Are you looking for marking each tick on the x-axis or labeling the x-axis?
The former does not make sense though, as each tick will take one character from the string provided. The string here will be treated as a list.
Code snippet:
ax.set_xticklabels("[Rotten Tomatoes]") # will label each tick as character from "[string]"
ax.set_xlabel(["Rotten Tomatoes"]) # will label the x-axis.