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不同氮浓度对一株产油绿球藻生长、脂类积累及脂肪酸分布的影响
No full text富含多不饱和脂肪酸的产油微藻是开发高值微藻油的理想原料,一株产油微藻是否具有高值油脂开发潜力需要评估其油脂产量、中性脂比例与多不饱和脂肪酸分布等指标。低氮胁迫是研究微藻油脂积累理想的方式之一,以一株产油绿球藻(Chlorococcum sp.)为实验材料,以硝酸钠(NaNO_3)为氮源,设置17.6 mmol/L、5.9 mmol/L和3.5 mmol/L三种氮浓度,跟踪测定产油绿球藻生长、脂类组成及多不饱和脂肪酸分布的时相变化。结果显示,3.5 mmol/L和5.9 mmol/L氮浓度条件下,产油绿球藻取得了2.55 g/L和2.51 g/L的总脂产量,远高于17.6 mmol/L氮浓度组的总脂产量(1.43 g/L);降低氮浓度可以提高中性脂比例,3.5mmol/L氮浓度组取得最高的中性脂比例,为88.6%总脂质(Total lipid,TL),高于5.9 mmol/L氮浓度组(86.3%TL)和17.6 mmol/L氮浓度组(80.5%TL);降低氮浓度可以改变产油绿球藻的脂肪酸在不同脂类分子中的分布,促进脂肪酸更多分布于中性脂中,其中,3.5 m mol/L TL氮浓度组培养结束时,α-亚麻酸在中性脂的比例由接种时的33.9%提高到86.5%。适宜氮浓度对于提高产油绿球藻总脂产量、中性脂比例而多不饱和脂肪酸分布具有重要作用,产油绿球藻积累的α-亚麻酸在低氮条件下更倾向于分布在中性脂中,是一株具有高值化微藻油开发价值的藻株
First echinoderm trehalase from a tropical sea cucumber (Holothuria leucospilota): Molecular cloning and mRNA expression in different tissues, embryonic and larval stages, and under a starvation challenge
No full textTrehalases are a group of enzymes that catalyse the conversion of trehalose to glucose, and they are observed in most organisms. In this study, the first echinoderm trehalase, designated Hl-Tre, was identified from a tropical sea cucumber, Holothuria leucospilota. The full-length cDNA of H. leucospilota trehalase (Hl-Tre) is 2461 bp in length with an open reading frame (ORF) of 1788 bp that encodes a 595-amino-acid protein with a deduced molecular weight of 67.95 KDa. The Hl-Tre protein contains a signal peptide at the N terminal and a functional trehalase domain, which includes the signature motifs 1 and 2. The mRNA expression of Hl-Tre was ubiquitously detected in all selected tissues, with the highest level being detected in the intestine. By in situ hybridization (ISH), the positive Hl-Tre signals were observed in the brush borders of the intestinal mucosa. In embryonic and larval stages, the transcript levels of Hl-Tre decreased during embryonic development and increased after the pentactula stage. After a challenge of starvation, the intestinal Hl-Tre mRNA levels were observed to be first decreased and partially recovered thereafter. Overall, our study provided the first evidence for trehalase in echinoderms and showed that this enzyme was potentially linked to a trehalose metabolic pathway in sea cucumbers
Biocompatible Surface-Coated Probe for in Vivo, in Situ, and Microscale Lipidomics of Small Biological Organisms and Cells Using Mass Spectrometry
No full textLipidomics is a significant way to understand the structural and functional roles that lipids play in biological systems. Although many mass spectrometry (MS)-based lipidomics strategies have recently achieve remarkable results, in vivo, in situ, and microscale lipidomics for small biological organisms and cells have not yet been obtained. In this article, we report a novel lipidomics methodology for in vivo, in situ, and microscale investigation of small biological organisms and cells using biocompatible surface-coated probe nanoelectrospray ionization mass spectrometry (BSCP-nanoESI-MS). A novel biocompatible surface-coated solid-phase microextration (SPME) probe is prepared, which possesses a probe-end diameter of less than 5 pim and shows excellent enrichment capacity toward lipid species. In vivo extraction of living biological organisms (e.g., zebrafishes), in situ sampling a precise position of small organisms (e.g., Daphnia magna), and even microscale analysis of single eukaryotic cells (e.g., HepG2) are easily achieved by the SPME probe. After extraction, the loaded SPME probe is directly applied for nanoESI-MS analysis, and a high-resolution mass spectrometer is employed for recording spectra and identifying lipid species. Compared with the conventional direct infusion shotgun MS lipidomics, our proposed methodology shows a similar result of lipid profiles but with simpler sample pretreatment, less sample consumption, and shorter analytical times. Lipidomics of zebrafish, Daphnia magna, and HepG2 cell populations were investigated by our proposed BSCP-nanoESl-MS methodology, and abundant lipid compositions were detected and identified and biomarkers were obtained via multivariate statistical analysis
Temperature-induced physiological stress and reproductive characteristics of the migratory seahorse Hippocampus erectus during a thermal stress simulation
No full textInshore-offshore migration occurs frequently in seahorse species, either because of prey opportunities or because they are driven by reproduction, and variations in water temperature may dramatically change migratory seahorse behavior and physiology. The present study investigated the behavioral and physiological responses of the lined seahorse Hippocampus erectus under thermal stress and evaluated the potential effects of different temperatures on its reproduction. The results showed that the thermal tolerance of the seahorses was time dependent. Acute thermal stress (30 degrees C, 2-10 h) increased the basal metabolic rate (breathing rate) and the expression of stress response genes (Hsp genes) significantly and further stimulated seahorse appetite. Chronic thermal treatment (30 degrees C, 4 weeks) led to a persistently higher basal metabolic rate, higher stress response gene expression and higher mortality rates, indicating that the seahorses could not acclimate to chronic thermal stress and might experience massive mortality rates due to excessively high basal metabolic rates and stress damage. Additionally, no significant negative effects on gonad development or reproductive endocrine regulation genes were observed in response to chronic thermal stress, suggesting that seahorse reproductive behavior could adapt to higher-temperature conditions during migration and within seahorse breeding grounds. In conclusion, this simulation experiment indicates that temperature variations during inshore-offshore migration have no effect on reproduction, but promote significantly high basal metabolic rates and stress responses. Therefore, we suggest that the observed high tolerance of seahorse reproduction is in line with the inshore-offshore reproductive migration pattern of lined seahorses. This article has an associated First Person interview with the first author of the paper
