Acyl-CoA binding protein is required for lipid droplet degradation in the diatom Phaeodactylum tricornutum.

Diatoms (Bacillariophyceae) accumulate neutral storage lipids in lipid droplets during stress conditions, which can be rapidly degraded and recycled when optimal conditions resume. Since nutrient and light availability fluctuate in marine environments, storage lipid turnover is essential for diatom dominance of marine ecosystems. Diatoms have garnered attention for their potential to provide a sustainable source of omega-3 fatty acids. Several independent proteomic studies of lipid droplets isolated from the model oleaginous pennate diatom Phaeodactylum tricornutum have identified a previously uncharacterized protein with an acyl-CoA binding (ACB) domain, Phatrdraft_48778, here referred to as Phaeodactylum tricornutum acyl-CoA binding protein (PtACBP). We report the phenotypic effects of CRISPR-Cas9 targeted genome editing of PtACBP. ptacbp mutants were defective in lipid droplet and triacylglycerol degradation, as well as lipid and eicosapentaenoic acid synthesis, during recovery from nitrogen starvation. Transcription of genes responsible for peroxisomal ß-oxidation, triacylglycerol lipolysis, and eicosapentaenoic acid synthesis was inhibited. A lipid-binding assay using a synthetic ACB domain from PtACBP indicated preferential binding specificity toward certain polar lipids. PtACBP fused to eGFP displayed an endomembrane-like pattern, which surrounded the periphery of lipid droplets. PtACBP is likely responsible for intracellular acyl transport, affecting cell division, development, photosynthesis, and stress response. A deeper understanding of the molecular mechanisms governing storage lipid turnover will be crucial for developing diatoms and other microalgae as biotechnological cell factories.

Dietary Application of the Microalga Lobosphaera incisa P127 Reduces Severity of Intestinal Inflammation, Modulates Gut-Associated Gene Expression, and Microbiome in the Zebrafish Model of IBD.

SCOPE: Microalgae are an emerging nutritional resource of biomolecules with potential to alleviate gut inflammation. The study explores the anti-inflammatory and immunomodulatory potential of the microalga Lobosphaera incisa P127, which accumulates a rare omega-6 LC-PUFA dihomo-É£-linolenic acid (DGLA) under nitrogen starvation. The therapeutic potential of dietary supplementation with P127 is investigated in the zebrafish model of IBD (TNBS-induced colitis). METHODS AND RESULTS: Guts are sampled from zebrafish fed experimental diets for 4 weeks, before and 24 h after TNBS challenge. Diets containing 15% non-starved (Ns) and 7.5% and 15% N-starved (St) algal biomass significantly attenuate the severity of gut injury and goblet cell depletion. In contrast, diets containing 7.5% Ns and DGLA ethyl ester have no effect on gut condition. Fish fed 15% St, high-DGLA biomass, have the fewest individuals with pathological alterations in the gut. Dietary inclusion of Ns and St distinctly modulates gut-associated expression of the immune and inflammatory genes. Fish fed 15% Ns biomass display a coordinated boost in immune gene expression and show major changes in the gut microbiome prior challenge. CONCLUSION: Dietary inclusion of L. incisa biomass at two physiological states, ameliorates TNBS-induced gut inflammation, suggesting the synergistic beneficial effects of biomass components not limited to DGLA.

Microbial Communities Involved in Methane, Sulfur, and Nitrogen Cycling in the Sediments of the Barents Sea.

A combination of physicochemical and radiotracer analysis, high-throughput sequencing of the 16S rRNA, and particulate methane monooxygenase subunit A (pmoA) genes was used to link a microbial community profile with methane, sulfur, and nitrogen cycling processes. The objects of study were surface sediments sampled at five stations in the northern part of the Barents Sea. The methane content in the upper layers (0-5 cm) ranged from 0.2 to 2.4 µM and increased with depth (16-19 cm) to 9.5 µM. The rate of methane oxidation in the oxic upper layers varied from 2 to 23 nmol CH4 L-1 day-1 and decreased to 0.3 nmol L-1 day-1 in the anoxic zone at a depth of 16-19 cm. Sulfate reduction rates were much higher, from 0.3 to 2.8 µmol L-1 day-1. In the surface sediments, ammonia-oxidizing Nitrosopumilaceae were abundant; the subsequent oxidation of nitrite to nitrate can be carried out by Nitrospira sp. Aerobic methane oxidation could be performed by uncultured deep-sea cluster 3 of gamma-proteobacterial methanotrophs. Undetectable low levels of methanogenesis were consistent with a near complete absence of methanogens. Anaerobic methane oxidation in the deeper sediments was likely performed by ANME-2a-2b and ANME-2c archaea in consortium with sulfate-reducing Desulfobacterota. Sulfide can be oxidized by nitrate-reducing Sulfurovum sp. Thus, the sulfur cycle was linked with the anaerobic oxidation of methane and the nitrogen cycle, which included the oxidation of ammonium to nitrate in the oxic zone and denitrification coupled to the oxidation of sulfide in the deeper sediments. Methane concentrations and rates of microbial biogeochemical processes in sediments in the northern part of the Barents Sea were noticeably higher than in oligotrophic areas of the Arctic Ocean, indicating that an increase in methane concentration significantly activates microbial processes.

