C16 Fatty Acids Research Articles

Acylserotonins – a new class of plant lipids with antioxidant activity and potential pharmacological applications

During analysis of components of baobab (Adansonia digitata) seed oil, several new fluorescent compounds were detected in HPLC chromatograms that were not found previously in any seed oils investigated so far. After preparative isolation of these compounds, structural analysis by NMR spectroscopy, UHPLC-HR-MS, GC-FID and spectroscopic methods were applied and allowed identification of these substances as series of N-acylserotonins containing saturated C22 to C26 fatty acids with minor contribution of C27 to C30 homologues. The main component was N-lignocerylserotonin and the content of odd carbon-atom-number fatty acids was unusually high among the homologues. The suggested structure of the investigated compounds was additionally confirmed by their chemical synthesis. Synthetic N-acylserotonins showed pronounced inhibition of membrane lipid peroxidation of liposomes prepared from chloroplast lipids, especially when the peroxidation was initiated by a water-soluble azo-initiator, AIPH. Comparative studies of the reaction rate constants of the N-acylserotonins and tocopherols with a stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) in solvents of different polarity revealed that N-acylserotonins showed similar activity to δ-tocopherol in this respect. The described compounds have been not reported before either in plants or in animals. This indicates that we have identified a new class of plant lipids with antioxidant properties that could have promising pharmacological activities.

Advanced treatment of chicken farm flushing wastewater by integrating Fenton oxidation and algal cultivation process for algal growth and nutrients removal

Algae based wastewater treatment has been considered as the most promising win-win strategy for nutrients removal and biomass accumulation. However, the poor linking between traditional wastewater treatment and algal cultivation limits the achievement of this goal. In this study, a novel combination of Fenton oxidation and algal cultivation (CFOAC) system was investigated for the treatment of chicken farm flushing wastewater (CFFW). Fenton oxidation (FO) was adopted to reduce the excessive ammonia nitrogen, which might inhibit the algal growth. The results showed that single FO pretreatment removed 70.5 %, 96.7 %, 86.1 %, and 96.2 % of TN, TAN, TP, and COD, respectively. The highest biomass (235.8 mg/L/d) and lipid (77.3 mg/L/d) productivities were achieved on optimized CFOAC system after 7 days batch cultivation. Accordingly, the nutrients removal efficiencies increased to almost 100 %. Further fatty acid profile analysis showed that algae grown on optimal CFOAC system accumulated a high level of total lipids (32.8 %) with C16–C18 fatty acid as the most abundant compositions (accounting for over 60.6 %), which were propitious to biodiesel production. In addition, this CFOAC system was magnified from 1 L flask to 50 L horizontal pipe photobioreactor (HPPB) in semi-continuously culture under optimal conditions. The average biomass and lipid productivities were 995.7 mg/L/d and 320.6 mg/L/d, respectively, when cultured at 6 days hydraulic retention time with 1/3 substitution every two days. These findings proved that the novel CFOAC system is efficient in nutrients removal, algal cultivation, and biomass production for advanced treatment of CFFW.

Effect of concentrate enriched with palmitic acid versus rapeseed oil on dairy performance, milk fatty acid composition, and mammary lipogenic gene expression in mid-lactation Holstein cows

