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1.
Nat Commun ; 10(1): 4234, 2019 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-31530807

RESUMO

Phytoplankton account for nearly half of global primary productivity and strongly affect the global carbon cycle, yet little is known about the forces that drive the evolution of these keystone microscopic organisms. Here we combine morphometric data from the fossil record of the ubiquitous coccolithophore genus Gephyrocapsa with genomic analyses of extant species to assess the genetic processes underlying Pleistocene palaeontological patterns. We demonstrate that all modern diversity in Gephyrocapsa (including Emiliania huxleyi) originated in a rapid species radiation during the last 0.6 Ma, coincident with the latest of the three pulses of Gephyrocapsa diversification and extinction documented in the fossil record. Our evolutionary genetic analyses indicate that new species in this genus have formed in sympatry or parapatry, with occasional hybridisation between species. This sheds light on the mode of speciation during evolutionary radiation of marine phytoplankton and provides a model of how new plankton species form.


Assuntos
Evolução Molecular , Haptófitas/genética , Fitoplâncton/genética , Variação Genética , Genoma , Haptófitas/classificação , Biologia Marinha , Filogenia , Fitoplâncton/classificação
2.
PLoS Pathog ; 15(4): e1007708, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-31017983

RESUMO

Infection by large dsDNA viruses can lead to a profound alteration of host transcriptome and metabolome in order to provide essential building blocks to support the high metabolic demand for viral assembly and egress. Host response to viral infection can typically lead to diverse phenotypic outcome that include shift in host life cycle and activation of anti-viral defense response. Nevertheless, there is a major bottleneck to discern between viral hijacking strategies and host defense responses when averaging bulk population response. Here we study the interaction between Emiliania huxleyi, a bloom-forming alga, and its specific virus (EhV), an ecologically important host-virus model system in the ocean. We quantified host and virus gene expression on a single-cell resolution during the course of infection, using automatic microfluidic setup that captures individual algal cells and multiplex quantitate PCR. We revealed high heterogeneity in viral gene expression among individual cells. Simultaneous measurements of expression profiles of host and virus genes at a single-cell level allowed mapping of infected cells into newly defined infection states and allowed detection specific host response in a subpopulation of infected cell which otherwise masked by the majority of the infected population. Intriguingly, resistant cells emerged during viral infection, showed unique expression profiles of metabolic genes which can provide the basis for discerning between viral resistant and susceptible cells within heterogeneous populations in the marine environment. We propose that resolving host-virus arms race at a single-cell level will provide important mechanistic insights into viral life cycles and will uncover host defense strategies.


Assuntos
Eutrofização , Genes Virais , Haptófitas/genética , Haptófitas/virologia , Phycodnaviridae/patogenicidade , Análise de Célula Única/métodos , Viroses/genética , Haptófitas/crescimento & desenvolvimento , Interações Hospedeiro-Patógeno , Phycodnaviridae/genética , Phycodnaviridae/isolamento & purificação , Transcriptoma , Viroses/virologia
3.
Geobiology ; 17(3): 272-280, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30720914

RESUMO

Members of the order Isochrysidales are unique among haptophyte lineages in being the exclusive producers of alkenones, long-chain ketones that are commonly used for paleotemperature reconstructions. Alkenone-producing haptophytes are divided into three major groups based largely on molecular ecological data: Group I is found in freshwater lakes, Group II commonly occurs in brackish and coastal marine environments, and Group III consists of open ocean species. Each group has distinct alkenone distributions; however, only Groups II and III Isochrysidales currently have cultured representatives. The uncultured Group I Isochrysidales are distinguished geochemically by the presence of tri-unsaturated alkenone isomers (C37:3b Me, C38:3b Et, C38:3b Me, C39:3b Et) present in water column and sediment samples, yet their genetic diversity, morphology, and environmental controls are largely unknown. Using small-subunit (SSU) ribosomal RNA (rRNA) marker gene amplicon high-throughput sequencing of environmental water column and sediment samples, we show that Group I is monophyletic with high phylogenetic diversity and contains a well-supported clade separating the previously described "EV" clade from the "Greenland" clade. We infer the first partial large-subunit (LSU) rRNA gene Group I sequence phylogeny, which uncovered additional well-supported clades embedded within Group I. Relative to Group II, Group I revealed higher levels of genetic diversity despite conservation of alkenone signatures and a closer evolutionary relationship with Group III. In Group I, the presence of the tri-unsaturated alkenone isomers appears to be conserved, which is not the case for Group II. This suggests differing environmental influences on Group I and II and perhaps uncovers evolutionary constraints on alkenone biosynthesis.


