24: Fungi Flashcards
Characteristics of Fungi, Classifications of Fungi, Ecology of Fungi, Fungal Parasites and Pathogens, Importance of Fungi in Human Life
How many species of fungi are there?
The kingdom Fungi includes an enormous variety of living organisms collectively referred to as Eumycota, or true Fungi. While scientists have identified about 100,000 species of fungi, this is only a fraction of the 1.5 million species of fungus likely present on Earth.
What are some examples of fungi?
Edible mushrooms, yeasts, black mold, and the producer of the antibiotic penicillin, Penicillium notatum, are all members of the kingdom Fungi.
Are fungi autotrophic or heterotrophic?
Fungi are not capable of photosynthesis; they are heterotrophic because they use complex organic compounds as sources of energy and carbon.
What are the fungi reproduction strategies?
Some fungal organisms multiply only asexually, whereas others undergo both asexual reproduction and sexual reproduction with alternation of generations. Most fungi produce a large number of spores, which are haploid cells that can undergo mitosis to form multicellular, haploid individuals.
What are mycorrhizae?
A mutualistic relationship between a plant and a fungus. Mycorrhizae are connections between fungal hyphae, which provide soil minerals to the plant, and plant roots, which provide carbohydrates to the fungus.
What is Dutch elm disease?
A serious infection caused by the fungus Ophiostoma ulmi. It is a particularly devastating type of fungal infestation that destroys many native species of elm (Ulmus sp.). The fungus infects the vascular system of the tree, which blocks water flow within the plant and mimics drought stress. The elm bark beetle acts as a vector, transmitting the disease from tree to tree. Accidentally introduced in the early 1930s, the fungus decimated elm trees across the continent. Many European and Asiatic elms are less susceptible to Dutch elm disease than American elms.
What is the impact of fungal infections on humans?
In humans, fungal infections are generally considered challenging to treat. Unlike bacteria, fungi do not respond to traditional antibiotic therapy, since they are eukaryotes. Fungal infections may prove deadly for individuals with compromised immune systems.
What are some of the commercial applications of fungi?
The food industry uses yeasts in baking, brewing, and cheese and wine making. Many industrial compounds are byproducts of fungal fermentation. Fungi are the source of many commercial enzymes and antibiotics.
What is a spore?
A haploid cell that can undergo mitosis to form a multicellular, haploid individual.
What is a coenocytic hypha?
Single hypha that lacks septa and contains many nuclei.
What are facultative anaerobes?
Organisms that can perform both aerobic and anaerobic respiration and can survive in oxygen-rich and oxygen-poor environments.
What is a haustoria?
Modified hypha on many parasitic fungi that penetrate the tissues of their hosts, release digestive enzymes, and/or absorb nutrients from the host.
What does it mean to be heterothallic?
Describes when only one mating type is present in an individual mycelium.
What does it mean to be homothallic?
Describes when both mating types are present in mycelium.
What is a hypha?
Fungal filament composed of one or more cells. Plural: hyphae.
What is karyogamy?
Fusion of nuclei.
What is a mycelium?
Mass of fungal hyphae.
What is mycology?
Scientific study of fungi.
What are obligate aerobes?
Organisms, such as humans, that must perform aerobic respiration to survive.
What are obligate anaerobes?
Organisms that only perform anaerobic respiration and often cannot survive in the presence of oxygen.
What is plasmogamy?
Fusion of cytoplasm.
What is a saprobe?
Organism that derives nutrients from decaying organic matter; also saprophyte.
What is a septum?
Cell wall division between hyphae. Plural: septa
What is a sporangium?
Reproductive sac that contains spores.
What is a thallus?
Vegetative body of a fungus. May be unicellular or multicellular.
What is a yeast?
General term used to describe unicellular fungi.
What are some reasons why fungi were previously classified as plants?
Fungi arose mostly sessile and seemingly rooted in place. They possess a stem-like structure similar to plants, as well as having a root-like fungal mycelium in the soil.
When did fungi first evolve?
Based on fossil evidence, fungi appeared in the pre-Cambrian era, about 950 million years ago.
Where are fungi found in the phylogenetic tree?
Molecular biology analysts of the fungal genome demonstrates that fungi are more closely related to animals than plants. They are a polyphyletic group of organisms that share characteristics, rather than sharing a common ancestor.