DGLA from the Microalga Lobosphaera Incsa P127 Modulates Inflammatory Response, Inhibits iNOS Expression and Alleviates NO Secretion in RAW264.7 Murine Macrophages.

Microalgae have been considered as a renewable source of nutritional, cosmetic and pharmaceutical compounds. The ability to produce health-beneficial long-chain polyunsaturated fatty acids (LC-PUFA) is of high interest. LC-PUFA and their metabolic lipid mediators, modulate key inflammatory pathways in numerous models. In particular, the metabolism of arachidonic acid under inflammatory challenge influences the immune reactivity of macrophages. However, less is known about another omega-6 LC-PUFA, dihomo-γ-linolenic acid (DGLA), which exhibits potent anti-inflammatory activities, which contrast with its delta-5 desaturase product, arachidonic acid (ARA). In this work, we examined whether administrating DGLA would modulate the inflammatory response in the RAW264.7 murine macrophage cell line. DGLA was applied for 24 h in the forms of carboxylic (free) acid, ethyl ester, and ethyl esters obtained from the DGLA-accumulating delta-5 desaturase mutant strain P127 of the green microalga Lobosphaera incisa. DGLA induced a dose-dependent increase in the RAW264.7 cells' basal secretion of the prostaglandin PGE1. Upon bacterial lipopolysaccharide (LPS) stimuli, the enhanced production of pro-inflammatory cytokines, tumor necrosis factor alpha (TNFα) and interleukin 1ß (IL-1ß), was affected little by DGLA, while interleukin 6 (IL-6), nitric oxide, and total reactive oxygen species (ROS) decreased significantly. DGLA administered at 100 µM in all forms attenuated the LPS-induced expression of the key inflammatory genes in a concerted manner, in particular iNOS, IL-6, and LxR, in the form of free acid. PGE1 was the major prostaglandin detected in DGLA-supplemented culture supernatants, whose production prevailed over ARA-derived PGE2 and PGD2, which were less affected by LPS-stimulation compared with the vehicle control. An overall pattern of change indicated DGLA's induced alleviation of the inflammatory state. Finally, our results indicate that microalgae-derived, DGLA-enriched ethyl esters (30%) exhibited similar activities to DGLA ethyl esters, strengthening the potential of this microalga as a potent source of this rare anti-inflammatory fatty acid.

Corrigendum to: 'Paleotemperature, geochemical and grain size data in Quaternary sediments from the Gloria Drift (Northwest Atlantic)' [Data in Brief 19 (2018) 758-761].

[This corrects the article DOI: 10.1016/j.dib.2018.05.105.].

Paleotemperature, geochemical and grain size data in Quaternary sediments from the Gloria Drift (Northwest Atlantic).

Data file presents information on the variation in sea surface temperatures (SST), as well as geochemical (e.g. stable isotope, calcium carbonate), micropaleontological and grain size data from the Gloria Drift (Northwest Atlantic). The data are obtained from the three marine sediment gravity core sections (AMK-4493, AI-3646 and AI-3415) which were formed during Quaternary period. Dataset contains SST values (winter and summer: 0-50 water layer) and ice-rafted debris (IRD) counts, each in 308 samples; stable isotope data (δ18O and δ13C) from 235 samples; calcium carbonate content from 351 samples; relative abundance of polar species of planktonic foraminifera Neogloboquadrina pachyderma (sinistral) (Ehrenberg) in 51 samples, data of grain size analysis in bulk sediments (123 samples) and carbonate-free sediments (664). These data provide information about conditions of sedimentation at the Gloria Drift area.