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Julie A Koester - One of the best experts on this subject based on the ideXlab platform.

  • Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii (Bacillariophyta)
    BMC Evolutionary Biology, 2017
    Co-Authors: Julie A Koester, Peter Von Dassow, Jarred E Swalwell, Elizabeth V. Armbrust
    Abstract:

    Background: Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions. Results: All isolates from the more regionally-localized population (population 2) possessed 1.94 ± 0.74 times the amount of DNA, grew more slowly, and were generally larger than isolates from the more globally distributed population (population 1). The ITS1 sequences, cell sizes, and genome sizes of isolates from New Zealand were the same as population 1 isolates from Puget Sound, but their growth rates were within the range of the slower-growing population 2 isolates. Importantly, the observed genome size difference between isolates from the two populations was stable regardless of time in culture or the changes in cell size that accompany the diatom life history. Conclusions: The observed twofold difference in genome size between the D. brightwellii populations suggests that whole genome duplication occurred within cells of population 1 ultimately giving rise to population 2 cells. The apparent regional localization of population 2 is consistent with a recent divergence between the populations, which are likely cryptic species. Genome size variation is known to occur in other diatom genera; we hypothesize that genome duplication may be an active and important mechanism of genetic and physiological diversification and speciation in diatoms.

  • Steady-state acclimated log2 growth rate (μ±2SE, n≥3) as a function of irradiance for big (B, large open symbols) and small (S, small closed symbols) isolates from two species, P1 (squares) and P2 (circles) of Ditylum brightwellii.
    2013
    Co-Authors: Susan C. Sharpe, Julie A Koester, Martina Loebl, Amanda M. Cockshutt, Douglas A. Campbell, Andrew J. Irwin, Zoe V. Finkel
    Abstract:

    Ditylum brightwellii P2 has 1.93±0.37 times the DNA content of P1.

  • Size-scaling exponents, b, from a linear regression of log growth rate µ = a+b log V using a different intercept, a, for each growth irradiance (not shown).
    2013
    Co-Authors: Susan C. Sharpe, Julie A Koester, Martina Loebl, Amanda M. Cockshutt, Douglas A. Campbell, Andrew J. Irwin, Zoe V. Finkel
    Abstract:

    A) Different metabolic size-scaling exponents are calculated for P1 and P2. B) Separate size-scaling exponents are calculated within and across the two species of Ditylum brightwellii, assuming that P2 has 2-times the DNA content and volume of P1.

  • Genomic evidence of speciation and adaptation in diatoms
    2012
    Co-Authors: Julie A Koester
    Abstract:

    Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions. All isolates from the more regionally-localized population (population 2) possessed 1.94 ± 0.74 times the amount of DNA, grew more slowly, and were generally larger than isolates from the more globally distributed population (population 1). The ITS1 sequences, cell sizes, and genome sizes of isolates from New Zealand were the same as population 1 isolates from Puget Sound, but their growth rates were within the range of the slower-growing population 2 isolates. Importantly, the observed genome size difference between isolates from the two populations was stable regardless of time in culture or the changes in cell size that accompany the diatom life history. The observed twofold difference in genome size between the D. brightwellii populations suggests that whole genome duplication occurred within cells of population 1 ultimately giving rise to population 2 cells. The apparent regional localization of population 2 is consistent with a recent divergence between the populations, which are likely cryptic species. Genome size variation is known to occur in other diatom genera; we hypothesize that genome duplication may be an active and important mechanism of genetic and physiological diversification and speciation in diatoms.

  • genome size differentiates co occurring populations of the planktonic diatom Ditylum brightwellii bacillariophyta
    BMC Evolutionary Biology, 2010
    Co-Authors: Julie A Koester, Jarred E Swalwell, Peter Von Dassow, Virginia E Armbrust
    Abstract:

    Background Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions.

Elizabeth V. Armbrust - One of the best experts on this subject based on the ideXlab platform.

  • Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii (Bacillariophyta)
    BMC Evolutionary Biology, 2017
    Co-Authors: Julie A Koester, Peter Von Dassow, Jarred E Swalwell, Elizabeth V. Armbrust
    Abstract:

    Background: Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions. Results: All isolates from the more regionally-localized population (population 2) possessed 1.94 ± 0.74 times the amount of DNA, grew more slowly, and were generally larger than isolates from the more globally distributed population (population 1). The ITS1 sequences, cell sizes, and genome sizes of isolates from New Zealand were the same as population 1 isolates from Puget Sound, but their growth rates were within the range of the slower-growing population 2 isolates. Importantly, the observed genome size difference between isolates from the two populations was stable regardless of time in culture or the changes in cell size that accompany the diatom life history. Conclusions: The observed twofold difference in genome size between the D. brightwellii populations suggests that whole genome duplication occurred within cells of population 1 ultimately giving rise to population 2 cells. The apparent regional localization of population 2 is consistent with a recent divergence between the populations, which are likely cryptic species. Genome size variation is known to occur in other diatom genera; we hypothesize that genome duplication may be an active and important mechanism of genetic and physiological diversification and speciation in diatoms.

  • Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii (Bacillariophyta)
    BMC evolutionary biology, 2010
    Co-Authors: Julie A Koester, Peter Von Dassow, Jarred E Swalwell, Elizabeth V. Armbrust
    Abstract:

    Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions. All isolates from the more regionally-localized population (population 2) possessed 1.94 ± 0.74 times the amount of DNA, grew more slowly, and were generally larger than isolates from the more globally distributed population (population 1). The ITS1 sequences, cell sizes, and genome sizes of isolates from New Zealand were the same as population 1 isolates from Puget Sound, but their growth rates were within the range of the slower-growing population 2 isolates. Importantly, the observed genome size difference between isolates from the two populations was stable regardless of time in culture or the changes in cell size that accompany the diatom life history. The observed two-fold difference in genome size between the D. brightwellii populations suggests that whole genome duplication occurred within cells of population 1 ultimately giving rise to population 2 cells. The apparent regional localization of population 2 is consistent with a recent divergence between the populations, which are likely cryptic species. Genome size variation is known to occur in other diatom genera; we hypothesize that genome duplication may be an active and important mechanism of genetic and physiological diversification and speciation in diatoms.

  • Metapopulation Structure in the Planktonic Diatom Ditylum brightwellii (Bacillariophyceae).
    Protist, 2008
    Co-Authors: Tatiana A. Rynearson, Ellen O. Lin, Elizabeth V. Armbrust
    Abstract:

    Approximately 200,000 diatom species are thought to exist and yet the underlying processes of speciation in diatoms are unknown. Because genetic subdivision within species can reveal potential speciation mechanisms, we examined genetic differentiation and patterns of gene flow among four populations of the diatom Ditylum brightwellii. Single-cell isolates were examined at two microsatellite markers and two rDNA loci (18S and internal transcribed spacer region I (ITSI)). Among isolates, rDNA sequences varied by 0.08±0.04% (18S) and 0.7±0.3% (ITSI) and there were no compensatory base pair changes in the predicted ITSI secondary structure, all suggesting that a single species was represented. Two numerically dominant ITSI sequence types were detected and their distribution among isolates from genetically distinct populations was significantly different. Two populations shared ITSI sequence type 1 and two shared ITSI sequence type 2, indicating differences in relatedness among populations. The signature of unequal gene flow among populations suggested that D. brightwellii exhibited a metapopulation structure: the species was subdivided into populations of populations. The identification of metapopulations suggests a possible mechanism of speciation through reduced levels of gene flow, providing newly evolved taxa with a large repository of genetic and physiological diversity and perhaps significant adaptive potential.

