AUROMEGA

• Eide, Marta; Goksøyr, Anders; Yadetie, Fekadu; Gilabert, Alejandra; Bartosova, Zdenka & Frøysa, Håvard Guldbrandsen [Show all 15 contributors for this article] (2023). Integrative omics-analysis of lipid metabolism regulation by peroxisome proliferator-activated receptor a and b agonists in male Atlantic cod. Frontiers in Physiology. 14. doi: 10.3389/fphys.2023.1129089. Full text in Research Archive Show summary

  Lipid metabolism is essential in maintaining energy homeostasis in multicellular organisms. In vertebrates, the peroxisome proliferator-activated receptors (PPARs, NR1C) regulate the expression of many genes involved in these processes. Atlantic cod (Gadus morhua) is an important fish species in the North Atlantic ecosystem and in human nutrition, with a highly fatty liver. Here we study the involvement of Atlantic cod Ppar a and b subtypes in systemic regulation of lipid metabolism using two model agonists after in vivo exposure. WY-14,643, a specific PPARA ligand in mammals, activated cod Ppara1 and Ppara2 in vitro. In vivo, WY-14,643 caused a shift in lipid transport both at transcriptional and translational level in cod. However, WY-14,643 induced fewer genes in the fatty acid beta-oxidation pathway compared to that observed in rodents. Although GW501516 serves as a specific PPARB/D ligand in mammals, this compound activated cod Ppara1 and Ppara2 as well as Pparb in vitro. In vivo, it further induced transcription of Ppar target genes and caused changes in lipid composition of liver and plasma. The integrative approach provide a foundation for understanding how Ppars are engaged in regulating lipid metabolism in Atlantic cod physiology. We have shown that WY-14,643 and GW501516 activate Atlantic cod Ppara and Pparb, affect genes in lipid metabolism pathways, and induce changes in the lipid composition in plasma and liver microsomal membranes. Particularly, the combined transcriptomic, proteomics and lipidomics analyses revealed that effects of WY-14,643 on lipid metabolism are similar to what is known in mammalian studies, suggesting conservation of Ppara functions in mediating lipid metabolic processes in fish. The alterations in the lipid profiles observed after Ppar agonist exposure suggest that other chemicals with similar Ppar receptor affinities may cause disturbances in the lipid regulation of fish.

• Rau, E-Ming; Aasen, Inga Marie; Bartosova, Zdenka; Bruheim, Per & Ertesvåg, Helga (2023). Utilizing lipidomics and fatty acid synthase inhibitors to explore lipid accumulation in two thraustochytrid species. Algal Research. ISSN 2211-9264. 71. doi: 10.1016/j.algal.2023.103091. Full text in Research Archive Show summary

  Thraustochytrids are marine protists with an excellent ability to produce health-beneficial docosahexaenoic acid (DHA)-rich lipids. Since the demand for DHA sources for food and feed is increasing, a deeper understanding of the potential to enhance the DHA-production in thraustochytrids is important for a sustainable DHA supply. In most thraustochytrids, including the strains used in this work, DHA is synthesized by a polyketide synthase-like pathway (PKS), and not through the common fatty acid synthetase (FAS) pathway. Both pathways use the same precursors. The aim of this study was to determine if inhibiting the production of fatty acids (FA) through the FAS pathway under nitrogen starvation would result in higher net DHA production rates measured as DHA content, and if the channeling of the synthesized fatty acids to different lipids species is similar in two different thraustochytrid strains. We found that the DHA production rates in Aurantiochytrium limacinum SR21 and Aurantiochytrium sp. T66 were not affected when treated with the FAS-inhibitor cerulenin, despite a reduction of FAS-derived FAs. This indicates that precursor availability is less likely to be the limiting factor for DHA synthesis. Still, cerulenin-treatment in the lipid accumulation phase resulted in higher concentrations of the triacylglycerol (TAG) TG(22:6/22:6/22:6) than in the untreated cells after three hours, demonstrating that FAS inhibition is a possible strategy to enhance the content of DHA-rich lipids. Moreover, the relatively high abundance of the diacylglycerol DG(22:6/22:6) suggests the presence of an obstacle for using DG(22:6/22:6) as substrate to synthesize DHA-rich TAGs, a step that potentially can be improved by metabolic engineering.