This study was performed to characterize the effect of a concentrate supplemented with free palmitic acid (4% on a DM basis; PA) or rapeseed oil (4% on a DM basis; RO) compared with a no-added-lipid control concentrate (CT) on the performance of dairy cows fed a corn silage-based diet over a 9-wk period. After a 3-wk pre-experimental period, 54 Holstein cows were randomly allocated to 3 experimental treatments to receive forage ad libitum with a fixed amount of CT, RO, or PA (8 kg/d for 2-yr-old primiparous; 10 kg/d for older cows). During the experiment, dry matter intake, milk yield and composition, fatty acid (FA) yields and FA profile, and feed efficiency were determined. At wk 9 of the experimental period, the mRNA levels of 10 genes involved in lipid metabolism in mammary tissue biopsy samples were measured. Compared with CT, RO and PA increased forage intake. Compared with CT, RO increased concentrate intake, the value being intermediate for PA. Compared with CT, RO increased milk yield (+2.0 kg/d) and decreased milk fat and protein content (-3.8 and -1.2 g/kg, respectively), whereas PA increased milk fat content (+4.1 g/kg). Compared with CT and RO treatments, PA increased milk fat yield (+179 g/d) and 3.5% fat-corrected milk and energy-corrected milk output (+2.8 and +2.3 kg/d, respectively), and thus improved feed efficiency (+7.3%). Compared with CT treatment, RO increased milk contents of the sum of >C16 FA, monounsaturated FA, polyunsaturated FA, trans FA, and n-3 FA, whereas PA decreased these FA contents (except n-3 FA) and also decreased n-6 FA. The variations in milk fat yield and content and FA secretion at wk 9 were not associated with modifications in mammary expression of 10 genes involved in major lipid pathways, except for the transcription factor PPARG1, which tended to be higher in PA versus RO treatment. This study demonstrated that PA improved milk fat yield and feed efficiency compared with RO and suggests that factors other than gene expression, such as substrate availability for mammary metabolism or other levels of regulation (transcriptional, posttranscriptional, translational or posttranslational), could play a key role in milk fat and FA responses to changes in diet composition in cows.

A STUDY OF ORM EXPRESSION CHANGES FUMONISIN B1-INDUCED PERTURBATIONS OF SPHINGOLIPID HOMEOSTASIS AND DIFFERENTIALLY TOUCHES CERAMIDE SYNTHASE ACTIVITIES

Sphingolipid synthesis is tightly regulated in eukaryotes. This regulation in plants ensures sufcient sphingolipids to support growth, while limiting accumulation of sphingolipid metabolites that induce programmed cell death (PCD). Serine palmitoyltransfersase (SPT) catalyzes the rst step in sphingolipid biosynthesis and is considered the primary sphingolipid homeostatic regulatory point. In this report, Arabidopsis putative SPT regulatory proteins, orosomucoid-like proteins AtORM1 and AtORM2 were found to physically interact with the Arabidopsis SPT and to suppress SPT activity when co-expressed with Arabidopsis SPT subunits LCB1 and LCB2 and the small subunit of SPT in a yeast SPT-decient mutant. Consistent with a role in SPT suppression, AtORM1 and AtORM2 overexpression lines displayed increased resistance to the PCD-inducing mycotoxin fumonisin B1 (FB1), with an accompanying reduced accumulation of longchain bases (LCBs) and C16-fatty acid-containing ceramide accumulation relative to wild type plants. Conversely, RNAi suppression lines of AtORM1 and AtORM2 displayed increased sensitivity to FB1 and an accompanying strong increase in LCBs and C16 fatty acid-containing ceramides relative to wild-type plants. Overexpression lines were also found to have reduced activity of the Class I ceramide synthase that uses C16-fatty acid acyl-CoA and dihydroxy LCB substrates, but increased activity of Class II ceramide synthases that use very long-chain fatty acylCoA and trihydroxy LCB substrates. RNAi suppression lines, in contrast, displayed increased Class I ceramide synthase activity, but reduced Class II ceramide synthase activity. These ndings indicate that ORM-mediation of SPT activity differentially regulates functionally distinct ceramide synthase activities as part of a broader sphingolipid homeostatic regulatory network.

A sequence variant in the diacylglycerol O-acyltransferase 2 gene influences palmitoleic acid content in pig muscle

The bulk of body fat in mammals is in the form of triacylglycerol. Diacylglycerol O-acyltransferase 2 (DGAT2) catalyses the terminal step in triacylglycerol synthesis. The proximity of DGAT2 with stearoyl-CoA desaturase (SCD) in the endoplasmic reticulum may facilitate provision of de novo SCD-mediated fatty acids as substrate for DGAT2. Here, we first searched for sequence variants in the DGAT2 gene to then validate their effect on fat content and fatty acid composition in muscle, subcutaneous fat and liver of 1129 Duroc pigs. A single nucleotide polymorphism in exon 9 (ss7315407085 G > A) was selected as a tag variant for the 33 sequence variants identified in the DGAT2 region. The DGAT2-G allele increased DGAT2 expression in muscle and had a positive impact on muscular C14 and C16 fatty acids at the expense of C18 fatty acids. Although there was no evidence for an interaction of DGAT2 with functional SCD genotypes, pigs carrying the DGAT2-G allele had proportionally more palmitoleic acid relative to palmitic acid. Our findings indicate that DGAT2 preferentially uptakes shorter rather than longer-chain fatty acids as substrate, especially if they are monounsaturated, and confirm that fatty acid metabolism in pigs is subjected to subtle tissue-specific genetic regulatory mechanisms.