  • GENETIC DIFFERENTIATION AMONG POPULATIONS OF THE PLANKTONIC MARINE DIATOM Ditylum BRIGHTWELLII (BACILLARIOPHYCEAE)1
    Journal of Phycology, 2004
    Co-Authors: Tatiana A. Rynearson, Elizabeth V. Armbrust
    Abstract:

    Population genetic structure was determined for the planktonic diatom Ditylum brightwellii (West) Grunow in two connected estuaries-Puget Sound and the Strait of Juan de Fuca (WA, USA). Three genetically distinct populations were detected that were characterized by different microsatellite allele distributions and unique alleles. Isolates from the two most genetically diverged populations displayed identical full-length 18S rDNA sequences suggesting that either a single or two recently diverged species were sampled. The extent of genetic differentiation between populations was not correlated with distance between water samples or time between sampling. Instead, distinct populations were associated with different estuaries. In Puget Sound waters, one population was detected three times over the course of 28 months. Cells from this population were likely maintained inside Puget Sound over long periods through water recirculation within the Sound. In Strait of Juan de Fuca waters, two additional populations were detected. Maximum growth rates of Puget Sound isolates were significantly different from Strait of Juan de Fuca isolates, indicating that populations were composed of cells with different physiological capabilities. The genetic and physiological differentiation observed between populations from intermixing estuaries suggested that genetic exchange between populations was restricted through differential selection. Despite the potential for widespread dispersal in planktonic organisms, it appears that populations with distinct genetic and physiological characteristics can be maintained over long time periods through a combination of hydrology and differential selection.

Edward J. Buskey - One of the best experts on this subject based on the ideXlab platform.

  • Feeding, growth, and behavior of the thecate heterotrophic dinoflagellate Oblea rotunda
    2015
    Co-Authors: Suzanne L. Strom, Edward J. Buskey
    Abstract:

    Laboratory experiments were performed to determine the growth and grazing capabilities of Oblea rotunda, a pallium-feeding dinoflagellate. Although Oblea can feed and grow on a wide range of phyto-plankton species, the highest observed growth rates (- 1 doubling d- *) were supported by the large diatom Ditylum brightwellii. Functional and numerical response curves, obtained with the green alga Dunaliella tertiolecta and D. brightwellii as foods, were typical in form of those obtained previously for other planktonic protozoans. Ditylum, however, consistently supported higher rates of growth and grazing than Dunaliella. Gross growth efficiencies for Oblea were relatively high. A chemosensory response to phy-toplankton exudates was observed during motion analysis of swimming behavior; no response to me-chanical cues was evident. Long-term behavioral responses to different phytoplankton species or con-centrations were not observed. The wide range of food species available to Oblea suggests that size- or taxon-based paramcterizations of such grazers in food-web models may be inadequate to describe actual grazing interactions. Heterotrophic dinoflagellates are a morpho-logically and functionally diverse group of pro-tozoans. Because their distribution is wide-spread, their abundance significant, and their range of food species large, they may be im-portant members of planktonic food webs (e.g

  • Feeding, growth, and behavior of the thecate heterotrophic dinoflagellate Oblea rotunda
    Limnology and Oceanography, 1993
    Co-Authors: Suzanne L. Strom, Edward J. Buskey
    Abstract:

    Laboratory experiments were performed to determine the growth and grazing capabilities of Oblea rotunda, a pallium-feeding dinoflagellate. Although Oblea can feed and grow on a wide range of phytoplankton species, the highest observed growth rates (- 1 doubling d- *) were supported by the large diatom Ditylum brightwellii. Functional and numerical response curves, obtained with the green alga Dunaliella tertiolecta and D. brightwellii as foods, were typical in form of those obtained previously for other planktonic protozoans. Ditylum, however, consistently supported higher rates of growth and grazing than Dunaliella. Gross growth efficiencies for Oblea were relatively high. A chemosensory response to phytoplankton exudates was observed during motion analysis of swimming behavior; no response to mechanical cues was evident. Long-term behavioral responses to different phytoplankton species or concentrations were not observed. The wide range of food species available to Oblea suggests that size- or taxon-based paramcterizations of such grazers in food-web models may be inadequate to describe actual grazing interactions. Heterotrophic dinoflagellates are a morphologically and functionally diverse group of protozoans. Because their distribution is widespread, their abundance significant, and their range of food species large, they may be important members of planktonic food webs (e.g. Beers et al. 1975; Smetacek 198 1; Lessard 1991). Although heterotrophic dinoflagellates have received the attention of taxonomists for over a century, little is known regarding the distribution of feeding modes among the various species. We know even less about potential rates of feeding and growth in these organisms. Dinoflagellate feeding mechanisms are varied (Gaines and Elbrachter 1987; Elbrachter 199 1); they include engulfing food cells, sucking out cell contents with an extensible peduncle (myzocytosis), and digesting food cells externally by means of a membranous veil (pallium feeding). Pallium feeding has been described by Jacobson and Anderson (1986) and appears to typify a substantial proportion of thecate het

Jinhwan Lee - One of the best experts on this subject based on the ideXlab platform.

