Marine diatoms rose to prominence about 100 million years ago and today generate most of the organic matter that serves as food for life in the sea. They exist in a dilute world where compounds essential for growth are recycled and shared, and they greatly influence global climate, atmospheric carbon dioxide concentration and marine ecosystem function. How these essential organisms will respond to the rapidly changing conditions in today's oceans is critical for the health of the environment and is being uncovered by studies of their genomes.

Diatoms are unicellular photosynthetic microalgae existing ubiquitously in marine and freshwater environments. This review focuses on high-value compounds produced from diatoms, including chrysolaminarin (Chrl), eicosapentaenoic acid (EPA), and fucoxanthin (Fx), which can be applied in aquaculture, human health foods, pharmaceuticals, and cosmetics. In addition, this review provides an overview of their biosynthesis in diatoms and technologies for production. EPA and Fx typically accumulate synergistically in diatoms, while Chrl competes with EPA and Fx for carbon precursors. Several diatom strains have been employed that simultaneously accumulate these three compounds, but limitations and challenges still exist during commercialization. To address the bottleneck in biomass and high-value compound production, the optimization of cultivation parameters, the trophic mode, elicitor- or bacteria-assisted stimulations, and genetic modifications via mutant breeding, adaptive evolution engineering, and metabolic engineering have been developed in diatoms to establish improved technologies. Currently, large-scale cultivation of diatoms occurs mostly in open ponds and photobioreactors in autotrophic mode. Mixotrophic cultivation and coextraction approaches for multiple products represent novel strategies for economically enhancing the future production of biomass and high-value compounds on an industrial scale.

Fucoxanthin, a natural product of carotenoids, is a potential drug source obtained from marine algae. The special chemical structure of fucoxanthin has equipped it with a variety of biological activities. Several studies have indicated that fucoxanthin has a potential protective effect on a variety of inflammation-related diseases. This mechanism may be related to fucoxanthin's strong antioxidant capacity and gut microbiota regulation. The key molecules that require consideration include nuclear factor erythroid 2-related factor 2, Akt serine/threonine kinase/phosphatidylinositol-3-kinase, extracellular signal-regulated kinase, adenosine monophosphate (AMP)-dependent protein kinase, cAMP response element binding protein, and peroxisome proliferator-activated receptorgammacoactivator-1alpha. The study summarizes the recent progress in the research based on the protective effect of fucoxanthin and its related molecular mechanism, in addition to the potential use of fucoxanthin as a promising compound for human inflammation-related diseases.

We investigated the effects of purified eicosapentaenoic acid (EPA) on vascular endothelial function and free fatty acid composition in Japanese hyperlipidemic subjects. In subjects with hyperlipidemia (total cholesterol >/=220 mg/dL and/or triglycerides >/=150 mg/dL), lipid profile and forearm blood flow (FBF) during reactive hyperemia were determined before and 3 months after supplementation with 1800 mg/day EPA. Peak FBF during reactive hyperemia was lower in the hyperlipidemic group than the normolipidemic group. EPA supplementation did not change serum levels of total, HDL, or LDL cholesterol, apolipoproteins, remnant-like particle (RLP) cholesterol, RLP triglycerides, or malondialdehyde-modified LDL cholesterol. EPA supplementation did not change total free fatty acid levels in serum, but changed the fatty acid composition, with increased EPA and decreased linoleic acid, gamma-linolenic acid, and dihomo-gamma-linolenic acid. EPA supplementation recovered peak FBF after 3 months. Peak FBF recovery was correlated positively with EPA and EPA/arachidonic acid levels and correlated inversely with dihomo-gamma-linolenic acid. EPA supplementation restores endothelium-dependent vasodilatation in hyperlipidemic patients despite having no effect on serum cholesterol and triglyceride patterns. These results suggest that EPA supplementation may improve vascular function at least partly via changes in fatty acid composition.

