Other spores are slimy and stick to the bodies of arthropods, like insects, to aid in their dispersal. Some spores are fired off in a sporangium and may travel distances of up to 2 meters, which is a huge distance considering the sporangia are only 80 micrometers in diameter. Fungi, together with bacteria, are decomposers, and their activities are necessary for the continued existence of the biosphere.
Decomposition releases carbon dioxide into the atmosphere and returns nitrogenous compounds to the soil where they can be recycled by plants and eventually animals. Since fungi are decomposers, they often come in conflict with human interests and are considered a nuisance, in some cases, a destructive hazard. Fungus can break down human-made wooden structures with their powerful enzymes as well as many other substances e.
Bread, fresh fruits, vegetables, and meat are particularly susceptible to fungal attack reducing nutritional value and palatability. Fungus may also produce toxins such as aflatoxin, which is highly carcinogenic and severely affects humans even when minute amounts are consumed.
Certain fungal yeasts are useful because they produce substances such as ethanol or carbon dioxide that play a key role in the brewing, baking, and wine-making industries.
Fungi are also important in producing many kinds of medicines. The most important of these are antibiotics, like penicillin, which is used to kill bacterial infections. Topic Editor "Fungi". In: Encyclopedia of Earth. Cutler J. Cleveland Washington, D. What is EOL? What's New? Penicillium produces the antibiotic penicillin Figure 5.
Many species of ascomycetes are medically important. Blastomyces dermatitidis is a dimorphic fungus that can cause blastomycosis , a respiratory infection that, if left untreated, can become disseminated to other body sites, sometimes leading to death.
Another important respiratory pathogen is the dimorphic fungus Histoplasma capsulatum Figure 2 , which is associated with birds and bats in the Ohio and Mississippi river valleys. Coccidioides immitis causes the serious lung disease Valley fever. Candida albicans , the most common cause of vaginal and other yeast infections, is also an ascomycete fungus; it is a part of the normal microbiota of the skin, intestine, genital tract, and ear Figure 5.
Ascomycetes also cause plant diseases, including ergot infections, Dutch elm disease, and powdery mildews. This and other Saccharomyces species are used for brewing beer.
Figure 7. The life cycle of an ascomycete is characterized by the production of asci during the sexual phase. The haploid phase is the predominant phase of the life cycle. The Basidiomycota basidiomycetes are fungi that have basidia club-shaped structures that produce basidiospores spores produced through budding within fruiting bodies called basidiocarps Figure 8.
They are important as decomposers and as food. This group includes rusts, stinkhorns, puffballs, and mushrooms. Several species are of particular importance.
Cryptococcus neoformans , a fungus commonly found as a yeast in the environment, can cause serious lung infections when inhaled by individuals with weakened immune systems. The edible meadow mushroom, Agricus campestris , is a basidiomycete, as is the poisonous mushroom Amanita phalloides , known as the death cap. The deadly toxins produced by A.
Figure 8. The life cycle of a basidiomycete alternates a haploid generation with a prolonged stage in which two nuclei dikaryon are present in the hyphae. Finally, the Microsporidia are unicellular fungi that are obligate intracellular parasites. They lack mitochondria, peroxisomes, and centrioles, but their spores release a unique polar tubule that pierces the host cell membrane to allow the fungus to gain entry into the cell.
A number of microsporidia are human pathogens, and infections with microsporidia are called microsporidiosis. One pathogenic species is Enterocystozoan bieneusi , which can cause symptoms such as diarrhea, cholecystitis inflammation of the gall bladder , and in rare cases, respiratory illness. Histoplasma capsulatum Aspergillus niger Basidiomycota Basidia.
Amanita phalloides Cryptococcus neoformans Amanita phalloides Microsporidia Lack mitochondria, peroxisomes, and centrioles. Spores produce a polar tube Enterocystozoan bieneusi Enterocystozoan bieneusi Microsporidia unidentified Zygomycota Mainly saprophytes. Zygospores Rhizopus stolonifera Mucor spp. Rhizopus sp. Think about It Which group of fungi appears to be associated with the greatest number of human diseases?
Eukaryotic Pathogens in Eukaryotic Hosts When we think about antimicrobial medications, antibiotics such as penicillin often come to mind. Penicillin and related antibiotics interfere with the synthesis of peptidoglycan cell walls, which effectively targets bacterial cells.
