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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Cobalamin uptake (⁵⁷Co-B12) |- | '''Approach:''' radiotracer (⁵⁷Co-labelled cobalamin) incubation |- | '''Context:''' incubation, lab |- | '''Spatial scale:''' point sample |- |..."

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Created page with "{{BreadcrumbsNutrients}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- __TOC__ <div class="model-box"> {| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Cobalamin uptake (57Co-B12) |- | '''Approach:''' radiotracer (57Co-labelled cobalamin) incubation |- | '''Context:''' incubation, lab |- | '''Spatial scale:''' point sample |- |..."

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* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]: [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Cobalamin uptake (57Co-B12)
|-
| '''Approach:''' radiotracer (57Co-labelled cobalamin) incubation
|-
| '''Context:''' incubation, lab
|-
| '''Spatial scale:''' point sample
|-
| '''Temporal scale:''' 4–24 h
|-
| '''Units:''' mol cell-1 d-1; mol L-1 d-1; mol mol C-1 d-1
|-
| '''Community captured:''' all (usually > 0.2 or 0.7 µm)
|-
| '''Co-measurements:''' biomass (Chl, cells, POC, cell volume)
|}
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== Method Overview ==

Cobalamin (vitamin B12) uptake rates are measured using 57Co-labelled cyanocobalamin (57Co-B12; half-life ~271 days, gamma emitter). The radiolabelled cobalamin is added to seawater at tracer concentrations under trace-metal-clean conditions and equilibrated with the sample. After incubation (4–24 h), cells are collected on filters, rinsed to remove surface-adsorbed cobalamin, and counted by gamma spectrometry. Uptake rates are calculated from the fraction of 57Co-B12 incorporated relative to total dissolved 57Co-B12<ref name="Bertrand2011">Bertrand, E. M., Saito, M. A., Rose, J. M., Riesselman, C. R., Lohan, M. C., Noble, A. E., Lee, P. A., & DiTullio, G. R. (2011). Vitamin B12 and iron colimitation of phytoplankton growth in the Ross Sea. ''Limnology and Oceanography'', 56(4), 1079–1091. https://doi.org/10.3389/fmicb.2011.00160</ref>.

Cobalamin is an essential cofactor that many phytoplankton cannot synthesize and must obtain from cobalamin-producing bacteria, making uptake rate measurements central to understanding phytoplankton–bacteria vitamin interactions.

=== Scale of measurement ===

Point sample after 4–24 h of incubation under trace-metal-clean conditions.

=== Data generated ===

Cobalamin uptake rates (mol cell-1 d-1 or mol L-1 d-1). Combined with cellular B12 quotas, the community's vitamin B12 demand and turnover can be characterized.

=== Units & currency ===

Units are mol cell-1 d-1, mol L-1 d-1, or mol mol C-1 d-1. The currency is Co (as cobalamin).

=== Sample size ===

Typical samples are < 1 L in volume.

=== Repositories & databases ===

== Limitations ==

The method assumes that 57Co remains associated with the intact cobalamin molecule throughout the incubation (no degradation of cobalamin to other Co-containing compounds). In practice, some B12 degradation can occur, leading to uptake of 57Co in non-cobalamin forms. Natural cobalamin-binding proteins in seawater can compete with cellular uptake, and their effect must be considered when estimating bioavailable cobalamin.

== Example Applications & Protocols ==

=== Classic examples ===
* Bertrand et al. (2011) ''Vitamin B12 and iron colimitation of phytoplankton growth in the Ross Sea'' <ref name="Bertrand2011" />

=== Recent applications ===
*

=== Common calculations/conversions ===
* B12 uptake rate = (cpmcells / cpmdissolved) × [B12,dissolved] / incubation time.

== References ==

[[Category:Main Pages|Model types]]

Cobalamin uptake with 57Cobalt-B12 - Revision history