Depression has become a common mental illness, and studies have shown that neuroinflammation is associated with depression. Ketamine is a rapid antidepressant. In order to obtain better antidepressant effects, it is necessary to explore the efficacy of combination therapy with ketamine and other antidepressants. DHA is an unsaturated fatty acid with excellent application prospects due to its safety and antidepressant effects. This study was designed to investigate the effect of ketamine combined with DHA on lipopolysaccharide-induced depression-like behavior. In behavioral experiments, lipopolysaccharide prolongs the immobility time of the forced swimming and tail suspension tests in rats and reduces the sucrose preference. The combination of ketamine and DHA can reverse these changes and work better than the single application. Nissl staining showed that ketamine combined with DHA can reverse the nerve damage caused by lipopolysaccharide. Cell morphology observation the combination of ketamine and DHA group was more complete than that of LPS group. The combination of ketamine and DHA significantly decreased the levels of IL-1, IL-6 and TNF-ain hippocampus and PC12 cells and increased the content of BDNF. Immunofluorescence results showed that ketamine combined with DHA can effectively inhibit PP65 nuclear translocation. Western blot results showed that ketamine combined with DHA can effectively inhibit the expression of NF-KB in hippocampus and PC12 cells, and increase the expression of P-CREB and BDNF. In summary, the combination of ketamine with DHA may be a more effective treatment for depression caused by inflammation and is mediated by inhibition of the inflammatory pathway.

Galactomannan (GM), 1,3-beta-D-glucan (BDG) and aspergillus-lateral flow device (LFD) are recognized as diagnostic tools for invasive aspergillosis (IA). The combined performance of these assays, however, is inconsistent in various studies. We undertook a meta-analysis of 13 studies involving 1513 patients to evaluate the utility of GM in combination with BDG or LFD for diagnosing IA. The pooled SEN, SPE, PLR, NLR and diagnostic odds ratio (DOR) were calculated and constructed to summarize the overall combined performance. Combining both positive results of GM and BDG assays leaded to the pooled SEN 0.49 (95%CI 0.27-0.72), SPE 0.98 (95%CI 0.94-1.00), PLR 31.68 (95%CI 5.36-187.37), NLR 0.52 (95%CI 0.32-0.84) and DOR 61.23 (95%CI 6.96-538.90). Comparing with GM and BDG assays, both positive results of GM and LFD leaded to high SEN, similar SPE, low PLR and NLR. At least one positive result of GM or LFD conferred great SEN 0.93 and low NLR 0.08. Both positive results of GM and BDG or LFD assay were in favor of confirming the existence of IA. And both negative results of GM and LFD were beneficial to rule out IA. Further studies with sufficient sample size should focus on the diagnostic performance and cost-effectiveness of these combined tests in clinical setting.

Marine diatoms have recently gained much attention as they are expected to be a promising resource for sustainable production of bioactive compounds such as carotenoids and biofuels as a future clean energy solution. To develop photosynthetic cell factories, it is important to improve diatoms for value-added products. In this study, we utilized UVC radiation to induce mutations in the marine diatom Phaeodactylum tricornutum and screened strains with enhanced accumulation of neutral lipids and carotenoids. Adaptive laboratory evolution (ALE) was also used in parallel to develop altered phenotypic and biological functions in P. tricornutum and it was reported for the first time that ALE was successfully applied on diatoms for the enhancement of growth performance and productivity of value-added carotenoids to date. Liquid chromatography-mass spectrometry (LC-MS) was utilized to study the composition of major pigments in the wild type P. tricornutum, UV mutants and ALE strains. UVC radiated strains exhibited higher accumulation of fucoxanthin as well as neutral lipids compared to their wild type counterpart. In addition to UV mutagenesis, P. tricornutum strains developed by ALE also yielded enhanced biomass production and fucoxanthin accumulation under combined red and blue light. In short, both UV mutagenesis and ALE appeared as an effective approach to developing desired phenotypes in the marine diatoms via electromagnetic radiation-induced oxidative stress.

A model for the prediction of eicosapentaenoic acid (EPA) productivity from Phaeodactylum tricornutum cultures that takes into account the existence of photolimitation and photoinhibition of growth under outdoor conditions is presented. The effects of the external irradiance on the culture surface, the average irradiance inside the culture, and the light regime at which the cells are exposed on pigments and EPA content are studied. The chlorophyll content decreases exponentially with the average irradiance, whereas the carotenoids content increases linearly with the external irradiance due to a higher extension of photoinhibition. A decrease in the fatty acid content of the biomass with irradiance on reactor surface is observed when photoinhibition becomes relevant. The average irradiance within the culture mainly influenced the fatty acid profile of the biomass. As the average irradiance becomes higher, percentages of saturated and monounsaturated fatty acids decrease, increasing the portion of EPA. By taking into account the different relationships among pigment and EPA content with the irradiance, the variation in EPA productivity over the year can be simulated as a function of average and external irradiance. For the two photobioreactors employed the maximum EPA productivity is attained in spring and fall (30 mg L(-1) day(-1) for tube diameter 0. 06 m and 50 mg L(-1) day(-1) for tube diameter 0.03 m). In winter, the biomass productivity is limited by low light availability although the EPA content is maximum. In summer, the biomass productivity is higher although the EPA content diminished by photoinhibition; the higher the dilution rate, the lower the minimum. Thus, the conditions that increase the biomass productivity and the polyunsaturated fatty acids content are in opposition, the optimum being reached by operating under photolimitation with high growth rates in order to produce a high proportion of polyunsaturated fatty acids.