Assuntos
Haptófitas/classificação , Haptófitas/metabolismo , Cetonas/análise , Lagos/química , Alaska , Evolução Biológica , DNA Ribossômico/análise , Alemanha , Haptófitas/genética , Islândia , Lagos/microbiologia , Filogenia , Análise de Sequência de RNA
4.
Mol Biol Evol ; 36(1): 4-14, 2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30351418

RESUMO

Larger populations are expected to have larger genetic diversity. However, as pointed out by Lewontin in 1974, the range of population sizes exceeds the range of genetic diversity by many orders of magnitude (a.k.a. "Lewontin's paradox," LP). The reasons for LP remain obscure. Here, This paper reports an extreme case of LP in astronomically large populations of the ubiquitous unicellular marine phytoplankton species Emiliania huxleyi (Haptophyta)-the species that accounts for 10-20% of primary productivity in the oceans and its blooms are so extensive that they are visible from space. This study demonstrates that despite the wide distribution and enormous population size, the world-wide sample of E. huxleyi strains with sequenced genomes represents a single cohesive species and contains surprisingly limited genetic diversity (π ∼ 0.006 per silent site). The patterns of polymorphism reveal even larger populations in the past, and frequent recombination (ρ ∼ 0.006) throughout the genome, ruling out demographic history and asexual reproduction as possible causes of low polymorphism in E. huxleyi. Natural selection wiping out genetic diversity at linked sites (a.k.a. "genetic draft") must be strong and frequent to account for low polymorphism in E. huxleyi. This study sheds the first light on poorly understood evolutionary genetic processes in astronomically large populations of marine microplankton.


Assuntos
Variação Genética , Haptófitas/genética , Fitoplâncton/genética , Taxa de Mutação , Densidade Demográfica , Seleção Genética
5.
Nat Commun ; 9(1): 5179, 2018 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-30518752

RESUMO

Sunlight is the dominant control on phytoplankton biosynthetic activity, and darkness deprives them of their primary external energy source. Changes in the biochemical composition of phytoplankton communities over diel light cycles and attendant consequences for carbon and energy flux in environments remain poorly elucidated. Here we use lipidomic data from the North Pacific subtropical gyre to show that biosynthesis of energy-rich triacylglycerols (TAGs) by eukaryotic nanophytoplankton during the day and their subsequent consumption at night drives a large and previously uncharacterized daily carbon cycle. Diel oscillations in TAG concentration comprise 23 ± 11% of primary production by eukaryotic nanophytoplankton representing a global flux of about 2.4 Pg C yr-1. Metatranscriptomic analyses of genes required for TAG biosynthesis indicate that haptophytes and dinoflagellates are active members in TAG production. Estimates suggest that these organisms could contain as much as 40% more calories at sunset than at sunrise due to TAG production.


Assuntos
Dinoflagelados/metabolismo , Dinoflagelados/efeitos da radiação , Haptófitas/metabolismo , Haptófitas/efeitos da radiação , Fitoplâncton/metabolismo , Fitoplâncton/efeitos da radiação , Triglicerídeos/biossíntese , Carbono/metabolismo , Ciclo do Carbono , Dinoflagelados/genética , Dinoflagelados/crescimento & desenvolvimento , Ecossistema , Haptófitas/genética , Haptófitas/crescimento & desenvolvimento , Oceanos e Mares , Fitoplâncton/crescimento & desenvolvimento , Luz Solar
6.
Protist ; 169(6): 958-975, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30453274

RESUMO

Ocean acidification (OA) and high light was found to negatively affect the Antarctic key species Phaeocystis antarctica, Fragilariopsis kerguelensis and Chaetoceros debilis. To unravel the underlying physiological response at the transcriptomic level, these species were grown under ambient and elevated pCO2 combined with low or high light. RNA sequencing revealed that the haptophyte was much more tolerant towards OA than the two diatoms as only these showed distinct OA-dependent gene regulation patterns. Under ambient pCO2, high light resulted in decreased glycolysis in P. antarctica. Contrastingly, upregulation of genes related to cell division and transcription as well as reduced expression of both cata- and anabolic carbon related pathways were seen in C. debilis. OA in combination with low light led to reduced respiration, but also surprisingly to higher expression of genes involved in light protection, transcription and translation in C. debilis. Though not affecting P. antarctica, OA combined with high light caused also photosensitivity in both diatoms. As additional response reallocation of carbon to lipids was found in C. debilis under these conditions. Overall, we conclude that P. antarctica is better adapted than the two diatoms to OA and high light.