Sources, Distribution and Paleoenvironmental Application of Fatty Acids in Speleothem Deposits From Krem Mawmluh, Northeast India

Integrated multiproxy geochemical studies are essential to reconstruct the paleoenvironment through different time scales. Pristine terrestrial archives such as speleothems provide an excellent opportunity to study these changes by measuring the stable isotope and biomarker trends preserved in these records. Here, we investigated fatty acids in drip water, moonmilk, and a stalagmite (KM-1) retrieved from Krem Mawmluh in northeast India to constrain the sources and distribution of these compounds. Besides, we tested their compatibility with established glycerol dialkyl glycerol tetraethers and stable isotope proxies in KM-1 to probe the use of fatty acid-derived proxies for paleoclimate reconstruction. We observe a similar composition of fatty acids in drip water as well as the cave deposits with significantly higher concentrations of fatty acids in drip water (10.6–124 μg/L) and moonmilk (1.32–16.5 μg/g) compared to the stalagmite (0.67–2.09 μg/g). In KM-1 stalagmite, fatty acids and the presence of azelaic acid transported from surface soils indicate that these compounds are derived from bacterial activity both within the cave and the overlying soil cover. The branched C15 fatty acid index (iso+anteiso C15/nC15) increases during the Holocene, suggesting enhanced microbial production under warm/wet conditions. Fluctuations in the fatty acid indices coincide with abrupt shifts in the TEX86 and BIT proxies reflecting the warm/wet Holocene and cold/dry Late Pleistocene. These trends imply the potential use of fatty acids for reconstructing past climate changes in speleothems but need more analytical reference points to provide statistical data.

Sustainable pilot‐scale production of a Salicornia oil, its conversion to certified aviation fuel, and techno‐economic analysis of the related biorefinery

AbstractThe 2 ha pilot‐plant Seawater Energy and Agriculture System (SEAS) in Abu Dhabi, United Arab Emirates (UAE), integrates aquaculture ponds, which produce fish and shrimp, with fields of Salicornia and mangrove used as a natural filter to clean the waste seawater from the ponds. The SEAS is a sustainable solution that addresses the food security issues of countries with large deserts or arid regions. At the same time, it produces economically viable fuels from biomass, using non‐arable lands and non‐drinkable water. After harvesting and pressing Salicornia seeds (2 t ha−1 year−1), a custom‐made process serves to pre‐treat the vegetable oil (0.7 t ha−1 year−1) containing 85 wt% C18 and 10 wt% C16 fatty acids as triglycerides. The first step of the UOP Ecofining® process produces an oil composed of linear C15‐C18 alkanes. Analytical data suggest the oil feed converts at 60 wt% by hydrodeoxygenation and at 40 wt% through decarboxylation/decarbonylation. The subsequent hydrocracking/isomerization step provided 3.4 wt% C1–C4, 34.8 wt% green naphtha, 47.5 wt% sustainable aviation fuel (SAF), and 14.2 wt% green diesel. After distillation, the SAF has been certified following ASTM D7566 before being blended with conventional jet fuel and used successfully on a commercial passenger flight in January 2019. The techno‐economic study shows that the biorefinery part is economically sustainable when reaching a production scale of 900bbd, required for a SEAS surface of 20 000 ha. At this scale, expected revenue and conversion costs per MT of feed are, respectively, $589 and $290. The resulting benefit, associated with a CAPEX of $115M, would lead to a payback time of 6.9 years. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Fatty acid composition of the methylotrophic yeast Komagataella phaffii grown under low- and high-methanol conditions.