  • Effect of temperature on changes in size and morphology of the marine diatom, Ditylum brightwellii (West) Grunow (Bacillariophyceae)
    Estuarine Coastal and Shelf Science, 2013
    Co-Authors: Seung Won Jung, Seok Jae Youn, Hyeon Ho Shin, Suk Min Yun, Jinhwan Lee
    Abstract:

    Abstract The objective of the present study was to assess size and morphological changes in response to temperature in the marine diatom, Ditylum brightwellii (West) Grunow, using ecological, morphological and physiological approaches. D. brightwellii has two distinct cell morphologies: prism (large-sized cell) and cylinder types (small-sized cell). In the coastal waters of South Korea, the prism type was found to be present at high frequency at low temperatures, whereas the cylinder type was predominant at high temperatures. Other environmental factors did not affect the presence of either cell type significantly. In growth experiments to determine the effect of temperature on the size of D. brightwellii, the abundance of the prism type increased at low temperature, but the abundance of the cylinder type increased at high temperature. These results are important for understanding temperature-induced size and morphological changes in D. brightwellii, and their potential role as an adaptive strategy.

  • classification into two types based on the morphological characteristics of the marine diatom Ditylum brightwellii west grunow in yellow sea korea
    Algae, 2007
    Co-Authors: Jinhwan Lee, Seok Jea Youn
    Abstract:

    This study deals with the taxonomy of the marine diatom Ditylum brightwellii (West) Grunow: shape, size and ratio, marginal ridge, labiate process, areolation, and seasonal distribution are all considered. Ditylum brightwellii were divided into two type; prism- and cylinder-shaped. Comparisons between specimens from the Yellow Sea were made on, (1) shape- prism types are prismatic-shaped and/or regular square or right-angled tetragon, cylinder types are cylinder-shaped and/or long right-angled tetragon in the girdle view, respectively; (2) size and ratiodiameters of prism types are 82.1 ± 2 µm, while those of cylinder types are 21.2 ± 5 µm and ratio of pervalvar axis/diameter- prism types cells are 1.0-1.5, but cylinder types are 3.9-5.5; (3) marginal ridges- prism types have dotted, while those of the cylinder-type cells have piece, slotted or fimbriated on the marginal ridge; (4) labiate process- both prism- and cylinder-types are central part in valve face, but length of labiate processes of prism types are longer than those of cylinder types; (5) cell margin- the girdle margin show many shallow furrows in prism type and smooth in cylinder type; (6) areolation- both prism- and cylinder-types are a radial pattern in the valve center, but areolae of prism types are larger than those of cylinder types; (7) seasonal distribution- cylinder types are dominated in summer and prism types in the other seasons.

Jan Rijstenbil - One of the best experts on this subject based on the ideXlab platform.

  • Effects of periodic, low UVA radiation on cell characteristics and oxidative stress in the marine planktonic diatom Ditylum brightwellii
    European Journal of Phycology, 2001
    Co-Authors: Jan Rijstenbil
    Abstract:

    A continuous culture experiment was conducted with the marine diatom Ditylum brighiwellii to assess the photo-oxidative effects of transition from dim light to high Light at three successive levels. The focus was on temporary stress by ambient WA at the water surface, via a simulation of the periodic ascent of diatoms caused by vertical mixing. Within a 14 h dim- light period, cells were exposed daily to 4 h of: (A) moderate PAR (100 mu mol photon m(-2) s(-1)), (B) high PAR (400 mu mol photon m(-2) s(-1)) and (C) high PAR (400-700 nm) plus 67 pmol photon m(-2) s(-1) (2.2 W m(-2)) UVA. Cell shape, life cycle and sinking rates were not affected by high PAR per se (mode B). The daily 4 h high-irradiance mode C, with additional UVA (WA:PAR = 0.016), caused an increase in cell diameter, a decrease in length axes, and a production of vegetative resting stages. Superoxide dismutase (SOD) activities, oxidized glutathione (GSSG) pools and malondialdehyde (MDA) contents increased as well, which indicates that this biologically effective WA dose (0.78 W m(-2)) promoted active oxygen production, oxidative stress and lipid peroxidation. Sinking rates in WA-exposed D. brightwellii were higher than in those grown without UVA. A close correlation between sinking rates and MDA contents suggests that UVA-induced lipid peroxidation has altered the membrane functions which regulate buoyancy in D. brightwellii. Although UVA-induced formation of resting cells will contribute to accelerated sinking, it is not evident that this can be considered as a stress avoidance mechanism under adverse light (WA) conditions. D. brightwellii proved to be sensitive to transitions from shade to natural surface irradiance conditions. In coastal waters, such large diatom species may experience oxidative stress after a few hours' residence near the water surface at ambient UVA levels. [KEYWORDS: cell size; Ditylum brightwellii; glutathione redox;lipid peroxidation; oxidative stress; planktonic diatom; resting stage; sinking rate; superoxide; ultraviolet-A Ultraviolet-b radiation; lipid-peroxidation; chlorella-vulgaris; photosynthetic pigment; superoxide-dismutase; thylakoid membranes; antioxidant systems; maize seedlings; sinking rates; phytoplankton]

  • Effects of periodic, low UVA radiation on cell characteristics and oxidative stress in the marine planktonic diatomDitylum brightwellii
    European Journal of Phycology, 2001
    Co-Authors: Jan Rijstenbil
    Abstract:

    A continuous culture experiment was conducted with the marine diatom Ditylum brighiwellii to assess the photo-oxidative effects of transition from dim light to high Light at three successive levels. The focus was on temporary stress by ambient WA at the water surface, via a simulation of the periodic ascent of diatoms caused by vertical mixing. Within a 14 h dim- light period, cells were exposed daily to 4 h of: (A) moderate PAR (100 mu mol photon m(-2) s(-1)), (B) high PAR (400 mu mol photon m(-2) s(-1)) and (C) high PAR (400-700 nm) plus 67 pmol photon m(-2) s(-1) (2.2 W m(-2)) UVA. Cell shape, life cycle and sinking rates were not affected by high PAR per se (mode B). The daily 4 h high-irradiance mode C, with additional UVA (WA:PAR = 0.016), caused an increase in cell diameter, a decrease in length axes, and a production of vegetative resting stages. Superoxide dismutase (SOD) activities, oxidized glutathione (GSSG) pools and malondialdehyde (MDA) contents increased as well, which indicates that this biologically effective WA dose (0.78 W m(-2)) promoted active oxygen production, oxidative stress and lipid peroxidation. Sinking rates in WA-exposed D. brightwellii were higher than in those grown without UVA. A close correlation between sinking rates and MDA contents suggests that UVA-induced lipid peroxidation has altered the membrane functions which regulate buoyancy in D. brightwellii. Although UVA-induced formation of resting cells will contribute to accelerated sinking, it is not evident that this can be considered as a stress avoidance mechanism under adverse light (WA) conditions. D. brightwellii proved to be sensitive to transitions from shade to natural surface irradiance conditions. In coastal waters, such large diatom species may experience oxidative stress after a few hours' residence near the water surface at ambient UVA levels. [KEYWORDS: cell size; Ditylum brightwellii; glutathione redox;lipid peroxidation; oxidative stress; planktonic diatom; resting stage; sinking rate; superoxide; ultraviolet-A Ultraviolet-b radiation; lipid-peroxidation; chlorella-vulgaris; photosynthetic pigment; superoxide-dismutase; thylakoid membranes; antioxidant systems; maize seedlings; sinking rates; phytoplankton