Assuntos
Ácidos/toxicidade , Adaptação Fisiológica , Luz , Fitoplâncton/efeitos dos fármacos , Fitoplâncton/efeitos da radiação , Estresse Fisiológico , Dióxido de Carbono/metabolismo , Diatomáceas/efeitos dos fármacos , Diatomáceas/genética , Diatomáceas/fisiologia , Diatomáceas/efeitos da radiação , Perfilação da Expressão Gênica , Haptófitas/efeitos dos fármacos , Haptófitas/genética , Haptófitas/fisiologia , Haptófitas/efeitos da radiação , Redes e Vias Metabólicas/genética , Oceanos e Mares , Fitoplâncton/genética , Fitoplâncton/fisiologia , Água do Mar/química , Análise de Sequência de RNA
7.
Environ Microbiol ; 20(11): 4157-4169, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30246477

RESUMO

Dimethylsulfide (DMS), a dominant organic sulfur species in the surface ocean, may act as a signalling molecule and contribute to mutualistic interactions between bacteria and marine algae. These proposed functions depend on the DMS concentration in the vicinity of microorganisms. Here, we modelled the DMS enrichment at the surface of DMS-releasing marine algal cells as a function of DMS production rate, algal cell radius and turbulence. Our results show that the DMS concentration at the surface of unstressed phytoplankton with low DMS production rates can be enriched by <1 nM, whereas for mechanically stressed algae with high activities of the enzyme DMSP-lyase (a coccolithophore and a dinoflagellate) DMS cell surface enrichments can reach ~10 nM, and could potentially reach µM levels in large cells. These DMS enrichments are much higher than the median DMS concentration in the surface ocean (1.9 nM), and thus may attract and support the growth of bacteria living in the phycosphere. The bacteria in turn may provide photoactive iron chelators (siderophores) that enhance algal iron uptake and provide algal growth factors such as auxins and vitamins. The present study highlights new insights on the extent and impact of microscale DMS enrichments at algal surfaces, thereby contributing to our understanding of the potential chemoattractant and mutualistic roles of DMS in marine microorganisms.


Assuntos
Haptófitas/metabolismo , Fitoplâncton/metabolismo , Sulfetos/metabolismo , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Liases de Carbono-Enxofre/genética , Liases de Carbono-Enxofre/metabolismo , Diatomáceas/enzimologia , Diatomáceas/genética , Diatomáceas/metabolismo , Dinoflagelados/enzimologia , Dinoflagelados/genética , Dinoflagelados/metabolismo , Ecossistema , Haptófitas/enzimologia , Haptófitas/genética , Ferro/metabolismo , Fitoplâncton/enzimologia , Fitoplâncton/genética , Água do Mar/microbiologia , Água do Mar/parasitologia , Sideróforos/metabolismo , Sulfetos/análise
8.
Sci Rep ; 8(1): 11230, 2018 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-30046151

RESUMO

Alkenones are unusual long-chain neutral lipids that were first identified in oceanic sediments. Currently they are regarded as reliable palaeothermometers, since their unsaturation status changes depending on temperature. These molecules are synthesised by specific haptophyte algae and are stored in the lipid body as the main energy storage molecules. However, the molecular mechanisms that regulate the alkenone biosynthetic pathway, especially the low temperature-dependent desaturation reaction, have not been elucidated. Here, using an alkenone-producing haptophyte alga, Tisochrysis lutea, we show that the alkenone desaturation reaction is catalysed by a newly identified desaturase. We first isolated two candidate desaturase genes and found that one of these genes was drastically upregulated in response to cold stress. Gas chromatographic analysis revealed that the overexpression of this gene, named as Akd1 finally, increased the conversion of di-unsaturated C37-alkenone to tri-unsaturated molecule by alkenone desaturation, even at a high temperature when endogenous desaturation is efficiently suppressed. We anticipate that the Akd1 gene will be of great help for elucidating more detailed mechanisms of temperature response of alkenone desaturation, and identification of active species contributing alkenone production in metagenomic and/or metatranscriptomic studies in the field of oceanic biogeochemistry.


