Bacteria:
* E. coli: A common bacterium found in the gut, some strains can cause food poisoning.
* Streptococcus pneumoniae: Can cause pneumonia, ear infections, and meningitis.
* Salmonella: A genus of bacteria that can cause food poisoning.
* Lactobacillus: Used in yogurt and other fermented foods, beneficial to gut health.
* Cyanobacteria: Photosynthetic bacteria, sometimes called blue-green algae, found in water.
Viruses:
* Influenza virus: Causes the flu.
* HIV: Causes AIDS.
* Coronavirus: Causes COVID-19.
* Poliovirus: Causes polio.
* Hepatitis viruses: Cause inflammation of the liver.
Fungi:
* Yeast: Used in breadmaking and brewing, some can cause infections.
* Mold: Found on food and other surfaces, some produce toxins.
* Ringworm: A fungal infection that causes a ring-shaped rash.
Protozoa:
* Amoeba: Single-celled organisms with a flexible body, some are parasites.
* Paramecium: Single-celled organisms with cilia for movement.
* Plasmodium: Causes malaria.
* Giardia: A parasite that causes intestinal illness.
Other:
* Algae: A diverse group of photosynthetic organisms, ranging from single-celled to multicellular.
* Mites: Tiny arthropods, some cause allergies.
* Ticks: Small blood-sucking arthropods that can transmit diseases.
* Nematodes: Roundworms, many are parasitic.
Important Note:
While the examples above are microscopic, keep in mind that some microscopic organisms can form colonies or clusters that are visible to the naked eye. For instance, a patch of mold on bread is made up of millions of microscopic fungal spores.