In this study, we analysed the intracellular fatty acid profiles of Komagataella phaffii during methylotrophic growth. K. phaffii grown on methanol had significantly lower total fatty acid contents in the cells compared with glucose-grown cells. C18 and C16 fatty acids were the predominant fatty acids in K. phaffii, although the contents of odd-chain fatty acids such as C17 fatty acids were also relatively high. Moreover, the intracellular fatty acid composition of K. phaffii changed in response to not only carbon sources but also methanol concentrations: C17 fatty acids and C18:2 content increased significantly as methanol concentration increased, whereas C18:1 and C18:3 contents were significantly lower in methanol-grown cells. The intracellular content of unidentified compounds (Cn H2n O4 ), on the other hand, was significantly greater in cells grown on methanol. As the intracellular contents of these Cn H2n O4 compounds were significantly higher in a gene-disrupted strain for glutathione peroxidase (gpx1Δ) than in the wild-type strain, we presume that the Cn H2n O4 compounds are fatty acid peroxides. These results indicate that K. phaffii can coordinate intracellular fatty acid composition during methylotrophic growth in order to adapt to high-methanol conditions and that certain fatty acid species such as C17:0, C17:1, C17:2 and C18:2 may be related to the physiological functions by which K. phaffii adapts to high-methanol conditions.

Peroxisomal Fatty Acid Oxidation and Glycolysis Are Triggered in Mouse Models of Lesional Atopic Dermatitis

Alterations of the lipid profile of the stratum corneum have an important role in the pathogenesis of atopic dermatitis (AD) because they contribute to epidermal barrier impairment. However, they have not previously been envisioned as a cellular response to altered metabolic requirements in AD epidermis. In this study, we report that the lipid composition in the epidermis of flaky tail, that is, ft/ft mice mimics that of human lesional AD (ADL) epidermis, both showing a shift toward shorter lipid species. The amounts of C24 and C26 free fatty acids and C24 and C26 ceramides—oxidized exclusively in peroxisomes—were reduced in the epidermis of ft/ft mice despite increased lipid synthesis, similar to that seen in human ADL edpidermis. Increased ACOX1 protein and activity in granular keratinocytes of ft/ft epidermis, altered lipid profile in human epidermal equivalents overexpressing ACOX1, and increased ACOX1 immunostaining in skin biopsies from patients with ADL suggest that peroxisomal β-oxidation significantly contributes to lipid signature in ADL epidermis. Moreover, we show that increased anaerobic glycolysis in ft/ft mouse epidermis is essential for keratinocyte proliferation and adenosine triphosphate synthesis but does not contribute to local inflammation. Thus, this work evidenced a metabolic shift toward enhanced peroxisomal β-oxidation and anaerobic glycolysis in ADL epidermis.

Fatty acid profiles of estuarine macroalgae are biomarkers of anthropogenic pressures: Development and application of a multivariate pressure index

Transitional ecosystems are among the most degraded ecosystems worldwide, with several groups of organisms investigated for their reliability as biological indicators of human-driven disturbances. Recently non-traditional biochemical biomarkers such as an individual's fatty acids profile have been identified as promising tools for assessing contaminant exposure. In this work, two abundant Atlantic benthic macroalgae (Ulva lactuca and Fucus vesiculosus species) were surveyed in three mudflat areas of the highly urbanized Tejo estuary, with increasing anthropogenic disturbance degrees (Alcochete, Rosário and Seixal mudflats, increasing in contamination by this order) and their fatty acids evaluated as potential biomarkers for exposure to contaminants known to have toxic effects on biota. In terms of contamination the metal pollution index of all the compartments analysed (sediment bioavailable and total metal concentrations and thallus metal concentrations) revealed the same tendencies with lower contamination levels in Alcochete, intermediate in Rosário and high contamination levels in Seixal. In the thallus of U. lactuca thallus could be observed a strong decrease in C18-fatty acids along the contamination gradient, likely due to lipid peroxidation from metal-generated reactive oxygen species. Nevertheless, an increase in stearic and hexadecatrienoic acids in the thallus from the most contaminated site suggested counteractive mechanisms maintain the production of C18-fatty acid pool. A similar response was found in F. vesiculosus but with palmitic acid acting as precursor for the synthesis of stearic acid, allowing the maintenance of oleic and linoleic acids levels in the membranes to counteract oxidative stress. Beyond the physiological interest of these mechanisms, fatty acid profiles were used to develop a novel multivariate pressure index (Multi-PI), that beyond the contaminant concentration would reflect the response of these biomonitor species towards anthropogenic disturbance, through the evaluation of fatty acid profiles, which are also key molecules from a trophic perspective within the estuarine system. The Multi-PI efficiency in responding to different environmental contamination degrees, was substantiated by strong and positive correlations with thallus and sediment contamination. This indicated that fatty acid profiles reflect thallus and benthic habitat contamination and are efficient biomarkers of environmental metal contamination. Therefore, the sessile and abundant nature of benthic macroalgae allied to their fatty acid responses can be leveraged as suitable biomarkers for contaminant monitoring in future impact assessment and ecotoxicology studies.