• Rau, E-Ming; Bartosova, Zdenka; Kristiansen, Kåre Andre; Aasen, Inga Marie; Bruheim, Per & Ertesvåg, Helga (2022). Overexpression of two new acyl-CoA:diacylglycerol acyltransferase 2-like acyl-CoA:sterol acyltransferases enhanced squalene accumulation in Aurantiochytrium limacinum. Frontiers in Microbiology. 13. doi: 10.3389/fmicb.2022.822254. Full text in Research Archive Show summary

  Thraustochytrids are heterotrophic marine eukaryotes known to accumulate large amounts of triacylglycerols, and they also synthesize terpenoids like carotenoids and squalene, which all have an increasing market demand. However, a more extensive knowledge of the lipid metabolism is needed to develop thraustochytrids for profitable biomanufacturing. In this study, two putative type-2 Acyl-CoA:diacylglycerol acyltransferases (DGAT2) genes of Aurantiochytrium sp. T66, T66ASATa, and T66ASATb, and their homologs in Aurantiochytrium limacinum SR21, AlASATa and AlASATb, were characterized. In A. limacinum SR21, genomic knockout of AlASATb reduced the amount of the steryl esters of palmitic acid, SE (16:0), and docosahexaenoic acid, SE (22:6). The double mutant of AlASATa and AlASATb produced even less of these steryl esters. The expression and overexpression of T66ASATb and AlASATb, respectively, enhanced SE (16:0) and SE (22:6) production more significantly than those of T66ASATa and AlASATa. In contrast, these mutations did not significantly change the level of triacylglycerols or other lipid classes. The results suggest that the four genes encoded proteins possessing acyl-CoA:sterol acyltransferase (ASAT) activity synthesizing both SE (16:0) and SE (22:6), but with the contribution from AlASATb and T66ASATb being more important than that of AlASATa and T66ASATa. Furthermore, the expression and overexpression of T66ASATb and AlASATb enhanced squalene accumulation in SR21 by up to 88%. The discovery highlights the functional diversity of DGAT2-like proteins and provides valuable information on steryl ester and squalene synthesis in thraustochytrids, paving the way to enhance squalene production through metabolic engineering.

• Rau, E-Ming; Aasen, Inga Marie & Ertesvåg, Helga (2021). A non-canonical Δ9-desaturase synthesizing palmitoleic acid identified in the thraustochytrid Aurantiochytrium sp. T66. Applied Microbiology and Biotechnology. ISSN 0175-7598. 105, p. 5931–5941. doi: 10.1007/s00253-021-11425-5. Full text in Research Archive Show summary

  Thraustochytrids are oleaginous marine eukaryotic microbes currently used to produce the essential omega-3 fatty acid docosahexaenoic acid (DHA, C22:6 n-3). To improve the production of this essential fatty acid by strain engineering, it is important to deeply understand how thraustochytrids synthesize fatty acids. While DHA is synthesized by a dedicated enzyme complex, other fatty acids are probably synthesized by the fatty acid synthase, followed by desaturases and elongases. Which unsaturated fatty acids are produced differs between different thraustochytrid genera and species; for example, Aurantiochytrium sp. T66, but not Aurantiochytrium limacinum SR21, synthesizes palmitoleic acid (C16:1 n-7) and vaccenic acid (C18:1 n-7). How strain T66 can produce these fatty acids has not been known, because BLAST analyses suggest that strain T66 does not encode any Δ9-desaturase-like enzyme. However, it does encode one Δ12-desaturase-like enzyme. In this study, the latter enzyme was expressed in A. limacinum SR21, and both C16:1 n-7 and C18:1 n-7 could be detected in the transgenic cells. Our results show that this desaturase, annotated T66Des9, is a Δ9-desaturase accepting C16:0 as a substrate. Phylogenetic studies indicate that the corresponding gene probably has evolved from a Δ12-desaturase-encoding gene. This possibility has not been reported earlier and is important to consider when one tries to deduce the potential a given organism has for producing unsaturated fatty acids based on its genome sequence alone.

