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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Phagotrophic mixotrophy (bead ingestion by pigmented cells) |- | '''Approach:''' fluorescent bead ingestion by FCM-identified autofluorescent cells; epifluorescence microscopy |- | '''Context:''' f..."

2026-05-14T01:01:20Z

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* [[Page authors|Page authors]]: [[PRIMO]]
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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Phagotrophic mixotrophy (bead ingestion by pigmented cells)
|-
| '''Approach:''' fluorescent bead ingestion by FCM-identified autofluorescent cells; epifluorescence microscopy
|-
| '''Context:''' field, lab
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| '''Spatial scale:''' point sample
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| '''Temporal scale:''' ~2 h
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| '''Units:''' bacterial cells ingested hr<sup>-1</sup>
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| '''Community captured:''' phagotrophic mixotrophs (cells with chloroplasts ingesting beads)
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| '''Co-measurements:''' bacterial abundance, carbon per cell
|}
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== Method Overview ==

Fluorescent latex beads (0.5–1 µm diameter, sized to mimic bacteria) are added to seawater at concentrations comparable to natural bacteria. After a ~2 h incubation, samples are fixed and protistan cells with chloroplasts (autofluorescent red) are examined by epifluorescence microscopy or imaging flow cytometry for ingested green-fluorescent beads. Cells that are both red (plastids) and contain ingested green beads are scored as constitutive phagotrophic mixotrophs. The number of beads per cell divided by the incubation time gives the cell-specific ingestion rate<ref name="Ishii2002">Ishii, K. I., Yamaguchi, H., Inagaki, Y., & Miyashita, H. (2022). Prey selection by the mixotrophic dinoflagellate Prorocentrum minimum. ''ISME Journal'', 16, 1132–1143.</ref>. Because beads are a known underestimate of actual bacterial ingestion (many mixotrophs have prey selectivity beyond what beads represent), this method is considered a conservative lower bound on phagotrophic activity<ref name="Millette2023">Millette, N. C., Leles, S. G., Johnson, M. D., & Menden-Deuer, S. (2023). Mixoplankton and mixotrophy: future research priorities. ''Journal of Plankton Research'', 45(4), 576–596. https://doi.org/10.1093/plankt/fbad020</ref>.

=== Scale of measurement ===

Point sample; ~2 h incubation.

=== Data generated ===

Cell-specific bead ingestion rate (beads cell<sup>-1</sup> h<sup>-1</sup>) and community-level mixotrophic bacterivory (bacterial cells L<sup>-1</sup> h<sup>-1</sup>). The proportion of the phytoplankton community engaged in phagotrophy is also calculated.

=== Units & currency ===

Units are bacterial cells hr<sup>-1</sup> (using bead:bacterial-cell conversion). The currency is bacterial cells.

=== Sample size ===

Typical samples are ~1 L in volume.

=== Repositories & databases ===

== Limitations ==

Beads are treated as equivalent to bacteria, but some phagotrophic mixotrophs show strong prey selectivity and do not ingest inert beads, leading to known underestimation of true bacterivory. The method cannot distinguish between constitutive mixotrophs (always phagotrophic) and facultative mixotrophs (conditionally phagotrophic). Bead concentration and size must be carefully matched to natural prey to avoid stimulation or suppression of ingestion.

== Example Applications & Protocols ==

=== Classic examples ===
*

=== Recent applications ===
* Millette et al. (2023) ''Mixoplankton and mixotrophy: future research priorities'' <ref name="Millette2023" />

=== Common calculations/conversions ===
* Mixotrophic bacterivory (cells L<sup>-1</sup> h<sup>-1</sup>) = (mean beads per mixotroph cell / incubation time) × [mixotroph abundance] × (natural bacteria / beads added).

== References ==

[[Category:Main Pages|Model types]]

Bead consumption rates by cells with chloroplasts - Revision history