing to P25's taking over. This work provides new insights into the interactive toxicity of nanoparticles and personal care products to freshwater photosynthetic organisms. The findings can help with risk evaluation for predicting outcomes of exposure to mixtures and with prioritizing further studies on joint toxicity.

The interactions between micro polyvinyl chloride (mPVC) and marine dinoflagellate Karenia mikimotoi: The inhibition of growth, chlorophyll and photosynthetic efficiency

Microplastics pose a great threat to entire marine ecosystems, but little is known about their impacts on phytoplankton, especially for the harmful dinoflagellates. In this study, effects of micro polyvinyl chloride (mPVC) on the growth, chlorophyll content and photosynthetic efficiency of the dinoflagellate Karenia mikimotoi at different periods (0, 24, 48, 72 and 96 h) were assessed using gradient concentrations (0, 5, 25, 50 and 100 mg L−1) of mPVC with a size of 1 μm. PVC microplastics had dose-dependent adverse effects on K. mikimotoi growth, chlorophyll content and photosynthetic efficiency. The density of algal cell decreased with increasing mPVC concentrations and the highest inhibitory rate (IR) was 45.8% at 24 h under 100 mg L−1 of mPVC. The total chlorophyll content and chlorophyll content in a single algal cell decreased at 96 h and the ФPSⅡ and Fv/Fm decreased 25.3% and 17.1%, respectively. The SEM images provided an intuitive visual method to observe the behaviors and interactions between microplastics and microalgae. It was found from the SEM images that microalgae was wrapped by microplastic beads. The physical blockage and aggregation were also responsible for the cytotoxicity of K. mikimotoi. Our study clarified that PVC microplastics can reduce algal growth, chlorophyll content and photosynthetic efficiency, and it is beneficial to evaluate the possible impact of plastics on aquatic ecosystems.

Astaxanthin accumulation in Haematococcus pluvialis observed through Fourier-transform infrared microspectroscopy imaging

Haematococcus pluvialis has emerged as a promising microalga for its rapid accumulation of astaxanthin. However, the underlying mechanism for astaxanthin biosynthesis is still unclear and needs further exploring in terms of the chemical changes of algal cell during the carotenogenesis pathway. In this study, the chemical changes were monitored in the algal cells exposed to carotenogenesis inhibitors by Fourier-transform infrared (FTIR) microspectroscopy imaging. The significant increase of signals at 3010 and 2925 cm−1 suggests the accumulation of carotenoids during the algal cell encysting. In contrast, a relatively low level of carotenoids in the algal cells contacted to nicotine and diphenylamine were observed for the biosynthesis blocking of β-carotene and astaxanthin. The decrease of the absorbance at 1740 and 1650 cm−1 indicates that lipids, proteins and astaxanthin biosynthesis were also inhibited by nicotine and diphenylamine while the cell wall biosynthesis was not disturbed by the inhibitors for the strong absorbance band at 1035 cm−1 assigned to polysaccharides. This work demonstrates that FTIR microspectroscopy imaging is an effective and none-invasive tool to analyze chemical changes and the components location in the single algal cell with high spatial resolution and it facilitates the study of carotenoid biosynthetic pathway.

Prolonged and highly efficient intracellular extraction of photosynthetic electrons from single algal cells by optimized nanoelectrode insertion

Harvesting photosynthetic electrons (PEs) from plant or algal cells can be a highly efficient and environmentally friendly way of generating renewable energy. Recent work on nanoelectrode insertion into algal cells has demonstrated the possibility to directly extract PEs from living algal cells with high efficiencies. However, the instability of the inserted cells limits the practicality of this technology. Here, the impact of nanoelectrode insertion on intracellular extraction of PEs is characterized with the goal of stabilizing algal cells after nanoelectrode insertion. Using nanoelectrodes <500 nm in diameter, algal cells remained stable for over one week after insertion and continued to provide PEs through direct extraction by the inserted nanoelectrodes. After nanoelectrode insertion, a photosynthetic current density of 6 mA·cm−2, which is several fold higher than the current densities attained using approaches based on isolated thylakoid membranes or photosystem I complexes, was observed in the dark and during illumination at various light intensities.