Assuntos
Alcenos/metabolismo , Vias Biossintéticas/genética , Ácidos Graxos Dessaturases/genética , Haptófitas/genética , Catálise , Resposta ao Choque Frio/genética , Regulação Enzimológica da Expressão Gênica/genética , Haptófitas/enzimologia , Haptófitas/fisiologia , Temperatura Ambiente
9.
ISME J ; 12(10): 2417-2432, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29899514

RESUMO

Short timescale observations are valuable for understanding microbial ecological processes. We assessed dynamics in relative abundance and potential activities by sequencing the small sub-unit ribosomal RNA gene (rRNA gene) and rRNA molecules (rRNA) of Bacteria, Archaea, and Eukaryota once to twice daily between March 2014 and May 2014 from the surface ocean off Catalina Island, California. Typically Ostreococcus, Braarudosphaera, Teleaulax, and Synechococcus dominated phytoplankton sequences (including chloroplasts) while SAR11, Sulfitobacter, and Fluviicola dominated non-phytoplankton Bacteria and Archaea. We observed short-lived increases of diatoms, mostly Pseudo-nitzschia and Chaetoceros, with quickly responding Bacteria and Archaea including Flavobacteriaceae (Polaribacter & Formosa), Roseovarius, and Euryarchaeota (MGII), notably the exact amplicon sequence variants we observed responding similarly to another diatom bloom nearby, 3 years prior. We observed correlations representing known interactions among abundant phytoplankton rRNA sequences, demonstrating the biogeochemical and ecological relevance of such interactions: (1) The kleptochloroplastidic ciliate Mesodinium 18S rRNA gene sequences and a single Teleaulax taxon (via 16S rRNA gene sequences) were correlated (Spearman r = 0.83) yet uncorrelated to a Teleaulax 18S rRNA gene OTU, or any other taxon (consistent with a kleptochloroplastidic or karyokleptic relationship) and (2) the photosynthetic prymnesiophyte Braarudosphaera bigelowii and two strains of diazotrophic cyanobacterium UCYN-A were correlated and each taxon was also correlated to other taxa, including B. bigelowii to a verrucomicrobium and a dictyochophyte phytoplankter (all r > 0.8). We also report strong correlations (r > 0.7) between various ciliates, bacteria, and phytoplankton, suggesting interactions via currently unknown mechanisms. These data reiterate the utility of high-frequency time series to show rapid microbial reactions to stimuli, and provide new information about in situ dynamics of previously recognized and hypothesized interactions.


Assuntos
Archaea/genética , Bactérias/genética , Haptófitas/genética , Fitoplâncton/genética , Plâncton/classificação , Plâncton/fisiologia , Diatomáceas/genética , Filogenia , RNA Ribossômico 16S/genética , RNA Ribossômico 18S/genética , Água do Mar/microbiologia
10.
PLoS One ; 13(5): e0196987, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29746519

RESUMO

The diversity of planktonic eukaryotic microbes was studied at a coastal station of the eastern English Channel (EEC) from March 2011 to July 2015 (77 samples) using high throughput sequencing (454-pyrosequencing and Illumina) of the V2-V3 hypervariable region of the 18S SSU rDNA gene. Similar estimations of OTU relative abundance and taxonomic distribution for the dominant higher taxonomic groups (contributing >1% of the total number of OTUs) were observed with the two methods (Kolmogorov-Smirnov p-value = 0.22). Eight super-groups were identified throughout all samples: Alveolata, Stramenopiles, Opisthokonta, Hacrobia, Archeaplastida, Apusozoa, Rhizaria, and Amoebozoa (ordered by decreasing OTU richness). To gain further insight into microbial activity in the EEC, ribosomal RNA was extracted for samples from 2013-2015 (30 samples). Analysis of 18S rDNA and rRNA sequences led to the detection of 696 and 700 OTUs, respectively. Cluster analysis based on OTUs' abundance indicated three major seasonal groups that were associated to spring, winter/autumn, and summer conditions. The clusters inferred from rRNA data showed a clearer seasonal representation of the community succession than the one based on rDNA. The rRNA/rDNA ratio was used as a proxy for relative cell activity. When all OTUs were considered, the average rRNA:rDNA ratio showed a linear trend around the 1:1 line, suggesting a linear relation between OTU abundance (rDNA) and activity (rRNA). However, this ratio was highly variable over time when considering individual OTUs. Interestingly, the OTU affiliated with P. globosa displayed rRNA:rDNA ratio that allowed to delimit high vs low abundance and high vs low activity periods. It unveiled quite well the Phaeocystis bloom dynamic regarding cell proliferation and activity, and could even be used as early indicator of an upcoming bloom.