Pilot-scale (0.19 m column diameter, 2 m tall, and 60 L working volume) outdoor vertical bubble column (BC) and airlift photobioreactors (a split-cylinder (SC) and a draft-tube airlift device (DT)) were compared for fed-batch mixotrophic culture of the microalga Phaeodactylum tricornutum UTEX 640. The cultures were started photoautotrophically until the onset of a quasi-steady-state biomass concentration of 3.4 g L(-)(1). After this, the cultures were supplemented with organic nutrient (glycerol 0.1 M) and a reduced nitrogen source, resulting in an immediate growth rate boost, which was repeated with successive additions of nutrients in all three photobioreactors. During this period the biomass productivity was enhanced compared to photoautotrophic cultures in the three reactors, although differences were found among them. These could be attributed to the different hydrodynamic behavior influencing the transport phenomena inside the cultures. A 25.4 g L(-)(1) maximum biomass concentration was attained in the SC. Further additions of nutrients did not promote any more growth. The consumption of glycerol was quantitative in the first additions but slowed at high biomass concentration, suggesting that a minimum amount of light is needed to sustain growth. No significant effect of the supplied organic nutrient on carotenoids and chlorophylls content was observed, although it had a profound effect on the fatty acid composition. Eicosapentaenoic acid (EPA) content was increased up to 3% (DW) in mixotrophic growth, giving a productivity of 56 mg L(-)(1) d(-)(1), a significant increase compared to the photoautotrophic control, which yielded a maximum EPA content of 1.9% (DW) and a productivity of 18 mg L(-)(1) d(-)(1). The maximum biomass and EPA volumetric yields obtained in this work are comparable with those reported for commercial photoautotrophic monoculture of large quantities of P. tricornutum in closed continuous-run tubular loop bioreactors with tubes that are typically less than 0.08 m in diameter. When the comparison is established in terms of productivities based on the land area occupied, the vertical airlift and bubble-column bioreactors are extraordinarily more productive.

Phaeodactylum tricornutum is a widely studied diatom and has been proposed as a source of oil and polyunsaturated fatty acids (PUFA), particularly eicosapentaenoic acid (EPA). Recent studies indicate that lipid accumulation occurs under nutritional stress. Aim of this research was to determine how changes in nitrogen availability affect productivity, oil yield, and fatty acid (FA) composition of P. tricornutum UTEX 640. After preliminary laboratory trials, outdoor experiments were carried out in 40-L GWP(R) reactors under different nitrogen regimes in batch. Nitrogen replete cultures achieved the highest productivity of biomass (about 18 g m(-2) d(-1) ) and EPA (about 0.35 g m(-2) d(-1) ), whereas nitrogen-starved cultures achieved the highest FA productivity (about 2.6 g m(-2) d(-1) ). The annual potential yield of P. tricornutum grown outdoors in GWP(R) reactors is 730 kg of EPA per hectare under nutrient-replete conditions and 5,800 kg of FA per hectare under nitrogen starvation. Biotechnol. Bioeng. 2017;114: 2204-2210. (c) 2017 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

