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The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
Earwax has antimicrobial properties that reduce the viability of bacteria and fungus in the human ear.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.
Acute bronchitis is an inflammation of the breathing tubes (bronchi), which causes increased mucus production and other changes. It is usually caused by bacteria or viruses, can be serious in people who have pulmonary or cardiac diseases, and can lead to pneumonia.