Kingdom FUNGI

-Brittany Marcus-Blank

To see fungi growing in action follow this link http://www.youtube.com/watch?v=puDkLFcCZyI


Cordyceps Fungus - The mind-control Killer-Fungi (2)



Diagnostic Characteristics
Kingdom Fungi are eukaryotic, meaning their cells contain a nucleus and organelles enclosed by a membrane, a thin layer of lipids that allows certain nutrients to pass through while others are kept out. Fungi are heterotrophs, organisms that cannot make their own food, so they get their food through absorption, absorbing small molecules from the surroundings. Fungi can be both single-celled or multi-cellular and they build their cell walls with chitin, a long strand of sugar molecules that provide structural support. Despite common misconceptions, Fungi are more closely related to animals than plants. (1) There are several similarities between fungi its sister group of animals, this is because they diverged from each other at a later time than they did with other life forms. They share with animals the ability to export hydrolytic enzymes that break down biopolymers, which can be absorbed for nutrition, but rather than requiring a stomach to accomplish digestion, fungi live in their own food supply and simply grow into new food as the local environment becomes nutrient depleted. Furthermore, individual fungi have the ability to communicate with other individuals chemically via pheromones. (5) (SS)

Habitat
Fungi like to live in their food source, which is usually in a moist environment. It is common to find fungi on old food that has been left out in the open, as well as in and on rotting logs. Being detritivores, organisms that break down nonliving organic matter, the fungi are partially responsible for the rotting of logs and the breakdown of plant litter. Fungi can also be found on shower curtains and even on clothing if it is left in a damp place. (1)
Fungi occur in almost every environment on earth and play important roles in the environment as detrivores. As fungi often have symbiotic relationships with plants and insects (be it parasitism, mutualism, or commencialism), fungi can often be found in the close proximity of their host organisms. (5) (KN). In order to ensure their survival, fungi produce compounds called myotoxins which are deadly and can be found in poisonous mushrooms(12) (OZ).

Basic Anatomy
31-01-fungal-mycelia-l.jpg
(1)

Fungi that are multi-cellular are made up of hyphae, tiny filaments that are composed of tubular walls surrounding the plasma membranes and cytoplasm, the entire contents of the cell. Hyphae are divided into cells by septa, pores that allow ribosomes, mitochondria and nuclei to flow through. Hyphae are a part of the mycelium, a densely branched network of hyphae, or the “interwoven mat” that makes up the feeding part of a fungus. On the other hand, some fungi's hyphae are not divided into cells and instead they have one continuous cytoplasm. They are known as coenocytic fungi and result from the repeated division of nuclei without the cytoplasm dividing. (1) A clear example of a coenocytic fungi is a Fairy ring, which may be one cell with millions of nuclei(ER)(6).
Fungi use their hyphae to expand their surface area to absorb more nutrients; this helps them grow in length but not width. The fungal mycelia cannot move, but they do not need to because fungi use their hyphae to expand into new territory. (1).
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(14)(RJS)
Transport of Materials
Fungi gain their nutrients through absorption. They secret enzymes, exoenzymes, into their food, which break down the complex molecules into simpler ones the fungi can absorb. Each cell can absorb its own nutrients, but nutrients can also pass between cells through the septa. Different fungi absorb food in different ways. Decomposers (saprobes) absorb nutrients from dead organisms (fallen logs or dead animals) or live animal wastes and their digestion decomposes the organic material. Parasitic fungi take nutrients from the live cells of their hosts; some parastic fungi are pathogenic and can cause a plant to become diseased. Mutualistic fungi are similar to parasitic fungi because they both absorb nutrients from their hosts, but mutualistic fungi always help out their host in some way (sometimes they help the plant take minerals from the soil). SV (1)

Reproduction



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These are the two cycles/stages of fungi reproduction (explained below). This type of reproduction involves alternation of generations.


(7 SES)

Fungi reproduce by releasing spores, small reproductive cells that bring rise to a new organism. This is done asexually, one parent that produces a genetically identical offspring, or sexually, two parents produce an offspring with a unique combination of both parent's genes. Fungi release a large number of spores that travel through wind or water to spread the spores around. (1) Most fungi are haploid, containing one set of chromosomes, except for the diploid, containing two sets of chromosomes, stage in their sexual reproduction cycle. Some mycelia become genetically diverse through the fusion of two hyphae with genetically different nuclei. These mycelia are called heterokaryon, “different nuclei”. This condition can help compensate for harmful mutations within one of the nuclei because there is genetic variation between the two nuclei. (1)
There are two stages in the sexual life style. The first stage is Plasmogamy, the fusion of two parents’ cytoplasm when their mycelia come together, and the second is karyogamy, the fusion of the haploid nuclei contributed by the two parents. The structures formed by the karyogamy are the only diploid stages in the life cycle. These two stages can be separated by any amount of time, from seconds to centuries. In between the two stages the haploid mycelium exists as a heterokaryon. In some special cases, the haploid nuclei pair off with two to a cell, one from each parent. The two nuclei in each cell do not fuse; they divide simultaneously as the mycelium grows and divides. (1)


