Root epidermis of a sugar beet seedling 14 days after inoculation. Visualization of DsRed-marked bacteria with CLSM. (a) Maximum projection of a confocal stack the region located approximately 3 cm under the stem and lateral roots colonized by Pseudomonas fluorescens L13-6-12 at a high cell density. The cells were observed in the intercellular space of the epidermis cell layer, forming clusters containing several hundred cells in the rhizoplane. (b) Maximum projection of a confocal stack showing Pseudomonas trivialis RE^*1-1-14 aligned along the epidermis cells and at the junctions of the epidermis to the lateral root. (c) Surface model of the framed area of (b) obtained with imaris^® 6.0 (Bitplane) clearly showing the bacterial cells also colonizing the internal parts of the surface of the sugar beet seedling. Green, root; red, bacterial cells; grey, surface matrix. (d) Maximum projection of confocal stack showing Serratia plymuthica 3Re4-18 cells (red) colonizing the surrounding area of the root (yellow), the rhizosphere. (e) xy, xz, and yz maximum projections showing a clear endophytic localization of small colonies and single cells of S. plymuthica 3Re4-18. (f) Surface model of (e) showing the endophytic localization of S. plymuthica 3Re4-18 in the three-dimensional space.