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Gamma-aminobutyric acid (GABA), widely existing in different organisms, is rapidly accumulated in plants in response to environmental stresses. The main biosynthesis and degradation pathways of GABA constitute the GABA shunt, which is tied to the tricarboxylic acid (TCA) cycle. GABA transaminase (GABA-T) and succinate semialdehyde dehydrogenase (SSADH) are two essential enzymes for the GABA degradation pathway. While there are abundant studies on GABA shunt in higher plants at the physiological and genetic levels, research on its role in microalgae remains limited. This study aimed at exploring the function of GABA-T and SSADH genes in Isochrysis zhanjiangensis, an important diet microalga, under different stresses. We cloned two GABA-T genes, IzGABA-T1 and IzGABA-T2, and one SSADH gene IzSSADH from Isochrysis zhanjiangensis and conducted heterologous expression experiments. The results showed that the overexpression of IzGABA-T1 or IzGABA-T2 enhanced the survival rates of yeast transformants under heat or NaCl stress, while the overexpression of IzSSADH improved yeast tolerance to NaCl stress but had no obvious effect on heat stress. Additionally, the results of quantitative real-time polymerase chain reaction (qPCR) showed that IzGABA-T1 transcription increased in the HT (salinity 25, 35°C) and LS (salinity 15, 25°C) groups. At 24 h, the IzGABA-T2 transcriptions increased in the HT, LS, and HS (salinity 35, 25°C) groups, but their transcription levels decreased in all groups at 48 h. IzSSADH transcription increased in the LS group. These results suggest that IzGABA-T1, IzGABA-T2, and IzSSADH are associated with temperature and salinity stresses and possess a certain preference for different stresses. [ABSTRACT FROM AUTHOR]

The primary cause of tool failure in rough cutting is the severe tool-chip friction brought on by chip adhesion and abrasive wear. To address the problem, the influence of combinations of micro-textures and AlCrN coating, and the sequence of their combinations on tool surface characteristics and cutting performance in dry cutting AISI 304 were investigated. The results of wettability and indentation tests indicate the micro-textures reduce the contact angle of the tool surface (by 13.26%) and increase the contact area between micro-textures and the coating, resulting in a better adhesive strength (grade HF3) for the first micro-textured and then AlCrN-coated tool (TCT). The results of cutting experiments demonstrate that the TCT's cutting performance is improved as the cutting speed increases between 50 and 141 m/min, with the highest reductions in main cutting force and radial cutting force reaching 27% and 38% at 141 m/min. The TCT's micro-textures reduce tool-chip contact area, while the intact AlCrN coating film decreases chip adhesion and improves the wear resistance of cutting tools. This study is expected to be applied to further improve the tool performance under dry and rough cutting conditions. [ABSTRACT FROM AUTHOR]

The morphology of the molten pool plays a crucial role in determining the surface quality of components during laser polishing of 304 stainless steel. Lens ultrasonic vibration significantly impacts the formation of the molten pool during ultrasonic vibration-assisted laser polishing. In this paper, experimental and numerical simulations were applied to investigate the surface properties of ultrasonic vibration-assisted laser polishing. A comparison was conducted between traditional laser polishing and ultrasonic vibration-assisted laser polishing in terms of the difference in peak temperature of the molten pool. The molten pool morphology obtained from the simulation is compared with the experiment results to verify the accuracy of the established model. Consequently, the model exhibits high precision and versatility, allowing for flexibility applied to laser polishing of other systems or materials. The dynamic changes of the temperature field, force field, and velocity field in the molten pool were discussed in detail to reveal the mechanism by which ultrasonic vibration influences. This research work contributes to understanding and guiding the surface formation during ultrasonic vibration-assisted laser polishing of 304 stainless steel. [ABSTRACT FROM AUTHOR]

Isochrysis zhangjiangensis is an important microalgal species used as bait in aquaculture. However, its optimal cultivation temperature is around 25 °C, limiting its use in summer when temperature is higher. To overcome this limitation, we aimed to develop a consortia of I. zhangjiangensis and bacteria that are more resistant to heat stress. Here, six thermotolerance-promoting bacterial strains were isolated from the culture of a heat-tolerant mutant strain of I. zhangjiangensis (IM), and identified as Algoriphagus marincola, Nocardioides sp., Pseudidiomarina sp., Labrenzia alba, Nitratireductor sp., and Staphylococcus haemolyticus. Further, co-culturing I. zhangjiangensis with A. marincola under high temperature conditions increased cell density, chlorophyll a, PSII maximum photochemical efficiency (Fv/Fm), and soluble protein content of microalgae. The presence of A. marincola positively influenced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and total antioxidant capacity (T-AOC) in I. zhangjiangensis cells, while concurrently reducing the levels of reactive oxygen species (ROS). Additionally, gene expression studies confirmed that co-culturing with A. marincola upregulated the expression of antioxidant-related genes (sod and pod) and stress tolerance genes (heat shock protein genes). Our findings indicate that A. marincola effectively helps I. zhangjiangensis withstand high temperature stress, leading to improved yield of microalgae during high temperature conditions. The thermotolerance-promoting bacteria can be exploited as potential inoculants for enhancing the productivity and sustainability of bait microalgae in aquaculture. [ABSTRACT FROM AUTHOR]

