any of the prokaryotes (bacteria and archaea), constituting the kingdom Monera.

The monerans are distinct from eukaryotic (eukaryote) organisms because of the structure and chemistry of their cells. As prokaryotes, they lack the definite nucleus and membrane-bound organelles (specialized cellular parts) of eukaryotic cells. They reproduce principally by transverse binary fission, although transfer of DNA among bacteria is widespread and forms the basis of recombinant DNA technology. See archaea; bacteria.