Microorganisms – Protists, Bacteria and Viruses

Protists Protists are eukaryotic – Which means they are cells with a nucleus. They can be unicellular or multicellular They can be animal-like, fungus-like or plant-like.

Some protists: amoeba amoeba ingesting a paramecium

Giardiasis Giardia cyst trophozoite

Bacteria Bacteria are prokaryotic cells. This means, they do NOT contain a nucleus. They have a Cell Wall and a Cell Membrane. Their genetic material (DNA) simply floats around in the cytoplasm. Many have flagella for locomotion.

The structure of a bacterium e-class on bacteria

Spherical Bacteria - Cocci

Rod-Shaped Bacteria – Bacilli (eg. E-coli)

Spirial Shaped Bacteria - Spirilla

Viruses Viruses are not living organisms. Without a host cell, viruses cannot carry out their life-sustaining functions or reproduce. They cannot synthesize proteins, because they lack ribosomes. They must use the ribosomes of their host cells. Viruses cannot generate or store energy because they lack mitochondria. They have to derive their energy from the host cell. They also parasitize the cell for basic building materials, such as amino acids, nucleotides, and lipids (fats).

Viruses have a “protein coat” with RNA or DNA on the inside Viruses have a “protein coat” with RNA or DNA on the inside. No other organelles.

1 Adsorption 2 Penetration 3 Early Replication 4 Late Replication 5 Maturation 6 Release