1 Mycology & K Fungi

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Introduction to Mycology &Kingdom of Fungi

4032604 Lecture 1



What is a fungus?

• A eukaryotic, heterotrophic organismdevoid of chlorophyll that obtains its

nutrients by absorption, and reproducesby spores.

• The primary carbohydrate storageproduct of fungi is glycogen.

•

Most fungi have a thalluscomposed ofhyphae (sing. hypha) that elongate by tipgrowth



Fungal hyphae form a networkcalled a mycelium (pl. mycelia)



Historical Perspective on classification of fungi

• Linnaeus “ M inerals exist; plants exist and

l ive; animals exist, l ive and sense .”

• Fungi are plants under this classificationof organisms.

–Reflected in terminology: e.g, saprophytes(vs. saprotrophs)



Classification

• Whittaker (1969) proposed 5 kingdoms:

– Prokaryotes, Eukaryotes (Animals, Plants,

Fungi, Protists)• At least 7 kingdoms are now recognized:

–

Eubacteria, Archaebacteria, Animalia,Plantae, Eumycota, Stramenopila(Chromista), Protoctista (Protozoa, Protista)





Fungi versus fungi

• The small case “fungus” is usedinclusively for a heterogenousgroup of

organisms that have traditionally beenstudied by mycologists.

•

“Fungi” refers to the organisms in theKingdom Fungi, the true fungi, alsocalled the “Eumycota”



http://www.ucmp.berkeley.edu/chromista/chromistasy.html







Kingdom Stramenopila (Chromista)Phyla: Oomycota

HyphochytriomycotaLabyrinthulomycota

Protists(Protoctists)Phyla: Plasmodiophoromycota

Dictyosteliomycota

Acrasiomycota

Myxomycota



How many species of fungi exist?

• Number described = 80,000 (+1,700 newspecies each year)

•Works on estimating fungi– Hawksworth, D. L. (1991). The fungal

dimension of biodiversity: magnitude,

significance, and conservation. MycologicalResearch 95: 641-655

– Hawksworth, D.L. (2001) The magnitude of

fungal diversity: the 1.5 million speciesestimate revisited. Mycological Research 105(12): 1422-1432.



• Flowering plants on British Isles described =2,000 species

• Fungi on British Isles described = 12,000

species• Ratio of 6 fungi to each plant species• Total number of described plant species =

250,000 (most plant species are believed to bedescribed)• 6 x 250,000=1.5 million species of fungi!•

Less than 5% of which are described, and atthe current rate of description, it will take>800 years to describe all extant species.



• Classification is the systematic arrangementof organisms into groups based on establishedcriteria.

• Systematics is the study of the relationshipsand classification of the living world in asystem or conceptual hierarchy. Taxonomy,nomenclature are subcategories ofsystematics.

• Taxonomy is the study of the theory, practiceand rules of classification of living and extinctorganisms.

• Nomenclature is the “allocation of scientificnames to the units a systematist considers to

merit formal recognition.” (Hawksworth etal., 1995. The Dictionary of the Fungi ).



Nomenclature

• The nomenclature of fungi is governed bythe I nternational Code for Botanical

Nomenclature , latest edition 1994, asadopted by the International BotanicalCongress.



Nomenclature: Hierarchical Classification

Kingdom Fungi

Phylum Basidiomycota

Class Basidiomycetes

Order Agaricales

Family Agaricaceae

GenusAgaricus

Species:Agaricus campestris L .



Agaricus campestris L .

• Agaricus campestris L. is the type species ofthe genusAgaricus L.

•campestris is the specific epithet

• Note that the genus and species are initalics (or underlined); the genus iscapitalized, the species epithet is in lowercase

•

L. stands for Linnaeus, the authority



Agaricus bisporus (Lange) Imbach

• Lange and Imbach are the authorities forthis species

• Lange was the first to describe thisfungus, asCoprinus bisporus

•Imbach later transferred the speciesbisporus to the genusAgaricus



• Authority –the author of a scientific name of ataxon; the person/ persons who formally

described and published the name.• What if there are several mycologists named

Lange, how do we know which one did the

work?• Standard abbreviations of authority names can

be found in theDictionary of the Fungi

(Hawksworth et al. 1995) andFungi on Plants

and Plant Products in the Uni ted States (Farr et al.

1989).



What is a species?

• Most fungi are morphospecies, or delimited onthe basis of phenotype, most commonly bymorphological characters.

• A biological species is “a population, or a groupof populations, among which there isinterbreeding. Two individuals might not be

able to interbreed, but they are still members ofthe same species (conspecific) if they are part ofthe same gene pool.” ( Futuyma, D.J . 1998.

Evolutionary Biology ).



What is a species?

• A phylogenetic species is “irreducible(basal) cluster of organisms diagnosably

different from other such clusters, andwithin which there is a parental pattern ofancestry and descent” (Cracraft, J . 1989.Speciation and I ts Consequences ).



