Microbes clean the environment

Have you seen a lemon, tomato or orange go rotten, with a powdery or cotton-like growth on it? Microbes have got into it. They are everywhere: in water, soil, air and on food.

So why do pickles and murabbas keep for months? Because they are made with lots of salt or sugar, which act as preservatives. Microbes need water to live, and so much salt or sugar draws the water out of them. A high concentration of salt or sugar does not let them grow.

Microbes live almost anywhere: in hot springs, in icy cold places, and at ordinary temperatures. Many live inside us: the bacteria in your intestine help you digest food.

Make manure (Activity 2.7). Half-fill a pot with garden soil, add fruit and vegetable peels, cover them with soil and leave it. In 2 to 3 weeks the peels have turned into a dark material: manure, rich in nutrients, which makes soil more fertile.

Who did it? Microbes in the soil, such as fungi and bacteria, slowly broke the peels down into simpler substances. Breaking down complex substances, such as fallen leaves, into simpler, nutrient-rich ones is called decomposition. The nutrients go back into the soil and help plants grow. Microbes also decompose the bodies of dead animals. So they recycle waste and return nutrients to nature. That is why gardeners put dry leaves and plant waste into pits. Manure forms best at the right temperature and the right amount of moisture.

Many microbes live where there is no oxygen. Some of them break down plant and animal waste or household wastewater and give off a mix of gases called biogas: mainly carbon dioxide and a lot of methane. Biogas is a fuel for cooking, heating, making electricity and even running vehicles.

Ananda Mohan Chakrabarty (1938–2020) studied bacteria. In 1971 he developed a special bacterium that could break down oil spills and help clean the environment. His discovery got a patent in 1980. A patent is a right that stops anyone else copying, using or selling an invention without the inventor's permission.