For the machining process of industrial parallel robots, the gravity generated by the weight of mobile platform and links will lead to the deviation of the expected machining trajectory of the tool head. In order to evaluate this deviation and then circumvent it, it is necessary to perform the robotic stiffness model. However, the influence of gravity is seldom considered in the previous stiffness analysis. This paper presents an effective stiffness modeling method for industrial parallel robots considering the link/joint compliance, the mobile platform/link gravity, and the mass center position of each link. First, the external gravity corresponding to each component is determined by the static model under the influence of gravity and mass center position. Then, the corresponding Jacobian matrix of each component is obtained by the kinematic model. Subsequently, the compliance of each component is obtained by cantilever beam theory and FEA-based virtual experiments. In turn, the stiffness model of the whole parallel robot is determined and the Cartesian stiffness matrix of the parallel robot is calculated at several positions. Moreover, the principal stiffness distribution of the tool head in each direction over the main workspace is predicted. Finally, the validity of the stiffness model with gravity is experimentally proved by the comparison of the calculated stiffness and measured stiffness in identical conditions. [ABSTRACT FROM AUTHOR]

To evaluate the pollution level and health risk of total petroleum hydrocarbon (TPH), seawater, sediments, and aquatic organisms were sampled from the southern sea area of Zhejiang Province (Yangtze River Delta, China) between 2017 and 2019. TPH was widely present in the aquatic environment and products, and its concentration was highly variable. The average value of pollution index (PI) exceeded 1 from 2017 to 2018, and 45.46–69.19% of seawater samples and 56.87–50.00% of sediment samples were polluted. The results showed significant differences in the TPH concentration in various species of aquatic organisms. The average TPH value in aquatic organisms could be ranked in the order as follows: bivalve > shrimp > crab > fish, further reflecting that the ability to accumulate and metabolize TPH existed differently among aquatic organisms within the same pond aquaculture environment. It was relatively safe to eat aquatic products since the exposure risk index was found to be far below the threshold value in this study. Therefore, it would be prudent to undertake regular monitoring of TPH to ensure effective ecosystem functioning and seafood safety in the southern Zhejiang ocean. [ABSTRACT FROM AUTHOR]

To construct an effective circular mix-culture model and investigate its culture capacity, we established one small and one large systems, with white shrimp (Litopenaeus vannamei) and razor clam (Sinonovacula constricta) cultured in separate ponds. The culture water from the L. vannamei was pumped to the S. constricta, and the culture water from the S. constricta overflowed back into the L. vannamei via gravity. In trial I, we tested four culture densities (groups 1–4), and monitored water quality, growth indices, and digestive and immune enzyme activities. From the results, the nitrogen and phosphorus levels generally increased then declined after 56 days, and were lower in groups 1 and 2. The specific growth rate of group 2 was the highest. After 56 days, activities of four digestive enzymes were increased in group 2, and lysozyme activity was significantly decreased in S. constricta in groups 1–4; Alkaline phosphatase activity of L. vannamei was increased in group 3, but decreased in S. constricta in groups 2–4; Acid phosphatase activity was significantly higher in groups 1–3 (P < 0.05), while SOD and CAT activities were significantly elevated in group 2 (P < 0.05). Thus, we applied group 2 density for trial II. In trial II, nitrogen and phosphorus concentrations declined significantly during the latter stages, and growth indices were higher than the control (P<0.05). The yields of L. vannamei and S. constricta were significantly higher than the control (P < 0.05). The results revealed a good circular mix-culture system with the optimal culture capacity for L. vannamei (40 ind m−2) and S. constricta (300 ind m−2), which provided a reference for the future culture of them. [ABSTRACT FROM AUTHOR]