Assuntos
Biodiversidade , Eutrofização/fisiologia , Haptófitas , Modelos Biológicos , Fitoplâncton , Microbiologia da Água , Haptófitas/genética , Haptófitas/crescimento & desenvolvimento , Fitoplâncton/genética , Fitoplâncton/crescimento & desenvolvimento
11.
Biochem Soc Trans ; 46(2): 413-421, 2018 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-29540506

RESUMO

Prymnesium parvum is a toxin-producing microalga that causes harmful algal blooms globally, which often result in large-scale fish kills that have severe ecological and economic implications. Although many toxins have previously been isolated from P. parvum, ambiguity still surrounds the responsible ichthyotoxins in P. parvum blooms and the biotic and abiotic factors that promote bloom toxicity. A major fish kill attributed to P. parvum occurred in Spring 2015 on the Norfolk Broads, a low-lying set of channels and lakes (Broads) found on the East of England. Here, we discuss how water samples taken during this bloom have led to diverse scientific advances ranging from toxin analysis to discovery of a new lytic virus of P. parvum, P. parvum DNA virus (PpDNAV-BW1). Taking recent literature into account, we propose key roles for sialic acids in this type of viral infection. Finally, we discuss recent practical detection and management strategies for controlling these devastating blooms.


Assuntos
Haptófitas/crescimento & desenvolvimento , Proliferação Nociva de Algas , Açúcares , Animais , DNA/genética , Inglaterra , Peixes , Haptófitas/genética , Haptófitas/metabolismo , Haptófitas/virologia , Toxinas Biológicas/metabolismo
12.
Appl Microbiol Biotechnol ; 102(10): 4255-4267, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29574616

RESUMO

Diatoms and haptophytes represent a key segment of the dominant phytoplankton communities that frequently form massive blooms in the photic zone of the ocean and are considered indicators of global climate changes. Diatoms and haptophytes also play a vital role in the biological carbon fixation in the carbon cycles. Carbon partitioning within diatoms and haptophytes possesses a wide range of chemical compounds and storage materials, such as lipids, carbohydrates, and chlorophyll. Among the marine microorganisms, diatoms and haptophytes have been recognized as promising sources of long- and very long-chain polyunsaturated fatty acids (PUFA). So far, a variety of approaches have been employed for genetic modification in the nuclei of diatoms and haptophytes. Studies on transformation and metabolic engineering in various intracellular genomes, such as chloroplast and mitochondria, are scarce. Particle bombardment, Agrobacterium and PEG-mediated gene transfer, and electroporation have been reported for foreign gene transformation into the diatoms and haptophytes. Antibiotics (G418 and chloramphenicol) and herbicides (zeocin, hygromycin, and norflurazon) have been successfully demonstrated as the best selection markers. Despite the availability of a wide range of molecular tools for foreign gene expression in microalgae, very few promoters (lhcf1, nr, h4, ef2, fcp, and pds) have been reported for diatoms and haptophytes. Therefore, in this review, we first summarize the significant progress that has been achieved in transgene expression in diatoms and haptophytes and highlight the importance and availability of recently developed novel tools that are suitable for transgenic expression in diatoms and haptophytes.


Assuntos
Diatomáceas/genética , Haptófitas/genética , Engenharia Metabólica/tendências , Transformação Genética
13.
Appl Biochem Biotechnol ; 185(4): 1100-1117, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29453614

RESUMO

Isochrysis is a genus of marine algae without cell wall and capable of accumulating lipids. In this study, the lipid production potential of Isochrysis was assessed by comparing 15 Isochrysis strains with respect to their growth rate, lipid production, and fatty acid profiles. Three best strains were selected (lipid productivity, 103.0~121.7 mg L-1 day-1) and their lipid-producing capacities were further examined under different controlled parameters, e.g., growth phase, medium nutrient, and light intensity in laboratory cultures. Furthermore, the three Isochrysis strains were monitored in outdoor panel photobioreactors with various initial cell densities and optical paths, and the strain CS177 demonstrated the superior potential for outdoor cultivation. A two-stage semi-continuous strategy for CS177 was subsequently developed, where high productivities of biomass (1.1 g L-1 day-1) and lipid (0.35 g L-1 day-1) were achieved. This is a comprehensive study to evaluate the lipid-producing capability of Isochrysis strains under both indoor and outdoor conditions. Results of the present work lay a solid foundation for the physiological and biochemical responses of Isochrysis to various conditions, shedding light on the future utilization of this cell wall-lacking marine alga for biofuel production.


