What do the ubiquitous microorganisms rely on to survive?

Produced by: Science Popularization China

Author: Guanshi Ruwei Team

Producer: China Science Expo

As we all know, organisms need to obtain raw materials and fuel from the outside world to carry out their life activities. In the words of biologists, the process by which organisms obtain the substances they need from the outside world for their life activities is nutrition. Nutrition is the basic function of organisms.

(Photo source: Veer Gallery)

Microorganisms are also living things, and nutrition is also the basis for their life activities. There is no essential difference between the nutrition required by microorganisms and the nutrition required by humans, but the things that can be provided to microorganisms as food are much more diverse than the types of food that humans or animals can use. The nutritional elements required by microorganisms can be divided into six categories, namely carbon source, nitrogen source, energy, inorganic salts, growth factors and water.

Carbon source

The main ingredients of the staple foods we often eat, such as rice, steamed bread or bread, are called carbohydrates. Because these compounds contain more carbon in their molecules, they are also called carbon sources. They are also a main food for microorganisms, because many components in microbial cells are made up of carbon, and carbon sources provide energy for microorganisms to move and carry out various life activities.

(Photo source: Veer Gallery)

The types of carbon sources that can be used by various microorganisms are extremely diverse, ranging from simple inorganic carbon-containing compounds such as carbon dioxide and carbonates to more complex organic substances (sugars, alcohols, acids, etc.) and more complex organic macromolecules such as proteins and nucleic acids. All of them can be decomposed and utilized by microorganisms as carbon sources. Even petroleum and nitrile compounds, xylene, phenol, etc. that are toxic to general organisms can be used as carbon sources by some microorganisms.

Oh, these little guys are really not picky eaters!

Microbiologists have used more than 90 carbon sources to feed a bacterium called Burkholderia cepacia, and found that it can not only use glucose and fructose, but also a lot of organic acids, and even carbolic acid (phenol) and compounds produced by the decay of corpses such as putrescine, spermine and tryptamine that are highly toxic to humans and animals. However, some microorganisms can only use a very limited variety of carbon sources. For example, methylotrophic bacteria can only use simple organic compounds such as methanol and methane as carbon sources.

Nitrogen source

The meat we eat or the milk we drink contain a lot of protein. Protein is composed of amino acids, which contain a lot of nitrogen, so this type of nutrition is called nitrogen source. Microorganisms can use more types of nitrogen sources than humans or plants. Microorganisms can use all nitrogen sources that plants and animals can use, and microorganisms can also use nitrogen in the air that plants and animals cannot use.

(Photo source: Veer Gallery)

Nitrogen source is the raw material for synthesizing protoplasm and other cell structures when microorganisms grow and reproduce. Just like a child who lacks protein for a long time will not grow tall, if there is a lack of nitrogen source, microorganisms will find it difficult to grow. Nitrogen source is generally not used as an energy source for microorganisms. However, some bacteria, such as nitrifying bacteria, can use ammonium salts and nitrites as nitrogen sources and energy sources.

energy

Energy is a substance that provides energy for microbial life activities. For example, sunlight is the direct energy source for many photosynthetic bacteria. Many substances in nature, such as glucose and starch, can be used as both carbon sources and energy sources. For some microorganisms, protein is a nutrient source that has three functions: carbon source, nitrogen source, and energy source. As for nitrogen in the air, it can only provide a nitrogen source.

(Photo source: Veer Gallery)

Inorganic salt

People need to eat salt and supplement calcium, and crops need to use wood ash to supplement potassium. Like ordinary organisms, microorganisms need the support of other substances in addition to carbon sources, nitrogen sources and energy sources, such as sulfur, phosphorus, sodium, potassium, magnesium, calcium, iron and other elements in their life activities. Most of the above elements are provided to microorganisms in the form of salt, so they are called inorganic salts or mineral nutrients. These inorganic salts are necessary components of life substances or are necessary to maintain normal life activities. Some are used to promote or inhibit the production of certain substances.

(Photo source: Veer Gallery)

Growth Factors

Humans and animals need vitamins, and many microorganisms also need vitamins. Vitamins are trace organic substances that microorganisms cannot synthesize on their own, and they are also indispensable substances for microorganisms to maintain their life activities. For example, yeast and lactic acid bacteria must be provided with vitamins from the outside to grow or grow well.

(Photo source: Veer Gallery)

Some microorganisms, such as E. coli, most fungi and actinomycetes, can synthesize growth factors by themselves and do not need to obtain them from the outside. Some microorganisms can produce excessive growth factors, so they can be used to produce vitamins. For example, vitamin B2 (riboflavin), which people often need to supplement, is produced by a yeast.

water

Like all living things, water is indispensable for the nutrition of microorganisms. Water is one of the main chemical components of microbial cells. Life activities are basically realized through a series of chemical reactions, most of which are carried out in water. The exchange of substances inside and outside cells is usually carried out in water; water can also maintain the molecular structure stability of macromolecules such as nucleic acids and proteins; water can also participate in chemical reactions in the body such as hydrolysis and hydration reactions.

(Photo source: Veer Gallery)

Conclusion

In nature, microorganisms obtain various nutrients needed for growth from their living environment. Microorganisms of various groups can grow and reproduce in different environments. There are subtle and difficult-to-separate connections between microorganisms and between microorganisms and other organisms.

Although microorganisms are so easy to keep alive, they are an indispensable part of the normal functioning of nature!

Editor: Sun Chenyu