The Kingdom of Mushrooms is a diverse group of organisms that are neither plants nor animals. They receive nutrition from other creatures, playing an important role in the process of environmental degradation. What organelles are absent in fungal cells? Which are present? How is this kingdom different from the kingdom of plants and animals?
What are mushrooms?
What do mushrooms in the forest have in common, bread, wine, beer and rotting organisms? Obviously, some of them are edible, while others are not. Mushrooms are found in nature, and wine and beer are beverages processed by humans. As for rotting organisms, they usually are not of much interest to most people.
Nevertheless, all these examples have a common thread - they belong to the kingdom of the Mushroom, which includes a huge variety of organisms that are neither plants nor animals. These unique multicellular eukaryotes are decomposers, which is vital for every ecosystem.
General characteristics and systematics of mushrooms
According to scientists, there are hundreds of thousands of species of mushrooms on Earth. At one time, it was believed that these organisms are simply primitive versions of plants. However, further discoveries led to the realization that mushrooms had many significant differences from both plants and animals, which gave them the right to belong to their own kingdom. Let's look at some common characteristics of these organisms.
- Members of the kingdom of mushrooms are eukaryotes, that is, they have complex cells with a nucleus and organelles. Most of them are multicellular, with the exception of single-stranded yeast. Structurally, fungi are composed of individual feathered threads, called hyphae, which group together to form a mycelium. The body of the mushrooms has a spongy structure, as it is composed of a mass of very tightly packed hyphae and, therefore, is not completely solid.
- All mushrooms are heterotrophic, which means that they cannot create their food like plants. They must receive nutrition from other organisms, they grow on them and absorb their nutrients.
Familiar mushrooms include yeast, mold, and the actual mushrooms. Let's consider these groups in more detail:
- Mushrooms. They usually grow in the presence of cool, humid weather. They usually consist of a stem with a hat, in which spores are created that are released to reproduce and colonize new environments. Many types of mushrooms are edible and tasty, others can be very toxic.
- Mold. Like the first group, this form is also very recognizable. Forget about a piece of cheese for a long time, and it is covered with green fluff, because of which mold is often called filamentous fungus. Specialized hyphae, called conidia, often pigmented and rise above the surface of the food source. These conidia are responsible for the production and release of mold spores for reproduction and development.
- Yeast. For the microbiologist, yeast is the most important type. This is a general term for any unicellular fungus (the first two groups are multicellular). The yeast cell is larger than the bacterial cell and contains the nucleus and other organelles. Reproduction is carried out by budding. The yeast is unicellular but eukaryotic, which makes them an important group of organisms for scientists.
General structural features
Here's another question: how can mushrooms just live and reproduce without being able to move? The answer lies in tiny microscopic reproductive structures known as spores. In contrast to the differentiation of cells in animals, almost every cell formed by a fungus can function as a “stem cell”.
The multicellular fruiting bodies of basidiomycete fungi consist of the same type of filamentous hyphae that form the feeding or mycelial phase, and there is practically no visible cell differentiation. Mushroom buds develop from masses of converging hyphae. Spores form in the cavities inside the fetal body.
Nuclei missing in fungal cells? Yes, and there are cell walls from chitin, mitochondria, and many other organelles. Mushrooms are unicellular or multicellular organisms. Unlike plants, there are no chloroplasts in the cells of the fungi, which means that they cannot produce food for themselves.
Mushrooms are important decomposers in most ecosystems
Their long fibrous cells can penetrate plants and animals, destroying them and enriching themselves with nutrients. Several species of fungi, mainly yeast, live harmlessly on the human body. What organoids are absent in fungal cells? They do not have chloroplasts at all. Since mushrooms can grow in the dark, they do not need chlorophyll and sunlight. Thus, they grow in a saprophytic diet.
Mushroom age
Ancient Earth had its share of dominant organisms. For most of the history of life, microscopic bacteria and archaea dominated the planet, floating and thriving in the ancient oceans, which covered most of the globe. Over time, organisms become larger and more complex. There was a time when organisms resembling insects dominated, and then fish and reptiles appeared. We all heard about dinosaurs ruling the Earth, and then mammals evolved. Now people are clearly the dominant organism.