Preparation of bio-oil from Scenedesmus acutus using thermochemical liquefaction in a 1 L reactor

Biomass from microalgae is a potential feedstock for biofuels production. It poses no threat to food security as it does not compete with agricultural crops for arable land. Scenedesmus acutus was used as feedstock to produce bio-oil in a large liquefaction reactor. The influence of reaction temperature (280–360ºC), reaction atmosphere (N2 or CO2) and solvent on bio-oil yield, C-16 fatty acid yield and oil properties were investigated. Oils were characterised using gas chromatography, Fourier transform infrared (FTIR) spectroscopy and ultimate analysis. Higher bio-oil yields were obtained in a CO2 atmosphere (250 g.kg-1 dry microalgae) than in a N2 atmosphere (210 g.kg-1 dry microalgae) whilst higher C16 fatty acid concentrations (600 g.kg-1 bio-oil) were recorded in N2 atmosphere compared to oil prepared in a CO2 atmosphere (500 g.kg-1 bio-oil). The oil yield increased to a maximum at 320°C, after which there were no significant changes. Highest bio-oil yields (425 g.kg-1 dry microalgae) were obtained in ethanol as solvent. FTIR spectroscopy and ultimate analysis showed that proteins present in the feedstock were degraded by breakage of peptide linkages, and nitrogen present in the oils is peptide fragments from protein degradation. The carbon content of all produced oils was high, but the hydrogen content was low, leading to low hydrogen/carbon ratios. Energy consumption and energy efficiency calculations showed that liquefaction in both reaction atmospheres results in a net energy gain, and a CO2 atmosphere is best for high energy efficiency.

Dating Lake Sediments Using Compound‐Specific 14C Analysis of C16 Fatty Acid: A Case Study From the Mount Fuji Volcanic Region, Japan

AbstractLake sediments in volcanic regions contain continuous records of past eruptions and their environmental consequences. However, the frequent scarcity of plant material in lake sediments makes it difficult to provide robust age estimates. In this study, we performed compound‐specific radiocarbon analysis (CSRA) of fatty acids in a sediment core from Lake Kawaguchi in the Mount Fuji volcanic region, Japan, to assess their potential for dating sediments. The C16 fatty acid in the core top sediments exhibits an almost identical age (983 ± 56 years BP) to that of dissolved inorganic carbon in the modern lake surface water, which confirms that the carbon of this compound is derived from lake phytoplankton. Comparison of the 14C age between the C16 fatty acid and a plant leaf at the widespread (Amagi‐Kawagodaira) tephra layer revealed a lake reservoir age of 1,003 ± 73 14C years at ca. 3,150 cal BP, which is consistent with the modern lake reservoir age and the 14C age of the C16 fatty acid in the core top sediments, within error. The reservoir‐corrected 14C age of the C16 fatty acid yielded a modeled age of 2,837 ± 78 cal BP for the Mount Fuji Tephra (Omuro scoria‐fall deposit) in the core. This age is in good agreement with the age determined from plant remains in the same core (2,938 ± 29 cal BP), indicating that CSRA of C16 fatty acid has the potential to date lake sediments after reservoir age correction, even in sediments with limited occurrence of plant macrofossils.

