Archaebacteria

The Kingdom Archaebacteria is a kingdom of single-celled microorganisms. These microbes (also called Archaea) are Prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles in their cells.

Trivia

 * Archaebacteria was originally part of the Monera Kingdom.
 * The Monera kingdom was broken up by Carl Woese in 1977 into Archaebacteria and Eubacteria.