These microbes (archaea; singular archaeon) are prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles in their cells. read more
Eubacteria and archaebacteria have a wide variety of shapes. However, these cell types have no membrane-bound organelles, they do not organize their DNA into a nucleus, and they are contained by cell membranes protected by cell walls. Both are relatively simple in structure, so most of their differences are chemical, not structural. read more