Medicine & Health
What is Bacteria?
Bacteria are tiny, single-celled living organisms found almost everywhere on Earth — in soil, water, and inside your body. Most are harmless or even helpful (like the ones that aid digestion), but some cause infections, and unlike viruses they can grow and reproduce on their own.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains bacteria.
Key things to understand
- 1Bacteria are single-celled microorganisms — living, complete cells that survive and reproduce independently.
- 2They're everywhere: in soil, oceans, deep ice, and especially in and on the human body.
- 3Most are harmless or beneficial — gut bacteria help digestion and make vitamins; only a minority cause disease.
- 4Harmful (pathogenic) bacteria cause infections like strep throat and tuberculosis, and are treated with antibiotics.
- 5They reproduce by splitting in two (binary fission), sometimes as often as every 20 minutes.
Frequently asked questions
- What's the difference between bacteria and a virus?
- Bacteria are living, single-celled organisms that reproduce on their own; viruses are much smaller, aren't truly alive, and need a host cell to multiply. Antibiotics work on bacteria, not viruses.
- Are all bacteria harmful?
- No — the vast majority are harmless or helpful. Your gut relies on trillions of beneficial bacteria. Only a small fraction (pathogens) cause disease.
- How are bacterial infections treated?
- With antibiotics, which kill bacteria or stop them multiplying. Overusing antibiotics can breed resistant bacteria, so they should be used carefully.