The Southern Ocean diatom Pseudo-nitzschia subcurvata flourished better under simulated glacial than interglacial ocean conditions: Combined effects of CO2 and iron.
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ABSTRACT:
SUBMITTER: Pagnone A
PROVIDER: S-EPMC8664213 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Ocean warming (OW) and acidification (OA) are recognized as two major climatic conditions influencing phytoplankton growth and nutritional or toxin content. However, there is limited knowledge on the responses of harmful algal bloom species that produce toxins. Here, the study provides quantitative and mechanistic understanding of the acclimation and adaptation responses of the domoic acid (DA) producing diatom Pseudo-nitzschia multiseries to rising temperature and pCO2 using both a one-year in situ bulk culture experiment, and an 800-day laboratory acclimation experiment. Ocean warming showed larger selective effects on growth and DA metabolism than ocean acidification. In a bulk culture experiment, increasing temperature +4 °C above ambient seawater temperature significantly increased DA concentration by up to 11-fold. In laboratory when the long-term warming acclimated samples were assayed under low temperatures, changes in growth rates and DA concentrations indicated that P. multiseries did not adapt to elevated temperature, but could instead rapidly and reversibly acclimate to temperature shifts. However, the warming-acclimated lines showed evidence of adaptation to elevated temperatures in the transcriptome data. Here the core gene expression was not reversed when warming-acclimated lines were moved back to the low temperature environment, which suggested that P. multiseries cells might adapt to rising temperature over longer timescales. The distinct strategies of phenotypic plasticity to rising temperature and pCO2 demonstrate a strong acclimation capacity for this bloom-forming toxic diatom in the future ocean.
| S-EPMC10030627 | biostudies-literature
Project description:Multiple species in the toxic marine diatom genus Pseudo-nitzschia have been identified in the Northwestern Atlantic region encompassing the Gulf of Maine (GOM), including the Bay of Fundy (BOF). To gain further knowledge of the taxonomic composition and toxicity of species in this region, Pseudo-nitzschia isolates (n=146) were isolated from samples collected during research cruises that provided broad spatial coverage across the GOM and the southern New England shelf, herein referred to as the GOM region, during 2007-2008. Isolates, and cells in field material collected at 38 stations, were identified using electron microscopy (EM). Eight species (P. americana, P. fraudulenta, P. subpacifica, P. heimii, P. pungens, P. seriata, P. delicatissima and P. turgidula), and a novel form, Pseudo-nitzschia sp. GOM, were identified. Species identity was confirmed by sequencing the large subunit of the ribosomal rDNA (28S) and the internal transcribed spacer 2 (ITS2) for six species (36 isolates). Phylogenetic analyses (including neighbor joining, maximum parsimony, and maximum likelihood estimates and ITS2 secondary structure analysis) and morphometric data supported the placement of P. sp. GOM in a novel clade that includes morphologically and genetically similar isolates from Australia and Spain and is genetically most similar to P. pseudodelicatissima and P. cuspidata. Seven species (46 isolates) were grown in nutrient-replete batch culture and aliquots consisting of cells and growth medium were screened by Biosense ASP ELISA to measure total domoic acid (DA) produced (intracellular + extracellular); P. americana and P. heimii were excluded from all toxin analyses as they did not persist in culture long enough for testing. All 46 isolates screened produced DA in culture and total DA varied among species (e.g., 0.04 to 320 ng ml-1 for P. pungens and P. sp. GOM isolates, respectively) and among isolates of the same species (e.g., 0.24 - 320 ng ml-1 for P. sp. GOM). The 15 most toxic isolates corresponded to P. seriata, P. sp. GOM and P. pungens, and fg DA cell-1 was determined for whole cultures (cells and medium) using ELISA and liquid chromatography (LC) with fluorescence detection (FLD); for seven isolates, toxin levels were also estimated using LC - with mass spectrometry and ultraviolet absorbance detection. Pseudo-nitzschia seriata was the most toxic species (up to 3,500 fg cell-1) and was observed in the GOM region during all cruises (i.e., during the months of April, May, June and October). Pseudo-nitzschia sp. GOM, observed only during September and October 2007, was less toxic (19 - 380 fg cell-1) than P. seriata but more toxic than P. pungens var. pungens (0. 4 fg cell-1). Quantitation of DA indicated that concentrations measured by LC and ELISA were positively and significantly correlated; the lower detection limit of the ELISA permitted quantification of toxicity in isolates that were found to be nontoxic with LC methods. The confirmation of at least seven toxic species and the broad spatial and temporal distribution of toxic Pseudo-nitzschia spp. have significant implications for the regional management of nearshore and offshore shellfisheries resources.
