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Extracellular DNA Alters Detection of Subtle Bacterial Responses to Soil Rewetting
H A Kittredge1,2,3, K M Dougherty1, Kathryn Glanville1,4
1Department of Integrative Biology, W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI, 49060, USA.
Microbial Ecology
|July 8, 2026
Summary
Extracellular DNA (exDNA) can mask subtle shifts in soil microbial communities during disturbances like drying-rewetting events. While not uniformly biasing results, exDNA may reduce the detectability of microbial responses in certain soils.
Area of Science:
- Environmental microbiology
- Soil science
- Molecular ecology
Background:
- DNA-based sequencing is standard for microbial community analysis.
- Extracellular DNA (exDNA) from dead cells can skew results.
- Disturbances like soil drying-rewetting increase microbial mortality and exDNA.
Purpose of the Study:
- To investigate if exDNA alters inference of bacterial responses to soil drying-rewetting.
- To compare exDNA effects in conventionally tilled corn and perennial switchgrass soils.
Main Methods:
- Quantified bacterial abundance (16S rRNA gene copies), alpha diversity, and community composition.
- Compared paired soil samples with and without exDNA using propidium monoazide (PMAxx) treatment.
- Simulated an 80 mm rainfall event after a 28-day drought.
Main Results:
- PMAxx treatment did not significantly alter overall temporal response patterns.
- PMAxx increased sensitivity for detecting some temporal changes in corn soils.
- exDNA pools were highest post-rewetting in corn soils, potentially masking responses.
- PMAxx had minor effects in switchgrass soils with weaker temporal responses.
Conclusions:
- exDNA does not uniformly bias soil microbial inference but can reduce detectability of subtle shifts.
- The influence of exDNA varies depending on soil type and disturbance intensity.
- Further research on microbial turnover and necromass dynamics is needed to predict exDNA influence.
