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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Most fungi that pathogenically affect humans live in soil. If a person is not healthy, has an open wound, or is immunocompromised, a fungal infection can be very aggressive.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.