Ni-Cr alloyed layers were synthesized on the surface of Q235 mild steel by double-glow plasma surface metallurgy with different electrode distance. The microstructure and phases of the alloyed layer were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD). The corrosion behavior of the Ni-Cr alloyed layers both in 3.5% NaCl and 0.5 M H2SO4 solution were systematically investigated by open-circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The obtained results reveal that the Ni-Cr alloyed layer consists of a deposited layer and an inter-diffusion layer. With increasing the electrode distance, the relative thickness, microstructure and phase composition of the Ni-Cr alloyed layers vary greatly. Polarization data show the Ni-Cr alloyed layer with the electrode distance of 15 mm has highest corrosion resistance and lowest corrosion rate, while EIS results reveal the same trend. The highest protective efficiency in 3.5% NaCl and 0.5 M H2SO4 solution are 99.23% and 99.92%, respectively, obtained for the Ni-Cr alloyed layer with 15 mm electrode distance. When the electrode distance is too large, a thin and porosity Ni-Cr alloyed layer, caused by low plasma density and Kirkendall effect, will be obtained, and will decrease the protective efficiency in corrosive medium. [ABSTRACT FROM AUTHOR]

Marine microalga Isochrysis galbana is an important feed species with a high nutritional value. Different from other unicellular algae, its cell contains two chloroplasts which are the major sites for lipid synthesis. Here, we optimized a chloroplast isolation approach suitable for the isolation of I. galbana chloroplasts and determined the purity and integrity of the isolated chloroplasts through microscopic observations and enzyme activity assay. The chloroplast lipids were analyzed with a ultrahigh-performance liquid chromatography-Q Exactive Orbitrap-mass spectrometry. This newly developed isolation approach is simple and reliable to isolate chloroplasts with high integrity and purity. The average yield of intact chloroplasts was 15.3%±0.1%. Glycolipids and acylglycerols were the main chloroplast lipids. Glycolipids accounted for 56.6% of chloroplast lipid. Digalactosyldiacylglycerol (DGDG), monogalactosyldiacylglycerol (MGDG) and sulfoquinovosyldiacylglycerol (SQDG) were the main glyceroglycolipids. The fatty acyl R1/R2 were mostly 18:4/16:1, 18:3/16:1 and 18:4/18:5 in DGDGs, 14:0/18:4, 18:4/18:5, 18:4/18:4 and 18:3/18:4 in MGDGs and 16:0/14:0, 16:0/18:3, and 18:4/18:3 in SQDGs. In addition, diacylglycerol (DAG) was the most abundant acylglycerols; the content of 22:6/18:4-DAG was the highest. There was a little amount of glycosphingolipid (GSL) in chloroplast. Digalactosylmonoglyceride (DGMG), monogalactosylmonoglyceride (MGMG), sulfoquinovosylmonoacylglycerol (SQMG), monoglyceride (MAG), phospholipids (PLs), ceramide (Cer) and betaine lipids were nearly undetectable in chloroplast. The fatty acid proportions of DGDGs, MGDGs, SQDGs, DAGs, triglycerides (TAGs) and GSLs were either higher or lower than or similar to those of whole-cell. Collectively, our isolation approach is applicable to many aspects of chloroplast biology, and may offer a reference for the isolation of chloroplasts from other marine microalgae. [ABSTRACT FROM AUTHOR]

Peroxisome proliferator activated receptors (PPAR) are kinds of key transcriptional factors in regulating LC-PUFA biosynthesis. Until now, little is known about PPAR in marine molluscs as well as in other invertebrates. Sinonovacula constricta is the first marine mollusc that is proved to possess the complete LC-PUFA biosynthetic pathway, and it can be a perfect representative to clarify this situation. In this study, the molecular properties of S. constricta PPAR were characterized, and corresponding potential regulatory roles in S. constricta Δ6 fatty acyl desaturase (Fad) transcription were estimated by dual luciferase assay. Results showed that two PPAR homologs (PPAR_a and _b) were identified in S. constricta. They both contain typical features of vertebrate PPAR, suggesting highly conserved functional regions in PPAR. By phylogenetic comparison, they are clearly different with vertebrate PPAR and can be divided into two distinctive sub-groups. Moreover, they show a high expression level in gill, labial palps, mantle and intestine. Their down-regulated expressions in trochophore larva and veliger larva might be attributed to food-deprivation. Additionally, the transcriptional activity of S. constricta Δ6 Fad promoter was significantly activated by both PPAR_a and _b, indicating that S. constricta PPAR might play a role in the regulation of LC-PUFA biosynthesis. To our knowledge, this is the first systematic analysis of PPAR in a marine mollusc. The results will provide a valuable reference for further researches on the function of marine molluscan PPAR and their underlying mechanisms in regulating LC-PUFA biosynthesis. [ABSTRACT FROM AUTHOR]

