Institute of Hydrobiology, Chinese Academy Of Sciences
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Nonlinear response of methane release to increased trophic state levels coupled with microbial processes in shallow lakes
No full textShallow lakes are a crucial source of methane (CH4), a potent greenhouse gas, to the atmosphere. However, large uncertainties still exist regarding the response of CH4 emissions to the increasing trophic levels of lakes as well as the underlying mechanisms. Here, we investigate the CH4 emission flux from lakes with different trophic states in the middle and lower reaches of the Yangtze River basin, China to evaluate the effect of the trophic lake index (TLI) on CH4 emissions. The mean CH4 emission fluxes from mesotrophic, eutrophic, middle-eutrophic, and hyper-eutrophic lakes were 0.1, 4.4, 12.0, and 130.4 mg m(-2) h(-1), respectively. Thus, the CH4 emission flux ranged widely and was positively correlated with the degree of eutrophication. The relative abundance of methanogens with respect to the total population for the mesotrophic, eutrophic, mid-eutrophic, and hyper-eutrophic states was 0.03%, 0.35%, 0.94%, and 1.17%, respectively. The biogeographic-scale pattern of lakes classified as each of these four trophic states indicated that CH4 emissions could be well-predicted by the NH4+-N concentration in the water column, as both NH4+-N and CH4 were produced during mineralisation of labile organic matter in lake sediment. In addition, the shift from clear to turbid water, which is an unhealthy evolution for lakes, was associated with a nonlinear increase in the CH4 emissions from the studied lakes. In particular, the hypereutrophic lakes functioned as CH4 emission hotspots. Our findings highlight that nutrient levels, as a potential facilitator of CH4 emissions, should be considered in future research to accurately evaluate the greenhouse gas emissions from shallow lakes. (C) 2020 Elsevier Ltd. All rights reserved
High-throughput fluorescence-activated cell sorting for cell wall-deficient microalgal mutants screening
No full textBioavailability and extraction efficiency of the natural antioxidant astaxanthin from the unicellular green alga Haematococcus pluvialis have been limited by the rigid algal cell walls. A high-throughput fluorescence-activated cell sorting (FACS) pipeline was developed in this study with the aim to screen cell wall-deficient mutants. The fluorescein-conjugated lectin-Ricinus communis Agglutinin I (RCA(120)) was used as a marker for binding the sugar moieties of the algal cell walls, which enabled discriminating the algal strains that differed in the cell walls. By utilizing the established FACS pipeline, a cell wall-deficient mutant (i.e. mutant-264) with the significantly reduced RCA(120)-fluorescein intensity was screened from the mutant library. The total content of the cell wall-associated sugars was reduced by 43.9% in the mutant-264 as compared to that of the wild type, with significant decrease in mannose, mannitol and galactose. The dry weight, astaxanthin content and extraction efficiency were improved by 21.1%, 13.1% and 16.5%, respectively, in mutant-264 as compared to that of the wild type. This study not only demonstrated the feasibility of utilization of the FACS-based high-throughput pipeline for cell wall mutant screening, but also delivered a novel promising H. pluvialis strain with multiple improved traits for industrial applications
Comprehensive utilization of the filamentous oleaginous microalga Tribonema utriculosum for the production of lipids and chrysolaminarin in a biorefinery concept
No full textPrevious studies have focused on the accumulation of lipid and palmitoleic acid in Tribonema spp., while chrysolaminarin produced by these filamentous oleaginous microalgae has rarely been reported. In this study, the effects of different initial nitrogen concentrations on the growth, lipid and chrysolaminarin accumulation of T. utriculosum were investigated, and the extraction route of lipid was also optimized, accompanied by the isolation and characterization of chrysolaminarin. The results showed that the highest biomass concentration (6.21 +/- 0.17 g/L) of T. utriculosum was obtained at 3 mM of initial nitrogen concentration with the lowest level of chrysolaminarin (10.74 +/- 0.42% of dry weight (DW)), while higher initial nitrogen concentrations were more conducive to lipid and chrysolaminarin accumulation, especially for 18 mM, leading to the highest lipid content (43.80 +/- 0.57% of DW). To minimize the