VMBO Year 3 · Classification · Section 4.3

Bacteria and fungi

What are bacteria and fungi?

Bacteria are single-celled organisms too small to see individually without a microscope. Fungi can be single-celled or multicellular. Yeasts are single-celled fungi, whereas many multicellular fungi consist of hyphae, thin branching threads. Individual hyphae are microscopic, but fungal colonies and mushrooms can be visible without a microscope.

Bacteria reproduce by division. Many yeasts reproduce by budding, in which a small outgrowth develops into a new cell. Multicellular fungi often produce spores, sometimes in fruiting bodies such as mushrooms.

Useful microorganisms

Many bacteria and fungi are decomposers. They break down dead organisms and waste materials, returning mineral nutrients to the environment. Humans also use them in food production:

• Bacteria help make yoghurt and sauerkraut.
• Yeast is used for bread, beer and wine.
• Particular moulds are used in mould-ripened cheeses.

Microorganisms also produce useful medicines and enzymes. Penicillin is an antibiotic originally obtained from a fungus; other antibiotics come from bacteria. Genetically modified bacteria can produce human insulin. Microbial enzymes are used in processes such as making sweeteners and producing laundry detergents.

Harmful bacteria and fungi

Some microorganisms cause food spoilage, making bread, meat or fruit unsuitable to eat. Others are pathogens, causing infections such as certain types of pneumonia or athlete's foot. Antibiotics act against susceptible bacteria, while antifungal medicines treat fungal infections. Antibiotics do not treat viruses, and resistance can make some bacterial infections difficult to treat. Good hygiene, including handwashing and appropriate food preparation, helps prevent infections.