• Rau, E-Ming & Ertesvåg, Helga (2021). Method Development Progress in Genetic Engineering of Thraustochytrids. Marine Drugs. 19(9). doi: 10.3390/MD19090515. Full text in Research Archive Show summary

  Thraustochytrids are unicellular, heterotrophic marine eukaryotes. Some species are known to store surplus carbon as intracellular lipids, and these also contain the long-chain polyunsaturated fatty acid docosahexaenoic acid (DHA). Most vertebrates are unable to synthesize sufficient amounts of DHA, and this fatty acid is essential for, e.g., marine fish, domesticated animals, and humans. Thraustochytrids may also produce other commercially valuable fatty acids and isoprenoids. Due to the great potential of thraustochytrids as producers of DHA and other lipid-related molecules, a need for more knowledge on this group of organisms is needed. This necessitates the ability to do genetic manipulation of the different strains. Thus far, this has been obtained for a few strains, while it has failed for other strains. Here, we systematically review the genetic transformation methods used for different thraustochytrid strains, with the aim of aiding studies on strains not yet successfully transformed. The designs of transformation cassettes are also described and compared. Moreover, the potential problems when trying to establish transformation protocols in new thraustochytrid species/strains are discussed, along with suggestions utilized in other organisms to overcome similar challenges. The approaches discussed in this review could be a starting point when designing protocols for other non-model organisms.

• Bartosova, Zdenka; Gonzalez, Susana Villa; Voigt, Andre & Bruheim, Per (2021). High throughput semi-quantitative UHPSFC-MS/MS lipid profiling and lipid class determination. Journal of Chromatographic Science. ISSN 0021-9665. 59(7), p. 670–680. doi: 10.1093/chromsci/bmaa121. Full text in Research Archive
• Bartosova, Zdenka; Ertesvåg, Helga; Nyfløt, Eirin Lishaugen; Kämpe, Kristoffer; Aasen, Inga Marie & Bruheim, Per (2021). Combined Metabolome and Lipidome analyses for in-depth characterization of lipid accumulation in the DHA producing Aurantiochytrium sp. T66. Metabolites. 11(3). doi: 10.3390/metabo11030135. Full text in Research Archive Show summary

  Thraustochytrids are marine heterotrophic microorganisms known for their potential to accumulate docosahexaenoic acid (DHA)-enriched lipids. There have been many attempts to improve thraustochytrid DHA bioprocesses, especially through traditional optimization of cultivation and media conditions. Nevertheless, thraustochytrid-based bioprocesses are still not commercially competitive for high volume-low cost production of DHA. Thus, it is realized that genetic and metabolic engineering strategies are needed for the development of commercially competitive thraustochytrid DHA cell factories. Here, we present an analytical workflow for high resolution phenotyping at metabolite and lipid levels to generate deeper insight into the thraustochytrid physiology, with particular focus on central carbon and redox metabolism. We use time-series sampling during unlimited growth and nitrogen depleted triggering of DHA synthesis and lipid accumulation (LA) to show-case our methodology. The mass spectrometric absolute quantitative metabolite profiling covered glycolytic, pentose phosphate pathway (PPP) and tricarboxylic acid cycle (TCA) metabolites, amino acids, complete (deoxy)nucleoside phosphate pools, CoA and NAD metabolites, while semiquantitative high-resolution supercritical fluid chromatography MS/MS was applied for the lipid profiling. Interestingly, trace amounts of a triacylglycerols (TG) with DHA incorporated in all three acyl positions was detected, while TGs 16:0_16:0_22:6 and 16:0_22:6_22:6 were among the dominant lipid species. The metabolite profiling data indicated that lipid accumulation is not limited by availability of the acyl chain carbon precursor acetyl-CoA nor reducing power (NADPH) but rather points to the TG head group precursor glycerol-3-phosphate as the potential cause at the metabolite level for the gradual decline in lipid production throughout the cultivation. This high-resolution phenotyping provides new knowledge of changes in the central metabolism during growth and LA in thraustochytrids and will guide target selection for metabolic engineering needed for further improvements of this DHA cell factory.

