Browsing by Author "Del Valle, Ilenne"

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    Artificial Soils Reveal Individual Factor Controls on Microbial Processes
    (American Society for Microbiology, 2022) Del Valle, Ilenne; Gao, Xiaodong; Ghezzehei, Teamrat A.; Silberg, Jonathan J.; Masiello, Caroline A.; Bioengineering; Biosciences; Chemical and Biomolecular Engineering; Chemistry; Earth, Environmental and Planetary Sciences
    Soil matrix properties influence microbial behaviors that underlie nutrient cycling, greenhouse gas production, and soil formation. However, the dynamic and heterogeneous nature of soils makes it challenging to untangle the effects of different matrix properties on microbial behaviors. To address this challenge, we developed a tunable artificial soil recipe and used these materials to study the abiotic mechanisms driving soil microbial growth and communication. When we used standardized matrices with varying textures to culture gas-reporting biosensors, we found that a Gram-negative bacterium (Escherichia coli) grew best in synthetic silt soils, remaining active over a wide range of soil matric potentials, while a Gram-positive bacterium (Bacillus subtilis) preferred sandy soils, sporulating at low water potentials. Soil texture, mineralogy, and alkalinity all attenuated the bioavailability of an acyl-homoserine lactone (AHL) signaling molecule that controls community-level microbial behaviors. Texture controlled the timing of AHL sensing, while AHL bioavailability was decreased ~105-fold by mineralogy and ~103-fold by alkalinity. Finally, we built artificial soils with a range of complexities that converge on the properties of one Mollisol. As artificial soil complexity increased to more closely resemble the Mollisol, microbial behaviors approached those occurring in the natural soil, with the notable exception of organic matter.
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    Charcoal Disrupts Soil Microbial Communication through a Combination of Signal Sorption and Hydrolysis
    (American Chemical Society, 2016) Gao, Xiaodong; Cheng, Hsiao-Ying; Del Valle, Ilenne; Liu, Shirley; Masiello, Caroline A.; Silberg, Jonathan J.; Bioengineering; Biosciences; Earth, Environmental and Planetary Sciences
    The presence of charcoal in soil triggers a range of biological effects that are not yet predictable, in part because it interferes with the functioning of chemical signals that microbes release into their environment to communicate. We do not fully understand the mechanisms by which charcoal alters the biologically available concentrations of these intercellular signals. Recently, charcoal has been shown to sorb the signaling molecules that microbes release, rendering them ineffective for intercellular communication. Here, we investigate a second, potentially more important mechanism of interference: signaling-molecule hydrolysis driven by charcoal-induced soil pH changes. We examined the effects of 10 charcoals on the bioavailable concentration of an acyl-homoserine lactone (AHL) used by many Gram-negative bacteria for cell–cell communication. We show that charcoals decrease the level of bioavailable AHL through sorption and pH-dependent hydrolysis of the lactone ring. We then built a quantitative model that predicts the half-lives of different microbial signaling compounds in the presence of charcoals varying in pH and surface area. Our model results suggest that the chemical effects of charcoal on pH-sensitive bacterial AHL signals will be fundamentally distinct from effects on pH-insensitive fungal signals, potentially leading to shifts in microbial community structures.
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    Translating New Synthetic Biology Advances for Biosensing Into the Earth and Environmental Sciences
    (Frontiers, 2021) Del Valle, Ilenne; Fulk, Emily M.; Kalvapalle, Prashant; Silberg, Jonathan J.; Masiello, Caroline A.; Stadler, Lauren B.; Bioengineering; Biosciences; Chemical and Biomolecular Engineering; Chemistry; Civil and Environmental Engineering
    The rapid diversification of synthetic biology tools holds promise in making some classically hard-to-solve environmental problems tractable. Here we review longstanding problems in the Earth and environmental sciences that could be addressed using engineered microbes as micron-scale sensors (biosensors). Biosensors can offer new perspectives on open questions, including understanding microbial behaviors in heterogeneous matrices like soils, sediments, and wastewater systems, tracking cryptic element cycling in the Earth system and establishing the dynamics of microbe-microbe, microbe-plant, and microbe-material interactions. Before these new tools can reach their potential, however, a suite of biological parts and microbial chassis appropriate for environmental conditions must be developed by the synthetic biology community. This includes diversifying sensing modules to obtain information relevant to environmental questions, creating output signals that allow dynamic reporting from hard-to-image environmental materials, and tuning these sensors so that they reliably function long enough to be useful for environmental studies. Finally, ethical questions related to the use of synthetic biosensors in environmental applications are discussed.