A system of sequential extraction and purification, coupled with ultra-performance liquid chromatography coupled with quadrupole electrostatic field orbital trap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-HRMS), was established and subsequently applied to the analysis of common carotenoids with very different physicochemical properties from aquatic organisms. In the first stage of extraction, free carotenoids were extracted with methanol (0.1% butylated hydroxytoluene (BHT)) and purified using hydrophile-lipophile balance column (HLB). In the second stage of extraction, extremely hydrophobic carotenoid esters were mainly extracted with methanol-dichloromethane (0.1% BHT) and purified using Alumina-N. In total, nearly 50 distinct carotenoid species were identified from common aquatic organisms by combining first-stage and second-stage solutions with recoveries of no less than 86.9%, which contained 25 free carotenoids and 24 carotenoid esters, respectively. Additionally, astacin diester 22:6/16:0, oxidized-astaxanthin diester 22:6/16:0, and adonixanthin diester 22:6/20:5 were identified for the first time from Penaeus monodon. Our results show that this methodology was a significant improvement over other alternatives for analyzing carotenoids because of its compatibility with free carotenoids and carotenoid esters and provides a technical guarantee not only for enriching carotenoid species but also for the tracing of metabolic pathways in aquatic organisms. [ABSTRACT FROM AUTHOR]

The freshwater microalga Haematococcus pluvialis accumulates large amounts of fatty acids in response to adverse conditions. However, the key fatty acid desaturase genes in H. pluvialis remain unknown. In this study, we cloned and functionally characterized a A12 fatty acid desaturase gene, and designated it as HpFAD2. The open reading frame of HpFAD2 consisted of 1137 base pairs and encoded 378 amino acids. The deduced polypeptide showed 70% identity to other endoplasmic reticulum Δ12 fatty acid desaturases, whereas it had only 44% identity to plastid Δ12 fatty acid desaturases. The PSORT algorithm and phylogenetic analysis further confirmed its affiliation to the endoplasmic reticulum Δ12 fatty acid desaturases. Heterologous expression was performed in Saccharomyces cerevisiae cells transformed with the recombinant plasmid pYES2-HpFAD2. Two additional fatty acids (C16:2 and C18:2) were detected in the yeast transformants. The results indicated Δ12 desaturation activity and substrate preference for C18:1 over C16:1. The transcriptional levels of H. pluvialis HpFAD2 at different growth stages were measured by quantitative polymerase chain reaction (PCR), indicating that the HpFAD2 transcriptional levels were significantly higher in red cells than those in green cells. Our study brings more insight into the fatty acid biosynthetic pathway of H. pluvialis. [ABSTRACT FROM AUTHOR]

The large-scale farming of Nannochloropsis spp. has long been subject to high temperature. Though salicylic acid is widely used to enhance the high temperature resistance of higher plants, related research in microalgae is still in its infancy. In this study, Nannochloropsis oceanica cells at 25 °C were transferred to high temperature (35 °C) for 96 h, during which period salicylic acid with various concentrations (0, 15, 25, 35, and 50 mg L−1) were added into high temperature groups. The results indicated that high temperature could heavily inhibit the growth of N. oceanica, and result in various physiological and biochemical changes. The addition of exogenous salicylic acid at moderate concentration distinctly alleviated the inhibition of heat stress on N. oceanica. Moreover, further analysis indicated that exogenous salicylic acid could significantly increase the contents of soluble sugars, soluble proteins, total unsaturated fatty acids, and catalase activity, but result in the decrease of the nitrate reductase activity, the malondialdehyde content, and fatty acid profile. Our results also demonstrated that salicylic acid at a concentration of 15 mg L−1 received the best growth performance of N. oceanica under 35 °C. This study investigates the thermal protection effect of salicylic acid on N. oceanica under high temperature, and can provide valuable information for the large-scale production of microalgae. [ABSTRACT FROM AUTHOR]

Using the case of Shanghai, this article, by starting with a discussion of the historical evolution of political legitimacy in China, analyzes the public sphere in Modern China and its native ideological origin, historical forms and functions in public opinion, and probes into its universality and particularity through a comparison with Jürgen Habermas's notion of the public sphere. [ABSTRACT FROM AUTHOR]

