You can find an uninvited guest, fungi, everywhere, including in a damp bathroom, in a shady corner, and forgotten leftover bread. When you see it looking like downy hair sitting on a wall or food, you cannot help but frown.

Fungi could pass as plants, but they are completely different. Unlike plants, fungi do not make their own energy through photosynthesis and live by absorbing external substances. Nevertheless, fungi have been thriving on Earth. They are the most abundant organisms on the planet, followed by plants and microorganisms.

Fungi reproduce by spreading microscopic spores in the air. The spores float freely and settle down when they find an environment suitable for reproduction. You can say that fungi are everywhere. No matter how tightly you close the lid of a jar, fungi can grow over time. This means that invisible spores have already entered the jar.

Being anywhere around us, fungi are both beneficial and harmful. For a long time, people have used fungi to make food. Aspergillus oryzae is used for making soybean paste and soy sauce, traditional Korean seasoning ingredients, which are made with meju (fermented soybeans). There are several types of fungi living on fermented soybeans. Likewise, in other countries, fungi are used when making cheese and salami, a type of sausage, for the flavor.

▲Meju (Image by GettyImagesBank)

You can also obtain medicines from them. Discovered by Alexander Fleming, penicillin is the most well-known example. Penicillin is created by green mold to kill bacteria. After Fleming's accidental discovery, several scientists worked to invent mankind's first antibiotic, which has saved numerous people’s lives. Other drugs are also made from substances obtained from fungi. For example, ciclosporin, a drug for preventing organ transplant rejection, is also produced from fungi.

On the other hand, some fungi are harmful to the human body. Mold on the walls is not aesthetically pleasing. Since it is not easy to get rid of, it is better to prevent it beforehand. In addition, mold growth will lead to more spores floating in the air, causing allergic reactions or respiratory disease. It can pose a serious threat to those with underlying conditions. Therefore, if your place is humid and easy for mold to grow, you need to pay more attention to your indoor environment.

Some diseases are caused by fungi; one example is ringworm. The disease is a fungal infection of the skin and nails. Infection causes a rash on the skin and itchiness. You may lose hair or have cracked nails. Infection can occur in several areas – when it is on the foot, it is called athlete's foot.

Toxins released by mold can be detrimental to health. If bread gets moldy, it is best to throw away the whole rather than just cutting out the moldy part. This is because if the mold is visible, it means that the entire food has already been contaminated, even if the rest of it looks fine.

Some mycotoxins are particularly dangerous. Aflatoxin produced by a fungus growing on nuts is a potent carcinogen. Contact with aflatoxins can lead to liver damage or liver cancer. A substance produced by ergot, a fungus that grows on rye, can cause hallucinations or poisoning when consumed. In the past, many Europeans who ate a lot of rye bread had to suffer without knowing the cause.

It is impossible to completely get rid of fungi in our everyday life. As such, we should always take cautions to live a healthy life. To prevent mold, it is necessary to air out your room frequently and keep the humidity at a moderate level. It is also a good idea to leave some space between furniture and the wall so that air can flow. Do not forget to never leave food out for too long!