Hotspots of root-exuded amino acids are created within a rhizosphere-on-a-chip

• Published in: Lab on a chip 2022-03, Vol.22 (5), p.954-963
• Main Authors: Aufrecht, Jayde, Khalid, Muneeba, Walton, Courtney L, Tate, Kylee, Cahill, John F, Retterer, Scott T
• Format: Article
• Language: English
• Subjects: Amino acids; Amino Acids - analysis; Amino Acids - metabolism; BASIC BIOLOGICAL SCIENCES; Carbon compounds; Complexity; Ecosystem; Exudation; Lab-On-A-Chip Devices; Mass spectrometry; Microfluidics; Microorganisms; Molecular structure; Plant Roots; Rhizosphere; Soil - chemistry; Soil Microbiology; Soil structure
• ISSN: 1473-0197; 1473-0189; 1473-0189
• DOI: 10.1039/d1lc00705j

The rhizosphere is a challenging ecosystem to study from a systems biology perspective due to its diverse chemical, physical, and biological characteristics. In the past decade, microfluidic platforms ( e.g. plant-on-a-chip) have created an alternative way to study whole rhizosphere organisms, like plants and microorganisms, under reduced-complexity conditions. However, in reducing the complexity of the environment, it is possible to inadvertently alter organism phenotype, which biases laboratory data compared to in situ experiments. To build back some of the complexity of the rhizosphere in a fully-defined, parameterized approach we have developed a rhizosphere-on-a-chip platform that mimics the physical structure of soil. We demonstrate, through computational simulation, how this synthetic soil structure can influence the emergence of molecular "hotspots" and "hotmoments" that arise naturally from the plant's exudation of labile carbon compounds. We establish the amenability of the rhizosphere-on-a-chip for long-term culture of Brachypodium distachyon , and experimentally validate the presence of exudate hotspots within the rhizosphere-on-a-chip pore spaces using liquid microjunction surface sampling probe mass spectrometry. A soil-mimicking rhizosphere-on-a-chip is amenable for long-term plant growth and enables simulation of root exudate diffusion and experimental validation of carbon hotspot formation from the interaction between roots and the synthetic soil grains.