• Røst, Lisa Marie; Thorfinnsdottir, Lilja Brekke; Kumar, Kanhaiya; Fuchino, Katsuya; Langørgen, Ida Eide & Bartosova, Zdenka [Show all 8 contributors for this article] (2020). Absolute Quantification of the Central Carbon Metabolome in Eight Commonly Applied Prokaryotic and Eukaryotic Model Systems. Metabolites. 10(74). doi: 10.3390/metabo10020074. Full text in Research Archive Show summary

  Absolute quantification of intracellular metabolite pools is a prerequisite for modeling and in-depth biological interpretation of metabolomics data. It is the final step of an elaborate metabolomics workflow, with challenges associated with all steps—from sampling to quantifying the physicochemically diverse metabolite pool. Chromatographic separation combined with mass spectrometric (MS) detection is the superior platform for high coverage, selective, and sensitive detection of metabolites. Herein, we apply our quantitative MS-metabolomics workflow to measure and present the central carbon metabolome of a panel of commonly applied biological model systems. The workflow includes three chromatographic methods combined with isotope dilution tandem mass spectrometry to allow for absolute quantification of 68 metabolites of glycolysis, the pentose phosphate pathway, the tricarboxylic acid cycle, and the amino acid and (deoxy) nucleoside pools. The biological model systems; Bacillus subtilis, Saccharomyces cerevisiae, two microalgal species, and four human cell lines were all cultured in commonly applied culture media and sampled in exponential growth phase. Both literature and databases are scarce with comprehensive metabolite datasets, and existing entries range over several orders of magnitude. The workflow and metabolite panel presented herein can be employed to expand the list of reference metabolomes, as encouraged by the metabolomics community, in a continued effort to develop and refine high-quality quantitative metabolomics workflows.

• Røst, Lisa Marie; Darestani, Armaghan Shafaei; Fuchino, Katsuya & Bruheim, Per (2020). Zwitterionic HILIC tandem mass spectrometry with isotope dilution for rapid, sensitive and robust quantification of pyridine nucleotides in biological extracts. Journal of chromatography. B. ISSN 1570-0232. 1144, p. 1–12. doi: 10.1016/j.jchromb.2020.122078. Full text in Research Archive Show summary

  The pyridine nucleotides nicotineamide adenine dinucleotide (NAD) and nicotineamide adenine dinucleotide phosphate (NADP) are conserved coenzymes across all domains of life, and are involved in more than 200 different hydride transfer reactions supporting essential catabolic and anabolic functions. The intracellular levels of these metabolites, and the ratio of their oxidized to reduced forms regulate an extensive network of reactions ranging beyond metabolism. Hence, monitoring their intracellular levels provides information about, but not limited to, the metabolic state of a cell or tissue. Interconversion between oxidized and reduced forms, varying pH liability and varying intracellular concentrations of the different species leaves absolute quantification of the pyridine nucleotides analytically challenging. These polar metabolites are poorly retained on conventional reverseed-phase stationary phases without ion-pair reagents that contaminates the LC-system. Herein we demonstrate that zwitterionic HILIC-tandem mass spectroemtry can be applied to successfully resolve the pyridine nucleotides in biological extracts in a fast, robust and highly sensitive way. The presented method applies isotope dilution to compensate potential loss of these labile metabolites and is validated for low, medium and high biomass samples of two popular biological model systems; Escherichia coli and the human cell line JJN-3. High stability and rapid sample preparation without solvent removal allows for long sequence runs, making this method ideal for high-throughput analysis of biological extracts.

