The mechanism of isotope fractionation during algal nitrate assimilation as illuminated by the 15N/14N of intracellular nitrate

Joseph Needoba, Daniel M. Sigman, Paul J. Harrison

Research output: Contribution to journalArticle

86 Citations (Scopus)

Abstract

The 15N/14N of nitrate in the external medium and intracellular pool of the cultured marine diatom Thalassiosira weissflogii (Grun.) Fryxell et Hasle was measured during nitrate assimilation under low light, a 12:12-h light:dark cycle, low temperature, or low iron conditions. The 15N/14N of the nitrate in the medium and the particulate matter both followed the predicted Rayleigh fractionation model, and the intracellular nitrate always had a higher 15N/14N than did the medium nitrate. When the experiments were compared, the results showed a negative correlation between the isotope fractionation factor and the difference in the 15N/14N between the two pools of nitrate. These observations imply that the variations in the isotope effect result from variations in the degree to which the fractionation by nitrate reductase is expressed outside the cell, which is, in turn, controlled by the rate of nitrate efflux relative to nitrate reduction. The low iron and low temperature experiments showed relatively small isotope effects but a large intracellular-medium difference in nitrate 15N/14N, consistent with a relative rate of efflux (compared with influx) that is small and similar to fast-growing cells. In contrast, large isotope effects and small intracellular-medium differences in nitrate 15N/14N were observed for low light and light:dark cycle grown cells and are explained by higher relative rates of nitrate efflux under these growth conditions.

Original languageEnglish (US)
Pages (from-to)517-522
Number of pages6
JournalJournal of Phycology
Volume40
Issue number3
StatePublished - Jun 2004
Externally publishedYes

Fingerprint

isotope fractionation
fractionation
nitrates
isotope
nitrate
isotopes
photoperiod
assimilation
iron
Bacillariophyceae
nitrate reduction
Thalassiosira
cells
nitrate reductase
particulates
temperature
particulate matter
diatom

Keywords

  • Efflux
  • Internal pool
  • Iron
  • Isotope fractionation
  • Light
  • Nitrate
  • Phytoplankton
  • Temperature
  • Thalassiosira weissflogii

ASJC Scopus subject areas

  • Aquatic Science
  • Plant Science

Cite this

The mechanism of isotope fractionation during algal nitrate assimilation as illuminated by the 15N/14N of intracellular nitrate. / Needoba, Joseph; Sigman, Daniel M.; Harrison, Paul J.

In: Journal of Phycology, Vol. 40, No. 3, 06.2004, p. 517-522.

Research output: Contribution to journalArticle

@article{815c87d187074eb7a28064fe70e6986b,
title = "The mechanism of isotope fractionation during algal nitrate assimilation as illuminated by the 15N/14N of intracellular nitrate",
abstract = "The 15N/14N of nitrate in the external medium and intracellular pool of the cultured marine diatom Thalassiosira weissflogii (Grun.) Fryxell et Hasle was measured during nitrate assimilation under low light, a 12:12-h light:dark cycle, low temperature, or low iron conditions. The 15N/14N of the nitrate in the medium and the particulate matter both followed the predicted Rayleigh fractionation model, and the intracellular nitrate always had a higher 15N/14N than did the medium nitrate. When the experiments were compared, the results showed a negative correlation between the isotope fractionation factor and the difference in the 15N/14N between the two pools of nitrate. These observations imply that the variations in the isotope effect result from variations in the degree to which the fractionation by nitrate reductase is expressed outside the cell, which is, in turn, controlled by the rate of nitrate efflux relative to nitrate reduction. The low iron and low temperature experiments showed relatively small isotope effects but a large intracellular-medium difference in nitrate 15N/14N, consistent with a relative rate of efflux (compared with influx) that is small and similar to fast-growing cells. In contrast, large isotope effects and small intracellular-medium differences in nitrate 15N/14N were observed for low light and light:dark cycle grown cells and are explained by higher relative rates of nitrate efflux under these growth conditions.",
keywords = "Efflux, Internal pool, Iron, Isotope fractionation, Light, Nitrate, Phytoplankton, Temperature, Thalassiosira weissflogii",
author = "Joseph Needoba and Sigman, {Daniel M.} and Harrison, {Paul J.}",
year = "2004",
month = "6",
language = "English (US)",
volume = "40",
pages = "517--522",
journal = "Journal of Phycology",
issn = "0022-3646",
publisher = "Wiley-Blackwell",
number = "3",

}

TY - JOUR

T1 - The mechanism of isotope fractionation during algal nitrate assimilation as illuminated by the 15N/14N of intracellular nitrate

AU - Needoba, Joseph

AU - Sigman, Daniel M.

AU - Harrison, Paul J.

PY - 2004/6

Y1 - 2004/6

N2 - The 15N/14N of nitrate in the external medium and intracellular pool of the cultured marine diatom Thalassiosira weissflogii (Grun.) Fryxell et Hasle was measured during nitrate assimilation under low light, a 12:12-h light:dark cycle, low temperature, or low iron conditions. The 15N/14N of the nitrate in the medium and the particulate matter both followed the predicted Rayleigh fractionation model, and the intracellular nitrate always had a higher 15N/14N than did the medium nitrate. When the experiments were compared, the results showed a negative correlation between the isotope fractionation factor and the difference in the 15N/14N between the two pools of nitrate. These observations imply that the variations in the isotope effect result from variations in the degree to which the fractionation by nitrate reductase is expressed outside the cell, which is, in turn, controlled by the rate of nitrate efflux relative to nitrate reduction. The low iron and low temperature experiments showed relatively small isotope effects but a large intracellular-medium difference in nitrate 15N/14N, consistent with a relative rate of efflux (compared with influx) that is small and similar to fast-growing cells. In contrast, large isotope effects and small intracellular-medium differences in nitrate 15N/14N were observed for low light and light:dark cycle grown cells and are explained by higher relative rates of nitrate efflux under these growth conditions.

AB - The 15N/14N of nitrate in the external medium and intracellular pool of the cultured marine diatom Thalassiosira weissflogii (Grun.) Fryxell et Hasle was measured during nitrate assimilation under low light, a 12:12-h light:dark cycle, low temperature, or low iron conditions. The 15N/14N of the nitrate in the medium and the particulate matter both followed the predicted Rayleigh fractionation model, and the intracellular nitrate always had a higher 15N/14N than did the medium nitrate. When the experiments were compared, the results showed a negative correlation between the isotope fractionation factor and the difference in the 15N/14N between the two pools of nitrate. These observations imply that the variations in the isotope effect result from variations in the degree to which the fractionation by nitrate reductase is expressed outside the cell, which is, in turn, controlled by the rate of nitrate efflux relative to nitrate reduction. The low iron and low temperature experiments showed relatively small isotope effects but a large intracellular-medium difference in nitrate 15N/14N, consistent with a relative rate of efflux (compared with influx) that is small and similar to fast-growing cells. In contrast, large isotope effects and small intracellular-medium differences in nitrate 15N/14N were observed for low light and light:dark cycle grown cells and are explained by higher relative rates of nitrate efflux under these growth conditions.

KW - Efflux

KW - Internal pool

KW - Iron

KW - Isotope fractionation

KW - Light

KW - Nitrate

KW - Phytoplankton

KW - Temperature

KW - Thalassiosira weissflogii

UR - http://www.scopus.com/inward/record.url?scp=2942564647&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=2942564647&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:2942564647

VL - 40

SP - 517

EP - 522

JO - Journal of Phycology

JF - Journal of Phycology

SN - 0022-3646

IS - 3

ER -