Assuntos
Biomassa , Haptófitas/crescimento & desenvolvimento , Lipídeos/biossíntese , Haptófitas/genética , Lipídeos/genética
14.
ISME J ; 12(5): 1360-1374, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29426951

RESUMO

Symbioses between eukaryotic algae and nitrogen-fixing cyanobacteria have been recognized in recent years as a key source of new nitrogen in the oceans. We investigated the composition of the small photosynthetic eukaryote communities associated with nitrogen-fixing cyanobacteria in the Brazilian South Atlantic Bight using a combination of flow cytometry sorting and high throughput sequencing of two genes: the V4 region of 18S rRNA and nifH. Two distinct eukaryotic communities were often encountered, one dominated by the Mamiellophyceae Bathycoccus and Ostreococcus, and one dominated by a prymnesiophyte known to live in symbiosis with the UCYN-A1 nitrogen-fixing cyanobacterium. Among nifH sequences, those from UCYN-A1 were most abundant but three other UCYN-A clades (A2, A3, A4) were also found. Network analysis confirmed the relation between A1 and A2 clades and their hypothesized hosts and pointed out to the potential association between novel clade A4 with Braarudosphaera bigelowii, previously hypothesized to host A2.


Assuntos
Cianobactérias/classificação , Haptófitas/microbiologia , Simbiose , Brasil , Cianobactérias/genética , Cianobactérias/isolamento & purificação , Cianobactérias/metabolismo , Haptófitas/classificação , Haptófitas/genética , Fixação de Nitrogênio , Oceanos e Mares , Fitoplâncton/genética , Fitoplâncton/microbiologia , Água do Mar/microbiologia , Clima Tropical
15.
Nat Ecol Evol ; 2(4): 611-613, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29434348

RESUMO

Climate change challenges plankton communities, but evolutionary adaptation could mitigate the potential impacts. Here, we tested with the phytoplankton species Emiliania huxleyi whether adaptation to a stressor under laboratory conditions leads to equivalent fitness gains in a more natural environment. We found that fitness advantages that had evolved under laboratory conditions were masked by pleiotropic effects in natural plankton communities. Moreover, new genotypes with highly variable competitive abilities evolved on timescales significantly shorter than climate change.


Assuntos
Adaptação Biológica , Evolução Biológica , Aptidão Genética , Haptófitas/fisiologia , Interações Microbianas/fisiologia , Pleiotropia Genética , Genótipo , Haptófitas/genética , Fitoplâncton/genética , Fitoplâncton/fisiologia
16.
Nat Microbiol ; 3(4): 430-439, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29483657

RESUMO

Dimethylsulfoniopropionate (DMSP) is a globally important organosulfur molecule and the major precursor for dimethyl sulfide. These compounds are important info-chemicals, key nutrients for marine microorganisms, and are involved in global sulfur cycling, atmospheric chemistry and cloud formation1-3. DMSP production was thought to be confined to eukaryotes, but heterotrophic bacteria can also produce DMSP through the pathway used by most phytoplankton 4 , and the DsyB enzyme catalysing the key step of this pathway in bacteria was recently identified 5 . However, eukaryotic phytoplankton probably produce most of Earth's DMSP, yet no DMSP biosynthesis genes have been identified in any such organisms. Here we identify functional dsyB homologues, termed DSYB, in many phytoplankton and corals. DSYB is a methylthiohydroxybutryate methyltransferase enzyme localized in the chloroplasts and mitochondria of the haptophyte Prymnesium parvum, and stable isotope tracking experiments support these organelles as sites of DMSP synthesis. DSYB transcription levels increased with DMSP concentrations in different phytoplankton and were indicative of intracellular DMSP. Identification of the eukaryotic DSYB sequences, along with bacterial dsyB, provides the first molecular tools to predict the relative contributions of eukaryotes and prokaryotes to global DMSP production. Furthermore, evolutionary analysis suggests that eukaryotic DSYB originated in bacteria and was passed to eukaryotes early in their evolution.


