All of the usual stuff we think of as “life”—things like trees, fungi, and animals—are eukaryotes, meaning that their cells contain a nucleus and other membrane-bound organelles.

Prokaryotes are divided into two distinct groups: the bacteria and the archaea, which scientists ... Prokaryotic cells are surrounded by a plasma membrane, but they have no internal membrane ...

This study represents the first successful cultivation of ultrasmall bacteria that parasitize archaea, which evolutionarily ... biological differences in cell membrane lipids, genetic information ...