Silicon Metabolism

The cells of Navicula pelliculosa (Bréb.) Hilse, when grown in media which contained 3.5, 8.3, and 34.0 mg. Si per liter, reproduced with generation (doubling) times of 20.4, 13.7, and 13.1 hours respectively. The degree of silicification of the cells in each culture initially fell with increasing population. After exponential growth had ceased, this value varied between 0.8 × 10−9 and 2.2 × 10−9 mg. Si per cell, depending on the amount of silicon originally present in the medium and on the age of the culture. When placed in a fresh silicate solution, the cells took up additional silicate with increases in silicon content of 50%, 90%, and 15%, respectively. Silica (SiO2) may represent from 4% to 22% of the dry weight of the cells. The average thickness of the frustules has been calculated to range between 200 and 600 Å.

Download Full-text

Silicon metabolism

Biological Trace Element Research ◽

10.1007/bf02785246 ◽

1992 ◽

Vol 34 (2) ◽

pp. 185-195 ◽

Cited By ~ 4

Author(s):

Jacek Najda ◽

Jan Gmiński ◽

Marian Dróżdż ◽

Alojzy Danch

Keyword(s):

Silicon Metabolism

Download Full-text

The Separation of 32Silicon from Contaminating 3H and 60Co by Incorporation into Diatoms

Zeitschrift für Naturforschung C ◽

10.1515/znc-1975-5-623 ◽

1975 ◽

Vol 30 (5-6) ◽

pp. 423-424 ◽

Cited By ~ 5

Author(s):

D. Werner ◽

H. D. Pawlitz ◽

R. Roth

Keyword(s):

Half Life ◽

Diatom Species ◽

Silicon Metabolism ◽

First Time ◽

Cyclotella Cryptica

Abstract 32Si (β-. 0,1 MeV, half life about 280 years) has been used, as for as we are aware, for the first time in bio logical and biochemical experiments . 32Si was incorporated by the pathway of the silicon metabolism into shells of two diatom species (Cyclotella cryptica and Nitzschia spec.) and reisolated by dissolving the shells. Contaminating isotopes 3H and 60Co with 10000 times more activity were largely removed by this procedure.

Download Full-text

SILICON METABOLISM IN DIATOMS: IMPLICATIONS FOR GROWTH

Journal of Phycology ◽

10.1046/j.1529-8817.2000.00019.x ◽

2000 ◽

Vol 36 (5) ◽

pp. 821-840 ◽

Cited By ~ 529

Author(s):

Veronique Martin-Jezequel ◽

Mark Hildebrand ◽

Mark A. Brzezinski

Keyword(s):

Silicon Metabolism

Download Full-text

A model for the effects of germanium on silica biomineralization in choanoflagellates

Journal of The Royal Society Interface ◽

10.1098/rsif.2016.0485 ◽

2016 ◽

Vol 13 (122) ◽

pp. 20160485 ◽

Cited By ~ 7

Author(s):

Alan O. Marron ◽

Helen Chappell ◽

Sarah Ratcliffe ◽

Raymond E. Goldstein

Keyword(s):

Silicic Acid ◽

General Toxicity ◽

Silicon Metabolism ◽

Widespread Phenomenon ◽

Silica Polymerization ◽

Species Specific ◽

Lorica Formation ◽

Germanium Silicon

Silica biomineralization is a widespread phenomenon of major biotechnological interest. Modifying biosilica with substances like germanium (Ge) can confer useful new properties, although exposure to high levels of Ge disrupts normal biosilicification. No clear mechanism explains why this disruption occurs. Here, we study the effect of Ge on loricate choanoflagellates, a group of protists that construct a species-specific extracellular lorica from multiple siliceous costal strips. High Ge exposures were toxic, whereas lower Ge exposures produced cells with incomplete or absent loricae. These effects can be ameliorated by restoring the germanium : silicon ratio, as observed in other biosilicifying organisms. We developed simulations of how Ge interacts with polymerizing silica. In our models, Ge is readily incorporated at the ends of silica forming from silicic acid condensation, but this prevents further silica polymerization. Our ‘Ge-capping’ model is supported by observations from loricate choanoflagellates. Ge exposure terminates costal strip synthesis and lorica formation, resulting in disruption to cytokinesis and fatal build-up of silicic acid. Applying the Ge-capping model to other siliceous organisms explains the general toxicity of Ge and identifies potential protective responses in metalloid uptake and sensing. This can improve the design of new silica biomaterials, and further our understanding of silicon metabolism.