• Heggeset, Tonje Marita Bjerkan; Ertesvåg, Helga; Liu, Bin; Ellingsen, Trond Erling; Vadstein, Olav & Aasen, Inga Marie (2019). Lipid and DHA-production in Aurantiochytrium sp. – Responses to nitrogen starvation and oxygen limitation revealed by analyses of production kinetics and global transcriptomes. Scientific Reports. 9(19470), p. 1–13. doi: 10.1038/s41598-019-55902-4. Full text in Research Archive Show summary

  Thraustochytrids of the genera Schizochytrium and Aurantiochytrium accumulate oils rich in the essential, marine n3 fatty acid docosahexaenoic acid (DHA). DHA production in Aurantiochytrium sp T66 was studied with the aim to provide more knowledge about factors that affect the DHA-productivities and the contributions of the two enzyme systems used for fatty acid synthesis in thraustochytrids, fatty acid synthetase (FAS) and PUFA-synthase. Fermentations with nitrogen starvation, which is well-known to initiate lipid accumulation in oleaginous organisms, were compared to fermentations with nitrogen in excess, obtained by oxygen limitation. The specific productivities of fatty acids originating from FAS were considerably higher under nitrogen starvation than with nitrogen in excess, while the specific productivities of DHA were the same at both conditions. Global transcriptome analysis showed significant up-regulation of FAS under N-deficient conditions, while the PUFA-synthase genes were only marginally upregulated. Neither of them was upregulated under O2-limitation where nitrogen was in excess, suggesting that N-starvation mainly affects the FAS and may be less important for the PUFA-synthase. The transcriptome analysis also revealed responses likely to be related to the generation of reducing power (NADPH) for fatty acid synthesis.

• Voigt, Andre & Almaas, Eivind (2019). Assessment of weighted topological overlap (wTO) to improve fidelity of gene co-expression networks. BMC Bioinformatics. 20(58), p. 1–11. doi: 10.1186/s12859-019-2596-9. Full text in Research Archive Show summary

  Background For more than a decade, gene expression data sets have been used as basis for the construction of co-expression networks used in systems biology investigations, leading to many important discoveries in a wide range of subjects spanning human disease to evolution and the development of organisms. A commonly encountered challenge in such investigations is first that of detecting, then subsequently removing, spurious correlations (i.e. links) in these networks. While access to a large number of measurements per gene would reduce this problem, often only a small number of measurements are available. The weighted Topological Overlap (wTO) measure, which incorporates information from the shared network-neighborhood of a given gene-pair into a single score, is a metric that is frequently used with the implicit expectation of producing higher-quality networks. However, the actual extent to which wTO improves on the accuracy of a co-expression analysis has not been quantified. Results Here, we used a large-sample biological data set containing 338 gene-expression measurements per gene as a reference system. From these data, we generated ensembles consisting of 10, 20 and 50 randomly selected measurements to emulate low-quality data sets, finding that the wTO measure consistently generates more robust scores than what results from simple correlation calculations. Furthermore, for the data sets consisting of only 10 and 20 samples per gene, we find that wTO serves as a better predictor of the correlation scores generated from the full data set. However, we find that using wTO as a score for network building substantially alters several topographical aspects of the resulting networks, with no conclusive evidence that the resulting structure is more accurate. Importantly, we find that the much used approach of applying a soft-threshold modifier to link weights prior to computing the wTO substantially decreases the robustness of the resulting wTO network, but increases the predictive power of wTO networks with regards to the reference correlation (soft threshold) network, particularly as the size of the data sets increases. Conclusion Our analysis demonstrates that, in agreement with previous assumptions, the wTO approach is capable of significantly improving the fidelity of co-expression networks, and that this effect is especially evident for cases of low-sample number gene-expression data sets.