Study of The Divergent Acyl Chain Specificities of The Class I Ceramide Synthases in Plants

Ceramide synthases catalyze the condensation of long-chain bases and fatty acyl-CoA to form the ceramide backbones of glycosphingolipids.The Class I and II ceramide synthases of plants have distinct substrate specificities that contribute to the divergent fatty acid chain-lengths and functions of plant sphingolipids. The Arabidopsis LOH2-encoded Class I ceramide synthase has been shown to have strong specificity for palmitoyl (16:0)-CoA that gives rise to ceramides with C16 fatty acids that are prevalent in dicot glucosylceramides. By contrast, glucosylceramides of many monocots and selected dicots are enriched in C18 and C20-ceramides. We hypothesized that these differences are due to functional and structural differences in LOH2 ceramide synthases. Consistent with this, we found that transgenic expression of a tomato LOH2 restored C16 fatty acid in glucosylceramides in an Arabidopsis loh2 mutant, whereas expression of a rice LOH2 resulted in C18- and C20-fatty acid-enriched glucosylceramides. To establish the structural basis for these different outcomes, we demonstrated that swapping a divergent 16 amino acid domain from the rice LOH2 to tomato LOH2 yielded C18- and C20-fatty acid-glucosylceramides when expressed in the loh2 mutant. By comparison of primary structures of LOH2 enzymes from diverse dicots and monocots, we identified a single amino acid that when mutated in the tomato LOH2 resulted in rice-type C18- and C20 fatty acid-glucosylceramides.We rationalize the altered LOH2 function in the context of the predicted LOH2 ceramide synthase secondary structure. Overall, our findings highlight the biochemical and genetic basis for divergent ceramide structures in dicots and monocots.

Annual productivity and lipid composition of native microalgae (Chlorophyta) at a pilot production facility in Southern California

Microalgae are an efficient platform for the sustainable production of foods, fuels, and bioproducts. Due to the vast natural diversity of microalgae, choosing an ideal species for production can be challenging, and laboratory-derived productivity data may be misleading. In the present study, nine species of green algae (Chlorophyta) were isolated directly from an outdoor pilot production facility, identified via sequencing and microscopy, cultured under standard laboratory conditions to assess lipid content, and then cultivated in 80-L cultures in a greenhouse over the course of a year to assess productivity. Analysis of lipid content from laboratory-grown cultures revealed that these strains had high concentrations of C16 and C18 fatty acids and lipid content not exceeding 30% of dry weight during growth phase. In the greenhouse, Parachlorella kessleri-SD23 had the highest annual productivity, yielding an annual average of approximately 19 g/m2/d and 88 mg/L/d of biomass productivity. Additionally, P. kessleri-SD23 had a total lipid content equal to about 19% of dry weight during growth phase under laboratory conditions with the highest concentration of C18:2 and C18:3 fatty acids among the isolates.

Enhancement of C6–C10 fatty acid ethyl esters production in Saccharomyces cerevisiae CA by metabolic engineering

C6–C10 fatty acid ethyl esters (FAEEs) are important aromatic substances in alcoholic beverages and include ethyl hexanoate (EH), ethyl octanoate (EO), and ethyl decanoate (ED). However, the biosynthesis capacity of these esters are limited because of poor precursor C6–C10 fatty acyl-CoA accumulation and low alcohol acyltransferase (AATase) activity levels in Saccharomyces cerevisiae. In this study, S. cerevisiae CA stain was selected as the host stain because of its relatively high C6–C10 FAEE productivity. Ester production was improved by metabolic engineering strategies. Acetaldehyde dehydrogenase (ALD6) and acetyl-CoA synthetase (ACS1) were overexpressed to enhance the acetyl-CoA precursor accumulation. Intracellular malonyl-CoA availability was also improved by acetyl-CoA decarboxylase (ACC1Ser659Ala, Ser1157Ala) overexpression. FAS1 and FAS2 (encoding fatty acid synthase) overexpression facilitated the condensation reactions to form C6–C10 fatty acyl-CoA from malonyl-CoA and acetyl-CoA precursors. Furthermore, the strawberry alcohol acyltransferase (SAAT) was introduced into S. cerevisiae CA to catalyze the formation of C6–C10 FAEEs from C6–C10 fatty acyl-CoA and ethanol substrates. As a consequence, the newly engineered strain achieved 25.89-, 7.27-, and 9.05-fold increases in extracellular EH (7.53 mg/L), EO (13.65 mg/L) and ED (13.87 mg/L) levels, respectively, compared to the wild-type strain CA.

