Arabidopsis Root Microbiome Microfluidic (ARMM) Device for Imaging Bacterial Colonization and Morphogenesis of Arabidopsis Roots

Imaging the spatiotemporal dynamics of host-microbiota interactions is of particular interest for augmenting our understanding of these complex systems. This is especially true of plant–microbe interactions happening around, on, and inside plant roots where relatively little is understood about the dynamics of these systems. Over the past decade, a number of microfluidic devices have been developed to grow plants hydroponically in gnotobiotic conditions and image morphogenesis of the root and/or dynamics with fluorescently labeled bacteria from the plant root microbiome. Here we describe the construction and use of our Arabidopsis Root Microbiome Microfluidic (ARMM) device for imaging fluorescent protein expressing bacteria and their colonization of Arabidopsis roots. In contrast to other plant root imaging devices, we designed this device to have a larger chamber for observing Arabidopsis root elongation and plant–microbe interactions with older seedlings (between 1.5 and 4 weeks after germination) and a 200 μm chamber depth to specifically maintain thin Arabidopsis roots within the focal distance of the confocal microscope. Our device incorporates a new approach to growing Arabidopsis seedlings in screw-top tube caps for simplified germination and transfer to the device. We present representative images from the ARMM device including high resolution cross section images of bacterial colonization at the root surface.