Which degrees are usually required to become a mycologist?
Mycology is a branch of microbiology, and many mycologists start their careers with a degree in microbiology. To become a mycologist, a bachelor’s degree in a biological science (preferably majoring in microbiology) and a master’s degree in mycology are minimally necessary.
What are some fields that mycologists can specialize in?
Taxonomy and fungal genomics, molecular and cellular biology, plant pathology, biotechnology, or biochemistry.
In what ways may mycologists practice medicine?
Some medical microbiologists concentrate on the study of infectious diseases caused by fungi (mycoses).
What are some examples of fungal infections identified and controlled by mycologists in collaboration with cross-disciplinary scientists?
Mycologists collaborate with zoologists and plant pathologists to identify and control difficult fungal infections, such as the devastating chestnut blight, the mysterious decline in frog populations in many areas of the world, or the deadly epidemic called white nose syndrome, which is decimating bats in the eastern United States.
What are some ways in which mycologists are employed in the public sector?
Government agencies hire mycologists as research scientists and technicians to monitor the health of crops, national parks, and national forests.
What are some ways in which mycologists are employed in the private sector?
Mycologists are employed in the private sector by companies that develop chemical and biological control products or new agricultural products, and by companies that provide disease control services.
Why are mycologists employed in the food industry?
Because of the key role played by fungi in the fermentation of alcohol and the preparation of many important foods, scientists with a good understanding of fungal physiology routinely work in the food technology industry.
How is mycology used in wine-making?
Oenology, the science of wine making, relies not only on the knowledge of grape varietals and soil composition, but also on a solid understanding of the characteristics of the wild yeasts that thrive in different wine-making regions. It is possible to purchase yeast strains isolated from specific grape-growing regions.
Who discovered the process of fermentation?
The great French chemist and microbiologist, Louis Pasteur, made many of his essential discoveries working on the humble brewer’s yeast, thus discovering the process of fermentation.
Does horizontal gene transfer occur in fungi?
A few types of fungi have structures comparable to bacterial plasmids, however the horizontal transfer of genetic information from one mature fungus to another rarely occurs in fungi.
In what ways do fungal cells differ from plant cells?
Unlike plant cells, fungal cells do not have chloroplasts or chlorophyll.
What are some properties of fungal pigments?
Many fungi display bright colors arising from other cellular pigments, ranging from red to green to black. Pigments in fungi are associated with the cell wall and play a protective role against ultraviolet radiation. Some fungal pigments are toxic.
What is Amanita muscaria (fly agaric)?
A poisonous mushroom native to temperate and boreal regions of North America that is recognizable by its bright red cap and white patches.
What are some properties of fungal cell walls?
Like plant cells, fungal cells have a thick cell wall. 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.
How do the plasma membranes of fungal cells differ from those of animal cells?
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.
What is the motility of fungi?
Most members of the kingdom Fungi are nonmotile. Flagella are produced only by the gametes in the primitive phylum Chytridiomycota.
What are dimorphic fungi?
Dimorphic fungi can change from the unicellular to multicellular state depending on environmental conditions.
What are some examples of unicellular fungi?
Saccharomyces cerevisiae (baker’s yeast) and the Candida species, including Candida albicans (the agent of candidiasis and thrush, a common fungal infection)
What are the morphological stages of multicellular fungi?
Most fungi are multicellular organisms. They display two distinct morphological stages: the vegetative and reproductive. The vegetative stage consists of a tangle of slender thread-like structures called hyphae, whereas the reproductive stage can be more conspicuous.
How large are hyphae?
Although individual hyphae must be observed under a microscope, the mycelium of a fungus can be very large.
What is Armillaria ostoyae/Armillaria solidipes (honey mushroom)?
A giant fungus that is considered to be the largest organism on Earth, spreading across more than 2000 acres of underground soil in eastern Oregon. It is estimated to be at least 2400 years old.
What is the effect of Neotestudina rosati on humans?
The mycelium of the fungus Neotestudina rosati can be pathogenic to humans. The fungus enters through a cut or scrape and develops a mycetoma, a chronic subcutaneous infection.
Are fungal hyphae separated by septa?