These antibiotics are useful because humans like all eukaryotes do not have peptidoglycan cell walls. Developing medications that are effective against eukaryotic cells but not harmful to human cells is more difficult. Despite huge morphological differences, the cells of humans, fungi, and protists are similar in terms of their ribosomes, cytoskeletons, and cell membranes. As a result, it is more challenging to develop medications that target protozoans and fungi in the same way that antibiotics target prokaryotes.
Fungicides have relatively limited modes of action. Because fungi have ergosterols instead of cholesterol in their cell membranes, the different enzymes involved in sterol production can be a target of some medications. The azole and morpholine fungicides interfere with the synthesis of membrane sterols. Unlike plant cells, fungal cells do not have chloroplasts or chlorophyll. Many fungi display bright colors arising from other cellular pigments, ranging from red to green to black.
The poisonous Amanita muscaria fly agaric is recognizable by its bright red cap with white patches. Pigments in fungi are associated with the cell wall. They play a protective role against ultraviolet radiation and can be toxic. The rigid layers of fungal cell walls contain complex polysaccharides called chitin and glucans.
Chitin, also found in the exoskeleton of insects, gives structural strength to the cell walls of fungi. The wall protects the cell from desiccation and predators. Fungi have plasma membranes similar to other eukaryotes, except that the structure is stabilized by ergosterol: a steroid molecule that replaces the cholesterol found in animal cell membranes.
Most members of the kingdom Fungi are nonmotile. The vegetative body of a fungus is a unicellular or multicellular thallus. Dimorphic fungi can change from the unicellular to multicellular state depending on environmental conditions. Unicellular fungi are generally referred to as yeasts. Most fungi are multicellular organisms. In Oregon, there is an example of dark honey fungus, Armillaria ostoyae , which has grown to around 8. Under the forest floor, you can typically find large mycelium that live by digesting the nutrients no other organisms can use.
In contrast to animals, fungal digestion does not take place internally but in the external environment. Fungi secrete highly efficient enzymes, which convert large, complex molecules into smaller compounds.
Fungi have a powerful arsenal of enzymes capable of breaking down various materials. For example, some of the enzymes can break down lignin in tree trunks, which would otherwise be very difficult to digest and would protect the tree from fungal attack. This includes everything from fallen leaves and tree trunks to dead animals and insects.
Organisms that live on these nutrient sources are called saprophytes. The dead organic material is made up of large complex compounds which powerful fungal enzymes break down into simple organic compounds that can be used as nutrients. This is not just because of the important function of biodegrading fungi in ecosystems, but also because of another group of fungi. The large surface area of the mycelium means that fungi are incredibly good at absorbing nutrients from the soil.
At the same time, their enzymes enable them to extract nutrients from the soil, which plants cannot. A plant provides itself with energy and sugar by taking carbon from the carbon dioxide in the air. But it also needs water and minerals, especially nitrogen and phosphorus. The problem with plant roots is that they are nowhere near as thin and fine as hyphae.
Fungi are much better equipped for this job. Moreover, their enzymes allow them to take up minerals, which plants cannot. According to the rules of this relationship, fungi supply the plant with minerals and water from the soil. In exchange, the fungi obtain sugars, which the plant has synthesized by photosynthesis. Mycorrhizal fungi are rarely found in other scenarios in nature, as they are highly dependent on obtaining sugars from plants.
Mycorrhizae are a prerequisite for the survival of these fungi. That is to say, the fungi are obligate symbionts. Mycorrhizae are not the only example of a mutualistic relationship in fungi. Lichen is a combined organism of fungi and algae or cyanobacteria and can found on surfaces such as rock. Algae or cyanobacteria can carry out photosynthesis and can therefore make organic compounds for both parties. The fungus can secrete acids that break down minerals from rock, and its hyphae are employed somewhat like an anchor to attach the organism firmly to the rock.
Fungi reproduce and spread with the help of spores. Spores are tiny particles, which distribute the fungi to new sites with good growing conditions. As soon as a spore lands in a favorable spot, a new fungal colony is established.
Spores are therefore an important part of the life cycle of almost all fungi, as they facilitate reproduction. To ensure that the spores spread, fungi have developed effective spore-producing structures.
Mushrooms fruiting bodies are a good example of this. Underneath the mushroom, millions of spores are disseminated out into the atmosphere from the gills or tubules.
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