Biology of Fungi - Youngstown State Universitycrcooper01.people.ysu.edu/Fungal Biology Lecture 1...

Lecture: What are Fungi? BIOL 4848/6948 - Fall 2009

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BIOL 4848/6948 (v. F09) Copyright © 2009 Chester R. Cooper, Jr.

What are Fungi?

Biology of Fungi


Fungi in the Tree of Life  Living organisms on

earth first arose about 3.5 billion years ago  Prokaryotic  Anaerobic

 Oldest fossils of fungi are about 460 million years old Fossilized perithecium of what is believed to be a

fungus of the genus Savoryella. Note the ascospores (arrow) within the ascocarp. Source: www.ucmp.berkeley.edu/fungi/fungifr.html


Fungi in the Tree of Life (cont.)

 Coincides with the rapid expansion of multi-cellular organisms

 Major multicellular eukaryotes are divided into Kingdoms  Animals  Plants  Fungi

Artistic vision of mushrooms among plants. Source: interactive.usc.edu/members/jchen/



 Each of these three kingdoms differ in their basic cellular structure and mode of nutrition (defined by Whittaker, 1969)  Plants - photosynthetic, cellulosic cell walls  Animals - digestive systems, wall-less cells  Fungi - absorptive nutrition, chitinous walls




Fungi in the Tree of Life (cont.)  The estimates for the expansion of

multicellular organisms are based upon phylogenetic analyses of Carl Woese  Examined ribosomal RNA (rRNA)

 Present in prokaryotes and eukaryotes  Relatively stable, but changes occur over time;

thereby acting as a chronometer  Distinguished three separate groups

(Domains) of living organisms


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Fungi in the Tree of Life (cont.)  Domains - rRNA sequence differences

correlate with differences in cellular structure and physiology  Bacteria - “true bacteria”  Archaea - “ancient prokaryotes”  Eucarya - eukaryotes

 Taxonomic grouping of “Kingdom” lies beneath that of “Domain”


Figure 1.1, Deacon (2006) Fungal Biology, 4th ed.


Fungi in the Tree of Life (cont.)  Though the fossil evidence suggests

fungi were present on earth about 450 million years ago, aquatic fungi (Phylum Chytridiomycota) most likely were present about a million years before this time

 About 354 - 417 million years ago, fungi evolved with primitive land plants


Fungi in the Tree of Life (cont.)  These plant-associated fungi probably

helped their photosynthetic partners gather nutrients from the harsh soils of the time

 These fungi were the early ancestors of the present day phylum Glomeromycota

 Despite plant-fungus co-evolution, fungi are more closely related to animals


Defining the Fungal Kingdom

 Mycology is the study of fungi  Myco- = fungi   -ology = the study of

 Mycology originally arose as a branch of botany because fungi were once believed to be “achlorophyllic” plants


Why Study the Fungi?  There are over 100,000 species of

known fungi and probably 15 times that many that have yet to be discovered

 Fungi are an extremely important part of the ecosystem  Recycling of minerals and carbon  Cause plant and animal diseases  Source of food, medicines, and chemicals   Important models in scientific research


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A Brief History of Fungi

 Greeks (about 300 B.C.) believed truffles were produced by thunder

 Oldest illustration of fungi was found among the ruins of Pompeii (A.D. 79) that depicted edible mushrooms

A truffle. Source: www.truffle-and-truffe.com


A Brief History of Fungi  Euripides (A.D. 450-456) recorded the

first mushroom poisoning deaths

Euripides. Source: uk.wikipedia.org Amanita muscaria, one of the most

poisonous mushrooms in the world. Source: www.myco-vaud.ch


A Brief History of Fungi (cont.)  During a period of the Middle Ages

(A.D. 1470 to 1670), books on ‘herbals’ were published that included illustrations and descriptions of fungi  Remarkably similar to those of Greeks  Used same methods to divide mushrooms

and truffles into poisonous and non-poisonous varieties


A Brief History of Fungi (cont.)   The German herbalist Jerome

Bock wrote in A.D. 1552: “Fungi and truffles are neither herbs, nor roots, nor flowers, nor seeds, but merely the superfluous moisture of earth, of trees, or rotten wood, and of other rotting things. This is plain from the fact that all fungi and truffles, especially those that are used for eating, grow commonly in thundery and wet weather.” [From Ainsworth (1976) Introduction to the History of Mycology, as cited in

Moore-Landecker (1996) Fundamentals of the Fungi, 4th ed.]

