Title

Quantifying Shifts in Soil Microbial Populations in Response to 2,4-Dichlorophenoxyacetic Acid Exposure

Presentation Type

Presentation

Abstract

2,4-dichlorophenoxyacetic acid (2,4-D) is the third most commonly used herbicide in the U.S., thanks to its ability to selectively control broad-leaf plants. The pathways enabling 2,4-D degradation in microbes are well characterized, and many native soil microbes are known to either possess plasmid or chromosomally-encoded DNA for such. Selection for 2,4-D degraders is known to occur in soils exposed to 2,4-D in-situ or in lab. However, there have been limited experiments in understanding how soil microbial populations from different, previously untreated soils respond to 2,4-D exposure, and the ecological dynamics of which specific pathway variants are selected for within each population due to herbicide concentration. We set out to explore these dynamics in 2,4-D naive soils around the Missoula Valley. Soils with no or minimal prior herbicide exposure were taken from the Garden City Harvest farm at River Road and from Mt. Sentinel. These soils were then amended in triplicate with either 2,4-D to 500 ppm, or with phosphate-buffer as a negative control, then incubated at room temperature in the dark over the course of several weeks. The amount of 2,4-D in the treated samples was monitored using HPLC and the soils were respiked to the initial concentration when≥80% had been degraded during the course of the experiment. At weekly intervals, the number of 2,4-D degraders in each sample were enumerated using MPN and 2,4-D minimal medium, while total aerobic, heterotrophic counts were obtained by plating on R2A general growth medium. Once the amendment series is completed, we will further analyze how each soil microbial community has responded based on genetic marker surveys. With further testing and experimentation, our research has the potential to illuminate the selective and ecological dynamics of soil microbial communities in response to 2,4-D exposure.

Category

Life Sciences

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Apr 17th, 2:40 PM Apr 17th, 3:00 PM

Quantifying Shifts in Soil Microbial Populations in Response to 2,4-Dichlorophenoxyacetic Acid Exposure

UC 332

2,4-dichlorophenoxyacetic acid (2,4-D) is the third most commonly used herbicide in the U.S., thanks to its ability to selectively control broad-leaf plants. The pathways enabling 2,4-D degradation in microbes are well characterized, and many native soil microbes are known to either possess plasmid or chromosomally-encoded DNA for such. Selection for 2,4-D degraders is known to occur in soils exposed to 2,4-D in-situ or in lab. However, there have been limited experiments in understanding how soil microbial populations from different, previously untreated soils respond to 2,4-D exposure, and the ecological dynamics of which specific pathway variants are selected for within each population due to herbicide concentration. We set out to explore these dynamics in 2,4-D naive soils around the Missoula Valley. Soils with no or minimal prior herbicide exposure were taken from the Garden City Harvest farm at River Road and from Mt. Sentinel. These soils were then amended in triplicate with either 2,4-D to 500 ppm, or with phosphate-buffer as a negative control, then incubated at room temperature in the dark over the course of several weeks. The amount of 2,4-D in the treated samples was monitored using HPLC and the soils were respiked to the initial concentration when≥80% had been degraded during the course of the experiment. At weekly intervals, the number of 2,4-D degraders in each sample were enumerated using MPN and 2,4-D minimal medium, while total aerobic, heterotrophic counts were obtained by plating on R2A general growth medium. Once the amendment series is completed, we will further analyze how each soil microbial community has responded based on genetic marker surveys. With further testing and experimentation, our research has the potential to illuminate the selective and ecological dynamics of soil microbial communities in response to 2,4-D exposure.