Fungi can be incredibly sophisticated multicellular organisms or single-celled organisms. They can be found in almost any location, but the majority of them dwell on land, primarily in soil or on plant matter. The decomposers are a group that thrives in the soil or on dead plant matter and is important to the cycling of carbon and other elements. Some are parasites of plants that spread illnesses like canker, rust, scabs, and mildew. Fungal diseases in crops can cause the farmer to lose a lot of money. A very small percentage of fungi can make animals sick. These include skin conditions that affect humans including athletes foot, ringworm, and thrush.
Types of Fungi
Fungi are classified according to their life cycles, whether or not they have a fruiting body, how those bodies are arranged, and the kind of spores (reproductive or distributional cells) they produce.
There are three main categories of fungi:
- Multicellular filamentous moulds.
- Macroscopic filamentous fungi that form large fruiting bodies. Sometimes the group is referred to as ‘mushrooms’, but the mushroom is just the part of the fungus we see above ground which is also known as the fruiting body.
- Single celled microscopic yeasts.
Multicellular Filamentous Moulds
Moulds are made up of very fine threads (hyphae). Hyphae multiply along their length and expand at the tip to form long, branching chains. The hyphae continue to develop and intertwine until they create a web of threads known as a mycelium. From the hyphal tip, digestive enzymes are released. These enzymes reduce the organic materials in the soil to smaller molecules that the fungus can consume.
Spores develop on some of the hyphal branches that shoot upward into the air. Spores are specialized structures with a covering that defends them from adverse environmental factors like drying out and high temperatures. 500 to 1000 of spores could fit on a pin because they are so small. Spores are similar to seeds as they enable the fungus to reproduce. Spores can be distributed by wind, rain, or insects. When the ideal conditions exist, they begin to proliferate and create new hyphae after finally landing in new habitats. Due to their inability to move, fungi employ spores to locate new environments with fewer rival organisms.
Macroscopic Filamentous Fungi
Mycelium production underground is also a method of growth for microscopic filamentous fungi. Because they generate visible fruiting bodies (usually known as mushrooms or toadstools) that contain the spores, they differ from moulds. The hyphae that make up the fruiting body are closely packed and divide to create the various components of the fungus’ structure, such as the cap and stem. Gills underneath the cap are covered with spores and a 10 cm diameter cap can produce up to 100 million spores per hour.
Single celled Microscopic Yeasts
Yeasts are tiny, solitary cells that resemble lemons and are comparable in size to red blood cells. They reproduce by splitting the original parent cell into two daughter cells. On the yeast cell’s surface, buds that have detached leave scars. Saccharomyces yeast, for example, is crucial to the baking and brewing processes. One of the most popular model organisms for genetic study is yeast, which is utilized, for instance, in cancer research. Other types of yeast, such as Candida, are opportunistic pathogens that infect people with weakened immune systems.
Classification of Fungi based on Spore Formation
Based on the way spores develop, fungi are divided into the following groups:
- Zygomycetes – These are formed by the fusion of two different cells. The sexual spores are known as zygospores, while the asexual spores are known as sporangiospores. The hyphae are without the septa. Example – Mucor.
- Ascomycetes – They are also called sac fungi. They can be coprophilous, decomposers, parasitic or saprophytic. The sexual spores are called ascospores. Asexual reproduction occurs by conidiospores. Example – Saccharomyces.
- Basidiomycetes – Mushrooms are the most commonly found basidiomycetes and mostly live as parasites. Sexual reproduction occurs by basidiospores. Asexual reproduction occurs by conidia, budding or fragmentation. Example- Agaricus.
- Deuteromycetes – They are otherwise called imperfect fungi as they do not follow the regular reproduction cycle as the other fungi. They do not reproduce sexually. Asexual reproduction occurs by conidia. Example – Trichoderma.
Fungal Symbiosis
The concept of symbiosis is the ecological interaction of two coexisting organisms, however it does not specify the nature of the interaction. Mutualistic describes a symbiotic partnership in which both association members gain. With a wide variety of species, including cyanobacteria, algae, plants, and mammals, fungi create mutualistic connections.
The endophytes, which are fungi that survive inside tissue without harming the host plant, are one type of fungal-plant mutualism. Toxins released by endophytes deter herbivores or provide tolerance to environmental stressors including microbial infection, drought, or heavy metals in the soil.
The most typical illustration is how most terrestrial plants collaborate with fungi through their roots. Mycorrhizae are formed when the plant’s roots bind to the fungus’s subterranean components (from the Greek words myco meaning fungus and rhizo meaning root). To transfer water and minerals from the soil into the plant in a mycorrhizal connection, the fungal mycelia employ their broad network of hyphae and large surface area in contact with the soil.
In return, the fungus receives components of photosynthesis from the plant to support its metabolism. Even certain plants, like orchids, have formed such a deep bond with fungi that without a fungal mycorrhiza partner, their seeds typically cannot germinate and florish.
Fungal Ecosystem Services
Fungi can decompose organic material that would not otherwise be regenerated in the ecosystem because to their adaptable metabolism. In spite of the fact that some elements, like nitrogen and phosphorus, are heavily needed by biological systems, they are not abundant in the environment unless this breakdown occurs. If fungus and bacteria did not release these elements into the environment through their metabolic activities, even trace elements that are found in small amounts in many ecosystems and are necessary for growth would remain bound up in rotting organic debris. Therefore, fungi enable the supply of nutrients required for the survival of other living organisms.
Fungi can perform a wide range of essential functions due to their diverse metabolic processes. They not only provide us with food and support healthy ecosystems, but they also directly contribute to the manufacturing of bread, cheese, beer, and various medicines. Some fungi are also extremely vulnerable to air pollution, particularly when nitrogen and sulfur levels are out of the ordinary. Currently, fungi are being researched as potential bioremediation methods. For instance, some fungal species can be utilized to break down heavy metals like cadmium and lead, polycyclic aromatic hydrocarbons (PAHs), and even diesel oil.
How Fungi helped Plants onto Land
Fungi and plants are closely related in terms of how they colonize the earth. It is obvious that fungi were necessary for plants to inhabit the earth 420 million years ago, at the very least. Before the development of plant roots, moss-like plants and endophytes were the first photosynthetic creatures on land to interact with fungi. Fungi assisted in supplying the necessary moisture because these plants could not live in locations that were always dry. A system of thin extensions from the rhizoids (rootlike structures seen in mosses), which are assumed to have had a selection benefit, subsequently developed into true roots in vascular plants.
These plants were able to get more nutrients in the soil than their rootless forebears because they had a larger surface area of interaction with fungal partners. The advantages of this connection gradually gave rise to the mycorrhizae that exist today; up to 90% of vascular plants have associations with fungus in their rhizosphere. According to a widely accepted idea, fungus played a crucial role in the development of the plant root system and the success of angiosperms (flowering plants).