biorefinery process cost, an optimized route for lipid extraction was suggested to simultaneously achieve the goal of disintegration of algal structure and extraction of intracellular polysaccharides by dilute acid pretreatment, which improved lipid extraction efficiency from 38.70% to 87.09%. Most importantly, a homogeneous chrysolaminarin was successfully isolated from T. utriculosum and characterized with an average molecular weight of 5.99 kDa. It was found to mainly comprise glucose (60.13%) and was linked by the beta-D-(1 -> 3) (main chain) and beta-D-(1 -> 6) (branch chain) glycosidic bonds. This study is the first report on the isolation and characterization of chrysolaminarin from microalgae Tribonema, and provides new insights into fully utilizing T. utriculosum biomass for broadening the potential applications of microalgae-based products
Regulation and remodeling of intermediate metabolite and membrane lipid during NaCl-induced stress in freshwater microalgaMicractiniumsp. XJ-2 for biofuel production
No full textMicroalgae can accumulate a large fraction of reduced carbon as lipids under NaCl stress. This study investigated the mechanism of carbon allocation and reduction and triacylglycerol (TAG) accumulation in microalgae under NaCl-induced stress.Micractiniumsp. XJ-2 was exposed to NaCl stress and cells were subjected to physiological, biochemical, and metabolic analyses to elucidate the stress-responsive mechanism. Lipid increased with NaCl concentration after 0-12 hr, then stabilized after 12-48 hr, and finally decreased after 48-72 hr, whereas TAG increased (0-48 hr) and then decreased (48-72 hr). Under NaCl-induced stress at lower concentrations, TAG accumulation, at first, mainly shown to rely on the carbon fixation through photosynthetic fixation, carbohydrate degradation, and membrane lipids remodeling. Moreover, carbon compounds generated by the degradation of some amino acids were reallocated and enhanced fatty acid synthesis. The remodeling of the membrane lipids of NaCl-induced microalgae relied on the following processes: (a) Increase in the amount of phospholipids and reduction in the amount of glycolipids and (b) extension of long-chain fatty acids. This study enhances our understanding of TAG production under NaCl stress and thus will provide a theoretical basis for the industrial application of NaCl-induced in the microalgal biodiesel industry
The intestinal microbiome of an Indo-Pacific humpback dolphin (Sousa chinensis) stranded near the Pearl River Estuary, China
No full textThe mammalian intestinal microbiome is critical for host health and disease resistance. However, the cetacean intestinal microbiota remains relatively unexplored. By using high-throughput 16S rRNA gene sequencing, we analyzed intestinal bacterial samples from an Indo-pacific humpback dolphin (Sousa chinensis) stranded near the Pearl River Estuary in China. The samples included 3 anatomical regions (foregut, midgut, and rectum) and 2 anatomical locations (content and mucus). Our analyses revealed that the dolphin intestinal bacteria contained 139 operational taxonomic units (OTUs), dominated at the phyla level byFirmicutes(47.05% in the content; 94.77% in the mucus), followed byBacteroidetes(23.63% in the content; 1.58% in the mucus) andGammaproteobacteria(14.82% in the content; 2.05% in the mucus). The intestinal bacteria had a small core community (15 OTUs, accounting for 99.74% of the reads), some of which could be potentially pathogenic to both human and dolphins. As an alternative to sampling the dolphin intestinal bacteria, fecal sampling could be used. Additionally, function potentials such as, xenobiotics biodegradation, beta-lactam resistance, and human disease-related pathways, were detected in the dolphin intestinal bacteria. These findings provide the first baseline knowledge of the intestinal microbiome of the Indo-Pacific humpback dolphin, which may offer new insights into cetacean conservation by using microbial surveillance
Probiotic modulation of perfluorobutanesulfonate toxicity in zebrafish: Disturbances in retinoid metabolism and visual physiology
