Domestication of marine microalga Nannochloropsis oceanica to freshwater medium and the physiological responses

Marine microalga Nannochloropsis oceanica LAMB0001 were domesticated(-73 0 generations,-two days each)to adapt freshwater BGll medium.A number of freshwater medium adapted colonyderived strains were obtained.The strains were verified phylogenetically to be N.oceanica LAMB0001 based on the 18 S ribosomal RNA gene.Freshwater-medium adapted strain(FA1)grew faster in the BG11 medium prepared with freshwater than wild-type N.oceanica grew in f/2 medium prepared with seawater.We assumed that(1)the expression patterns of the genes that expressed differentially between FA1 and the wild-type N.oceanica exposing to the BG11 medium(WT-F)have been reprogrammed;(2)the physiological processes in which these genes involved have been modified;and(3)a Gene Ontology(GO)term or a KEGG pathway enriched by DEGs between FA1 and WT-F has been up-or down-regulated if it was enriched simultaneously by up-or down-regulated DEGs between FA1 and WT-F,respectively.Under these assumptions,we found that FA1 reprogrammed the expression patterns of a set of genes that involved in cell adhesion,membrane and membrane integrity,material transportation,cell movement,and cellular signaling network.These changes in cellular functions and metabolic pathways indicate that the microalga modified its gene expression pattern in a wide function range and at a high regulation rank in order to adapt to the freshwater medium.It is feasible to domesticate marine microalgae to a freshwater habitat,which may aid to modify their cultivation performances.     

Effect of growth phase on the fatty acid compositions of four species of marine diatoms

The fatty acid compositions of four species of marine diatoms (Chaetoceros gracilis MACC/B13, Cylindrotheca fusiformis MACC/B211, Phaeodactylum tricornutum MACC/B221 and Nitzschia closterium MACC/B222), cultivated at 22 ℃±1 ℃ with the salinity of 28 in f/2 medium and harvested in the exponential growth phase, the early stationary phase and the late stationary phase, were determined. The results showed that growth phase has significant effect on most fatty acid contents in the four species of marine diatoms. The proportions of 16:0 and 16: 1n-7 fatty acids increased while those of 16 :3n-4 and eicosapentaenoic acid (EPA) decreased with increasing culture age in all species studied. The subtotal of saturated fatty acids (SFA) increased with the increasing culture age in all species with the exception of B13. The subtotal of monounsaturated fatty acids (MUFA) increased while that of polyunsaturated fatty acids (PUFA) decreased with culture age in the four species of marine diatoms. MUFA reached their lowest value in the exponential growth phase, whereas PUFA reached their highest value in the same phase.     

Effect of Long-Term Low-Salinity Culture on the Survival,Growth, and Nutrient Composition of Mud Crab Scylla paramamosain

This study investigated the effects of long-term low-salinity on the growth performance,proximate composition,amino acid and fatty acid profiles of Scylla paramamosain.The salinity of the low-salinity-culture group(LC)and maintained-salinity-cul-ture group(MC)were set at 5 and 25 respectively.After rearing for 30 d,the survival rate(SR)of the LC group was significantly lower,whereas the average daily molting frequency(ADMF)was significantly higher than those in MC group(P<0.05).There were no significant difference for weight gain rate(WGR)and specific growth rate(SGR)between the two groups.The moisture content of the LC group was slightly higher than the MC group without significant difference.The contents of ash,crude lipid and crude pro-tein in the LC group were lower than those in the MC group,but no significant differences were found except for ash content.A total of 17 free amino acids and 23 fatty acids were identified from the muscle of S.paramamosain.The total amino acids(TAA),essen-tial amino acids(EAA)and essential amino acid index(EAAI)had no significant difference between the two groups.The crabs from LC group had a significantly higher HUFA,including EPA,DHA,ARA.The percentage of n-3 PUFA and the ratio of n-3/n-6 PUFA were significantly higher in the LC group.These results indicated that S.paramamosain rearing at low salinity had significantly de-creased SR;however,the low-salinity environment significantly promoted the accumulation of unsaturated fatty acids(UFAs),espe-cially the n-3 PUFA,which might be related to the osmoregulation mechanism.     