Jerome Bock.

Source: www.nndb.com


A Brief History of Fungi (cont.)  Other cultures also believed the fungi

originated from thunder and lightning  Hindu god Soma was a child of

thunderstorms who offered hallucinogenic fluids from Amanita muscaria, one of the world’s most poisonous mushrooms

 Similar legends existed in Guatemala and Mexico


A Brief History of Fungi (cont.)

 Modern times in the study of fungi began with the invention of the microscope (about 1590-1600) by Hans and Zacharias Janssen of Holland

Zacharias Janssen. Source: www.astrophotoclub.com/history/telescope.htm


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A Brief History of Fungi (cont.)  Robert Hooke used

the microscope to make the first drawings of a microscopic fungus (Mucor or Rhizopus) in 1665 and published them in his book Micrographia

Hooke’s drawing in Micrographia. Source: www.unb.br/ib/cel/microbiologia


A Brief History of Fungi (cont.)   In 1699, fungi are found

to be a component of lichens

 Anton van Leeuwenhoek observes yeasts using a microscope (1673)

British Soldier Lichen. Source: www.buenavistatownship.org


A Brief History of Fungi (cont.)  Hereafter, the study of fungi

exploded with many different contributions over the next 300 years, including the one gene-one enzyme hypothesis (Beadle and Tatum, 1941) and the 2001 Nobel Prize for cell division studies in yeast

Source: www.laskerfoundation.org


Defining the Fungal Kingdom

 Fungi are simple, eukaryotic microbes  Many are microscopic  Studies typically

employ standard microbiological techniques

Macroscopic (above; from Kendrick) and microscopic (below;

from Cooper) fungi


Defining the Fungal Kingdom (cont.)

 Mycologists (fungal biologists) have traditionally studied not only the true fungi (e.g., mildew), but also fungus-like organisms (e.g., slime molds) Physarum polycephalum, a slime mold, growing

out of Petri dishes (upper image) and a closer view of the plasmodium phase (lower image) Source: waynesword.palomar.edu/slime1.htm



 The kingdom Mycota is comprised of the true fungi

 True fungi have the following features:  Eukaryotic Transmission electron micrograph of a fungal cell

showing typical eukaryotic structures. Source: www.stchas.edu/faculty/zfitzgerald/fungi.jpg


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 Fungal features (cont.):  Typically grow as

filaments, termed hyphae (sing., hypha) via apical growth [the latter differs from the growth of other filamentous organisms]

Scanning electron micrograph of a fungal hyphae growing on the surface of a leaf. Source: www.abdn.ac.uk/ims/h-em/images/sem4/pages/fungal-hyphae-on-leaf.html



Apical growth of a fungal hypha of Sclerotinia sclerotiorum. Source: Fungal Cell Biology Group (www.fungalcell.org)



Hyphal strand of a Streptomyces species. Note the newly dividing cell (arrow). Source: zoology.okstate.edu/zoo_lrc/biol1114/sample_tests/preview_material/exam1/s03/preview-exam1_s03.htm



 Fungal features (cont.):  Fungal hyphae

repeatedly branch to form a network of filaments termed a mycelium (sing., mycelia)

Drawing of a mycelium. Source: www8.nos.noaa.gov/coris_glossary/index.aspx?letter=m



 Fungal features (cont.):  Some fungi grow as a single-celled entity,

termed a yeast, that grows either by a budding process or via binary fission

Budding yeast (left) and fission yeast (left). Sources: www.biochem.wisc.edu/yeastclub and www.steve.gb.com/science/model_organisms.html


Defining the Fungal Kingdom (cont.)   Fungal features (cont.):

  Some fungi can switch growth forms between a hyphal phase and a yeast phase, a property known as dimorphism   Typically induced by environmental

conditions   A number of such fungi are disease-

causing agents of humans and animals

Dimorphism of Candida albicans. Source: www.explorepub.com/articles/darkfield_charts/fungus9.html