Assuntos
Cloroplastos/enzimologia , Haptófitas/enzimologia , Metiltransferases/genética , Mitocôndrias/enzimologia , Compostos de Sulfônio/metabolismo , Cloroplastos/genética , Cloroplastos/metabolismo , Diatomáceas/enzimologia , Diatomáceas/genética , Dinoflagelados/enzimologia , Dinoflagelados/genética , Haptófitas/genética , Metiltransferases/metabolismo , Mitocôndrias/genética , Mitocôndrias/metabolismo , Fitoplâncton/metabolismo
17.
FEMS Microbiol Ecol ; 94(4)2018 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-29360960

RESUMO

Photosynthetic picoeukaryotes (PPEs) play an important role in aquatic ecosystem functioning. There is still a relative lack of information on freshwater PPEs, especially in eutrophic lakes. We used a combination of flow cytometric sorting and pyrosequencing to investigate the PPEs community structure in more than 20 mesotrophic and eutrophic lakes along the middle-lower reaches of the Yangtze River in China. The abundance of PPEs ranged between 2.04 × 103 and 5.92 × 103 cells mL-1. The contribution of PPEs to total picophytoplankton abundance was generally higher in eutrophic lakes than in mesotrophic lakes. The sequencing results indicated that the Shannon diversity of PPEs was significantly higher in mesotrophic lakes than in eutrophic lakes. At the class level, PPEs were mainly dominated by three taxonomic groups, including Cryptophyceae, Coscinodiscophyceae and Chlorophyceae, and 15 additional known phytoplankton classes, including Synurophyceae, Dinophyceae, Chrysophyceae, Trebouxiophyceae and Prymnesiophyceae, were identified. Coscinodiscophyceae dominated in the most eutrophic lakes, while Chrysophyceae, Dinophyceae and other classes of PPEs were more abundant in the mesotrophic lakes. We also observed several PPEs operational taxonomic units, and those affiliated with Cyclotella atomus, Chlamydomonas sp. and Poterioochromonas malhamensis tended to be more prevalent in the eutrophic lakes. The canonical correspondence analysis and Mantel analysis highlighted the importance of environmental parameters as key drivers of PPEs community composition.


Assuntos
Chrysophyta/isolamento & purificação , Criptófitas/isolamento & purificação , Diatomáceas/isolamento & purificação , Dinoflagelados/isolamento & purificação , Haptófitas/isolamento & purificação , Lagos/parasitologia , Fitoplâncton/isolamento & purificação , Rios/parasitologia , Estramenópilas/isolamento & purificação , China , Clorófitas/classificação , Clorófitas/genética , Chrysophyta/classificação , Chrysophyta/genética , Criptófitas/classificação , Criptófitas/genética , Diatomáceas/classificação , Diatomáceas/genética , Dinoflagelados/classificação , Dinoflagelados/genética , Ecossistema , Citometria de Fluxo , Haptófitas/classificação , Haptófitas/genética , Fotossíntese , Fitoplâncton/classificação , Fitoplâncton/genética , Estramenópilas/classificação , Estramenópilas/genética
18.
Glob Chang Biol ; 24(7): 3055-3064, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29356310

RESUMO

Coccolithophores are important oceanic primary producers not only in terms of photosynthesis but also because they produce calcite plates called coccoliths. Ongoing ocean acidification associated with changing seawater carbonate chemistry may impair calcification and other metabolic functions in coccolithophores. While short-term ocean acidification effects on calcification and other properties have been examined in a variety of coccolithophore species, long-term adaptive responses have scarcely been documented, other than for the single species Emiliania huxleyi. Here, we investigated the effects of ocean acidification on another ecologically important coccolithophore species, Gephyrocapsa oceanica, following 1,000 generations of growth under elevated CO2 conditions (1,000 µatm). High CO2 -selected populations exhibited reduced growth rates and enhanced particulate organic carbon (POC) and nitrogen (PON) production, relative to populations selected under ambient CO2 (400 µatm). Particulate inorganic carbon (PIC) and PIC/POC ratios decreased progressively throughout the selection period in high CO2 -selected cell lines. All of these trait changes persisted when high CO2 -grown populations were moved back to ambient CO2 conditions for about 10 generations. The results suggest that the calcification of some coccolithophores may be more heavily impaired by ocean acidification than previously predicted based on short-term studies, with potentially large implications for the ocean's carbon cycle under accelerating anthropogenic influences.