Peroxisome-driven ether-linked phospholipids biosynthesis is essential for ferroptosis

It is well established that ferroptosis is primarily induced by peroxidation of long-chain poly-unsaturated fatty acid (PUFA) through nonenzymatic oxidation by free radicals or enzymatic stimulation of lipoxygenase. Although there is emerging evidence that long-chain saturated fatty acid (SFA) might be implicated in ferroptosis, it remains unclear whether and how SFA participates in the process of ferroptosis. Using endogenous metabolites and genome-wide CRISPR screening, we have identified FAR1 as a critical factor for SFA-mediated ferroptosis. FAR1 catalyzes the reduction of C16 or C18 saturated fatty acid to fatty alcohol, which is required for the synthesis of alkyl-ether lipids and plasmalogens. Inactivation of FAR1 diminishes SFA-dependent ferroptosis. Furthermore, FAR1-mediated ferroptosis is dependent on peroxisome-driven ether phospholipid biosynthesis. Strikingly, TMEM189, a newly identified gene which introduces vinyl-ether double bond into alkyl-ether lipids to generate plasmalogens abrogates FAR1-alkyl-ether lipids axis induced ferroptosis. Our study reveals a new FAR1-ether lipids-TMEM189 axis dependent ferroptosis pathway and suggests TMEM189 as a promising druggable target for anticancer therapy.

Multiscale Microbial Preservation and Biogeochemical Signals in a Modern Hot-Spring Siliceous Sinter Rich in CO2 Emissions, Krýsuvík Geothermal Field, Iceland

The microbial communities inferred in silica sinter rocks, based on multiscale morphological features (fabrics and textures) and the presence of lipid biomarkers and their carbon isotopic composition, are evaluated in the Krýsuvík geothermal area of Iceland. Close to vent environments (T > 75 °C and pH 1.7‒3), stream floors are capped with homogeneous vitreous crusts and breccia levels, with no distinct recognizable silicified microbes. About 4 m far from the vents (T 75‒60 °C and pH 3‒6) and beyond (T < 60 °C and pH 6‒7.6), microbial sinters, including wavy and palisade laminated and bubble fabrics, differ between abandoned meanders and desiccated ponds. Fabric and texture variances are related to changes in the ratio of filament/coccoid silicified microbes and associated porosity. Coatings of epicellular silica, less than 2 µm thick, favor identification of individual microbial filaments, whereas coalescence of opal spheres into agglomerates precludes recognition of original microbial textures and silicified microbes. Episodic fluctuations in the physico-chemical conditions of surface waters controlled the acidic hydrolysis of biomarkers. Wavy laminated fabrics from pond margins comprise fatty acids, mono- and dialkyl glycerol, mono- and diethers, monoalkyl glycerol esters and small traces of 10-methyl branched C16 and C18 fatty acids and archaeol, indicative of intergrowths of cyanobacteria, Aquificales, and sulfate reducing bacteria and methanogenic archaea. In contrast, wavy laminated fabrics from abandoned meanders and palisade laminated fabrics from ponds differ in their branched fatty acids and the presence vs. absence of bacteriohopanetetrol, reflecting different cyanobacterial contributions. δ13C values of biomarkers range from −22.7 to −32.9‰, but their values in the wavy (pond) and bubble fabrics have much wider ranges than those of the wavy (meander), palisade, and vitreous fabrics, reflecting dissolved inorganic carbon (DIC) sources and a decrease in 13C downstream outflow channels, with heavier values closer to vents and depleted values in ponds.

Convergence of sphingolipid desaturation across over 500 million years of plant evolution.

