What are the steps involved in the formation of a root nodule?

(N/A) The formation of root nodules involves a series of complex interactions between the host plant and $Rhizobium$ bacteria:
$1$. $Rhizobium$ bacteria multiply and form colonies,which attach to the root hairs and epidermal cells.
$2$. The root hairs curl due to bacterial infection and are subsequently invaded by the bacteria.
$3$. An infection thread is formed,which carries the bacteria into the cortex of the root.
$4$. The bacteria are released into the cortical cells,where they differentiate into rod-shaped structures called bacteroids.
$5$. The infection triggers cell division in the cortex and pericycle,leading to the formation of root nodules.
$6$. Finally,these nodules establish a direct vascular connection with the host plant to facilitate nutrient exchange.