Our understanding of plant-microbe interactions in the soil is limited by the difficulty of observing processes at the microscopic scale throughout plants’ large volume of influence. This research presents the development of three-dimensional live microscopy for resolving plant-microbe interactions across the environment of an entire seedling growing in transparent soil in tailor-made mesocosms, maintaining physical conditions for the culture of both plants and microorganisms.
A tailor-made, dual-illumination light sheet system acquired photons scattered from the plant while fluorescence emissions were simultaneously captured from transparent soil particles and labeled microorganisms, allowing the generation of quantitative data on samples ∼3,600 mm3 in size, with as good as 5 µm resolution at a rate of up to one scan every 30 min. The system tracked the movement of Bacillus subtilis populations in the rhizosphere of lettuce plants in real time, revealing previously unseen patterns of activity. Motile bacteria favored small pore spaces over the surface of soil particles, colonizing the root in a pulsatile manner.
Migrations appeared to be directed toward the root cap, the point of 'first contact', before the subsequent colonization of mature epidermis cells. These findings show that microscopes dedicated to live environmental studies present an invaluable tool to understand plant-microbe interactions.
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Plant–environment microscopy tracks interactions of Bacillus subtilis with plant roots across the entire rhizosphere
Yangminghao Liu, Daniel Patko, Ilonka Engelhardt, Timothy S. George, Nicola R. Stanley-all, Vincent Ladmiral, Bruno Ameduri, Tim J. Daniell, Nicola Holden, Michael P. MacDonald, Lionel X. Dupuy
Proceedings of the National Academy of Sciences Nov 2021, 118 (48) e2109176118; DOI: 10.1073/pnas.2109176118