Which steps are associated with nodule formation?

(N/A) Nodule formation involves a sequence of multiple interactions between Rhizobium and the roots of the host plant.
The steps are as follows:
$1$. Rhizobia multiply and colonize the surroundings of roots,attach to epidermal and root hair cells,and cause the root hair to curl. The bacteria then invade the root hair.
$2$. An infection thread is produced,carrying the bacteria into the cortex of the root.
$3$. The bacteria are released from the thread into the cells,leading to their differentiation into specialized nitrogen-fixing cells.
$4$. The nodule thus formed establishes a direct vascular connection with the host for the exchange of nutrients.