Background: Sinonovacula constricta is an economically important bivalve species in China, Korea and Japan that widely resides in estuarine and coastal areas where salinity fluctuates rapidly. However, little is known about its adaptation mechanisms to acute salt stresses. Objective: To reveal the underlying molecular mechanisms involved in acute salt stresses in juvenile S. constricta. Methods: Nine cDNA libraries (triplicate each trial) were established from juvenile S. constricta, which were subjected to low salinity (5 psu), optimal salinity (15 psu) and high salinity (25 psu) for 6 h, respectively. Results: Illumina sequencing generated 478,587,310 clean reads totally, which were assembled into 427,057 transcripts of 246,672 unigenes. Compared with the control, 1259 and 2163 differentially expressed genes (DEGs) were identified under acute low and high salt stresses, respectively. GO and KEGG enrichment analyses of DEGs revealed that several key metabolic modulations were mainly responsible for the acute salt stresses. According to the significantly highlighted KEGG pathways, some key DEGs were identified and discussed in details. Notably, based on which, some potential osmolytes were further speculated. Conclusion: Here, we carried out a unique report of comparative transcriptome analyses in juvenile S. constricta in response to acute salt stresses. The identified DEGs and their significantly enriched GO terms and KEGG pathways were critical for understanding and further investigating the underlying the physical and biochemical performances, and ultimately facilitated S. constricta breeding. Besides, the transcriptome data greatly enriched the genetic information of S. constricta, which were valuable for promoting its molecular biology researches. [ABSTRACT FROM AUTHOR]

Volatiles with a pleasant smell are typical characteristics of both raw and cooked seafood. However, the effect of salinity on volatiles in marine bivalves remains unclear. In the current study, the volatiles in raw and cooked Sinonovacula constricta cultured under different salinities were investigated by head space-solid phase microextraction and gas chromatography-mass spectrometry. Overall 28 volatiles were identified in the raw samples and mainly comprised 1-pentanol (15.32-23.95%), 1,5-octadien-3-ol (14.20-16.73%) and 1-octen-3-ol (14.20-15.63%). A total of 41 volatiles, dominated by pentanal (32.33-46.80%), 1-pentanol (10.88-16.48%) and hexanal (5.64-13.70%), were determined in the cooked samples. Irrespective of whether they were raw or had been cooked, S. constricta cultured under high salinity possessed more abundant volatiles than those reared under low salinity. When the culture salinity of S. constricta was raised, changes in the volatile content occurred. For S. constricta cultured at low salinity, rearing at high salinity for several days prior to harvest could greatly improve the volatile content. This finding is of value for the improvement of volatiles important for odor and taste in other marine bivalves. [ABSTRACT FROM AUTHOR]

Much attention has been paid on studies of astaxanthin accumulation process in Haematococcus pluvialis industry. However, growth of H. pluvialis in motile vegetative stage is still the most important and problematic part in the whole cultivation process, such as low growth rate and cell yields. Motile vegetative cells are extremely sensitive to various stresses which make it difficult to maintain the cells of this state to grow. Previous reports showed that motile vegetative cells may have higher biomass yields if applied monochromatic red light. However, metabolic responses of these cells are not completely understood, which constraints application of this illumination protocol in industry. The aim of this study was to examine how critical biochemical changes of H. pluvialis motile vegetative cells were affected by red light when compared with white light. Variation of photosynthetic pigments composition and lipids were mainly studied. By comparing growth process of cultures in red light and white light, prominent variation of pigments composition and lipids changes were observed. The results showed that, even though cell proliferation was the same during exponential growth phase, variation of photosynthetic pigment composition and lipids occurred. The final biomass of cell number was higher in red light group than in white light group. The variations were significant different. Increase or decrease of major photosynthetic membrane lipids to some extent did not influence photosynthesis of the vegetative cells during this phase. However, vegetative cells under polychromatic white light other than monochromatic red light need further metabolic process to adjust its pigment composition and lipids, possibly this is energetically and biochemically unfavorable for motile vegetative cells to growth under white light, a light condition normally not considered as a stress. [ABSTRACT FROM AUTHOR]

Salmonella is a major pathogen that causes acute foodborne outbreaks worldwide. Seafood, particularly shellfish, is a proven source of Salmonella spp. infection because many people prefer to eat it raw or lightly cooked. However, traditional identification methods are too time-consuming and complex to detect contamination of bacteria in the food chain in a timely manner, and few studies have aimed to identify Salmonella in shellfish early in the supply chain. We herein developed a method for rapid detection of Salmonella in shellfish based on the method of recombinase polymerase amplification (RPA) combined with lateral flow dipstick (LFD), which targets the invasion gene A (invA). The RPA-LFD was able to function at 30-45 °C, and at the temperature of 40 °C, it only took 8 min of amplification to reach the test threshold of amplicons. The established method had both a good specificity and a sensitivity of 100 fg DNA per reaction (20 µL). Regarding practical performance, RPA-LFD performed better than real-time PCR. Another advantage of RPA-LFD is that it was capable of being performed without expensive equipments. Thus, RPA-LFD has potential for further development as a detection kit for Salmonella in shellfish and other foods under field conditions. [ABSTRACT FROM AUTHOR]

