WHY DON'T MUSHROOMS MAKE THEIR OWN FOOD? - BIOLOGY - 2025

The fungi do not produce their own food because they lack chlorophyll, or any other molecule that absorbs solar energy. For this reason, they are incapable of photosynthesis, which has made their survival strategies have diversified, as we will see later.

With the term fungus -from Latin fungi, plural fungus- a group of eukaryotic organisms, without chlorophyll, body with filaments, that make up the kingdom Fungi. The word fungus comes from the Latin fungus, which means mushroom.

Figure 1. The beautiful “bridal veil” mushroom in Corcovado National Park, Costa Rica. Source: Tyler Enders, from Wikimedia Commons

Originally fungi were included in the plant group and later it was decided to classify them as a particular kingdom. At present, the molecular study of several genes reports a striking similarity between fungi and animals.

Additionally, fungi have chitin as a structural compound, as do some animals (shrimp in their shells) and no plants.

Organisms belonging to the kingdom of fungi include truffles, mushrooms, yeasts, molds, and other organisms. The Fungi kingdom forms a group of rank equal to that of plants and animals.

Why are fungi unable to produce their food?

Through photosynthesis, plants and algae store solar energy in the form of chemical energy in carbohydrates that serve as food.

The fundamental reason why fungi cannot produce their food is because they do not have chlorophyll, nor any other molecule capable of absorbing sunlight and, therefore, they are incapable of photosynthesis.

Fungi are heterotrophic organisms that need to feed on other organisms, living or dead, since they do not have an independent food-producing system, such as photosynthesis.

Reserve substances

Fungi have the ability to store glycogen and lipids as reserve substances, in contrast to plants that reserve starch.

What do we know about mushrooms in general?

Fungi, like bacteria, live in all environments and it is estimated that so far only about 81,000 species have been identified, which could represent 5% of the total that are supposed to exist on the planet.

Figure 2. Amanita muscaria, a very attractive and poisonous multicellular mushroom. Onderwijsgek at nl.wikipedia

Many fungi infect crops, food, animals, plants in general, buildings, clothing and humans. In contrast, many fungi are the source of a wide range of antibiotics and other medications. Many fungal species are used in biotechnology in the production of enzymes, organic acids, bread, cheeses, wine and beer.

There are also many species of edible mushrooms such as mushrooms (Agaricus bisporus), Portobello (the largest variety of Agaricus bisporus), Huitlacoche (Ustilago maidis), a parasitic fungus of corn, very popular in Mexican cuisine; shiitake (Lentinula edodis), Porcinis (Boletus edulis), among many others.

Figure 3. The huitlacoche fungus (Ustilago maydis) is considered a pest for corn producers, but in Mexico it is considered a delicacy. Source: Amada44, from Wikimedia Commons

What are mushrooms like?

Fungi are immobile organisms. A few species are unicellular such as yeast, but most are multicellular.

Cell structure

All the species of the Fungi kingdom are eukaryotes; that is, its cells have a differentiated nucleus, which contains the genetic information enclosed and protected by a nuclear membrane. They have an organized cytoplasm, with organelles that also have membranes and that function in an interconnected way.

Fungi do not have chloroplasts as cytoplasmic organelles, therefore they do not have chlorophyll, a photosynthetic pigment.

Figure 4. Yellow Fungus. Source: Author Heribert Dezeo at:

Rigid cell walls containing chitin

The cell walls of fungi are made up of chitin, a carbohydrate that is only present in the hard exoskeleton of some arthropod animals: arachnids, crustaceans (such as shrimp) and insects (such as beetles), annelid ketae and does not appear in plants.

Morphology

The body of multicellular fungi is filamentous; each filament is called hypha and the set of hyphae form the mycelium; this mycelium is diffuse and microscopic.

The hyphae may or may not have septa or septa. The partitions may have simple pores, as is the case in ascomycetes, or complex pores called dolipores, in basidiomycetes.

Reproduction

The vast majority of fungi reproduce both types: sexual and asexual. Asexual reproduction can occur through hyphae - the hyphae fragment and each fragment can develop into a new individual - or through spores.

The sexual reproduction of a considerable number of fungi takes place in three stages:

-Plasmogamy, where contact of protoplasm occurs.

-Cariogamy or nucleus fusion stage.

–Meiosis or cell division process where the number of chromosomes is reduced by half.

Figure 5. Porcelain fungus. Source: pixabay.com.

How is the nutrition of mushrooms?

The feeding of the fungi is heterotrophic of the osmotrophic type. Heterotrophic organisms feed on other organisms, living or dead.

The term osmotrophic refers to the characteristic of fungi to absorb their nutrients in the form of dissolved substances; For this they have an external digestion, as they excrete digestive enzymes that degrade complex molecules present in their environment, transforming them into simpler ones that can be easily absorbed.

From the point of view of their nutrition, fungi can be saprobes, parasites or symbionts:

Saprobes

They feed on dead organic matter, both animal and plant. Saprobic fungi play a very important role within the trophic chains of ecosystems.

Together with bacteria, they are the great decomposers, which, by degrading complex molecules from animal and plant remains, reinsert nutrients in the form of simple molecules in the matter cycle of the ecosystem.

The importance of decomposers within an ecosystem is equivalent to that of producers, since both produce nutrients for the rest of the members of the trophic chains.

Parasites

Parasitic organisms feed on the living tissue of other organisms. Parasitic fungi settle in the organs of plants and animals, causing damage to their tissues.

There are obligate parasitic fungi and facultative parasites, which can change from the parasitic way of life to another that is more convenient for them (for example saprobia), depending on the possibilities of the environment that surrounds them.

Symbiotes

Symbionts associate with other organisms in life forms that bring benefits to both participants. For example, fungi can associate with algae and form lichens, where the fungus takes nutrients from the photosynthetic algae and functions as a protective organism against some enemies. Sometimes the alga and the fungus develop combined forms of reproduction.

References

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3. Dighton, J. (2016). Fungi Ecosystem Processes. 2 ^nd Boca Raton: CRC Press.
4. Kavanah, K. Editor. (2017). Fungi: Biology and Applications. New York: John Wiley.
5. Liu, D., Cheng, H., Bussmann, RW, Guo, Z., Liu, B. and Long, C. (2018). An ethnobotanical survey of edible fungi in Chuxiong City, Yunnan, China. Journal of Ethnobiology and Ethnomedicine. 14: 42-52. doi: 10.1186 / s13002-018-0239-2
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