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A vacuole-like compartment concentrates a disordered calcium phase in a key coccolithophorid alga.

Sviben S, Gal A, Hood MA, Bertinetti L, Politi Y, Bennet M, Krishnamoorthy P, Schertel A, Wirth R, Sorrentino A, Pereiro E, Faivre D, Scheffel A - Nat Commun (2016)

Bottom Line: We identify a compartment, distinct from the coccolith-producing compartment, filled with high concentrations of a disordered form of calcium.The amounts of calcium stored in this reservoir seem to be dynamic and at a certain stage the compartment is in direct contact with the coccolith-producing vesicle, suggesting an active role in coccolith formation.Our findings provide insights into calcium accumulation in this important calcifying organism.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck Institute of Molecular Plant Physiology, Potsdam-Golm 14476, Germany.

ABSTRACT
Coccoliths are calcitic particles produced inside the cells of unicellular marine algae known as coccolithophores. They are abundant components of sea-floor carbonates, and the stoichiometry of calcium to other elements in fossil coccoliths is widely used to infer past environmental conditions. Here we study cryo-preserved cells of the dominant coccolithophore Emiliania huxleyi using state-of-the-art nanoscale imaging and spectroscopy. We identify a compartment, distinct from the coccolith-producing compartment, filled with high concentrations of a disordered form of calcium. Co-localized with calcium are high concentrations of phosphorus and minor concentrations of other cations. The amounts of calcium stored in this reservoir seem to be dynamic and at a certain stage the compartment is in direct contact with the coccolith-producing vesicle, suggesting an active role in coccolith formation. Our findings provide insights into calcium accumulation in this important calcifying organism.

No MeSH data available.


Related in: MedlinePlus

Cells without Ca-rich body contained a compartment filled with dilutedconcentrations of calcium and phosphorus.(a–e) Slices from cryo-FIB-SEM image series ofhigh-pressure frozen E. huxleyi cells imaged in secondary electronmode (a,c,e) and backscattered electron mode(b,d), showing coccolith calcite (blue arrowhead), thedense Ca–P-rich body (red arrow) and a pool of diluted concentrationsof Ca (orange arrow, framed orange in e) in close contact. The whiteline in e frames the coccolith vesicle–reticular body system.(f) HAADF-STEM image of a thin-sectioned cell showing the nucleus(N), the chloroplast (Chl), coccolith calcite (blue arrowhead), thecoccolith vesicle–reticular body system (framed white) and thevacuole-like compartment containing Ca and P (framed orange). (g) EDXspectra taken from inside the compartment framed orange in f and ofcytosol. The epoxy resin contributes to the C peak and therefore the Csignal does not represent in vivo concentrations.
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f6: Cells without Ca-rich body contained a compartment filled with dilutedconcentrations of calcium and phosphorus.(a–e) Slices from cryo-FIB-SEM image series ofhigh-pressure frozen E. huxleyi cells imaged in secondary electronmode (a,c,e) and backscattered electron mode(b,d), showing coccolith calcite (blue arrowhead), thedense Ca–P-rich body (red arrow) and a pool of diluted concentrationsof Ca (orange arrow, framed orange in e) in close contact. The whiteline in e frames the coccolith vesicle–reticular body system.(f) HAADF-STEM image of a thin-sectioned cell showing the nucleus(N), the chloroplast (Chl), coccolith calcite (blue arrowhead), thecoccolith vesicle–reticular body system (framed white) and thevacuole-like compartment containing Ca and P (framed orange). (g) EDXspectra taken from inside the compartment framed orange in f and ofcytosol. The epoxy resin contributes to the C peak and therefore the Csignal does not represent in vivo concentrations.

Mentions: The relatively low degree of synchronization between the cells of the sameculture enabled the observation of variation in the appearance of the Ca-richbody. In the cryo-FIB-SEM images of some cells, a second phase with contrastintermediate between the cytoplasm and the Ca-rich body was observed, which ismost likely also Ca but at a concentration lower than in the body (Fig. 6a–c). Assigning this second phase to be a morediluted, Ca pool is supported by a similar observation that was made in thecryo-soft-X-ray images, where some Ca-rich bodies were surrounded by a scatteredcloud of low concentrations of calcium (Fig. 2a). Usingcoccolith calcite and culture medium as Ca reference concentrations, wecalculated the average Ca concentration for several ‘clouds' to bebetween 1 and 2 M. In accordance with these observations, we also saw inthin-sectioned cells a large compartment filled with diluted concentrations ofCa and P (Fig. 6d). The membranes delimiting the lowconcentrated Ca pools were seen in close contact with the coccolithvesicle–reticular body system (Fig. 6c,d). Thisconfiguration may allow the direct transfer of Ca and other trace elements foundin coccolith calcite from the storage compartment into the coccolithvesicle.


