Size-fractionated extract spiking
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| Allelopathy (size-fractionated extract spiking) |
|---|
| Approach: size-fractionated culture extracts added to target species; growth or Fv/Fm response measured |
| Context: lab |
| Spatial scale: culture flask (point) |
| Temporal scale: hours to days |
| Units: cells L-1 d-1; Fv/Fm |
| Community captured: individual target species |
| Co-measurements: temperature, PAR; sometimes pH and salinity |
Method Overview
Cell-free extracts or filtrates from a potentially allelopathic species are size-fractionated by molecular weight cutoff ultrafiltration membranes (e.g., < 1 kDa, 1–10 kDa, 10–100 kDa, > 100 kDa) or by reverse-phase solid-phase extraction (SPE) into polarity fractions. Each fraction is then added separately to cultures of a target species. The effect of each fraction on target species growth rate or photosynthetic efficiency (Fv/Fm) is quantified relative to solvent controls[1]. This approach identifies the molecular size range (and sometimes polarity class) of the allelopathic compound(s), aiding in their chemical characterization.
Scale of measurement
Laboratory culture; no direct in situ spatial scale. Hours to days incubation per fraction.
Data generated
Growth rate or Fv/Fm of the target species in response to each size fraction. The fraction(s) causing significant inhibition narrow down the molecular size class of the allelopathic compound.
Units & currency
Units are cells L-1 d-1 (growth) or Fv/Fm. The currency is cell abundance or photon relaxation.
Sample size
Typical samples are < 1 L in volume per fraction.
Repositories & databases
Limitations
The size fractionation assumes that the allelopathic compound is in a specific size class and that fractionation does not alter its activity (e.g., through pH changes during ultrafiltration or solid phase extraction). Compounds may interact synergistically across fractions, making single-fraction bioassays incomplete. The assumption that a specific compound or fraction exerts the allelopathic effect must be verified by chemical identification and dose-response experiments.
Example Applications & Protocols
Classic examples
- Wu et al. (2010) Allelopathic control of cyanobacterial blooms by periphyton biofilms [1]
Recent applications
Common calculations/conversions
- % inhibition per fraction = (Fv/Fmcontrol − Fv/Fmfraction) / Fv/Fmcontrol × 100; highest inhibition identifies the active size class.
References
- ↑ 1.0 1.1 Wu, J.-T., Chiang, Y.-R., Huang, W.-Y., & Jane, W.-N. (2010). Allelopathic control of cyanobacterial blooms by periphyton biofilms. Environmental Microbiology, 13(3), 604–615. https://doi.org/10.1111/j.1462-2920.2010.02363.x