Microorganisms can be divided into two groups:
1. Archea
• Archea are prokaryotic unicellular organisms without cell nucleus or other membrane bound-organelles.
• Their membrane is built from ether lipids, which differs them from bacteria’s cell membrane.
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2. Bacteria
• Bacteria are also unicellular prokaryotic organisms.
• Bacterial cell membranes are made from phosphoglycerides with ester bonds. Bacterial genome is in a form of circular chromosome.
• They reproduce by binary fission or by budding.
Besides, prokaryotes (Archea and Bacteria) a large number of eukaryotes are also microorganisms. Unicellular eukaryotes contain organelles such as the cell nucleus, the Golgi apparatus and mitochondria. Usually, they reproduce asexually by mitosis. An example of eukaryotic microorganism is Protist.
