Year 1 · Classification · Section 3.6

Bacteria

Structure

Bacteria are prokaryotes: unicellular organisms without a nucleus. They are very small. You can see bacteria with a suitable light microscope, but an electron microscope reveals much finer detail.

Reproduction

Bacteria reproduce by cell division, usually called binary fission. One cell divides into two daughter cells, which grow and can divide again.

Under favourable conditions, some bacteria can divide about every twenty minutes. This allows a population to grow rapidly; division rates vary with species and conditions.

Benefits and harm

Bacteria live almost everywhere, including on and inside the human body. Gut bacteria help break down some food components, while bacteria on the skin can help prevent harmful microorganisms from establishing themselves.

Many bacteria feed on dead organic material and play an important role in recycling substances. Their growth in food can also cause spoilage.

Some bacteria cause diseases, including cholera, tuberculosis and some forms of pneumonia. Bacterial infections may be treated with suitable antibiotics, such as penicillin for susceptible bacteria. Not every antibiotic works against every bacterium.

Biotechnology

Bacteria are deliberately used to make foods. Lactic acid bacteria convert sugars in milk into lactic acid, helping produce sour foods such as yoghurt.

Bacteria also help make sauerkraut by converting sugars in cabbage into lactic acid, making it sour and changing its texture. Using organisms to make products is called biotechnology.