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Thursday, April 26, 2018 at 12:20pm to 1:10pm
Sirois abstract: Extracellular DNA (eDNA), defined as any DNA molecule not contained within a cell, is ubiquitous in soils and may persist for many years. When using high-throughput gene sequencing and other culture-independent methods to estimate microbial community composition, eDNA from long-dead cells may bias results, interfering with our ability to understand the important roles microbes play in soil ecology. To better understand the impacts of eDNA on estimates of community composition, we tested the impacts of soil moisture, soil temperature, agricultural management, and habitat type on the degradation/persistence dynamics of eDNA in soils using both high-throughput sequencing and qPCR. We found that eDNA tended to degrade rapidly but that degradation rates depend on climatic conditions and edaphic characteristics. We also found that small amounts of eDNA may persist indefinitely under certain conditions but that the ability of this persistent eDNA to impact microbial community analyses will depend on method sensitivity and experimental objectives.
Dokuchayeva Abstract: Toxic metals in sewage sludge contaminate soil and create risk for agriculture, as well as for humans, animals and plants in the surrounding environment. A heavy application of metal-contaminated sewage sludge occurred in the Cornell orchard area in 1978. The objectives of my research are to determine the effect of long-term aging on heavy metal (Cd, Cu, Pb, Zn, and Ni) distribution and behavior in the soil, including solubility, mobility, bioavailability, and thus, toxicity. The methods include measurement of extractability by reagents with selective ability to dissolve different forms of the metals, as well as assays of soil health.