What are Fungi?
to understand this let’s start with something familiar: we always have seen a green, black or cottony growth on the bread or a common mushroom a cap-like structure normally seen on the deadwood or in a garden is referred to as a fungus. This is just a common identification but how biologists describe fungi?
Although Fungi is a nigher plant nor animal, Historically, they were included in the plant kingdom; however, because of lack of chlorophyll and are distinguished by unique structural and physiological features (i.e., components of the cell wall and cell membrane), they have been separated from plants.
In addition, fungi are clearly distinguished from all other living organisms, including animals, by their principal modes of vegetative growth and nutrient intake. About 80,000 to 120,000 species of fungi have been described to date, although the total number of species is estimated at around 1.5 to 5.1 million.
With photosynthetic pigments chlorophyll being absent, it has a heterotrophic mode of nutrition. In contrast to animals that typically feed by ingestion, fungi obtain their nutrients by extracellular digestion due to the activity of secreted enzymes, followed by absorption of the solubilized breakdown products. absorption can be seen as the ultimate determinant of the fungal lifestyle.
The colonization of a food source, once reached, is achieved most efficiently by growth as a system of branching tubes called hyphae, which together make up the mycelium.
Hyphae are generally quite uniform in a different taxonomic group of fungi. One of the few features of distinction that they do offer is the presence or absence of cross walled septa. Not all fungi grow as hyphae. Some grow as discrete yeast cells that reproduce by fission or, more frequently budding. Mainly it is reproduced by means of sexually or asexually both.
With this unique morphological characteristic, it grows in a wide range of habitat that we dissed below.
Habitat of fungi.
They colonize almost every habitat on earth where the organic matter is present, but they First prefer a dark and humid environment. They can successfully colonize in hostile environments, such as tundra. However, about 80% of members from the kingdom fungi grow in the forest where the dark and dumb environment is the rich in decaying debris from plants and animals.
Usually, fungi grow in a wide range of habitat from the terrestrial ecosystem to the aquatic ecosystem. they also found in the most extreme environment that we can’t even imagine.
For example; from dry welly of Antarctica to water held in tropical bromeliads and the extreme environment like acidic and basal water, in high temperature and pressure, even recently NASA found that fungi can grow at the highly radiated environment that is 200 times more than those that can kill a human.
As we discussed above that they found everywhere they are searched for, but the most important thing is:
Where the majority of the fungi Found?
All members of the kingdom fungi prefer dark and humid conditions. Out of this majority of the members of this kingdom found in either soil or dead matter, and many are symbiotic of plant, animal, algae, and other fungi.
Because of that, they are primary decomposers of organic matter in terrestrial ecosystems along with bacteria. and this decomposition leads to the return of the nutrient into the soil and environment.
Out of these terrestrial member over 80% of the known fungi are associated with trees either as symbiont or parasite. The symbiotic relation between tree root and fungi are known as mycorrhizal association.
Some other fungi such as Marasmius oreades, and an edible mushroom, Agaricus campestris, etc., prefer open and grassy places. while some of the others prefer to grow on animal dung that is known as coprophilous fungi ( Chaetomium spp.)
Out of these some coprophilous fungi require specific types of animal dung to complete their life cycle. (For example; Coprinus radiatus and Panaeolus campanulatus are almost exclusively restricted to horse dung).
some members of kingdom fungi are only preferred to inhabit in water. For example; the member of fungal phyla: Chytridiomycota or we can say that all chytrids are preferred to inhabit in water. Even if some of them found in a terrestrial environment they also depend on the water to complete their life cycle.
Some of the parasitic fungi found inside the host. ( not all fungi that found inside the host is parasitic such as the member of Neocallimastigomycota are found in the rumen of animal that helps digest food.)
The well-known species of parasitic fungus is Cordyceps sinensis, also known as the zombie fungi which is an insect parasite. as you can see in below image it uses the whole body of the insect as a host and kills the host.
Other fungi, such as Coccidioides immitis, that cause Pneumonia when it’s spores are inhaled and colonized in human lung.
History of fungi
The word “fungus” is directly adopted from the Latin word “fungus”. The term “fungus” was derived from the Greek word ‘sponges‘ means the Microscopic structure and morphology of mushroom and molds.
