Root hair 1.Recognition and attachment (rhicadhesin-mediated) Rhizobial cell 2.Excretion of nod factors by bacterium causing root hair curling 3.Invasion.Rhizobia penetrate root hair and multiply within an "infection thread" 4.Bacteria in infection thread grow toward root cell Infection thread Figure 19-61 part 1 Brock Biology of Microorganisms 11/e 2006 Pearson Prentice Hall,Inc. 16 Microbiology,Shanghai Jiao Tong University16 Microbiology, Shanghai Jiao Tong University