What about mushrooms? About 250 million years ago, the land was inhabited by ancient plants and animals. However, there was a period when more than 90% of life on Earth disappeared. Animals were destroyed, as well as plants. Billions of trees have turned into massive fields of dead wood. And what thrives on dead wood and dead animal tissue? That's right, mushrooms.
Mushrooms - eukaryotes
Are there nuclei in fungal cells? Do they have cell walls? Mushrooms are eukaryotes. This means that fungal cells have a nucleus, like the cells of plants and animals, and this distinguishes them from bacteria and archaea. These organisms are not phototrophs, since they cannot use light to generate energy, which distinguishes them from plants. The cell walls of fungi are unique in that they contain a large amount of chitin, a structural component found only in the cell walls of fungi. Chitin makes cell walls stiff.
Way of food - saprophytes
Chloroplasts are what are absent in the cells of fungi and they cannot carry out photosynthesis. How do they get their own nutrients? Many mushrooms are saprophytes. These are organisms that acquire nutrients from dead organic matter. These mushrooms are actually very important for the health of the ecosystem, they quickly destroy plant and animal material and return it to nature in a more convenient form.
The structure and functions of fungal cells
Fungi are unicellular or multicellular thick-celled heterotrophic decomposing organisms that feed on decaying matter and form bundles of filaments. There are certain similarities and differences in the structure of the cells of plants, animals, and fungi. The walls of fungal cells are stiff and contain complex polysaccharides called chitin and glucans (glucose polymers).
Ergosterol is a steroid molecule in cell membranes that replaces cholesterol found in animal cell membranes. Other components include chitosan, melanin, and lipids. Before answering the question of which organelles are absent in the cells of the fungi, let's describe what it is all the same. This large kingdom has a complex cellular organization. Being eukaryotes, fungal cells contain a membrane-bound nucleus, where DNA is wrapped around histone proteins.
Some types have structures comparable to bacterial plasmids (DNA loops). Fungal cells also contain mitochondria and a complex system of internal membranes, including the endoplasmic reticulum and the Golgi apparatus. Pigments in fungi are associated with the cell wall. They play a protective role against ultraviolet radiation and can be toxic.
Mushrooms - plants - animals: similarities and differences
Most fungi build their cell walls from chitin. This is the same material as the hard outer shells of insects and other arthropods. Plants do not have chitin. Mushrooms feed by absorbing nutrients from the organic material in which they live. They do not have a stomach, but must digest their food before it can pass through the cell wall into hyphae. In this case, acids and enzymes are released, which destroy the surrounding organic material into simple molecules that they easily absorb - this is called composting.
Mushrooms are nutritious: they are a good source of B vitamins, especially niacin and riboflavin, and occupy leading positions in protein content. But since they have low levels of fat and calories, Western nutritionists mistakenly considered them to have no nutritional value. However, in dried form, mushrooms have almost as much protein as veal and a significant amount of complex carbohydrates called polysaccharides.
The cell of animal plants and fungi: structural features
Despite the apparent cellular similarity, the cells of plants, animals and fungi have significant differences:
- The cells of plants and fungi on top of the membrane have a dense membrane, which consists of carbohydrates. In the former, it consists of cellulose, and in the latter, of chitin. An animal cell does not have such a membrane at all; there is only a cell membrane.
- In plant cells, there are plastids in the cytoplasm. For example, in leaf cells they are green. In other cells, these organelles may be yellow, orange or red or have no color at all. Green plastids are called chloroplasts. These are the components that are absent in the cells of the fungi. They are also absent in animal cells.
- Animals feed on prepared organic substances created by plants. A stored nutrient in fungal cells is glycogen carbohydrate, as in animals, and not starch, as in plants.
Mushrooms can be unicellular, multicellular, or dimorphic. It depends on environmental conditions. At the morphological vegetative stage, they consist of a string of thin, filiform hyphae. Mushrooms love to live in a humid and slightly acidic environment, and they can also grow without light or oxygen.
Mushrooms are saprophytic heterotrophs because they use dead or decaying organic matter as a carbon source. In the cells of fungi there are no plastids and chloroplasts, which distinguishes them from plants, and the presence of an additional membrane over the cell membrane (as well as the inability to get over) distinguishes them from animals.