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 Fungal features (cont.):  Heterotrophic (chemo-organotrophs) -

require preformed organic compounds  Absorb nutrients after degradation by

exogenously released enzymes


Defining the Fungal Kingdom (cont.)  Fungal features (cont.):

 Unique cell wall components  Chitin  Glucans  Rare instances of cellulose, but definitely fungal

cell walls are not as rich in this polymer as are plants



 Typically have haploid nuclei  Hyphae often have a number of haploid nuclei

present in each cell  Some yeasts have a single diploid nucleus

 Reproduce both sexually and asexually, typically through the production of spores



Asexual mitotically-derived spores (conidia; orange arrow in above figure) of the fungus Scedosporium apiospermum and the

meiotically-derived spores (ascospores within a specialized structure termed a cleistothecium; white arrow in figure to the

right) of the sexual form of the same organism given the designation Pseudallescheria boydii



 Other differences [Deacon, Table 1.1] between fungi and animals and plants include:  Histone types  Sensitivity of microtubules to inhibitors  Manner of lysine biosynthesis  Membrane sterols  Organellar structure/morphology


Major Activities of Fungi

 Plant parasites   Irish potato blight of

the 1840s  Dutch elm disease  Disappearance of

frogs in Costa Rica Phytophthora infestans growing into the leaf of a potato plant (above) and the

resulting rotting tuber from infection by this fungus (right). Sources: www.seedquest.com/News/releases/2005/may/12297.htm and

www.science.siu.edu/plant-biology/PLB117/JPEG%20files/potato.blight.jpg


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Major Activities of Fungi

 Plant symbionts  Lichens (can also

form with cyanobacteria)

 Mycorrhiza

Mycorhizzal fungus associated with roots of a pine. Source: www.virtualmuseum.ca/Exhibitions/Mushroom/English/Species/mycorrhizal.html


Major Activities of Fungi (cont.)

 Human pathogens  About 200 known species of fungi are

known to infect humans  Diverse diseases including:

 Dandruff   “ring worm”  Pneumocystis infection of HIV-infected persons  Candidiasis


Major Activities of Fungi (cont.)

 Biological control agents  Mycoparasites (other fungi)  Entomopathogens (insects)  Nematophagous (nematodes)

Nematode trapping fungus. Source: Kendrick


Major Activities of Fungi (cont.)  Decomposition

 Cellulose (plant material)  Rumen fungi in cows  Dry rot Dry rot due to the fungus Serpula lacrymans.

Source: www.grzyby.pl/gatunki/Serpula_lacrymans.htm


Major Activities of Fungi (cont.)  Toxin production (mycotoxins)

 Aflatoxins (peanuts and grains)  Mushroom poisoning

Moldy corn due to the aflatoxin producer Aspergillus flavus. Source: www.ipm.iastate.edu/ipm/icm/2001/10-22-2001/earrot.html


Fungi in Biotechnology

 Foods and flavorings  Edible mushrooms

 5 million tons produced worth $14 billion (1994)  Diverse types now widely available in

supermarkets  Alcoholic beverages  Breads, cheeses, soy sauce  Quorn mycoprotein


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Fungi in Biotechnology (cont.)

 Fungal metabolites  Two categories

 Primary - intermediates or end products of common metabolic pathways essential for normal cellular function

 Secondary - diverse range of compounds formed by specific pathways of a given organism and not essential for growth (but may provide some selection advantage)



 Fungal metabolites (cont.)  Examples of primary metabolites

 Citric acid (estimated 200,000 tons produced in the year 2000) [soft drinks]

 Gluconic acid (estimated annual production of 100,000 tons) [food additive]

  Itaconic acid (estimated annual production of 80,000 tons) [paint and adhesive manufacture]



 Fungal metabolites (cont.)  Examples of secondary metabolites

 β-lactam antibiotics, e.g., penicillins and cephalosporins

 Non-β-lactam antibiotics, e.g., griseofulvin, gliotoxin, ciclosporins

 Pullulan - film-wrap for food in Japan  Chitosan - sewage clarification, plant defense

initiator



 Enzymes and enzymic conversions  Extracellular enzymes  Commercially valuable roles

 Food industry  Bioconversions

 Heterologous gene products - expression of foreign proteins by fungi having medical/industrial applications

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