A vacuole-like compartment concentrates a disordered calcium phase in a key coccolithophorid alga.

Sviben S, Gal A, Hood MA, Bertinetti L, Politi Y, Bennet M, Krishnamoorthy P, Schertel A, Wirth R, Sorrentino A, Pereiro E, Faivre D, Scheffel A - Nat Commun (2016)

Cells without Ca-rich body contained a compartment filled with dilutedconcentrations of calcium and phosphorus.(a–e) Slices from cryo-FIB-SEM image series ofhigh-pressure frozen E. huxleyi cells imaged in secondary electronmode (a,c,e) and backscattered electron mode(b,d), showing coccolith calcite (blue arrowhead), thedense Ca–P-rich body (red arrow) and a pool of diluted concentrationsof Ca (orange arrow, framed orange in e) in close contact. The whiteline in e frames the coccolith vesicle–reticular body system.(f) HAADF-STEM image of a thin-sectioned cell showing the nucleus(N), the chloroplast (Chl), coccolith calcite (blue arrowhead), thecoccolith vesicle–reticular body system (framed white) and thevacuole-like compartment containing Ca and P (framed orange). (g) EDXspectra taken from inside the compartment framed orange in f and ofcytosol. The epoxy resin contributes to the C peak and therefore the Csignal does not represent in vivo concentrations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834641&req=5

f6: Cells without Ca-rich body contained a compartment filled with dilutedconcentrations of calcium and phosphorus.(a–e) Slices from cryo-FIB-SEM image series ofhigh-pressure frozen E. huxleyi cells imaged in secondary electronmode (a,c,e) and backscattered electron mode(b,d), showing coccolith calcite (blue arrowhead), thedense Ca–P-rich body (red arrow) and a pool of diluted concentrationsof Ca (orange arrow, framed orange in e) in close contact. The whiteline in e frames the coccolith vesicle–reticular body system.(f) HAADF-STEM image of a thin-sectioned cell showing the nucleus(N), the chloroplast (Chl), coccolith calcite (blue arrowhead), thecoccolith vesicle–reticular body system (framed white) and thevacuole-like compartment containing Ca and P (framed orange). (g) EDXspectra taken from inside the compartment framed orange in f and ofcytosol. The epoxy resin contributes to the C peak and therefore the Csignal does not represent in vivo concentrations.
Mentions: The relatively low degree of synchronization between the cells of the sameculture enabled the observation of variation in the appearance of the Ca-richbody. In the cryo-FIB-SEM images of some cells, a second phase with contrastintermediate between the cytoplasm and the Ca-rich body was observed, which ismost likely also Ca but at a concentration lower than in the body (Fig. 6a–c). Assigning this second phase to be a morediluted, Ca pool is supported by a similar observation that was made in thecryo-soft-X-ray images, where some Ca-rich bodies were surrounded by a scatteredcloud of low concentrations of calcium (Fig. 2a). Usingcoccolith calcite and culture medium as Ca reference concentrations, wecalculated the average Ca concentration for several ‘clouds' to bebetween 1 and 2 M. In accordance with these observations, we also saw inthin-sectioned cells a large compartment filled with diluted concentrations ofCa and P (Fig. 6d). The membranes delimiting the lowconcentrated Ca pools were seen in close contact with the coccolithvesicle–reticular body system (Fig. 6c,d). Thisconfiguration may allow the direct transfer of Ca and other trace elements foundin coccolith calcite from the storage compartment into the coccolithvesicle.

Bottom Line: We identify a compartment, distinct from the coccolith-producing compartment, filled with high concentrations of a disordered form of calcium.The amounts of calcium stored in this reservoir seem to be dynamic and at a certain stage the compartment is in direct contact with the coccolith-producing vesicle, suggesting an active role in coccolith formation.Our findings provide insights into calcium accumulation in this important calcifying organism.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck Institute of Molecular Plant Physiology, Potsdam-Golm 14476, Germany.

ABSTRACT
Coccoliths are calcitic particles produced inside the cells of unicellular marine algae known as coccolithophores. They are abundant components of sea-floor carbonates, and the stoichiometry of calcium to other elements in fossil coccoliths is widely used to infer past environmental conditions. Here we study cryo-preserved cells of the dominant coccolithophore Emiliania huxleyi using state-of-the-art nanoscale imaging and spectroscopy. We identify a compartment, distinct from the coccolith-producing compartment, filled with high concentrations of a disordered form of calcium. Co-localized with calcium are high concentrations of phosphorus and minor concentrations of other cations. The amounts of calcium stored in this reservoir seem to be dynamic and at a certain stage the compartment is in direct contact with the coccolith-producing vesicle, suggesting an active role in coccolith formation. Our findings provide insights into calcium accumulation in this important calcifying organism.

No MeSH data available.


Related in: MedlinePlus