No full textPerfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb gut microbiota, retinoid metabolism and visual signaling in teleosts, while probiotic supplementation can shape gut microbial community to improve retinoid absorption. However, it remains unknown whether probiotic bacteria can modulate the toxicities of PFBS on retinoid metabolism and visual physiology. In the present study, adult zebrafish were exposed for 28 days to 0,10 and 100 mu g/L PFBS, with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic was examined regarding retinoid dynamics (intestine, liver and eye) and visual stimuli transmission. PFBS single exposures remarkably inhibited the absorption of retinyl ester in female intestines, which were, however, restored by probiotic to normal status. Although coexposure scenarios markedly increased the hepatic storage of retinyl ester in females, mobilization of retinol was reduced in livers by single or combined exposures regardless of sex. In the eyes, transport and catalytic conversion of retinol to retinal and retinoic acid were interrupted by PFBS alone, which were efficiently antagonized by probiotic presumably through an indirect action. In response to the availability of retinal chromophore, transcriptions of opsins and arrestin genes were altered adaptively to control visual perception and termination. Neurotransmission across retina circuitry was changed accordingly, centering on epinephrine and norepinephrine. In summary, the present study found the efficient modulation of probiotic on retinoid metabolic disorders of PFBS pollution, which subsequently impacted visual signaling. A future work is warranted to provide mechanistic clues in retinoid interaction. (C) 2020 Elsevier Ltd. All rights reserved
Probiotic modulation of perfluorobutanesulfonate toxicity in zebrafish: Disturbances in retinoid metabolism and visual physiology
No full textPerfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb gut microbiota, retinoid metabolism and visual signaling in teleosts, while probiotic supplementation can shape gut microbial community to improve retinoid absorption. However, it remains unknown whether probiotic bacteria can modulate the toxicities of PFBS on retinoid metabolism and visual physiology. In the present study, adult zebrafish were exposed for 28 days to 0,10 and 100 mu g/L PFBS, with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic was examined regarding retinoid dynamics (intestine, liver and eye) and visual stimuli transmission. PFBS single exposures remarkably inhibited the absorption of retinyl ester in female intestines, which were, however, restored by probiotic to normal status. Although coexposure scenarios markedly increased the hepatic storage of retinyl ester in females, mobilization of retinol was reduced in livers by single or combined exposures regardless of sex. In the eyes, transport and catalytic conversion of retinol to retinal and retinoic acid were interrupted by PFBS alone, which were efficiently antagonized by probiotic presumably through an indirect action. In response to the availability of retinal chromophore, transcriptions of opsins and arrestin genes were altered adaptively to control visual perception and termination. Neurotransmission across retina circuitry was changed accordingly, centering on epinephrine and norepinephrine. In summary, the present study found the efficient modulation of probiotic on retinoid metabolic disorders of PFBS pollution, which subsequently impacted visual signaling. A future work is warranted to provide mechanistic clues in retinoid interaction. (C) 2020 Elsevier Ltd. All rights reserved
Photoperiod and temperature as dominant environmental drivers triggering secondary growth resumption in Northern Hemisphere conifers
No full textWood formation consumes around 15% of the anthropogenic CO2 emissions per year and plays a critical role in long-term sequestration of carbon on Earth. However, the exogenous factors driving wood formation onset and the underlying cellular mechanisms are still poorly understood and quantified, and this hampers an effective assessment of terrestrial forest productivity and carbon budget under global warming. Here, we used an extensive collection of unique datasets of weekly xylem tissue formation (wood formation) from 21 coniferous species across the Northern Hemisphere (latitudes 23 to 67 degrees N) to present a quantitative demonstration that the onset of wood formation in Northern Hemisphere conifers is primarily driven by photoperiod and mean annual temperature (MAT), and only secondarily by spring forcing, winter chilling, and moisture availability. Photoperiod interacts with MAT and plays the dominant role in regulating the onset of secondary meristem growth, contrary to its as-yet-unquantified role in affecting the springtime phenology of primary meristems. The unique relationships between exogenous factors and wood formation could help to predict how forest ecosystems respond and adapt to climate warming and could provide a better understanding of the feedback occurring between vegetation and climate that is mediated by phenology. Our study quantifies the role of major environmental drivers for incorporation into state-of-the-art Earth system models (ESM5), thereby providing an improved assessment of long-term and high-resolution observations of biogeochemical cycles across terrestrial biomes