Tiacumicin Congeners with Improved Antibacterial Activity from a Halogenase-Inactivated Mutant
No full textTiacumicin B (1, also known as fidaxomicin or difimicin) is a marketed drug for the treatment of Clostridium difficile infections. The biosynthetic pathway of 1 has been studied in Dactylosporangium aurantiacum subsp. hamdenensis NRRL 18085 and has enabled the identification of TiaM as a tailoring dihalogenase. Herein we report the isolation, structure elucidation, and bioactivity evaluation of 14 tiacumicin congeners (including 11 new ones) from the tiaM-inactivated mutant. A new tiacumicin congener, 3, with a propyl group at C-7 ''' of the aromatic ring was found to exhibit improved antibacterial activity
Eutrophication indirectly reduced carbon sequestration in a tropical seagrass bed
No full textAims Seagrass beds occur globally and are substantial blue carbon sinks, yet factors that affect sediment organic carbon (SOC) sequestration are poorly characterized. We investigated the influences of eutrophication on SOC sequestration capacity in a mixed seagrass bed dominated by Thalassia hemprichii and Enhalus acoroides. Methods We surveyed a tropical seagrass bed in the South China Sea along fish farming-induced gradients of nutrients to assess the variability of SOC content and composition in 30-cm-long sediment cores. Results No significant difference was observed for the SOC content and stock between the two species. Significantly higher microbial biomass carbon and SOC density were observed at the surface 3 cm layer under E. acoroides, and the longer roots of E. acoroides enhanced the seagrass contribution to the SOC near the root tip. SOC had a statistically lower concentration in the sediment layers where the seagrass roots primarily thrive close to fish farming, but greater exchangeable organic carbon was found in all the sediment layers as they approached fish farming. Nutrient enrichment markedly induced a larger ratio of labile C pools in almost all sediment layers. The mean SOC stock in the seagrass bed in Xincun Bay was 6.80 +/- 1.03 Mg C/ha, and it showed insignificant variation along the nutrient gradient. Conclusions Eutrophication may indirectly reduce the SOC sequestration capacity in the seagrass bed by enhancing labile organic carbon with a shorter resident time, and measures should be taken to reduce nutrient input into the seagrass bed to enhance its carbon sink
Phytoplankton response to a plume front in the northern South China Sea
No full textDue to a strong river discharge during April-June 2016, a persistent salinity front, with freshwater flushing seaward on the surface but seawater moving landward at the bottom, was formed in the coastal waters west of the Pearl River estuary (PRE) over the northern South China Sea (NSCS) shelf. Hydrographic measurements revealed that the salinity front was influenced by both the river plume and coastal upwelling. On shipboard nutrient-enrichment experiments with size-fractionation chlorophyll a measurements were taken on both sides of the front as well as in the frontal zone to diagnose the spatial variations of phytoplankton physiology across the frontal system. We also assessed the size-fractionated responses of phytoplankton to the treatment of plume water at the frontal zone and the sea side of the front. The biological impact of vertical mixing or upwelling was further examined by the response of surface phytoplankton to the addition of local bottom water. Our results suggested that there was a large variation in phytoplankton physiology on the sea side of the front, driven by dynamic nutrient fluxes, although P limitation was prevailing on the shore side of the front and at the frontal zone. The spreading of plume water at the frontal zone would directly improve the growth of microphytoplankton, while nano-and picophytoplankton growths could have become saturated at high percentages of plume water. Also, the mixing of bottom water would stimulate the growth of surface phytoplankton on both sides of the front by altering the surface N/P ratio to make it closer to the Redfield stoichiometry. In summary, phytoplankton growth and physiology could be profoundly influenced by the physical dynamics in the frontal system during the spring-summer of 2016
Assessing the relationship between the abundance and properties of microplastics in water and in mussels
