The pattern of bacterial colonization on the roots was monitored two weeks after transplantation. Root samples were cut to lengths of 0.2–0.5 cm and visualized using a CLSM (Leica Model TCS SP2, Heidelberg, Germany) with excitation wavelengths of 488 nm. Emitted light in the range of 500–600 nm was collected for the GFP. Images were generated with version 2.61 of the Leica confocal software. After being soaked for 15 min in a suspension containing 108 cells of GFP-tagged N43 per ml, the roots were immediately observed to establish a positive control.