Evidence shows that ancient humans are use Fungi for their benefit. Ötzi the Iceman, a well-preserved mummy of a 5,300 -year-old Neolithic man found frozen in Australian Alps. Carries two species of polypore mushrooms that may be used as tinder (Formes fomentarius) or Medicinal purpose ( Piptoporus betulinus).
On the other hand, Some of the oldest written records contain a reference to the destruction of crops that were probably caused by pathogenic molds.
Who discovered fungi ?
No data shows that who discovered fungi. As shown in the above section that ancient people also used it as food and medicine. So here we discuss who introduced or connect the two worlds, here I said two worlds because I think fungi has it’s own world. And at that stage of technology, we don’t know as much about Kindom fungi. Our information about this tiny organism is still limited.
After the development of the microscope in the 17th century. The first fungal spores were observed by Giambattista Della Porta in 1588. However, detailed work in the development of microscopy is considered to be the Publication of Pier Antonio Michelin’s 1729. He worked on Nova plantarum genera. Micheli not only observed spores but also showed that under the proper condition.
General characteristics of Kingdom fungi.
- it is eukaryotic organisms that mean they have a true nucleus and membrane-bound granules that are enclosed in membranes.
- They are non-vascular organisms. They do not have a vascular system. Xylem and Phloem are absent.
- it has a cell wall that is a complex and flexible structure composed basically of chitin, α- and β- linked glucans, glycoproteins, and pigments. (plants also have cell walls, but animals don’t have cell walls).
- There is no embryonic stage for fungus.
- They reproduce by means of spores. There are sexual and asexual spores.
- Sexual spores are Oospores, Zygospores, Ascospores, Basidiospores, etc. Asexual spores are Sporangiospores, Zoospores, Conidia, etc. The formation of sexual and asexual spores is truly dependent on the fungal species.
- They are typically non-motile but zoospore producing fungi having flagellated zoospores which can move.
- Fungi exhibit the phenomenon of alternation of generation. They have both haploid and diploid stages.
- Fungi are achlorophyllous, which means they lack the chlorophyll pigments present in the chloroplasts in plant cells and which are necessary for photosynthesis.
- The vegetative body of the fungus may be unicellular or multicellular (composed of microscopic threads called hyphae. Hyphae can grow and form a network called a mycelium.). Yeasts are unicellular fungi that do not produce hyphae.
- As mentioned above there structure of the cell wall is similar to plants but chemically the cell wall is composed of chitin (C8H13O5N)n.
- The cell membrane of a fungus has a unique sterol and ergosterol.
- Fungi are heterotrophic organisms. They obtain their food and energy from organic substances, plant, and animal matters.
- Fungi intact nutrition by absorption for that it digests the food first and then ingests the food, to accomplish this it produces exoenzymes, for example- Hydrolases, Lyases, Oxidoreductase, Transferase, etc.
- Fungi store their food as starch.
- Many of the fungi have a small nucleus with repetitive DNA.
- During mitosis, the nuclear envelope is not dissolved.
- Nutrition in fungi – they are saprophytes (gets energy from dead and decaying matters), or parasites (lives in a host, attack and kill) or symbionts (mutually beneficial).
- The optimum temperature of growth for most saprophytic fungi is 20-30°C while (30-37)°C for parasitic fungi.
- The growth rate of fungi is slower than that of bacteria, normally take 48 to 72 hrs.
- It Reproduce by means of both sexual and asexual. The sexual state is referred to as teleomorph (fruiting body), the asexual state is referred to as anamorph (mold-like).
- Reproduction occurs by both asexual (Axamorph) and sexual (Teliomorph) mode:
- Asexual methods: fragmentation, somatic budding, fission, asexual spore formation
- Sexual methods: gametic copulation, gamete-gametangium population, gametangium copulation, somatic copulation, and Spermatization.
- Pheromone is a chemical substance produced by fungi, which leads to the sexual reproduction between male and female fungi cells.
- Some are macroscopic and can be seen by naked eyes. Mold or mushrooms are examples of macroscopic forms of fungus.
- Examples: Candida albicans, Aspergillus, Blastomyces, Coccidioides, Cryptococcus neoformans, Histoplasma, Pneumocystis jirovecii, etc.