Download Full-text

SILICON METABOLISM IN DIATOMS

The Journal of General Physiology ◽

10.1085/jgp.37.5.589 ◽

1954 ◽

Vol 37 (5) ◽

pp. 589-599 ◽

Cited By ~ 75

Author(s):

Joyce C. Lewin

Keyword(s):

Ascorbic Acid ◽

Cell Membrane ◽

Sodium Arsenite ◽

Silicate Solution ◽

Distilled Water ◽

Silicon Uptake ◽

Aerobic Process ◽

Silicon Metabolism ◽

Growing Conditions ◽

Silica Frustules

1. Cells of the fresh water diatom Navicula pelliculosa may be grown in a mineral medium containing a low concentration of silicon. When transferred to a fresh silicate solution and incubated under non-growing conditions such deficient cells rapidly take up silicon from the medium. 2. The utilization of silicon is an aerobic process. 3. When deficient cells are washed with distilled water or saline, their ability to utilize silicon is impaired whereas respiration is unaffected. 4. The ability of washed cells to take up silicon can be partially restored with sulfate or ascorbic acid, and is completely restored by Na2S, Na2S2O3, glutathione, l-cysteine, dl-methionine, or ascorbic acid plus sulfate. 5. The sulfhydryl reagent, CdCl2, inhibits silicon utilization of unwashed cells at concentrations which do not affect respiration. This inhibition similarly is reversed by glutathione or cysteine. 6. However, sodium iodoacetate or sodium arsenite inhibits respiration and silicon utilization at the same concentrations. 7. The silicon taken up by deficient cells is deposited at the cell surface as a thickening of the existing silica frustules. 8. Sulfhydryl groups in the cell membrane may be involved in silicon uptake by diatoms.

Download Full-text

SILICON METABOLISM IN DIATOMS

The Journal of General Physiology ◽

10.1085/jgp.39.1.1 ◽

1955 ◽

Vol 39 (1) ◽

pp. 1-10 ◽

Cited By ~ 77

Author(s):

Joyce C. Lewin

Keyword(s):

Carbon Dioxide ◽

Oxygen Uptake ◽

Respiratory Quotient ◽

Aerobic Respiration ◽

Carbon Dioxide Evolution ◽

Exogenous Glucose ◽

Silicon Uptake ◽

Silicon Metabolism ◽

Respiratory Stimulation ◽

Stimulation Of

1. Evidence is presented that silicon uptake in the diatom Navicula pelliculosa is linked with aerobic respiration. 2. Cyanide, fluoride, iodoacetate, arsenite, azide, and fluoroacetate, at concentrations inhibitory to respiration, were also inhibitory to silicon uptake. 3. 2,4-Dinitrophenol (1 to 2 x 10–5 M) stimulated respiration by 100 per cent, but almost completely inhibited silicon uptake. 4. The respiratory quotient of non-Si-deficient cells decreased from 0.93 to 0.75 after 4 days of starvation in darkness. Glucose (1 per cent) raised the respiratory quotient of such starved cells to 1.05. 5. Silicate (20 mg. Si/liter) stimulated respiration of unstarved Si-deficient cells by about 40 per cent. The effect of silicate on the respiration of Si-deficient cells which had been starved in darkness for 4 days was less marked. 6. The respiratory quotient of Si-deficient cells decreased from 0.8–0.9 to 0.3 after 4 days of starvation in darkness. The addition of silicate to starved cells raised the quotient to 0.5. This represented a 25 per cent stimulation of oxygen uptake concomitant with a 90 per cent stimulation of carbon dioxide evolution. 7. Glucose (1 per cent) caused an increase of respiratory quotient in starved cells from 0.3 to 0.7–0.8. The addition of silicate had no effect on the R.Q. during the oxidation of exogenous glucose. 8. Substrates (glucose, fructose, galactose, lactate, succinate, citrate, glycerol), which caused a stimulation of respiration in starved cells, also stimulated silicon uptake by those cells. However, the stimulation of silicon uptake (50 to 100 per cent) was not proportional to the respiratory stimulation by these substrates (30 to 300 per cent).

Download Full-text