Isochrysis galbana is a species of marine microalgae that is principally used to feed the larvae and early juveniles of bivalve mollusks (e.g., ark shells, clams, mussels, oysters and scallops). The artificial hatchery stages of most of these larvae are primarily occur during high-temperature seasons, when the water temperature in the breeding pool frequently exceeds 30 °C and even reaches 35 °C, which may change the lipid composition of I. galbana, thus affecting its nutritional value. In this experiment, we investigated changes in the lipid composition of I. galbana Parke at high temperature using ultra-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. The results showed that the sulfoquinovosyldiacylglycerol (SQDG), monogalactosyldiacylglycerol (MGDG), diacylglycerylcarboxyhydroxymethylcholine (DGCC) and digalactosyldiacylglycerol (DGDG) contents increased during growth at 20 and 35 °C. Conversely, the lyso-SQDG, lyso-MGDG, lyso-DGDG, lyso-DGCC and triacylglycerol (TAG) contents clearly decreased. Moreover, higher SQDG, MGDG, DGDG and DGCC contents and lower lyso-lipid and TAG contents were observed in I. galbana Parke grown at 35 versus 20 °C. In addition, the content of docosahexaenoic acid (DHA) improved at 20 and 35 °C during growth, and DHA accumulated to greater levels at 35 °C than at 20 °C at the same time points. These results revealed an increase in DHA content as the temperature rose, which indicated that the nutritional value of I. galbana Parke during logarithmic phase improved in the same cultured time with an increasing temperature. [ABSTRACT FROM AUTHOR]

Based on the growing concern for global warming, changes in the lipid profile of the red alga Pyropia haitanensis were examined under different high temperatures. Lipidomes of P. haitanensis cultured at 20 °C as the control group, and 25, 28, and 35 °C as the high-temperature group, were systematically characterized using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and multivariate statistical analysis. Lipidomics analysis identified a total of 39 lipids as lipid biomarkers belonging to the classes including DAG, DGDG, Lyso-MGDG, Lyso-DGDG, SQDG, Lyso-SQDG, Lyso-PA, Lyso-PC, Lyso-PE, Lyso-PI, Lyso-PG, and PIP. The levels of glycolipids, Lyso-PE, Lyso-PI, Lyso-PG, and PIP decreased as the culture temperature increased from 20 to 35 °C. Biomarker-based heat map and box-plots showed the differences in lipid biomarker expression among the four elevated temperatures. The up- or downregulation of these lipid biomarkers offers plausible physiological insights into lipid metabolism in P. haitanensis in response to high-temperature stress. [ABSTRACT FROM AUTHOR]

A sensitive method based on electrospray ionization tandem mass spectrometry was used to profile glycerolipids in Pyropia haitanensis and their changes responding to agaro-oligosaccharides. Ten monogalactosyldiacylglycerols (MGDGs), twelve digalactosyldiacylglycerols (DGDGs), five sulfoquinovosyldiacylglycerols (SQDGs), five phosphatidylglycerols (PGs), fifteen phosphatidylcholins (PCs), three phosphatidic acids (PAs), and three phosphatidylethanolamines (PEs) were identified in P. haitanensis. We found the SQDG was the most abundant species, followed by MGDG, DGDG, PG, PC, PE, and PA of the total glycerolipids. The predominant lipid species contained C20 fatty acids at sn-1/ sn-2 positions, which was different from higher plants. Changes in membrane lipid species occurred when P. haitanensis were treated with agaro-oligosaccharides. At first, agaro-oligosaccharides induced an increase in total glycerolipids including the galactolipids such as MGDG (20:5/20:5) and phospholipids such as PC (18:3/20:5), suggesting that agaro-oligosaccharides caused changes of lipids in chloroplasts and plasma membrane. With increased treatment time, a large decline in major plasma membrane lipids (PCs and PEs) was observed, but not galactolipids (MGDGs and DGDGs), suggesting that the lipid changes occurred mainly at the plasma membrane after prolonged treatment. [ABSTRACT FROM AUTHOR]

