View source for Pulse-chase labeling of bacterial prey

{{BreadcrumbsInteractions}}

* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]:  [[User:Hagi BucknWise|Hagen Buck-Wiese]]
----

__TOC__
<div class="model-box">
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Bacterivory by mixotrophs (pulse-chase <sup>14</sup>C)
|-
| '''Approach:''' <sup>14</sup>C pulse labelling of bacterial prey; radioactivity in FCM-sorted pigmented cells
|-
| '''Context:''' incubation, field
|-
| '''Spatial scale:''' point sample
|-
| '''Temporal scale:''' hours
|-
| '''Units:''' prey cell<sup>-1</sup> h<sup>-1</sup>
|-
| '''Community captured:''' specific FCM-defined populations (unpigmented heterotrophs; pigmented mixotrophs)
|-
| '''Co-measurements:''' cell abundances
|}
</div>
<div style="clear:both"></div>

== Method Overview ==

<sup>14</sup>C-labelled bacteria (pulse phase) are added to seawater samples and allowed to be ingested by grazers. After a short pulse incubation, samples are fixed and specific cell populations are sorted by flow cytometry based on their optical properties — distinguishing unpigmented heterotrophic protists from pigmented (autofluorescent) cells, which may include constitutive mixotrophs. The radioactivity in each sorted population is measured by liquid scintillation counting. The radioactivity per sorted pigmented cell, relative to the specific radioactivity of the labelled bacterial prey, gives the ingestion rate of bacteria by that population. This approach uniquely identifies bacterivory in autofluorescent (phytoplankton-like) cells, directly demonstrating mixotrophy in situ<ref name="Zubkov2008">Zubkov, M. V., & Tarran, G. A. (2008). High bacterivory by the smallest phytoplankton in the North Atlantic Ocean. ''Nature'', 455, 224–226. https://doi.org/10.1038/nature07236</ref>.

=== Scale of measurement ===

Hours of incubation required to allow detectable ingestion.

=== Data generated ===

Per-cell bacterial ingestion rates (prey cell<sup>-1</sup> h<sup>-1</sup>) for specific FCM-sorted populations, including pigmented mixotrophic cells.

=== Units & currency ===

Units are prey cell<sup>-1</sup> h<sup>-1</sup>. The currency is cells.

=== Sample size ===

Typical samples are < 1 L in volume.

=== Repositories & databases ===

== Limitations ==

The assumption is that all radioactivity in the sorted pigmented cell fraction arose from bacterial ingestion (bacterivory), rather than other reasons for co-associations such as stickiness or bacterial attachment to cell surfaces. Contamination of the sorted fraction by unlabelled bacteria can inflate apparent ingestion rates. FCM sorting throughput limits the number of cells collected per sample.

== Example Applications & Protocols ==

=== Classic examples ===
* Zubkov & Tarran (2008) ''High bacterivory by the smallest phytoplankton in the North Atlantic Ocean'' <ref name="Zubkov2008" />

=== Recent applications ===
*

=== Common calculations/conversions ===
* Ingestion rate = (cpm<sub>sorted pigmented cells</sub> / cpm<sub>labelled bacterium</sub><sup>-1</sup>) / (number of sorted cells × incubation time).

== References ==

[[Category:Main Pages|Model types]]