Single cell lipid profiling of Scenedesmus quadricauda CASA-CC202 under nitrogen starved condition by surface enhanced Raman scattering (SERS) fingerprinting

Oleaginous microalgae tend to accumulate neutral lipids as their energy reserve mainly in the form of triacylglycerol (TAG) which can be utilized as the precursor molecule for biodiesel and other nutraceutical application. The TAG level and the fatty acid composition of microalgae modulated by exposing the algal strains to different physicochemical, nutritional and environmental factors. Nitrogen starvation is considered as an important and practically feasible way by which the lipid content can be enriched in large scale production. In the present investigation, Scenedesmus quadricauda CASA-CC202, oleaginous microalgae with high biomass productivity has been subjected to nitrogen starvation and the stress mediated lipids were analyzed on a single cell basis. As a new insight, we have successfully identified the unsaturated and saturated functionalities of fatty acids by surface enhanced Raman scattering (SERS) spectral footprint under nitrogen starved condition in acidic and, neutral pH. In addition, other macromolecules like chlorophyll, carotenoids, proteins and carbohydrates were also selectively mapped. Most promising SERS mapping pattern of single algal cells depicts high lipid rich component under nitrogen starved condition and degree of unsaturation vs. saturation has been validated through SERS spectral analysis by comparing with the Raman spectra of standard fatty acids. Moreover, the present investigation, clearly distinguish the lipids from other macromolecules like protein, carbohydrate and photosynthetic pigments in whole cell. Finally, SERS based analysis dually by spectral and mapping techniques of lipid enriched S. quadricauda CASA-CC202 has been superimposed with Nile red staining of the same algal cells which unambiguously identify the neutral lipid components under the starved condition.

Improvement of phytoplankton culture isolation using single cell sorting by flow cytometry.

Flow cytometry provides a tool to physically sort single algal cells in order to obtain clonal cultures. During sorting, cells are submitted to physical stress factors such as high fluidic pressure, exposure to the laser beam, electrostatic charges, deflection through high voltage fields, and collisions with container surfaces. All of these can damage the cells of interest and success rates for initiation of cultures from flow-sorted cells are generally very low. We found that the addition of bovine serum albumin in the culture medium into which cells were sorted drastically improved the success of initiation of pico- and nano-eukaryotic phytoplankton strains. Adding a mixture of antibiotics (Penicillin, Neomycin, Streptomycin) to the medium in order to slow down bacterial growth further improved culture development. This approach was successfully used to isolate taxonomically diverse strains, including novel taxa, from a fresh sample obtained in the English Channel and from enrichment cultures established during an Atlantic meridional transect cruise. We anticipate that these improvements will be useful to clone or purify existing cultures and to isolate novel cultures from oceanic samples.

Optimized Nanoelectrode Geomerty for Enhanced Direct Extraction of Photosynthetic Electrons from Living Single Algal Cells

