General: Types of Microorganisms

Microorganisms are living organisms so tiny that we cannot see them with the naked eye. This is also a great to micro-organisms. Different types of micro-organisms include mould yeasts, and . Microorganisms are present everywhere. They are found in soil, , animals, plants, people, etc. In food, they are often undesirable because they can cause spoilage or are pathogenic. However, micro-organisms can also be desirable. This is the with , where bacteria, moulds and yeasts are used to produce food. Below, we will briefly discuss the different types of micro-organisms. They are ordered by size, starting with the largest.

Fungi (Related to Mycotoxin Table)

are by far the largest group of microorganisms. Currently, there are an estimated 2,000 species of fungi known, out of a total of 200,000 fungal species. 
Fungi (fungi) are microorganisms that are often stringy in structure and very different in shape. The threads often have a woolly appearance and are red, green or white. Due to the thread formation, the fungus grows throughout the . We cannot see the threads, but we can see the ‘’. Moulds reproduce through the formation of spores. These spores form at the end of the fungal threads. When a spore is ripe, it lets go and is carried away by air currents. This means spores can get onto other in a refrigerator or pantry. The naked eye cannot see these spores. 
There are fungi which have a beneficial effect and which are not harmful. These include penicillin, which is made by fungi, and blue-vein cheese. Another is edible mushrooms, such as mushrooms and truffles. But some fungi can be harmful. These moulds can produce toxins (mycotoxins). Eating these toxins can lead to food poisoning, accompanied by nausea and diarrhoea. In some cases, these toxins are so toxic that they are potentially carcinogenic. 


Yeasts are unicellular micro-organisms belonging to the family of fungi. They are often spherical or bud-shaped and somewhat mobile. You will find them everywhere in nature, especially in plants and fruit. They are essential for many fermentation processes as they provide the alcohol in beer and wine and make our rise. Yeasts live mainly off carbohydrates (sugars) and, to a lesser extent, off proteins. The carbohydrates are, for the most part, converted into alcohol and carbon dioxide. Yeasts also provide a pleasant odour. 
There are many types of . The most common yeast is the species Saccharomyces cerevisiae. This yeast is also known as baker’s yeast and brewer’s yeast.

Bacteria (Related to the pathogenic bacteria table)

Bacteria are single-cell micro-organisms that are so small you can only see them with a microscope. Bacteria present in food cannot be seen, smelled or tasted. These bacteria can be good or pathogenic. Bacteria are everywhere. In the human gut alone, billions of bacteria are divided into hundreds of species. 
Bacteria can multiply rapidly. They do this by dividing themselves into two. These two new bacteria then divide in two again. For example, at room , millions of bacteria can form from a single in about 7 hours. Bacteria can grow when water and nutrients are present. Bacteria grow fastest at a temperature of between 20-40°C. However, they also grow at low temperatures. However, they also grow at low temperatures. When the products are , the bacteria no longer grow. However, they will not die either! For bacteria, there doesn’t have to be oxygen. Some bacteria grow well with oxygen, but many grow well with little or no oxygen. During the growth of the bacteria, the product is “eaten”. This creates various products, the best known of which is acid. When a lot of growth occurs, the product will also smell and taste sour. In the worst case, the product will start to smell. 
Just as with moulds, there are both harmful and beneficial bacteria. Some bacteria produce toxins that can make you sick (food poisoning) or even kill you. There are also bacteria, which can make you sick (food infection) or kill you. The best-known bacteria that cause illness are , and . These three bacteria can occur in foodstuffs. These bacteria will be discussed in more detail later. Besides the harmful bacteria, there are also many valuable bacteria. For example, certain bacteria are used to prepare cheese and dry goods. These take care of the ripening of the product. However, the beneficial bacteria used for dry sausage, for example, cause spoilage in other products.

Viruses (Related to the virus table)

Viruses are the smallest micro-organisms we know. Viruses often have futuristic shapes. For example, they can resemble a lunar lander. Viruses do their harmful work by injecting a package of their DNA into a host cell. With this, they ensure multiplication. Viruses always need a host cell to be able to reproduce. However, they cannot just use any cell for this. Viruses are particular in which cells they use to multiply. This makes it possible to use some viruses to fight bacteria where other means cannot be used. These viruses that attack specific bacteria are called bacteriophages.

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