Time-resolved RNA-seq provided a new understanding of intestinal immune response of European eel (Anguilla anguilla) following infection with Aeromonas hydrophila
No full textNo studies systematically examined the intestinal immune response for yellow stage of European eel (Anguilla anguilla) with Aeromonas hydrophila infection by time-resolved RNA-seq. Here, we examined transcriptional profiles of the intestines at three-time points following infection with A. hydrophila. Intraperitoneal injections caused mortalities within 48 h post-injection (hpi), with the survival rate 87.5% at 24 hpi and 83.9% at 48 hpi. The result from KEGG pathway enrichment analysis showed that the immune related "cytosolic DNA-sensing pathway" was significantly enriched at the first and second time points (6 hpi and 18 hpi), with the upregulated expression of irf3, ill b, tnfaip3, cxcl8a, ap1-2, c-fos, polr3d, polr3g and polr3k both at 6 hpi and 18 hpi, but not at the third time point (36 hpi). According to the KEGG annotation, 326 immune and inflammation-related DEGs were found. The co-expression network of those 326 DEGs revealed the existence of three modules, and tlrl was found to be in the center of the biggest module which contained massive DEGs from "signal transduction" and "transport and catabolism". The c3 isoforms showed different expression pattern among the three time points, indicating a unique activation of complement systems at 18 hpi. Furthermore, two cathelicidins (aaCATH_1 and aaCATH_2) were highly up-regulated at the first two time points, and the bacterial growth inhibition assay revealed their antibacterial properties against A. hydrophila. Our data indicated the important roles of cytosolic DNA-sensing pathway, as well as transcripts including tlr1, c3, polr and cathelicidins in the intestine of A. anguilla in response to A. hydrophila infection. The present study will provide leads for functional studies of host-pathogen interactions
Transcriptional Programs Underlying Cold Acclimation of Common Carp (Cyprinus carpioL.)
No full textProperly regulated transcriptional responses to environmental perturbations are critical for the fitness of fish. Although gene expression profiles in the tissues of common carp upon cold stress were previously characterized, the transcriptional programs underlying cold acclimation are still not well known. In this study, the ability of three common carp strains including Hebao red carp (HB), Songpu mirror carp (SPM) and Yellow river carp (YR) to establish cold resistance after acclimation to a mild hypothermia stress at 18 degrees C for 24 h was confirmed by measurements of the critical thermal minimums (CTMin). The gene expression profiles of the brain and the heart from these strains under both control and cold-acclimated conditions were characterized with RNA-sequencing. The data of the three common carp strains with different genetic background were combined in the differential gene expression analyses to balance the effects of genetic diversity on gene expression. Marked effects of tissue origins on the cold-induced transcriptional responses were revealed by comparing the differentially expressed gene (DEG) lists of the two tissues. Functional categories including spliceosome and RNA splicing were highly enriched in the DEGs of both tissues. However, steroid biosynthesis was specifically enriched in DEGs of the brain and response to unfolded protein was solely enriched in DEGs of the heart. Consistent with the up-regulation of the genes involved in cholesterol biosynthesis, total cholesterol content of the brain was significantly increased upon cold stress. Moreover, cold-induced alternative splicing (AS) events were explored and AS of therbmx(RNA-binding motif protein, X chromosome) gene was confirmed by real-time quantitative PCR. Finally, a core set of cold responsive genes (CRGs) were defined by comparative transcriptomic analyses. Our data provide insights into the transcriptional programs underlying cold acclimation of common carp and offer valuable clues for further investigating the genetic determinants for cold resistance of farmed fish