| S-EPMC4133141 | biostudies-literature
Project description:A broad diversity of sex-determining systems has evolved in eukaryotes. However, information on the mechanisms of sex determination for unicellular microalgae is limited, including for diatoms, key-players of ocean food webs. Here we report the identification of a mating type (MT) determining gene for the diatom Pseudo-nitzschia multistriata. By comparing the expression profile of the two MTs, we find five MT-biased genes, of which one, MRP3, is expressed exclusively in MT+ strains in a monoallelic manner. A short tandem repeat of specific length in the region upstream of MRP3 is consistently present in MT+ and absent in MT- strains. MRP3 overexpression in an MT- strain induces sex reversal: the transgenic MT- can mate with another MT- strain and displays altered regulation of the other MT-biased genes, indicating that they lie downstream. Our data show that a relatively simple genetic program is involved in defining the MT in P. multistriata.
| S-EPMC6261938 | biostudies-literature
Project description:Pseudo-nitzschia-specific PCR primers (PnAll F/R) were designed to amplify a polymorphic region of the internal transcribed spacer 1 (ITS1) from at least 11 Pseudo-nitzschia species. The primers were used to generate environmental clone libraries from Puget Sound, Washington, and Vancouver Island, British Columbia, to confirm that the primers were specific for Pseudo-nitzschia and to determine the extent of ITS1 sequence diversity within individual species. All environmental ITS1 sequences generated with PnAll primers displayed the greatest similarity to known Pseudo-nitzschia ITS1 sequences. The length of cloned ITS1 fragments differed among species but was conserved within a species. Intraspecific genotypes exhibited <3% sequence divergence for seven of the 10 species detected in clone libraries. Several ITS1 genotypes unique to the Pacific Northwest were identified in environmental samples, and other genotypes were more broadly distributed. The Pseudo-nitzschia primers were also used to develop an automated ribosomal intergenic spacer analysis (ARISA) to rapidly identify Pseudo-nitzschia species in environmental samples based on species-specific variation in the length of the targeted ITS1 region. The ARISA peaks were then associated with the environmental clone sequences for Pseudo-nitzschia species. Surveying the genetic composition of communities at both the inter- and intraspecific levels will enhance our understanding of Pseudo-nitzschia bloom dynamics.
| S-EPMC3873754 | biostudies-literature
Project description:Different clades belonging to the cosmopolitan marine diatom Pseudo-nitzschia pungens appear to be present in different oceanic environments, however, a 'hybrid zone', where populations of different clades interbreed, has also been reported. Many studies have investigated the sexual reproduction of P. pungens, focused on morphology and life cycle, rather than the role of sexual reproduction in mixing the genomes of their parents. We carried out crossing experiments to determine the sexual compatibility/incompatibility between different clades of P. pungens, and examined the genetic polymorphism in the ITS2 region. Sexual reproduction did not occur only between clades II and III under any of experimental temperature conditions. Four offspring strains were established between clade I and III successfully. Strains established from offspring were found interbreed with other offspring strains as well as viable with their parental strains. We confirmed the hybrid sequence patterns between clades I and III and found novel sequence types including polymorphic single nucleotide polymorphisms (SNPs) in the offspring strains. Our results implicate that gene exchange and mixing between different clades are still possible, and that sexual reproduction is a significant ecological strategy to maintain the genetic diversity within this diatom species.
| S-EPMC7326933 | biostudies-literature
Project description:Biological relevance and intent of the experiment: Given their abundance in the oceans and the exceptional adaptive capacities that make them capable of colonizing the most disparate habitats, diatoms constitute a group of microalgae of considerable ecological importance. This experiment aims to provide a molecular characterization of sexual reproduction for the diatom Pseudo-nitzschia multistriata, in relation to the consumption of nutrients and the impact on the marine ecosystem, by exploring the gene expression changes occurring at different time points in the cells involved in the process. Experimental workflow: Cell cultures of P. multistriata belonging to opposite mating types (MT- and MT+) were grown in 12L/12D cycles at 18°C under normal light conditions (60 uE) and crossed at a final cell density of 20.000 cells/ml using half volume from each MT. Samples for transcriptomic analyses were collected at three time points for sexually reproducing cells (1 hour: T1, 24 hours: T2 and 120 hours: T3), and at one time point (24 hours: T2) for parental monocultures grown in parallel as control condition.
2021-11-24 | E-MTAB-8854 | biostudies-arrayexpress
Project description:Pseudo-nitzschia multistriata is a planktonic marine diatom with a diplontic life cycle comprising a short sexual phase, during which gametes are produced following the encounter of two diploid cells of opposite mating type (MT). Gene expression studies have highlighted the presence of substantial changes occurring at the onset of sexual reproduction. Herein, we have hypothesized that the amount and nature of cellular metabolites varies along the mating process. To capture the metabolome of Pseudo-nitzschia multistriata at different harvesting times in an unbiased manner, we undertook an untargeted metabolomics approach based on liquid chromatography-tandem mass spectrometry. Using three different extraction steps, the method revealed pronounced differences in the metabolic profiles between control cells in the vegetative phase (MT+ and MT-) and mixed strains of opposite MTs (cross) undergoing sexual reproduction. Of the 2408 high-quality features obtained, 70 known metabolites could be identified based on in-house libraries and online databases; additional 46 features could be classified by molecular networking of tandem mass spectra. The reduction of phytol detected in the cross can be linked to the general downregulation of photosynthesis during sexual reproduction observed elsewhere. Moreover, the role of highly regulated compounds such as 7-dehydrodesmosterol, whose changes in abundance were the highest in the experiment, oleamide, ectoine, or trigonelline is discussed.