Plant cells highly efficiently convert solar energy into photosynthetic electrons during photosynthesis. The photosynthetic electrons (PEs) are transported via redox reactions between molecules in the thylakoid membrane of plant cells. Most of the PEs are utilized for cell growth and small fractions are stored in a form of carbohydrates within plant cells. There have been various approaches to harvest the PEs from the photosynthetic electron transfer chain during photosynthesis. These works have focused on indirect extraction of PEs from isolated photosynthetic components such as photosystem I (PSI) or fragments of thylakoid membrane that contains most of molecules involved in photosynthetic electron transfer. However, despite many advances made from those approaches, there are still challenges such as limited stability of isolated photosynthetic molecules and lowered efficiency due to use of mediators. We previously reported the feasibility of “direct” extraction of PEs from living single algal cells using AFM-compatible nanoelectrodes (NEs). Although the result demonstrated continuous extraction of PEs from living cells at high efficiency, fabrication of the customized NEs was expensive and had poor yield. More importantly, gradual leakage from algal cells occurred after NE insertion into plant cells, resulting in limited PE extraction for only up to an hour. In this study, we aimed to study NE geometry that enabled longer direct extraction of PEs from living algal cells that our previous work without using any mediator. For this, we developed horizontally-tilted cantilever NE system by which NE insertion into living cells could be optically monitored in situ and light-triggered PE extraction could be performed. A commercial AFM tip was custom-shaped into a cantilever with a nanowire (NW) at one end using focused ion beam (FIB). The NW was coated with Au and insulated with a Si3N4 passivation layer by CVD processes. For highly-localized electrochemical functions, another FIB milling was performed to expose the embedded Au only at the tip of the NW. First, we studied how the NW size affected the long-term stability of algal cells after NW insertion. Algal cells were stable for up to about 17 hours when they were inserted by NWs thinner than 500 nm, and they even proliferated after NW insertion. The electrochemical performance of the NW electrode was confirmed with the characteristics of an ultramicro electrode by running cyclic voltammetry analysis using potassium ferricyanide (K3[Fe(CN)6], 0.01M) as a redox system and potassium nitrate (KNO3, 0.1M) as an supporting electrolyte. Light-triggered electrical currents were measured after NW insertion into algal cells with light intensity of 99 μmol·m-2s-1 and potential of 0.4V (versus Ag/AgCl) applied to the NW. Potential-dependent analysis for photocurrents was performed to identify the donor of PEs. Disappearance of the light-triggered currents upon application of photosystem inhibitors also confirmed the currents originated from photosynthesis. Finally, long-term monitoring of cell stability and extraction of PEs was demonstrated for 17 hours after NW insertion into algal cells.

Raman and fluorescence microscopy sensing energy-transducing and energy-storing structures in microalgae

Chlorophylls and carotenoids are core components of photosynthetic energy transduction in algal cells, whereas starch, lipids, and polyphosphates represent energy reserves. All these biomolecules exhibit characteristic molecular vibrations that were sensed and localized in individual cells of Desmodesmus quadricauda and Chlorella vulgaris by confocal Raman microscopy. In the same cells, fluorescence of chlorophylls and of lipid bodies stained with Nile Red was mapped using the same instrument. In the first of the three consecutive scans, a low-power and short-exposure excitation by a green 532nm laser was used to map chlorophyll fluorescence. In the second scan, the full power of a 785nm laser was used for Raman mapping of carotenoids. The third scan was performed again with the 532nm laser to map non-fluorescent biomolecules such as lipids, proteins, starch, and polyphosphates. Before the third scan, chlorophyll fluorescence was suppressed by photobleaching a wide area using a strongly defocused 532nm laser beam. Raman microscopy was used for the first time to localize polyphosphate granules within a single algal cell in the context of other relevant bio-energetic structures. The new information represents an opportunity for algal cell phenotyping.

Black silicon SERS substrate: Effect of surface morphology on SERS detection and application of single algal cell analysis

In this study, we have investigated the effect of the surface morphology of the black silicon substrate on surface enhanced Raman spectroscopy (SERS) and explored its application of single algal cell detection. By adjusting the O2 and SF6 flow rates in the cryogenic plasma etching process, different surface morphologies of the black silicon substrate was produced without performing the lithographic process. It was found the Raman signals were better enhanced as the tip density of the black silicon substrate increased. In addition, as the thickness of the deposited gold layer increased, the SERS effect increased as well, which could be owing to the generation of more hot spots by bridging individual silicon tips through deposition of gold layer. For the black silicon substrate with tip density of 30tips/μm2 and covered by 400nm deposited gold layer, the detection limit of 10fM R6G solution concentration with uniform SERS effect across the substrate was achieved. Furthermore, detection of individual algal cell (Chlorella vulgaris) was performed at the SERS substrate as fabricated and the Raman signals of carotenoid and lipid were substantially enhanced.