Impacta of CO2 enrichment on growth and photosynthesis in freshwater and marine diatoms

The physiological responses of Nitzschia palea Kiitzing, a freshwater diatom, to elevated CO2 were investigated and compared with those of a marine diatom, Chaetoceros muelleri Lemmermann previously reported. Elevated CO2 concentration to 700 μl/L increased the dissolved inorganic carbon (DIC) and lowered the pH in the cultures of N. palea, thus enhancing the growth by 4%-20% during the whole growth period. High CO2-grown N. palea cells showed lower levels of dark respiration rates and higher Ik values. Light-saturated photosynthetic rates and photosynthetic efficiencies decreased in N. palea with the doubling CO2 concentration in airflow to the bottom of cultures, although the doubling CO2 concentration in airflow to the surface cultures had few effects on these two photosynthetic parameters. N. palea cells were found to be capable of using HCO3- in addition to gaseous CO2, and the CO2 enrichment decreased their affinity for HCO3- and CO2. Although doubled CO2 level would enhance the biomass of N. palea and C. muelleri to different extents, compared with the marine diatom, it had a significant effect on the specific growth rates of N. palea. In addition, the responses of photosynthetic parameters of N. palea to doubled CO2 concentration were almost opposite to those of C. muelleri.     

A comparative analysis of fatty acid composition and fucoxanthin content in six <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis> strains from diff erent origins

Phaeodactylum tricornutum is a potential livestock for the combined production of eicosapentaenoic acid (EPA) and fucoxanthin. In this study, six marine diatom strains identified as P. tricornutum were cultured and their total lipid, fatty acid composition and major photosynthetic pigments determined. It was found that the cell dry weight concentration and mean growth rate ranged between 0.24–0.36 g/L and 0.31–0.33/d, respectively. Among the strains, SCSIO771 presented the highest total lipid content, followed by SCSIO828, and the prominent fatty acids in all strains were C16:0, C16:1, C18:1, and C20:5 (EPA). Polyunsaturated fatty acids, including C16:2, C18:2, and EPA, comprised a significant proportion of the total fatty acids. EPA was markedly high in all strains, with the highest in SCSIO828 at 25.65% of total fatty acids. Fucoxanthin was the most abundant pigment in all strains, with the highest in SCSIO828 as well, at 5.50 mg/g. The collective results suggested that strain SCSIO828 could be considered a good candidate for the concurrent production of EPA and fucoxanthin.     

Production of γ-linolenic acid and stearidonic acid by <Emphasis Type="Italic">Synechococcus</Emphasis> sp. PCC7002 containing cyanobacterial fatty acid desaturase genes

Genetic modification is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be used to modify fatty acid metabolism. Synechococcus sp. PCC7002, a fast-growing cyanobacterium, does not contain a Δ6 desaturase gene and is therefore unable to synthesize γ-linolenic acid (GLA) and stearidonic acid (SDA), which are important in human health. In this work, we constructed recombinant vectors Syd6D, Syd15D and Syd6Dd15D to express the Δ15 desaturase and Δ6 desaturase genes from Synechocystis PCC6803 in Synechococcus sp. PCC7002, with the aim of expressing polyunsaturated fatty acids. Overexpression of the Δ15 desaturase gene in Synechococcus resulted in 5.4 times greater accumulation of α-linolenic acid compared with the wild-type while Δ6 desaturase gene expression produced both GLA and SDA. Co-expression of the two genes resulted in low-level accumulation of GLA but much larger amounts of SDA, accounting for as much to 11.64% of the total fatty acid content.     

Cloning and characterization of a delta-6 desaturase encoding gene from Nannochloropsis oculata

A gene(NANOC-D6D) encoding a desaturase that removes two hydrogen atoms from fatty acids at delta 6 position was isolated from a cDNA library of Nannochloropsis oculata(Droop) D.J.Hibberd(Eustigmatophyceae).The unicellular marine microalga N.oculata synthesizes rich long chain polyunsaturated fatty acids(LCPUFAs),including eicosapentaenoic acid(20:5n-3,EPA).The deduced protein contains 474 amino acids that fold into 4 trans-membrane domains.The neighbor-joining phylogenetic tree indicates that NANOC-D6D is ...     

Construction and characterization of a normalized cDNA library of Nannochloropsis oculata (Eustigmatophyceae)

We constructed and characterized a normalized cDNA library of Nannochloropsis oculata CS-179, and obtained 905 nonredundant sequences (NRSs) ranging from 431–1 756 bp in length. Among them, 496 were very similar to nonredundant ones in the GenBank (E ≤1.0e-05), and 349 ESTs had significant hits with the clusters of eukaryotic orthologous groups (KOG). Bases G and/or C at the third position of codons of 14 amino acid residues suggested a strong bias in the conserved domain of 362 NRSs (>60%). We also identified the unigenes encoding phosphorus and nitrogen transporters, suggesting that N. oculata could efficiently transport and metabolize phosphorus and nitrogen, and recognized the unigenes that involved in biosynthesis and storage of both fatty acids and polyunsaturated fatty acids (PUFAs), which will facilitate the demonstration of eicosapentaenoic acid (EPA) biosynthesis pathway of N. oculata. In comparison with the original cDNA library, the normalized library significantly increased the efficiencies of random sequencing and rarely expressed genes discovering, and decreased the frequency of abundant gene sequences.     

