bacteria

Bacteria are tiny, single-celled living organisms (microbes) that are found almost everywhere—air, water, soil, and even inside our bodies.

• What they look like: Bacteria are so small that you need a microscope to see them. Common shapes include round (cocci), rod-shaped (bacilli), and spiral (spirilla).
• How they live and multiply: Most bacteria reproduce very fast by splitting into two (binary fission). This is why infections can spread quickly inside the body.
• Why some bacteria cause disease: Disease-causing bacteria (a type of pathogen) can harm the body by damaging tissues or releasing toxins. Examples of bacterial diseases include typhoid and tuberculosis.
• Many bacteria are helpful: “Good” bacteria in our intestines help in digestion and make some vitamins. Bacteria are also used to make foods like curd/yogurt (Lactobacillus helps turn milk into curd).
• Bacteria vs viruses (easy difference): Bacteria are living cells that can grow on their own, while viruses are not complete cells and can multiply only inside a host’s cells.
• How we control harmful bacteria: Antibiotics can kill or stop the growth of many bacteria (but they do not work on viruses), and hygiene plus safe food and water help prevent bacterial diseases.

Bacteria are a great example of how the same kind of microbe can be both useful and harmful, depending on the type and where it grows.