No full textMicroplastic pollution is increasingly becoming a great environmental concern worldwide. Microplastics have been found in many marine organisms as a result of increasing plastic pollution within marine environments. However, the relationship between micoplastics in organisms and their living environment is still relatively poorly understood. In the present study, we investigated microplastic pollution in the water and themussels (Mytilus edulis, Perna viridis) at 25 sites along the coastal waters of China. Wealso, for the first time, conducted an exposure experiment in parallel on the same site using M. edulis in the laboratory. A strong positive linear relationship was found between microplastic levels in thewater and in the mussels. Fiberswere the dominantmicroplastics. The sizes ofmicroplastics in themussels were smaller than those in the water. During exposure experiments, the abundance of microbeads was significantly higher than that of fibers, even though the nominal abundance of fiberswas eight times that ofmicrobeads. In general, our results supported positive and quantitative correlations ofmicroplastics in mussels and in their surroundingwaters and that mussels were more likely to ingest smaller microplastics. Laboratory exposure experiment is a good way to understand the relative impacts of microplastics ingested by marine organisms. However, significant differences in the results between exposure experiments and field investigations indicated that further efforts are needed to simulate the diverse environmentally relevant properties of microplastics. (C) 2017 Elsevier B.V. All rights reserved
Proteome and Transcriptome Analysis of Ovary, Intersex Gonads, and Testis Reveals Potential Key Sex Reversal/Differentiation Genes and Mechanism in Scallop Chlamys nobilis
No full textBivalve mollusks exhibit hermaphroditism and sex reversal/differentiation. Studies generally focus on transcriptional profiling and specific genes related to sex determination and differentiation. Few studies on sex reversal/differentiation have been reported. A combination analysis of gonad proteomics and transcriptomics was conducted on Chlamys nobilis to provide a systematic understanding of sex reversal/differentiation in bivalves. We obtained 4258 unique peptides and 93,731 unigenes with good correlation between messenger RNA and protein levels. Candidate genes in sex reversal/differentiation were found: 15 genes differentially expressed between sexes were identified and 12 had obvious sexual functions. Three novel genes (foxl2, beta-catenin, and sry) were expressed highly in intersex individuals and were likely involved in the control of gonadal sex in C. nobilis. High expression of foxl2 or beta-catenin may inhibit sry and activate 5-HT receptor and vitellogenin to maintain female development. High expression of sry may inhibit foxl2 and beta-catenin and activate dmrt2, fem-1, sfp2, sa6, Amy-1, APCP4, and PLK to maintain male function. High expression of sry, foxl2, and beta-catenin in C. nobilis may be involved in promoting and maintaining sex reversal/differentiation. The downstream regulator may not be dimorphic expressed genes, but genes expressed in intersex individuals, males and females. Different expression patterns of sex-related genes and gonadal histological characteristics suggested that C. nobilis may change its sex from male to female. These findings suggest highly conserved sex reversal/differentiation with diverged regulatory pathways during C. nobilis evolution. This study provides valuable genetic resources for understanding sex reversal/differentiation (intersex) mechanisms and pathways underlying bivalve reproductive regulation
Soil carbon storage in mangroves is primarily controlled by soil properties: A study at Dongzhai Bay, China
No full textCoastal wetlands are well known for their considerable capacity to store carbon (C). However, the spatial patterns and major controls of soil C concentration and C density in coastal wetlands remain poorly known. We measured soil total C concentration up to one meter depth and assessed environmental and biological factors influencing soil C input and decomposition processes across various geomorphologic settings and mangrove forest types at Dongzhai Bay, China. Structural equation modeling (SEM) was used to determine the causal pathways of influencing factors on soil C concentration. We found that the variation pattern of soil C concentration across geomorphologic settings and forest types was mirrored by soil properties. From 68 to 94% (varying with soil depth) variations of soil C concentration were explained by the inter-related influencing factors included in SEM. In the upper 60 cm soil layers, soil moisture was the most important factor affecting soil C concentration. In the 60-100 cm subsoil zone, the proportion of finer soil particles was the primary control of soil C concentration variation. In contrast, aboveground biomass and nearness of sampling site to the open water, which affect autochthonous and allochthonous C inputs, had relatively weak effects on soil C concentration compared to soil properties, which affect C decomposition. Soil C concentration was a good predictor of soil C density at all soil depths. The results suggest that top-and subsoil C concentrations in mangroves are subjected to different environmental controls, but taken together, mangrove soil C storage may be primarily controlled by soil property-mediated C decomposition rate. Subsoil C deserves more attention since it may respond differently to environmental changes than the better-known topsoil C. (c) 2017 Published by Elsevier B.V