• Gysi, Deisy Morselli; Voigt, Andre; Fragoso, Tiago de Miranda; Almaas, Eivind & Nowick, Katja (2018). wTO: An R package for computing weighted topological overlap and a consensus network with integrated visualization tool. BMC Bioinformatics. 19(392), p. 1–16. doi: 10.1186/s12859-018-2351-7. Full text in Research Archive Show summary

  Background Network analyses, such as of gene co-expression networks, metabolic networks and ecological networks have become a central approach for the systems-level study of biological data. Several software packages exist for generating and analyzing such networks, either from correlation scores or the absolute value of a transformed score called weighted topological overlap (wTO). However, since gene regulatory processes can up- or down-regulate genes, it is of great interest to explicitly consider both positive and negative correlations when constructing a gene co-expression network. Results Here, we present an R package for calculating the weighted topological overlap (wTO), that, in contrast to existing packages, explicitly addresses the sign of the wTO values, and is thus especially valuable for the analysis of gene regulatory networks. The package includes the calculation of p-values (raw and adjusted) for each pairwise gene score. Our package also allows the calculation of networks from time series (without replicates). Since networks from independent datasets (biological repeats or related studies) are not the same due to technical and biological noise in the data, we additionally, incorporated a novel method for calculating a consensus network (CN) from two or more networks into our Rpackage. To graphically inspect the resulting networks, the R package contains a visualization tool, which allows for the direct network manipulation and access of node and link information. When testing the package on a standard laptop computer, we can conduct all calculations for systems of more than 20,000 genes in under two hours. We compare our new wTO package to state of art packages and demonstrate the application of the wTO and CN functions using 3 independently derived datasets from healthy human pre-frontal cortex samples. To showcase an example for the time series application we utilized a metagenomics data set. Conclusion In this work, we developed a software package that allows the computation of wTO networks, CNs and a visualization tool in the R statistical environment. It is publicly available on CRAN repositories under the GPL −2 Open Source License (https://cran.r-project.org/web/packages/wTO/).

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• Heggeset, Tonje Marita Bjerkan & Nærdal, Ingemar (2024). Harvesting the riches of earth through bioprospecting and biotechnological exploitation of genomic data. Full text in Research Archive
• Rau, E-Ming (2021). Utilizing inhibitors and genetic engineering to study the biosynthesis of unsaturated fatty acids and lipids in two thraustochytrid strains. Full text in Research Archive Show summary

  Thraustochytrids are oleaginous heterotrophic marine eukaryotic microbes known to produce large amounts of docosahexaenoic acid (DHA)-containing triacylglycerols (TAGs), and they also synthesize other unsaturated fatty acids like palmitoleic acid (C16:1 n-7) and vaccenic acid (C18:1 n-7), and other terpenoids like squalene. These compounds have great economic value and are in high demand. However, DHA produced from thraustochytrids is still more costly than from fish oil whose availability is limited and unstable. Hence, a deeper understanding of the lipid metabolism and genetic manipulation tools in thraustochytrids is vital to developing high productive strains for profitable biomanufacturing. Here, the results suggest that precursor availability for the Polyketide synthase pathway is not the rate-limiting factor for DHA synthesis. FAS inhibition could enhance DHA-rich triacylglycerol (TAG) production. T66Des9 was then identified as a Δ12-desaturase-like Δ9-desaturase, contributing to the production of C16:1 n-7 and, indirectly, C18:1 n-7. Furthermore, four Acyl-CoA:diacylglycerol acyltransferases (DGAT)-like genes encoded proteins were identified to possess acyl-CoA:sterol acyltransferase (ASAT) activity, contributing to the production of steryl esters. In addition, the expression two of the four genes enhanced squalene production in SR21. The discoveries of the above-mentioned genes pave the way to enhance DHA-rich TAG, C16:1 n-7, C18:1 n-7, and squalene production in thraustochytrids through metabolic engineering, and highlight the enzyme functional diversity.

• Rau, E-Ming; Ertesvåg, Helga; Collier, Jackie L & Aasen, Inga Marie (2021). A Novel Protein of the Thraustochytrid Aurantiochytrium sp. T66 Homologous to Δ12-desaturases Has Δ9- desaturase Activity and Synthesizes Palmitoleic Acid. Full text in Research Archive Show summary

