The symbiotic interaction between soil bacteria of the genera Rhizobium, Azorhizobium or Bradyrhizobium (generally referred to as rhizobia) and plants of the Leguminosae family result in the formation of nodules, new organs in which the bacteria reduce nitrogen into ammonia which can subsequently be utilized by the plant (for reviews on nodulation see Mylona et al. 1995; Denarie et al. 1996; Long 1996; Hirsch and LaRue 1997). In a large number of interactions bacterial infection takes place through the development of an infection thread in root hairs of the host plant (reviewed by Kijne 1992). In this chapter I will first briefly describe the growth and structure of root hairs and recapitulate the relevant aspects of the infection process before going into detail of the changes in the organization of the microtubular cytoskeleton in root hairs during infection with rhizobia.