For plants, acclimation to low temperatures is fundamental to survival. This process involves the modification of lipids to maintain membrane fluidity. We previously identified a new cold-induced putative desaturase in Physcomitrium (Physcomitrella) patens. Lipid profiles of null mutants of this gene lack sphingolipids containing monounsaturated C24 fatty acids, classifying the new protein as sphingolipid fatty acid denaturase (PpSFD). PpSFD mutants showed a cold-sensitive phenotype as well as higher susceptibility to the oomycete Pythium, assigning functions in stress tolerance for PpSFD. Ectopic expression of PpSFD in the Atads2.1 (acyl coenzyme A desaturase-like 2) Arabidopsis thaliana mutant functionally complemented its cold-sensitive phenotype. While these two enzymes catalyse a similar reaction, their evolutionary origin is clearly different since AtADS2 is a methyl-end desaturase whereas PpSFD is a cytochrome b5 fusion desaturase. Altogether, we suggest that adjustment of membrane fluidity evolved independently in mosses and seed plants, which diverged more than 500 million years ago.

A novel charge derivatization-direct infusion mass spectrometry method for the quantitative analysis of C1–C8 fatty acids in rubber seed oil-based biodiesel

The free fatty acids that contain one to eight carbons (C1–C8) in biodiesel would affect the quality of biodiesel. It is still a matter of challenge to simultaneously determine the composition of C1–C8 fatty acids in seed oil and seed oil-based biodiesel. Herein, a novel method of charge derivatization coupling with direct infusion mass spectrometry (CD-DIMS) was developed for the determination of the C1–C8 fatty acids in biodiesels. A fixed-charge derivatization reagent, 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide (CMCT), was used to convert fatty acids into their cationic derivatives, which significantly improved the sensitivity and selectivity of detection. Good linearity was observed with the limits of detection (LODs) in the range of 0.0002–0.001 μg mL−1 for the investigated fatty acids. The recovery was in the range of 85.1%–101.9% and the matrix effect was within the range of 75.5–93.2%. The developed method was carried out to analyze C1–C8 fatty acids in rubber seed oil (RSO) and RSO-based biodiesels produced by different catalysts, including NaOH, TiO2, and carbodiimide. It was also applied to the dynamic monitoring of C1–C8 fatty acids in RSO and produced RSO biodiesels during the oxidation process. As results, formic acid, acetic acid, and propionic acid were detected in aged RSO and biodiesel samples. The contents of formic acid, acetic acid, and propionic acid all increased in aged RSO and biodiesels, but with different growth rates. These results demonstrated that the developed CD-DIMS method can provide a quick, accurate, and sensitive analysis of C1–C8 fatty acids in seed oil and biodiesel samples.

Abundant synthesis of long-chain polyunsaturated fatty acids in Eutreptiella sp. (Euglenozoa) revealed by chromatographic and transcriptomic analyses.

Algal lipids are important molecules to store energy in algae and transfer energy in the marine food chain, and are potential materials for high value nutraceuticals (e.g., omega-3 fatty acids) or biofuel production. However, how lipid biosynthesis is regulated is not well understood in many species including Eutreptiella from the phylum of Euglenozoa. Here, we characterized the fatty acid (FA) profile of an Eutreptiella species isolated from Long Island Sound, USA, using gas chromatography-tandem mass spectrometry (GC/MS/MS) and investigated their biosynthesis pathways by transcriptome sequencing. We discovered 24 types of FAs including a relatively high proportion of long-chain unsaturated FAs. The abundances of C16, C18, and saturated FAs decreased when phosphate in the culture medium was depleted. Among the 24 FAs, docosahexaenoic acid (C22:6∆4,7,10,13,16,19 ) was most abundant, suggesting that Eutreptiella sp. preferentially invests in the synthesis of long-chain polyunsaturated fatty acids (LC-PFAs). Further transcriptomic analysis revealed that Eutreptiella sp. likely synthesizes LC-PFAs via ∆8 pathway and uses type I and II fatty acid synthases. Using RT-qPCR, we found that some of the lipid synthesis genes, such as β-ketoacyl-ACP reductase, fatty acid desaturase, acetyl-CoA carboxylase, acyl carrier protein, ∆8 desaturase, and Acyl-ACP thioesterase, were more actively expressed during light period, and two carbon fixation genes were up-regulated in the high-lipid illuminated cultures, suggesting a linkage between photosynthesis and lipid production. The lipid profile renders Eutreptiella sp. a nutritional prey and valuable source for nutraceuticals, and the biosynthesis pathway documented here will be useful for future research and applications.