Microalgae are recognized as promising producers of many bioactive products, but their utility is limited due to high production costs. We subjected the marine diatom Odontella aurita to three nitrogen supply regimes [initial low nitrogen (ILN), initial high nitrogen (IHN), and initial high nitrogen plus supplementary nitrogen (SN)] to investigate the accumulation of three high-value bioactive components: fucoxanthin, chrysolaminarin and eicosapentaenoic acid (EPA). We found that SN conditions maximized fucoxanthin accumulation: a maximum productivity of 6.01 mg L(-1) d(-1) was obtained, a 4.32-fold and 1.42-fold increase over production in the ILN and IHN groups, respectively. After nitrogen was depleted in the growth medium, chrysolaminarin became the dominant energy storage compound. Chrysolaminarin content rose to 60.33% of dry weight (DW) in the ILN group, and 46.27% of DW in the IHN group. Variations in fatty acid composition across the different nitrogen supply regimes indicated that EPA primarily accumulated in the glycolipids, especially when nitrogen supply was sufficient. The maximum productivity of chrysolaminarin (161.55 mg L(-1) d(-1)) and EPA (9.37 mg L(-1) d(-1)) was observed in the IHN group. However, IHN conditions did not maximize overall content of either compound. Our results demonstrated that O. aurita is potentially useful as a producer of a variety of bioactive products; the compounds produced by this species can be controlled by altering the nitrogen supply.

The aim of this study was to determine a compatible method for co-production of fucoxanthin and eicosapentaenoic acid of diatom Nitzschia laevis by mixotrophic and heterotrophic cultivation modes in view of cell growth, targeting products' contents, photosynthesis-related characteristics and carbon partitioning. The results showed that mixotrophic mode enhanced fucoxanthin and eicosapentaenoic acid yields by increasing their precursors of pyruvate and acetyl-CoA at the expense of starch. The increase of chlorophylls and glyceraldehyde 3-phosphate indicated the development of Calvin cycle and carbon repartitioning in mixotrophic mode. Consequently, microalgal cells in mixotrophic mode achieved much higher fucoxanthin (60.12%) and eicosapentaenoic acid (50.67%) contents, and lower starch content (30.2%) compared with heterotrophic mode. Furthermore, fucoxanthin content was positively correlated with eicosapentaenoic acid content (adjusted R(2)=0.96). Taken together, these results showed that the mixotrophic mode could be a promising approach for the co-production of fucoxanthin and eicosapentaenoic acid by Nitzschia laevis.

Under nutrient deplete conditions, diatoms accumulate between 15% to 25% of their dry weight as lipids, primarily as triacylglycerols (TAGs). As in most eukaryotes, these organisms produce TAGs via the acyl-CoA dependent Kennedy pathway. The last step in this pathway is catalyzed by diacylglycerol acyltransferase (DGAT) that acylates diacylglycerol (DAG) to produce TAG. To test our hypothesis that DGAT plays a major role in controlling the flux of carbon towards lipids, we overexpressed a specific type II DGAT gene, DGAT2D, in the model diatom Phaeodactylum tricornutum. The transformants had 50- to 100-fold higher DGAT2D mRNA levels and the abundance of the enzyme increased 30- to 50-fold. More important, these cells had a 2-fold higher total lipid content and incorporated carbon into lipids more efficiently than the wild type (WT) while growing only 15% slower at light saturation. Based on a flux analysis using (13) C as a tracer, we found that the increase in lipids was achieved via increased fluxes through pyruvate and acetyl-CoA. Our results reveal overexpression of DAGT2D increases the flux of photosynthetically fixed carbon towards lipids, and leads to a higher lipid content than exponentially grown WT cells.

Biologically derived fuels are viable alternatives to traditional fossil fuels, and microalgae are a particularly promising source, but improvements are required throughout the production process to increase productivity and reduce cost. Metabolic engineering to increase yields of biofuel-relevant lipids in these organisms without compromising growth is an important aspect of advancing economic feasibility. We report that the targeted knockdown of a multifunctional lipase/phospholipase/acyltransferase increased lipid yields without affecting growth in the diatom Thalassiosira pseudonana. Antisense-expressing knockdown strains 1A6 and 1B1 exhibited wild-type-like growth and increased lipid content under both continuous light and alternating light/dark conditions. Strains 1A6 and 1B1, respectively, contained 2.4- and 3.3-fold higher lipid content than wild-type during exponential growth, and 4.1- and 3.2-fold higher lipid content than wild-type after 40 h of silicon starvation. Analyses of fatty acids, lipid classes, and membrane stability in the transgenic strains suggest a role for this enzyme in membrane lipid turnover and lipid homeostasis. These results demonstrate that targeted metabolic manipulations can be used to increase lipid accumulation in eukaryotic microalgae without compromising growth.

