Only in 1967 electron microscopy studies revealed that many diseases which were thought to be caused by viruses were actually associated with wall-less endo-cellular parasitic prokaryotic cells (reviewed in 1). Two different morphological types of wall-less prokaryotes were detected in plant phloem: ...
Spirulina cells are packed with photosynthetic thylakoid membranes and surrounded by the cytoplasmic and outer membranes. They carry a single copy of the circular chromosome organized in a prokaryotic-type nucleoid. Studies of fossil microorganisms in Precambrian rocks (3.5–0.5 billion years ago) ...