Diatoms are considered to have great potential as new biofuel sources because they can effectively accumulate triacylglycerols (TAGs). Detailed structure information of TAG in diatoms is much needed not only for the assessment of biofuel quality such as fatty acid chain length and unsaturation degree but also for the tracing of biosynthetic precursors because the biosynthesis of TAG is typically completed by utilizing the diacylglycerol acyltransferase in the cytoplasm. In this report, a comprehensive characterization of TAGs in marine diatoms was performed using ultra performance liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry. Many types of major TAGs were identified for the first time in these diatoms: 12 TAGs in Chaetoceros debilis, 9 TAGs in Phaeodactylum tricornutum Bohlin, 16 TAGs in Nitzschia closterium f. minutissima, 16 TAGs in Thalassiosira weissflogii, 13 TAGs in Thalassiosira sp., 16 TAGs in Stephanodiscus asteaea and 7 TAGs in Skeletonema costatum. Semi-quantification of TAGs in these diatoms was also carried out, and it was found that the contents of individual TAGs ranged from 0.5 ± 0.1 to 217.9 ± 8.1 nmol mg total lipids. In addition, the total lipid contents in diatoms ranged from 143.6 ± 16.3 to 201.1 ± 16.3 mg g dry microalgae and the total TAG contents ranged from 36.8 ± 9.5 to 793.2 ± 54.4 nmol mg total lipids. By comparative analysis of the compositions and concentrations of major TAGs in the seven algal strains, N. closterium f . minutissima with high abundance of TAGs containing the most monounsaturated fatty acids (mainly palmitoleic acid) was considered as one of the most promising diatom strains for microalgal biofuel production. Additionally, based on the information of sn-2 fatty acid obtained (mainly C16 in the sn-2 position), we propose the hypothesis that TAGs in diatoms are mainly derived from lipids in chloroplasts through the prokaryotic biosynthesis pathway, including monogalactosyldiacylglycerol and digalactosyldiacylglycerol. [ABSTRACT FROM AUTHOR]

The marine red alga Pyropia haitanensis (Protoflorideophyceae, Bangiaceae) has a nonvascular and multicellular structure and emerged earlier in evolution than other cultivatable red algae. It has been reported that lipid mediators from both the eicosanoid and octadecanoid pathways are involved in the innate immunity of other marine algae. But the defense strategies of P. haitanensis are not clearly understood. Here, we investigated the lipid defense of P. haitanensis elicited by agaro-oligosaccharides. The results indicate that the resistance of P. haitanensis was elicited and hydrogen peroxide was released by agaro-oligosaccharides. In P. haitanensis, C20 fatty acids are the essential fatty acids. Phospholipase A 2 was activated, and the free fatty acids decreased 3 h after treatment with agaro-oligosaccharides. Gas chromatography–mass spectrometry analyses revealed that the contents of volatile organic compounds increased after treatment for 3 h, which indicated that these free fatty acids were metabolized to volatile organic compounds. In conclusion, the lipid metabolic defense pathway of P. haitanensis was mainly via the C20 metabolism pathway. The C20 fatty acid was rapidly metabolized to volatile organic compounds, but not oxidized to oxylipins in response to agaro-oligosaccharides. [ABSTRACT FROM AUTHOR]

Changes in membrane lipid composition play multiple roles in plant adaptation and survival in the face of chilling and freezing damage. The ultra-performance liquid chromatography/quadrupole-TOF-MS (UPLC/Q-TOF-MS)-based approach was developed for investigating the lipid changes during cold exposure in Stephanodiscus sp. followed by multivariate statistical analysis including principal components analysis, partial least squares discriminant analysis and orthogonal projection on latent structure discriminant analysis for data classification and potential biomarkers selection. The analysis demonstrated dramatic lipid alterations take place in both extraplastidic and plastidic membranes. Thirty-eight lipid molecules were selected and identified as putative biomarkers, including chlorophyll a degradation products, triacylglycerol, phosphatidylcholine, phosphatidylglycerol, sulfo-quinovosyldiacylglycerol, monogalactosyldiacylglyceroll, lyso-phosphatidylglycerol, lyso-phosphatidylcholine, lyso-monogalactosyldiacylglycerol and lyso-sulfoquinovosyldiacylglycerol. These metabolites have been shown previously to function in energy storage, membrane stability and photosynthesis efficiency. This study is the first one using UPLC/Q-TOF-MS-based lipidomic profiling with multivariate statistical analysis to explore the lipidomic changes of microalgae in response to stress conditions, which promotes better understanding of their physiology and ecology. [ABSTRACT FROM AUTHOR]

A facile method based on high performance liquid chromatography coupled with electrospray ionization tandem triple quadrupole mass spectrometry (HPLC-ESI-QqQ-MS) has been established to investigate the production of the oxidized scytonemin by Nostoc commune Vauch in different environmental conditions. In optimized HPLC-ESI-QqQ-MS conditions, the oxidized scytonemin can be effectively detected in selected reaction monitoring (SRM) mode. After regression, high linearity of the calibration curve was achieved with a correlation coefficient ( r) at 0.99. The limit of detection and limit of quantification were 0.03 and 0.10 ng mL, respectively. The recovery of the oxidized scytonemin was at 76.90 %, and the relative standard deviations of inter- and intraday precisions were lower than 8.95 % ( n = 4). Subsequently, the production of the oxidized scytonemin from N. commune has been investigated in different culture conditions. High culture temperature, strong illumination intensity, and light-dark cycle (12:12 h) were found to be good for producing the oxidized scytonemin by N. commune. In short, the HPLC-QqQ-SRM-MS method is a powerful tool for comprehensive analysis of the oxidized scytonemin from N. commune, owing to its excellent selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