Efficient coagulation of microalgae in cultures with filamentous fungi

To overcome the daunting technical barriers of algae biofuels and photosynthetic biorefineries, a novel cultivation technology has been developed to concentrate, harvest, and enhance microalgae-based biofuels and bioproducts through pelletization. The technology involves the co-cultivation of microalgae with fungi to achieve optimized pelletization with a 2-to-10-mm diameter. This pelletization enables the complete removal of single algal cells from the liquid medium to allow their extraction and harvest by simple filtration. In addition, the pelletization process results in significantly increased biomass, lipid, and bioproduct yields. If successfully scaled up, this technology has the potential to improve the sustainability and economic viability of the production of algal biofuels.

Analysis of single algal cells by combining mass spectrometry with Raman and fluorescence mapping

In order to investigate metabolic properties of single cells of freshwater algae (Haematococcus pluvialis), we implement matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) in combination with microspectroscopic mapping. Straightforward coupling of these two detection platforms was possible thanks to the self-aliquoting properties of micro-arrays for mass spectrometry (MAMS). Following Raman and fluorescence imaging, the isolated cells were covered with a MALDI matrix for targeted metabolic analysis by MALDI-MS. The three consecutive measurements carried out on the same cells yielded complementary information. Using this method, we were able to study the encystment of H. pluvialis - by monitoring the adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio during the build-up of astaxanthin in the cells as well as the release of β-carotene, the precursor of astaxanthin, into the cytosol.

Biosynthesis of Triacylglycerols (TAGs) in Plants and algae

Triacylglycerols (TAGs), which consist of three fatty acids bound to a glycerol backbone, are major storage lipids that accumulate in developing seeds, flower petals, pollen grains, and fruits of innumerous plant species. These storage lipids are of great nutritional and nutraceutical value and, thus, are a common source of edible oils for human consumption and industrial purposes. Two metabolic pathways for the production of TAGs have been clarified: an acyl CoA-dependent pathway and an acyl-CoA-independent pathway. Lipid metabolism, specially the pathways to fatty acids and TAG biosynthesis, is relatively well understood in plants, but poorly known in algae. It is generally accepted that the basic pathways of fatty acid and TAG biosynthesis in algae are analogous to those of higher plants. However, unlike higher plants where individual classes of lipids may be synthesized and localized in a specific cell, tissue or organ, the complete pathway, from carbon dioxide fixation to TAG synthesis and sequestration, takes place within a single algal cell. Another distinguishing feature of some algae is the large amounts of very long-chain polyunsaturated fatty acids (VLC-PUFAs) as major fatty acid components. Nowadays, the focus of attention in biotechnology is the isolation of novel fatty acid metabolizing genes, especially elongases and desaturases that are responsible for PUFAs synthesis, from different species of algae, and its transfer to plants. The aim is to boost the seed oil content and to generate desirable fatty acids in oilseed crops through genetic engineering approaches. This paper presents the current knowledge of the neutral storage lipids in plants and algae from fatty acid biosynthesis to TAG accumulation.

Effects of acidified seawater on coral calcification and symbiotic algae on the massive coral Porites australiensis

We investigated the effect of acidified seawater on calcification and symbiotic algae (zooxanthellae density, chlorophyll content per single algal cell, fluorescence yield ( Fv/ Fm)) on a massive coral, Porites australiensis, a common species in the Ryukyu Archipelago of Japan. We found that acidified seawater significantly decreased the calcification and fluorescence yield, but did not affect zooxanthellae density and chlorophyll content per single algal cell. This indicates low levels of photoacclimation to acidified seawater in this species, and this is contrary to the findings of previous studies of Acropora species. A significant correlation between calcification and fluorescence yield was observed, indicating the presence of a strong relationship between calcification and algal photosynthesis. Our results indicate that endosymbiont photosynthetic dysfunction may enhance the decrease of coral calcification in future acidified ocean conditions. Calcification and fluorescence yield among colonies clearly differed, showing that the response to acidified seawater is highly variable among colonies in natural coral populations.