Most fungal hyphae are divided into separate cells by endwalls called septa (septated). In most phyla of fungi, tiny holes in the septa allow for the rapid flow of nutrients and small molecules from cell to cell along the hypha. They are described as perforated septa. The hyphae in bread molds (which belong to the phylum Zygomycota) are not separated by septa. Instead, they are formed by large cells containing many nuclei, an arrangment described as coenocytic hyphae.
In which environmental conditions can fungi be found?
Fungi thrive in environments that are moist and slightly acidic, and can grow with or without light. They vary in their oxygen requirement. Most fungi are obligate aerobes, other species are obligate anaerobes, and some are intermediate, being facultative anaerobes.
What is an example of fungi that are obligate anaerobes?
The chytridiomycetes that reside in the rumen of cattle are obligate anaerobes.
Do yeasts require oxygen?
Yeasts are facultative anaerobes. The alcohol produced from yeast fermentation is used in wine and beer production.
In what ways is fungal nutrition similar to animal nutrition?
Like animals, fungi are heterotrophs; they use complex organic compounds as a source of carbon, rather than fix carbon dioxide from the atmosphere as do some bacteria and most plants. In addition, fungi do not fix nitrogen from the atmosphere. Like animals, they must obtain it from their diet. As with animal cells, the polysaccharide of storage is glycogen, rather than starch, as found in plants.
In what ways is fungal nutrition different from that of animals?
Unlike most animals, which ingest food and then digest it internally in specialized organs, fungi perform these steps in the reverse order; digestion precedes ingestion. First, exoenzymes are transported out of the hyphae, where they process nutrients in the environment. Then, the smaller molecules produced by this external digestion are absorbed through the large surface area of the mycelium.
What role do fungi play in an ecosystem?
Fungi are mostly saprobes; they obtain their nutrients from dead or decomposing organic matter: mainly plant material. Fungal exoenzymes are able to break down insoluble polysaccharides, such as the cellulose and lignin of dead wood, into readily absorbable glucose molecules. The carbon, nitrogen, and other elements are thus released into the environment.
How can fungi be used in bioremediation?
Because of their varied metabolic pathways, fungi fulfill an important ecological role and are being investigated as potential tools in bioremediation. For example, some species of fungi can be used to break down diesel oil and polycyclic aromatic hydrocarbons (PAHs). Other species take up heavy metals, such as cadmium and lead.
What are some examples of parasitic fungi in plants?
Smut and Dutch elm disease.
What are some examples of parasitic fungi in humans?
Athlete’s foot and candidiasis (thrush).
What are some nutrition strategies for fungi in nitrogen-poor environments?
In environments poor in nitrogen, some fungi resort to predation of nematodes (small non-segmented roundworms). Species of Arthrobotrys fungi have a number of mechanisms to trap nematodes. One mechanism involves constricting rings within the network of hyphae. The rings swell when they touch the nematode, gripping it in a tight hold. The fungus penetrates the tissue of the worm by extending specialized hyphae called haustoria.
What are perfect vs. imperfect fungi?
Perfect fungi reproduce both sexually and asexually, while the so-called imperfect fungi reproduce only asexually (by mitosis).
In which type of reproduction are fungal spores produced?
In both sexual and asexual reproduction.
What are some ways in which spores are dispersed?
Fungi produce spores that disperse from the parent organism by either floating on the wind or hitching a ride on an animal.
How large are fungal spores compared to plant seeds?
Fungal spores are smaller and lighter than plant seeds.
What are three ways that asexual reproduction is performed in fungi?
Fungi reproduce asexually by fragmentation, budding, or producing spores. Fragments of hyphae can grow new colonies. Somatic cells in yeast form buds.
How is budding performed in fungi?
During budding (a type of cytokinesis), a bulge forms on the side of the cell, the nucleus divides mitotically, and the bud ultimately detaches itself from the mother cell.
What is Histoplasma capsulatum?
A pathogenic yeast that primarily infects lungs but can spread to other tissues, causing histoplasmosis, a potentially fatal disease.
How are spores used by fungi in asexual reproduction?
The most common mode of asexual reproduction is through the formation of asexual spores. Spores allow the fungi to expand their distribution and colonize new environments. They may be released from the parent thallus either outside or within a special reproductive sac called a sporangium.