Comparative study of the nutritional composition and toxic elements of farmed and wild Chanodichthys mongolicus

Information of the difference in quality between farmed and wild fish is central to better ensuring fish products produced in aquaculture meet regulatory and consumer requirements.Proximate composition,amino acid and fatty acid profiles,and toxic elements contents of farmed and wild Chanodichthys mongolicus were established and compared.Significantly higher crude protein content while lower moisture content in farmed fish compared to wild fish were observed(P0.05).The percentages of total amino acids(TAA),total essential amino acids(TEAA),total non-essential amino acids(TNEAA)and total delicious amino acids(TDAA) in farmed fish were all significantly higher than those in the wild equivalent(PO.05).Compared to the FAO/WHO recommended reference values,the ratios of TEAA/TAA(39.84%-40.33%) were comparable to 40%and TEAA/TNEAA(66.22%-67.60%) were above 60%.Fatty acid profiles in both fanned and wild C.mongolicus were dominated by monounsaturated fatty acid(MUFA),with farmed fish contained much more MUFA content compared to wild counterpart(P0.05).Notably,wild fish exhibited significantly higher levels of total polyunsaturated fatty acid(PUFA) including eicosapentaenoic acid(EPA) and docosahexaenoic acid(DHA) than farmed fish(P0.05).The EPA(C_(20:5n3))and linoleic acid(C_(18:2n6)) were the predominant PUFA in wild and fanned C.mongolicus,respectively.Moreover,farmed fish displayed an overall lower toxic element levels(As,Cd,Pb and Hg) in comparison with wild fish,and both were far lower than the established limit standard.In conclusion,our results suggest that the nutritional quality of farmed C.mongolicus was inferior to their wild counterpart with respect to fatty acids nutrition,and therefore further studies should focus on the improving C.mongolicus diet in order to enhance the overall nutritional composition.     

龙虎斑鱼肌肉营养成分分析

对龙虎斑鱼的肌肉进行营养成分分析和肉质评价,结果表明,龙虎斑鱼新鲜肌肉中粗脂肪质量分数4.18%,粗蛋白质量分数17.05%,粗灰分质量分数1.24%,水分质量分数80.19%.肌肉蛋白质中共检测出氨基酸种类有17 种,占新鲜肌肉样品的质量分数为17.88%;7 种必需氨基酸（EAA）占新鲜肌肉样品的质量分数为7.79%,占氨基酸总量的43.57%;4 种鲜味氨基酸（DAA）占新鲜肌肉样品的质量分数为6.17%,占氨基酸总量的34.51%;必需氨基酸指数（EAAI）为101.35,其氨基酸组成比例符合FAO/WHO 标准.新鲜肌肉中共检测出脂肪酸种类有14 种.其中7 种饱和脂肪酸（SFA）占总脂肪酸的质量分数为47.29%;4 种单不饱和脂肪酸（MUFA）占总脂肪酸的质量分数为18.86%;3 种多不饱和脂肪酸（PUFA）占总脂肪酸的质量分数为33.86%,DHA 质量分数占脂肪酸总量的30.24%.龙虎斑鱼营养价值较高,海鲜味浓郁.     

