There are some intracellular parasites of prokaryotes. This is a group of small, highly motile bacteria, that adhere to the wall of the host, penetrate through to the periplasm where they replicate, causing eventual lysis of cell. Organisms of this type are called bdellovibrios, and perhaps occur in soil.
The blue-green bacteria are typical prokaryotes. They evolve oxygen during photosynthesis and have chlorophyll a, a pigment also found in all algae. They are very ancient. They are perhaps major primary producers in the world's oceans, and many are ecologically important as fixers of atmospheric nitrogen.
Myxobacteria (also called fruiting bacteria) form fruit bodies, specialised multicellular structures like slime molds. Some cells at tips of fruit body produce cysts. They are most complex in behaviour and life cycle patterns found in prokaryotes.