Most microalgae are obligate photoautotrophs and their growth is strictly dependent on the generation of photosynthetically derived energy. We show that the microalga Phaeodactylum tricornutum can be genetically engineered to thrive on exogenous glucose in the absence of light through the introduction of a gene encoding a glucose transporter (glut1 or hup1). This demonstrates that a fundamental change in the metabolism of an organism can be accomplished through the introduction of a single gene. This also represents progress toward the use of fermentation technology for large-scale commercial exploitation of algae by reducing limitations associated with light-dependent growth.

Background: Microalgae accumulate lipids when exposed to stressful conditions such as nutrient limitation that can be used to generate biofuels. Nitrogen limitation or deprivation is a strategy widely employed to elicit this response. However, this strategy is associated with a reduction in the microalgal growth, leading to overall poor lipid productivities. Here, we investigated the combined effect of a reduced source of nitrogen (ammonium) and super-saturating light intensities on the growth and induction of lipid accumulation in two model but diverse microalgal species, Phaeodactylum tricornutum and Nannochloropsis oceanica. We hypothesized that the lower energy cost of assimilating ammonium would allow the organisms to use more reductant power for lipid biosynthesis without compromising growth and that this would be further stimulated by the effect of high light (1000 micromol m(-2) s(-1)) stress. We studied the changes in growth and physiology of both species when grown in culture media that either contained nitrate or ammonium as the nitrogen source, and an additional medium that contained ammonium with tungsten in place of molybdenum and compared this with growth in media without nitrogen. We focused our investigation on the early stages of exposure to the treatments to correspond to events relevant to induction of lipid accumulation in these two species. Results: At super-saturating light intensities, lipid productivity in P. tricornutum increased twofold when grown in ammonium compared to nitrogen free medium that increased further when tungsten was present in the medium in place of molybdenum. Conversely, N. oceanica growth and physiology was not compromised by the high light intensities used, and the use of ammonium had a negative effect on the lipid productivity, which was even more marked when tungsten was present. Conclusions: Whilst the use of ammonium and super-saturating light intensities in P. tricornutum was revealed to be a good strategy for increasing lipid biosynthesis, no changes in the lipid productivity of N. oceanica were observed, under these conditions. Both results provide relevant direction for the better design of processes to produce biofuels in microalgae by manipulating growth conditions without the need to subject them to genetic engineering manipulation.

We determined the quantum requirements for growth (1/varphimu ) and fatty acid (FA) biosynthesis (1/varphiFA ) in the marine diatom, Phaeodactylum tricornutum, grown in nutrient replete conditions with nitrate or ammonium as nitrogen sources, and under nitrogen limitation, achieved by transferring cells into nitrogen free medium or by inhibiting nitrate assimilation with tungstate. A treatment in which tungstate was supplemented to cells grown with ammonium was also included. In nutrient replete conditions, cells grew exponentially and possessed virtually identical 1/varphimu of 40-44 mol photons . mol C(-1) . In parallel, 1/varphiFA varied between 380 and 409 mol photons . mol C(-1) in the presence of nitrate, but declined to 348 mol photons . mol C(-1) with ammonium and to 250 mol photons . mol C(-1) with ammonium plus tungstate, indicating an increase in the efficiency of FA biosynthesis relative to cells grown on nitrate of 8% and 35%, respectively. While the molecular mechanism for this effect remains poorly understood, the results unambiguously reveal that cells grown on ammonium are able to direct more reductant to lipids. This analysis suggests that when cells are grown with a reduced nitrogen source, fatty acid biosynthesis can effectively become a sink for excess absorbed light, compensating for the absence of energetically demanding nitrate assimilation reactions. Our data further suggest that optimal lipid production efficiency is achieved when cells are in exponential growth, when nitrate assimilation is inhibited, and ammonium is the sole nitrogen source.