Major Types
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Phylogeny of Fungi (4)
(HS 4)

Phylum Chytridiomycota: Chytrids are mainly aquatic primitive fungi that form uniflagellated, containing only one part that is specialized for locomotion, spores called zoospores. Because of the zoospores, Chytrids used to be considered a part of the kingdom Protista. Chytrids use absorption for nutrition and their cells walls are made out of chitin. They also have key enzymes and metabolic pathways that most fungi have but fungus like organisms do not contain. (1)
Phylum Zygomycota: Fungi are mostly terrestrial and live in soil or on decaying plants and animals. One type forms mycorrhizae, mutually benefiting associations with the roots of plants. Zygomycete hyphae are coenocytic and only have septa on reproductive cells. A common Zygomycete is black bread mold. (1)
Phylum Ascomycota: Sac fungi or ascomycetes live in both marine and terrestrial habitats. About half the ascomycete species live within algae in mutually benefiting situations called lichens. The defining feature of ascomycetes is that they produce sexual spores in the saclike asci. Most sac fungi participate in their sexual life in macroscopic fruiting bodies, asocarps, which is where the asci are found. Ascomycetes produce asexually through asexual spores that are produced externally at the tips conidiophores, specialized hyphae. (1)
Phylum Basidiomycota: These fungi are commonly referred to as club fungus and include mushrooms, shelf fungi and rusts. Basidiomycetes are decomposers of wood and other plant material that include particularly destructive plant parasites. The life cycle usually includes a long-lived dikaryotic mycelium what reproduces sexually by producing elaborate fruiting bodies called basidiocarps. A mushroom is an example of a basidiocarps and it is possible to erect a fruiting structure in just a few hours. This is how a ring of mushrooms may appear suddenly overnight. (1)
Molds: A mold is a rapidly growing asexually reproducing fungus. The mycelia of these fungi grow as parasites, such as bread mold. Molds go through multiple reproductive stages, but the term “mold” only applies to the asexual stages, such as in early life when a mold produces asexual spores. Molds are considered deuteromycetes or "imperfect fungi" because they have no known sexual stages, which is referred to as the "perfect stage." (1) Molds have striking similarities with fungi in the Class Ascomyceteae, which has led biologists to believe that imperfect fungi are part of that class. In addition, some biologists believe that the imperfect fungi actually do have a perfect stage, but it wasn't present when they were examined. Some imperfect fungi may have completely lost the ability to have a perfect stage, making them true imperfect fungi (3) (DP).
Yeasts: Yeasts are unicellular fungi that inhabit liquid or moist habitats. Yeast reproduce asexually either through simple cell division or by pinching of small “bud cells” off a parent cell. Yeats can also grow as simple, irregular filaments, meaning they divide using abnormal stuctural patterns(8 VM). Yeast is used to raise bread and ferment alcohol. Yeast can cause problems by growing too rapidly or releasing harmful substances when growing on the vaginal lining, therefore causing a “yeast infection.” (1) The picture below is of yest theat is budding. The larger section of the "pinched" cells are the parent cells and the smaller part is the bud. (1) (RK) 31-15-BuddingYeast.jpg
http://io.uwinnipeg.ca/~simmons/16cm05/1116/31-15-BuddingYeast.jpg
Lichens: Lichen is a mutually benefiting association of millions of photosynthetic microorganisms held in a mesh of fungal hyphae. The photosynthetic partners are usually unicellular, cyanobacteria, or green algae. The merge of fungus and algae is so thorough lichens were given their own genus and species name. The fungus usually gives the lichen its structure and the hyphae account for most of its mass; the alga is the layer underneath the surface. The alga provides the food and the fungus provides a suitable environment for growth. Lichen can live in environments where neither fungi nor algae could live alone. Lichens are important pioneer species on newly cleared rock and soil surfaces. (1)
During reproduction, the fungi and algae may reproduce separately, with the fungus forming ascocarps or basidiocarps and the algae undergoing asexual cell division. They may also reproduce together asexually. This is done either through the fragmentation of the parent lichen, or by forming soredia, small groups of hyphae and algae (1) [HZ].
lichens.jpg
(This image represents the the unique shapes and colors of the lichens. YS)
Mycorrhizae: Mycorrhizae are mutually benefiting relationships of plant roots and fungi. The extensions of the fungi mycelium from the hyphae that form the mycorrhizae greatly increase the absorption surface of the plant roots. The fungus and the plant exchange nutrients; the fungus absorbs them from within the soil and the plant produces them independently. The fungi involved are permanently associated with their hosts. (1) Since the fungus is receiving carbohydrates from the plant, the plant, in turn, is able to grow more effectively. This is called a symbiotic relationship. Specifically this type of relationship (between the plant roots and fungi) is mutualism since the relationship is mutually beneficial for both the plant roots and the fungi. (Jesse Carmen) [10]