  Background Thraustochytrids are marine microeukaryotes known for the ability to accumulate high levels of the fatty acid docosahexaenoic acid (DHA, 22:6 n-3). Due to the remarkable benefits of DHA to human health, there is an increasing demand for sustainable DHA sources. Fatty acid profiles are different among several thraustochytrid genera and species. Palmitoleic acid (C16:1 n-7) and vaccenic acid (C18:1 n-7) are synthesized by Aurantiochytrium sp. T66 (T66), but not by Aurantiochytrium limacinum SR21. However, the genome of T66 does not contain proteins homologous to any known Δ9-desaturase, the enzyme converting palmitic acid (C16:0) to C16:1 n-7. Moreover, T66 encodes a protein with a high degree of homology to known Δ12-desaturases. An identical protein from Thraustochytrium sp. ATCC 26185 was shown not to have Δ12-desaturase activity by expression in Escherichia coli (Meesapyodsuk and Qiu, 2016). Objectives Since it is important to comprehensively understand the fatty acid synthesis pathways of thraustochytrids to enhance DHA production. In this study, we aimed to identify the enzyme that desaturates the C16:0 fatty acid to C16:1 n-7. Methods Heterologous expression of the T66 protein homologous to Δ12-desaturases in A. limacinum SR21 was performed, followed by fatty acid profiling. The potential evolutionary processes of the protein were analyzed by phylogenetic analyses. Results We demonstrated that the T66 protein homologous to Δ12-desaturases, is a Δ9-desaturase that synthesizes C16:1 n-7 using C16:0 as a substrate. C18:1 n-7 can then be produced from the elongation of C16:1 n-7. The protein was named T66Des9.The result provides substantial knowledge of the differences of unsaturated fatty acid metabolic pathways among thraustochytrid strains, which is an asset in optimizing strain engineering strategies. Furthermore, T66des9 probably evolved from a Δ12-desaturase-encoding gene, suggesting the prediction of desaturase functions can be challenging without considering potential evolutionary processes, which might affect the interpretation of unsaturated fatty acid metabolic pathways in the organisms of interest.

• Rau, E-Ming (2021). A Δ12-desaturase homolog of thraustochytrid Aurantiochytrium sp. T66 has Δ9-desaturase activity and plays a role in producing palmitoleic acid and vaccenic acid. Full text in Research Archive Show summary

  Health-beneficial palmitoleic acid and vaccenic acid were produced in an oleaginous microeukaryote thraustochytrid Aurantiochytrium limacinum SR21 by heterologous expression of a Δ12-desaturase homolog from Aurantiochytrium sp. T66, indicating the protein is more likely to be a Δ9-desaturase that synthesizes palmitoleic acid with palmitic acid as substrates.

• Rau, E-Ming (2020). The AUROMEGA project-a brief introduction. Full text in Research Archive Show summary

  Thraustochytrids are eukaryotic microorganisms known to accumulate large amounts of DHA. In addition to the PKS pathway, DHA might also be synthesized through the FAS pathway, implying the importance of desaturases. Strain T66 produces 16:1 and 18:1. Does the putative desaturase 2957 makes those? Genetic engineering of T66 has failed regardless of numerous attempts. However, strain SR21 does not produce these fatty acids. We made a gene knock-in of the desaturase in SR21, and the mutant produced 16:1 and 18:1. Knowledge of The diversity of metabolic pathways among thraustochytrids strains can give us hints on genetic engineering strategies to further increase DHA production.

• Almaas, Eivind (2020). Stories of network analysis: Cellular metabolism to COVID-19. Full text in Research Archive
• Aasen, Inga Marie (2019). Production of omega3 fatty acids for salmon feed by heterotrophic microorganisms. Full text in Research Archive
• Aasen, Inga Marie; Haslene-Hox, Hanne; Ertesvåg, Helga; Heggeset, Tonje Marita Bjerkan & Bruheim, Per (2019). Fatty acid synthesis in Aurantiochytrium sp, revealed by analyses of growth and production kinetics and global proteomes. Full text in Research Archive
• Aasen, Inga Marie; Haslene-Hox, Hanne; Stafsnes, Marit Hallvardsdotter; Heggeset, Tonje Marita Bjerkan & Bruheim, Per (2019). Lipid accumulation and DHA synthesis in Aurantiochytrium sp, elucidated by transcriptome, proteome and metabolome analyses. Full text in Research Archive
• Bartosova, Zdenka; Stafsnes, Marit Hallvardsdotter; Voigt, Andre & Bruheim, Per (2019). Supercritical fluid chromatography with mass spectrometry: A versatile tool for lipid profiling and lipid class quantitation. Full text in Research Archive
• Heggeset, Tonje Marita Bjerkan; Ertesvåg, Helga; Liu, Bin & Aasen, Inga Marie (2019). Genome annotation and transcriptome analysis of the lipid- and DHA-accumulating Aurantiochytrium sp. T66. Full text in Research Archive Show summary

