Oxford Read & Discover – Unit 9: Useful Microbes

Đoạn giới thiệu

Do you know that there can be a kilogram of bacteria in a person’s stomach? Don’t be scared! Many microbes are very useful – they help people and Earth to stay well.

Đoạn 1: Microbes inside us

After you eat, some of the bacteria in your stomach help your body to break down the food into sugar that your cells can use for energy. They also help you to get important substances like vitamins from the food, and they stop infections from bad bacteria that can give you stomach ache. To help the useful bacteria in your stomach, you should eat more foods like fruit, vegetables, brown bread, and brown pasta. You shouldn’t eat too many sweet and fatty foods like ice cream, chocolate, or French fries.

Đoạn 2: Microbes and Food

People use some microbes to make food. Yeasts are microbes that people use to make bread. When yeast is mixed with flour, salt, sugar, and water, it feeds on the sugar and makes carbon dioxide and other substances. The carbon dioxide makes the bread become bigger and lighter. When the bread is cooked, the other substances help to flavor it.

Đoạn 3: Storing Food

Some bacteria make lactic acid that stops food going bad, so that we can store it for longer. People use lactic acid bacteria to make foods like soy sauce, sauerkraut, and kimchi. To make kimchi, salt is mixed with cabbage. Bacteria eat sugar from the cabbage and make lactic acid that stops the cabbage going bad.

This gives kimchi its sour flavor.

Đoạn 4: Microbes and Fuel

A fuel is a substance that people use to make heat and to make machines work. People use bacteria to change waste into fuel! They put plant and animal waste inside a biodigester, where bacteria feed on it. When they feed, the bacteria make a fuel called methane. The biodigester stores the methane so that people can use it for cooking food and heating water.

Đoạn 5: Soil Microbes

There are bacteria in soil that help to break down plant and animal waste into tiny pieces. When they do this, they give back some of the nutrients from the waste into the soil. Plants use these nutrients to help them to grow. People make compost by collecting food waste and plant waste together. Bacteria in the waste help to break it down into compost. Farmers and gardeners mix the compost with soil to help plants to grow well. So without microbes like bacteria, there would be no life on Earth!