Main nutritional contents of 30 Dalian coastal microalgae species

This paper reports results of study on the contents of proteins, amino acids, polysaccharose and uronic acids in 30 species of macroalgae from Shicao, Heishijiao, Shimiao, and Xiaofujiazhuang in the vicinity of Dalian City, N.E.China. The results showed that the protein contents of the 30 algae from highest (112.55μg/ml) to the lowest (0.24 p.g/ml) was in the descending order of Dictyopteris ndalata, Gelidium vagum,Gymnogongrus japonican, Ectocarpus confervoides, Tinocladia crassa, Sargassum thunberii. In general, the protein content in red algae was higher than that in brown algae. The content of free ami no acids showed nosignificent differences from 7.44μg/ml-4.96μg/ml in all these algae, in the descending order of Gymnogongrusrus japonican, Sargassum confusum, Undoria pinnatifida, Laminaria japonica and Ectocarpus confervoides. The content of polysaccharose varied from 168.2 gg/ml-22.15 p.g/ml in the descending order of Symphyocladiaia tiuscula, Scytosiphon lomentarius, Desmarestia viridis., Tinocladia crassa, Gracilaria asiatica and Porphyra yezoensis. The content of uronic acids is from 196.24μg/ml-20.77μg/ml in the descending order of Ulva lactuca,Symphyoclaldia latiuscula, Scytosiphon lomentarius, Ceramimum kondoi, Gracilaria vemucosa and Porphyra yezoensis. The fatty acids in 30 species of algae belong to Rhodophyta, Chlorophyta and Phaeophyta. Most phaeophytes have many (4-12) types of fatty acids.     

养殖海鲡肌肉的生化组成

对海鲡肌肉的营养成分含量及氨基酸、脂肪酸、无机质组成进行了研究，结果表明，海鲡的蛋白质和脂肪含量分别为21.5%和5.5%，必需氨基酸和鲜味氨基酸分别占氨基酸总量的40.9%和37.8%，不饱和脂肪酸占脂肪酸总量的65.2%，其中C205和C226的含量分别为4.5%和12.0%，3.4kg阶段的养殖海鲡肌肉的必需氨基酸和呈味氨基酸的比率最高。     

Sequence Comparison of Partial Cytochrome b Genes of Two Coilia species

1Introduction Japanese grenadier anchovy,Coilia ectenes Jordanet Seale(1905),is distributed in the northwest Pacif-ic.The congener,Osbeck's grenadier anchovy,Coil-ia mystus(Linnaeus,1758),is widely distributed inthe west Pacific.Both species inhabit coastal watersand estuaries and can reach up to rivers.The twospecies are important contributors to the coastal fish-eries of China(Zheng et al.,2003).Many studies on the fishery biology of the twospecies have been conducted(Zheng et al.,2003)…     

Effects of iron electrovalence and species on growth and astaxanthin production of Haematococcus pluvialis

To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron eleetrovalencies (Fe2+-EDTA and Fe3+-EDTA) and species (Fe-EDTA, Fe(OH)32x and FeC6H5O7) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe3+-EDTA, Fe2+-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell)was obtained under conditions of 18 μmol/L Fe2+-EDTA, despite the lower cell density (2.3x105 cell/ml)in such condition. Fe3+-EDTA is more effective than Fe2+-EDTA in improving the cell growth. Especially,the maximal steady-state cell density, 2.9x105 cell/ml was obtained at 18 μmol/L Fe3+-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH)32x, FeC6H5O7) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC6H5O7 performed the best. Under the condition of a higher concentration (36 μmol/L) of FEC6H5O7, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC6H5O7, Fe(OH)32x/x and EDTA-Fe.     

Metabolomic Fingerprint of the Model Ciliate,Tetrahymena thermophila Determined by Untargeted Profiling Using Gas Chromatography-Mass Spectrometry

The ciliate Tetrahymena is a valuable model organism in the studies of ecotoxicology. Changes in intracellular metabolism are caused by exogenous chemicals in the environment. Intracellular metabolite changes signify toxic effects and can be monitored by metabolomics analysis. In this work, a protocol for the GC-MS-based metabolomic analysis of Tetrahymena was established. Different extraction solvents showed divergent effects on the metabolomic analysis of Tetrahymena thermophila. The peak intensity of metabolites detected in the samples of extraction solvent Formula 1(F1) was the strongest and stable, while 61 metabolites were identified. Formula 1 showed an excellent extraction performance for carbohydrates. In the samples of extraction solvent Formula 2(F2), 66 metabolites were characterized, and fatty acid metabolites were extracted. Meanwhile, 57 and 58 metabolites were characterized in the extraction with Formula 3(F3) and Formula 4(F4), respectively. However, the peak intensity of the metabolites was low, and the metabolites were unstable. These results indicated that different extraction solvents substantially affected the detected coverage and peak intensity of intracellular metabolites. A total of 74 metabolites(19 amino acids, 11 organic acids, 2 inorganic acids, 11 fatty acids, 11 carbohydrates, 3 glycosides, 4 alcohols, 6 amines, and 7 other compounds) were identified in all experimental groups. Among these metabolites, amino acids, glycerol, myoinositol, and unsaturated fatty acids may become potential biomarkers of metabolite set enrichment analysis for detecting the ability of T. thermophila against environmental stresses.