Environmental Adaptations

Fungi are very flexible in terms of their environment. They are typically present wherever adequate moisture, temperature, and organic substrates are available(8 VM). It can grow in warm, moist forests, as well as very cold areas(8 VM). Optimum conditions for growth and reproduction vary widely with fungal species(8 VM). Fungi and bacteria are the primary decomposers, organisms that feed on dead plants and animals therefore making the nutrients available to the ecosystem, within ecosystems. Fungi are adapted because they have invasive hyphae that will enter the tissue of dead organic matter and secret exoenzymes that break down the complex molecules. Fungi generally live in their food and secret enzymes out to digest it; fungi chooses its environment based on the availability of food. In addition, fungi are nonmotile because their hyphae can extend and explore any new territory; they do not need to be able to move. Fungi have also evolved multiple mutually benefiting relationships with other oranisms such as lichens and mycorrhizae so they can live in certain other environments.(1)

Importance of Fungi (9, DJ)
Fungi are very important to humans because they are effect our daily lives (9, DJ). Not only are fungi used by humans as biodegraders, an agent which accelerates the decomposition of items, fungi is responsible for many plant and animal (including human) diseases like ringworm (9, DJ). One example of a medicine is penicillin, which is a well-known and commonly used antibiotic. It comes from a type of fungus called penicillium (13) (JAC). Fungi is also involved in the fermentation process; the saccharomyces species is used in beer, wine, and breadmaking (9, DJ). Also, certain types of fungi are used in biochemical production (Aspergillus niger is used to produce citric acid) (9, DJ).


Review Questions

1) How do fungi conduct reproduction? (NK)
2) Describe the four major phylums of Fungi (AR)
3) What do Fungi need in order to survive? (BL)
4) Explain the importance of fungi’s role as a detrivore in the ecosystem. (Nangia)


Works Cited:

1. Campbell, Neil A., and Jane B. Reece. Biology. Boston: Benjamin-Cummings Company, 2001. 616-631
2. http://www.youtube.com/watch?v=RuopJYLBvrI
3.
Bessey, Ernst A. "Morphology and taxonomy of fungi." Biodiversity Heritage Library. 30 Nov. 2008 <http://www.biodiversitylibrary.org/title/5663>.
(4) Carr, Dr.Steven M. "Phylogeny of Fungi." 1999. Memorial University fo Newfoundland. 3 Dec. 2008 <http://www.mun.ca/biology/scarr/phylogeny_of_fungi.htm>.
5.) Blackwell, Meredith, Rytas Vilgalys, Timothy Y. James, and John W. Taylor. "Fungi." Tree Of Life. 21 Feb. 2008. 7 Dec. 2008 <http://tolweb.org/fungi>.
6) Hawksworth, D. L. 1991. The fungal dimension of biodiversity: magnitude, significance, and conservation. Mycological Research 95:641-655.s
7) "Sexual Reproduction." Kingdom Fungi. 7 Dec. 2008. < http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb2pg20.htm>
8) "Fungi."7 Dec. 2008<http://tolweb.org/fungi>
9) Tariq, Vicki. "Importance of Fungi." Fungi Online. 14 Oct. 2007. British Mycological Society. 8 Dec. 2008 http://www.fungionline.org.uk/1intro/5importance.html.
10) "Symbiosis: Mycorrhizae and Lichens." 11 December 2008. <http://www.botany.hawaii.edu/faculty/wong/BOT135/Lect26.htm>.
11)http://images.google.com/imgres?imgurl=http:www.naturalsciences.org/education/treks/journaling_06/images/lichens.jpg&imgrefurl=http://www.naturalsciences.org/education/treks/journaling_06/pages/lichens.html&usg=__B2CeagtRplw48hVlGTMGQXzGqfw=&h=600&w=450&sz=111&hl=en&start=2&um=1&tbnid=vTKQzk72vPTe_M:&tbnh=135&tbnw=101&prev=/images%3Fq%3DLichens%26um%3D1%26hl%3Den%26sa%3DG
12."Fungus." Wikipedia. 13 December 2008 http://en.wikipedia.org/wiki/Fungi
13. "The Importance Of Fungi." Offwell Woodland & Wildlife Trust. 14 Dec. 2008 <http://www.countrysideinfo.co.uk/fungi/importce.htm>.
14. Miller, Julie. "Stalk and Cap Model." 18 Dec 2008 <http://images.google.com/imgres?imgurl=http:
www.bio.brandeis.edu/fieldbio/Fungi_Miller_Stevens_Rumann/
Page Edited by: DP; Hilary Stepansky, Sarah Vlach, SS, Ethan Richman, Grace Rehnquist, Kevin Nayer, Sarah Schwarzschild, Vonai Moyo, Daisy Joo, Jesse Carmen, Omer Zaidi, Rachel Kornetsky, Josh Czik, NK, Becca Levenson, Meru Nangia