| S-EPMC7345340 | biostudies-literature
Project description:Oxylipins are low-molecular weight secondary metabolites derived from the incorporation of oxygen into the carbon chains of polyunsaturated fatty acids (PUFAs). Oxylipins are produced in many prokaryotic and eukaryotic lineages where they are involved in a broad spectrum of actions spanning from stress and defense responses, regulation of growth and development, signaling, and innate immunity. We explored the diversity in oxylipin patterns in the marine planktonic diatom Pseudo-nitzschia. This genus includes several species only distinguishable with the aid of molecular markers. Oxylipin profiles of cultured strains were obtained by reverse phase column on a liquid chromatograph equipped with UV photodiode detector and q-ToF mass spectrometer. Lipoxygenase compounds were mapped on phylogenies of the genus Pseudo-nitzschia inferred from the nuclear encoded hyper-variable region of the LSU rDNA and the plastid encoded rbcL. Results showed that the genus Pseudo-nitzschia exhibits a rich and varied lipoxygenase metabolism of eicosapentaenoic acid (EPA), with a high level of specificity for oxylipin markers that generally corroborated the genotypic delineation, even among genetically closely related cryptic species. These results suggest that oxylipin profiles constitute additional identification tools for Pseudo-nitzschia species providing a functional support to species delineation obtained with molecular markers and morphological traits. The exploration of the diversity, patterns and plasticity of oxylipin production across diatom species and genera will also provide insights on the ecological functions of these secondary metabolites and on the selective pressures driving their diversification.
| S-EPMC3754938 | biostudies-literature
Project description:Coinciding with global warming, Arctic sea ice has rapidly decreased during the last four decades and climate scenarios suggest that sea ice may completely disappear during summer within the next about 50-100 years. Here we produce Arctic sea ice biomarker proxy records for the penultimate glacial (Marine Isotope Stage 6) and the subsequent last interglacial (Marine Isotope Stage 5e). The latter is a time interval when the high latitudes were significantly warmer than today. We document that even under such warmer climate conditions, sea ice existed in the central Arctic Ocean during summer, whereas sea ice was significantly reduced along the Barents Sea continental margin influenced by Atlantic Water inflow. Our proxy reconstruction of the last interglacial sea ice cover is supported by climate simulations, although some proxy data/model inconsistencies still exist. During late Marine Isotope Stage 6, polynya-type conditions occurred off the major ice sheets along the northern Barents and East Siberian continental margins, contradicting a giant Marine Isotope Stage 6 ice shelf that covered the entire Arctic Ocean.Coinciding with global warming, Arctic sea ice has rapidly decreased during the last four decades. Here, using biomarker records, the authors show that permanent sea ice was still present in the central Arctic Ocean during the last interglacial, when high latitudes were warmer than present.
| S-EPMC5575311 | biostudies-literature
Project description:The association of phytoplankton with bacteria is ubiquitous in nature and the bacteria that associate with different phytoplankton species are very diverse. The influence of these bacteria in the physiology and ecology of the host and the evolutionary forces that shape the relationship are still not understood. In this study, we used the Pseudo-nitzschia-microbiota association to determine (1) if algal species with distinct domoic acid (DA) production are selection factors that structures the bacterial community, (2) if host-specificity and co-adaptation govern the association, (3) the functional roles of isolated member of microbiota on diatom-hosts fitness and (4) the influence of microbiota in changing the phenotype of the diatom hosts with regards to toxin production. Analysis of the pyrosequencing-derived 16S rDNA data suggests that the three tested species of Pseudo-nitzschia, which vary in toxin production, have phylogenetically distinct bacterial communities, and toxic Pseudo-nitzschia have lower microbial diversity than non-toxic Pseudo-nitzschia. Transplant experiments showed that isolated members of the microbiota are mutualistic to their native hosts but some are commensal or parasitic to foreign hosts, hinting at co-evolution between partners. Moreover, Pseudo-nitzschia host can gain protection from algalytic bacteria by maintaining association with its microbiota. Pseudo-nitzschia also exhibit different phenotypic expression with regards to DA production, and this depends on the bacterial species with which the host associates. Hence, the influences of the microbiota on diatom host physiology should be considered when studying the biology and ecology of marine diatoms.
| S-EPMC3869016 | biostudies-literature