Assuntos
Adaptação Fisiológica/genética , Dióxido de Carbono/administração & dosagem , Dióxido de Carbono/farmacologia , Haptófitas/efeitos dos fármacos , Seleção Genética , Carbono/metabolismo , Carbonatos/metabolismo , Haptófitas/genética , Haptófitas/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Nitrogênio/metabolismo , Fotossíntese/efeitos dos fármacos , Água do Mar/química
19.
Microb Ecol ; 75(3): 582-597, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28942559

RESUMO

The White Sea is a unique marine environment combining features of temperate and Arctic seas. The composition and abundance of photosynthetic picoeukaryotes (PPEs) were investigated in the land-fast ice of the White Sea, Russia, in March 2013 and 2014. High-throughput tag sequencing (Illumina MiSeq system) of the V4 region of the 18S rRNA gene was used to reveal the diversity of PPE ice community. The integrated PPE abundance varied from 11 × 106 cells/m2 to 364 × 106 cells/m2; the integrated biomass ranged from 0.02 to 0.26 mg С/m2. The composition of sea-ice PPEs was represented by 16 algae genera belonging to eight classes and three super-groups. Chlorophyta, especially Mamiellophyceae, dominated among ice PPEs. The detailed analysis revealed the latent diversity of Micromonas and Mantоniella. Micromonas clade E2 revealed in the subarctic White Sea ice indicates that the area of distribution of this species is wider than previously thought. We suppose there exists a new Micromonas clade F. Micromonas clade C and Minutocellulus polymorphus were first discovered in the ice and extend the modern concept of sympagic communities' diversity generally and highlights the importance of further targeting subarctic sea ice for microbial study.


Assuntos
Eucariotos/classificação , Eucariotos/fisiologia , Camada de Gelo/parasitologia , Fotossíntese , Filogenia , Regiões Árticas , Biodiversidade , Biomassa , Clorofila/análise , Clorófitas/classificação , Clorófitas/genética , Clorófitas/fisiologia , DNA/análise , DNA/isolamento & purificação , Eucariotos/genética , Eucariotos/isolamento & purificação , Haptófitas/classificação , Haptófitas/genética , Haptófitas/fisiologia , Sequenciamento de Nucleotídeos em Larga Escala , Camada de Gelo/química , RNA Ribossômico 18S/genética , Federação Russa , Estações do Ano , Água do Mar/parasitologia , Estramenópilas/classificação , Estramenópilas/genética , Estramenópilas/isolamento & purificação , Estramenópilas/fisiologia , Temperatura Ambiente
20.
Arch Microbiol ; 200(3): 413-422, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29184974

RESUMO

Lytic viral infection and programmed cell death (PCD) are thought to represent two distinct death mechanisms in phytoplankton, unicellular photoautotrophs that drift with ocean currents. PCD (apoptosis) is mainly brought about by the activation of caspases, a protease family with unique substrate selectivity. Here, we demonstrated that virus infection induced apoptosis of marine coccolithophorid Emiliania huxleyi BOF92 involving activation of metacaspase. E. huxleyi cells exhibited cell death process akin to that of apoptosis when exposed to virus infection. We observed typical hallmarks of apoptosis including cell shrinkage, associated nuclear morphological changes and DNA fragmentation. Immunoblotting revealed that antibody against human active-caspase-3 shared epitopes with a protein of ≈ 23 kDa; whose pattern of expression correlated with the onset of cell death. Moreover, analysis on two-dimensional gel electrophoresis revealed that two spots of active caspase-3 co-migrated with the different isoelectric points. Phosphatase treatment of cytosolic extracts containing active caspases-3 showed a mobility shift, suggesting that phosphorylated form of this enzyme might be present in the extracts. Computational prediction of phosphorylation sites based on the amino acid sequence of E. huxleyi metacaspase showed multiple phosphorylated sites for serine, threonine and tyrosine residues. This is the first report showing that phosphorylation modification of metacaspase in E. huxleyi might be required for certain biochemical and morphological changes during virus induced apoptosis.


Assuntos
Apoptose , Caspases/metabolismo , Vírus Gigantes/fisiologia , Haptófitas/enzimologia , Fitoplâncton/enzimologia , Sequência de Aminoácidos , Caspases/genética , Sequência Conservada , Fragmentação do DNA , Expressão Gênica , Haptófitas/genética , Haptófitas/ultraestrutura , Haptófitas/virologia , Fosforilação , Processamento de Proteína Pós-Traducional
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