  Thraustochytrids of the genera Schizochytrium and Aurantiochytrium accumulate oils rich in the essential, marine n3 fatty acid docosahexaenoic acid (DHA). As part of studies of the DHA-production in Aurantiochytrium sp. T66 (ATCC® PRA-276™), the 43 Mbp draft genome was annotated based on ab-initio prediction combined with RNA-Seq mapping. The genome encodes 11683 putative genes, of which functional information could be assigned to 9090. T66 show high sequence similarity to Aurantiochytrium sp. S-3 (ATCC® 26185™), despite the publicly available genome record of S-3 covering only 18.1 Mbp. A global transcriptome analysis was carried out with the aim to provide more knowledge about factors that affect the DHA-productivities and the contributions of the two enzyme systems used for fatty acid synthesis in thraustochytrids, fatty acid synthetase (FAS) and Polyunsaturated fatty acid (PUFA) synthase. Batch cultivation with nitrogen starvation, which is well-known to initiate lipid accumulation in oleaginous organisms, were compared to cultivation with nitrogen in excess, where lipid accumulation was obtained by oxygen limitation. A significant upregulation of FAS under N-deficient conditions was found, while the PUFA-synthase genes were only marginally upregulated. Neither of them was upregulated under O2-limitation where nitrogen was in excess, suggesting that Nstarvation mainly affects the FAS and may be less important for the PUFA-synthase. The transcriptome analysis also revealed responses likely to be related to the generation of reducing power (NADPH) for fatty acid synthesis.

• Bartosova, Zdenka; Gonzalez, Susana Villa & Bruheim, Per (2019). High-throughput method for lipidomic analysis and semi-quantification of lipid classes. Full text in Research Archive
• Stafsnes, Marit Hallvardsdotter; Bartosova, Zdenka & Bruheim, Per (2019). Metabolomics and fluxomics - essential approaches in optimization of bioprocesses. Full text in Research Archive
• Ertesvåg, Helga; Haslene-Hox, Hanne; Aasen, Inga Marie; Almaas, Eivind; Bartosova, Zdenka & Heggeset, Tonje Marita Bjerkan [Show all 11 contributors for this article] (2019). Industrial microbiology – 'omics methods and modelling as tools for process optimization. Full text in Research Archive
• Aasen, Inga Marie; Bartosova, Zdenka; Haslene-Hox, Hanne; Heggeset, Tonje Marita Bjerkan; Stafsnes, Marit Hallvardsdotter & Bruheim, Per [Show all 7 contributors for this article] (2019). Elucidating lipid accumulation and DHA synthesis in Aurantiochytrium sp. strain T66 using -omics technologies. Full text in Research Archive
• Aasen, Inga Marie; Ertesvåg, Helga; Heggeset, Tonje Marita Bjerkan; Vadstein, Olav & Sevgeli, Huseyin (2018). Production of heterotrophic microorganisms for use as a source of long-chain omega3 fatty acids in aquafeed. Full text in Research Archive
• Aasen, Inga Marie (2018). Production of EPA/DHA by heterotrophic microorganisms: How can GMO contribute? Full text in Research Archive
• Aasen, Inga Marie; Ertesvåg, Helga; Heggeset, Tonje Marita Bjerkan; Vadstein, Olav; Broli, Gunn & Sevgeli, Huseyin [Show all 7 contributors for this article] (2018). Heterotrofe mikroorganismer som kilde for omega3-fettsyrer i fiskefôr. Full text in Research Archive

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