Ultra Performance Liquid Chromatography-Electrospray ionization-Quadrupole-Time of Flight Mass Spectrometry (UPLC-ESI-Q-TOF-MS) is a powerful lipidomic tool. In this study, we developed a UPLC/Q-TOF-MS based method to investigate the lipid metabolomic changes in different growth phases of Nitzschia closterium f. minutissima. The data classification and biomarker selection were carried out by using multivariate statistical analysis, including principal components analysis (PCA), projection to latent structures with discriminant analysis (PLS-DA), and orthogonal projection to latent structures with discriminant analysis (OPLS-DA). We discovered that the intercellular lipid metabolites were significantly different among exponential, early stationary and late stationary phases. Thirty-one lipid molecules were selected and identified as putative biomarkers, including free fatty acid, Harderoporphyrin, phosphatidylglycerol, 1,2-diacyglycerl-3-O-4′-(N,N-trimethy)-homoserine, triacylglycerol, cholesterol, sulfoquinovosyldiacylglycerol, lyso-sulfoquinovosyldiacylglycerol, monogalactosyldiacylglycerol, digalactosyldiacylglycerol and lyso-digalactosyldiacylglycerol. These lipids have been shown previously to function in energy storage, membrane stability and photosynthesis efficiency during the growth of diatoms. Further analysis on the putative biomarkers demonstrated that nitrate starvation played critical role in the transition from exponential phase to stationary phase in N. closterium. This study is the first one to explore the lipidomic changes of microalgae in different growth phases, which promotes better understanding of their physiology and ecology. [ABSTRACT FROM AUTHOR]

The serum polar lipid metabolic changes for two common cage-cultured fishes, yellow coraker Pseudosciaena crocea and Japanese seabass Lateolabrax japonicus, after tropical storm attack have been studied by ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC-qTOF-MS). The full scan mass spectrometry combined with principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) indicated that yellow croaker underwent significant chemico-physiological changes during the recovery process, whereas Japanese seabass did not show such noticeable time-dependent consistent metabolites change patterns. Further identification of the metabolite biomarkers showed the increase of phosphatidylcholine with high unsaturated fatty acid and lysophospholipids, and the decrease of phosphatidylcholine with saturated fatty acids and plasmologens, which indicated the need of energy supplement and successive stressful inflammation. The increase of taurocholic acid and decrease of cortol could be regarded as the physiological alleviation measure during the recovery period. This is the first metabolomic study to tackle the fish physiological response for the complex environmental changes, and demonstrated that lipidomics is an effective analytical tool for predicting the stress resistance of fish to ultra uncontrolled environmental stress. [ABSTRACT FROM AUTHOR]

Precise structural identification of photosynthetic polar glycerolipids in microalga Tetraselmis chuii has been established using Ultra Performance Liquid Chromatography-Electrospray ionization-Quadrupole-Time of Flight Mass Spectrometry (UPLC-ESI-Q-TOF-MS) by direct analysis of the total lipids extract. The mass spectrometry was performed in reflective time-of-flight using electron spraying ionization in both positive and negative modes. The structural determination was based on the characteristic product ions yielded by different glycerolipids under ESI-MS/MS mode, and confirmed the molecular species by the carboxylate anions produced by glycerolipids in the negative mode. As a result, more than 40 lipid molecular species, including 11 monogalactosyldiacylglycerols (MGDG), 7 digalactosyldiacylglycerols (DGDG), 16 sulfoquinovosyldiacylglycerols (SQDG), and 9 phosphatidylglycerols (PG), were detected in Tetraselmis chuii, which had never been identified before in this microalga. Furthermore, some intact lipid molecules with hydroxylated fatty acids that could not be detected by the traditional GC-MS method were found this time, providing novel information for the photosynthetic lipidome of Tetraselmis chuii. Comparative studies on fatty acids at the sn-2 position showed that SQDG and MGDG are dominantly biosynthesized through the prokaryotic pathway, PG is a typically mixed biosynthetic pathway, while DGDG is somewhat peculiar with C14:0 and C16:0 at its sn-2 position. This method could provide a full structural profile of intact photosynthetic lipid molecular species, which may be applied to study the physiological and ecological functions of lipid by monitoring their individual changes. [ABSTRACT FROM AUTHOR]