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Altered growth and death in dilution-based viral predation assays
Ben Knowles1,2,3,4,5, Juan A Bonachela6, Nick Cieslik1
1Department of Marine and Coastal Science, Rutgers University, New Brunswick, New Jersey, United States of America.
Plos One
|July 7, 2023
Summary
Viral lysis assays using dilution methods may be flawed. Dilution unexpectedly decreased phytoplankton growth by altering predation and nutrient availability, not just viral infection rates.
Area of Science:
- Marine microbiology
- Aquatic ecology
- Phytoplankton-virus interactions
Background:
- Viral lysis is a major driver of phytoplankton mortality.
- Dilution assays are commonly used to estimate viral lysis rates.
- These assays assume dilution reduces viral infection, increasing host growth.
Purpose of the Study:
- To test a miniaturized, high-throughput dilution assay for viral lysis.
- To investigate counterintuitive declines in phytoplankton density observed in dilution assays.
- To identify factors causing these unexpected results and re-evaluate assay assumptions.
Main Methods:
- Developed a miniaturized, flow cytometric microplate dilution assay.
- Collected samples from a suburban pond and the North Atlantic Ocean.
- Conducted theoretical, environmental, and experimental analyses to explain results.
Main Results:
- Dilution exacerbated phytoplankton decline, contrary to expectations.
- Observed density- and physiology-dependent effects on predation and nutrient limitation.
- Found that these effects, not viral lysis, drove phytoplankton loss.
Conclusions:
- Standard dilution assays may be invalidated by altered phytoplankton growth dynamics.
- The observed phytoplankton declines are volume-independent and sensitive to dilution.
- A new framework is proposed to account for altered growth and predation in dilution assays.