Marine microalgae exhibit a diversified phosphorus physiology and have also been recently found to show high inter-taxa variability in their phosphate induced-polar lipids' remodelling. Identification of phosphorus physiology aspects that are more related to lipid remodelling can contribute to better understanding of such intricate phytoplankton lipid metabolism. Therefore, some aspects of phosphorus physiology related to its uptake, storage and use were evaluated in a taxonomically diversified group of nine marine microalgae that was arranged into three subgroups, each of them including species showing similar polar lipid responses to phosphate. Luxury phosphate uptake (PU) was the physiological aspect best associated to microalgal polar lipid metabolism as it was maximal in species (Picochlorum atomus, Tetraselmis suecica and Nannochloropsis gaditana) that were able to counterbalance between phospholipids (PL) and betaine lipids (BL). Cryptophytes (Rhodomonas baltica, Chroomonas placoidea), characterized by their constitutive BL and flexible PL contents in response to phosphate, had almost no luxury PU and showed higher phosphorus cell quota (QP) under phosphate deprivation. Haptophyes (Isochrysis galbana, Diacronema vlkianum), with constitutive BL contents and permanently minimal PL contents, showed the lowest QP when deprived of phosphate while their luxury PU was below that for green microalgae. Induction of alkaline phosphatase activity following phosphate depletion was maximal in diatoms (Phaeodactylum tricornutum, Chaetoceros gracilis) and I. galbana but it was unrelated to lipid remodelling. Despite strong influence of taxonomy, polar lipid remodelling accounted for 38.8% of total variation when microalgae were ordinated using their physiological responses to phosphorus as descriptive variables.

Phosphorus is an important macronutrient. To understand the molecular and cellular responses to phosphorus stress better, transcriptome profiling in combination with biochemical investigations was conducted in the model diatom Phaeodactylum tricornutum. Out of 10 402 predicted genes, 2491 and 405 genes were significantly upregulated or downregulated respectively. Unsurprisingly, genes associated with phosphate uptake were upregulated, such as the phosphate transporters and alkaline phosphatases. Genes encoding stress-shock proteins were accordingly upregulated, including genes associated with stress-responsive proteins, signal transduction and secondary metabolism. Additionally, genes related to protein translation, carbon fixation, glycolysis and the citric acid cycle were also upregulated. Genes associated with gene transcription were downregulated, thereby resulting in the upregulation of translation to compensate for the limited supply of messenger RNA. The downregulation of genes related to beta-oxidation could contribute to the accumulation of fatty acids. Accordingly, triacylglycerols, which are important for energy storage, were determined to increase by 1.65-fold. Intracellular membranes, other than chloroplast membranes, tended to be dispersed; this finding was in accordance with the increased transcription of a total of 11 genes encoding putative phospholipases. Taken together, this work revealed the coordination of multiple metabolic pathways and certain key genes in the adaptation of P. tricornutum to phosphorus stress.

Diatoms are the most successful biomass producers worldwide. Therefore, physiological and chemical methods to measure the cell response to a variety of abiotic factors are the focus of recent research. We used the two model diatoms Cyclotella meneghiniana and Skeletonema costatum for the development of Fourier transform infrared (FTIR) spectroscopy-based methods to measure simultaneously the elemental composition of the cells and their cell-specific physiological properties. The cells were grown in chemostat cultures to study the response of Si limitation. The model organisms showed different reactions in terms of their cell properties. Si limitation was accompanied by a drop in the growth rate, a reduced content in Si per cell and a decreased Si : C ratio. Furthermore, the C allocation pattern was changed in both diatoms under Si limitation, as shown by FTIR spectroscopy. Moreover, we used FTIR spectra to develop PLS (partial least square) regression methods to predict the Si content and the Si : C ratio for single as well as multiple species. All PLS regression models were validated by standard chemical methods and showed good prediction accuracy, with the coefficient of determination R(2) being >/=0.93. We could show that it is possible to monitor phytoplankton properties such as C allocation, the Si content and the Si : C ratio at the same time via FTIR spectroscopy.

For 40 million years, diatoms have dominated the reverse weathering of silica on Earth. These photosynthetic protists take up dissolved silicic acid from the water and precipitate opaline silica to form their cell wall. We show that the biosilica of diatoms is an effective pH buffer, enabling the enzymatic conversion of bicarbonate to CO2, an important step in inorganic carbon acquisition by these organisms. Because diatoms are responsible for one-quarter of global primary production and for a large fraction of the carbon exported to the deep sea, the global cycles of Si and C may be linked mechanistically.

Phaeodactylum tricornutum Bohlin is an ideal model diatom; its complete genome is known, and it is an important economic microalgae. Although silicon is not required in laboratory and factory culture of this species, previous studies have shown that silicon starvation can lead to differential expression of miRNAs. The role that silicon plays in P. tricornutum growth in nature is poorly understood. In this study, we compared the growth rate of silicon starved P. tricornutum with that of normal cultured cells under different culture conditions. Pigment analysis, photosynthesis measurement, lipid analysis, and proteomic analysis showed that silicon plays an important role in P. tricornutum growth and that its presence allows the organism to grow well under green light and low temperature.