Root hair Recognition and attachment (rhicadhesin-mediated) Critical steps in root Rhizobial cell nodule formation Excretion of nod factors Step 1:Recognition and attachment by bacterium causing root hair curling of bacterium to root hairs Invasion.Rhizobia penetrate Step 2:Excretion of nod factors by root hair and multiply within an "infection thread" the bacterium Bacteria in infection thread grow toward Step 3:Bacterial invasion of the root root cell Infection thread hair Invaded plant cells and those nearby are Step 4:Travel to the main root via stimulated to divide the infection thread Formation of bacteroid state within plant root cells Step 5:Formation of bacteroid state within plant cells Step 6:Continued plant and bacterial division,forming the Soil mature root nodule Nodules Continued plant and bacterial cell division leads to nodules 2012 Pearson Education,Inc.Critical steps in root nodule formation Step 1: Recognition and attachment of bacterium to root hairs Step 2: Excretion of nod factors by the bacterium Step 3: Bacterial invasion of the root hair Step 4: Travel to the main root via the infection thread Step 5: Formation of bacteroid state within plant cells Step 6: Continued plant and bacterial division, forming the mature root nodule