• For mycologists, species concepts andspecies recognition are problematic. J ohn

Taylor and colleagues have proposed arecognition concept that is rapidly gainingpopularity among mycologists using a

phylogenetic approach. This concept istermed “Genealogical ConcordancePhylogenetic Species Recognition” (GCPSR)and encompasses a phylogenetic approachbased on concordance (agreement) ofmultiple gene genealogies (Taylor et al.,2000. Fungal Genetics and Biology 31: 21-32).

Whystudy fungi?



Why study fungi?

• Fungi are among the most diverse organisms on Earth,

and are considered only second to the Insects in speciesdiversity.





Associations

• Fungi are involved in symbioticrelationships with a number of organisms

– Lichens– Mycorrhizas

–

Endophytes– Mutualists



Decomposers

• As saprotrophs, particularly asdecomposers, fungi are essential

components of the carbon cycle and areamong the few organisms that can breakdown lignin



Pathogens

• Fungi are important as pathogens ofanimals and plants.

– Over 70% of all plant diseases are caused byfungi



Industrial applications

• Ethanol

– Brewing and baking

• Organic acids– Citric acid for soft drinks

•Antibiotics– Penicillin, griseofulvin, cyclosporin, etc.

•

Enzymes– Pecticenzymes, hemicellulase, etc.



Introduction to Kingdom Fungi

M d f t iti



Modes of nutrition

• Fungi=absorptive heterotrophs

• Animals=phagotrophicheterotroph

• Heterotroph:– an organism incapable of synthesizing carbohydrates

from inorganic sources, and which must feed on

organic materials produced by other organisms

• Plants=autotrophs

H h ( i l h h )



Hyphae (singular, hypha)

• Cylindrical, branching filamentscomposed of a tubular cell wall filled with

cytoplasm and organelles• Most fungal hyphae are 2-10 m diameter



http://www.uoguelph.ca/~gbarron/MISCELLANEOUS/hairpen.htm



Fungal cell wall composition



Fungal cell wall composition

• Structural components:– chitin microfibrils [ß(1-4)-linked polymer of

N-acetylglucosamine]

– chitosan in Zygomycota[ß(1-4)-linkedpolymer of glucosamine]

–

ß-linked glucans• Gel-like components:

– Mannoproteins(form matrix throughout

wall)

Other cell wall components



Other cell wall components

• Antigenic glycoproteins, agglutinans,adhesions—on cell wall surface

• Melanins—dark brown to black pigments,(confer resistance to enzyme lysis, confer mechanicalstrength and protect cells from UV light, solar radiationand desiccation)

• Sporopollenin (aromatic polymer found in spore wallsof some fungi. Confers properties similar to melanin)

• Plasma membrane—semi-permeable



Septa



Septa

• Septa—regular cross-walls formed in hyphae.Hyphae with septa are septate, those lackingsepta except to delimit reproductive structures

and aging hyphae are called aseptateorcoenocytic.– primary septa are formed as a process of hyphal

extension and generally have a septal pore, whichallows for cytoplasmic and organelle movement.

– Secondary or adventitious septa are imperforate,formed to wall off ageing parts of the mycelium.

KingdomFungi



Kingdom Fungi

• Chytridiomycota—lack true hyphae

• Zygomycota—coenocytic hyphae

• Ascomycota—septate hyphae– Simple septa, Woronin bodies

• Basidiomycota—septate hyphae– Doliporesepta, parenthesomes

Septal pores Ascomycota



Septal pores--Ascomycota

• Woronin bodies



Fungal nuclei



Fungal nuclei

– 1--3 m diam

– 3--40 chromosomes

–

Up to 13--40 Mb (million base pairs) DNAcoding for 6,000 to 13,000 genes

– Intranuclear division--nuclear envelope

remains intact during mitosis (unlike plantsand animals)



Organism # bp # genes

Escherichia coli 4,600,000 4288

Saccharomyces cerevisiae 13,000,000 5885

Caenorhabditis elegans ~100,000,000 ~14,000

Arabidopsis thaliana ~120,000,000 ~10,000

Drosophila melanogaster ~170,000,000 ~12,000

humans ~3,400,000,000 ~80,000

http://www.genetics.wisc.edu/index.html

http://genome-www.stanford.edu/Saccharomyces/

http://helios.bto.ed.ac.uk/mbx/C_elegans/Ce_intro.html#top

http://sequence-www.stanford.edu/ara/ArabidopsisSeqStanford.html

http://fruitfly.berkeley.edu/

http://www.ornl.gov/hgmis/

http://www.genetics.wisc.edu/index.html

http://genome-www.stanford.edu/Saccharomyces/

http://helios.bto.ed.ac.uk/mbx/C_elegans/Ce_intro.html#top

http://sequence-www.stanford.edu/ara/ArabidopsisSeqStanford.html

http://fruitfly.berkeley.edu/

http://www.ornl.gov/hgmis/



Fungal nuclei



Fungal nuclei

•Nuclear associated organelles(NAOs):

–Associated with the nuclear envelope

– Function as microtubule-organizing

centers during mitosis and meiosis•Spindle pole bodies

– In fungi that lack a flagellated stage in lifecycle

•Centrioles

– In fungi and other organisms possessing

flagellated stage in lifecycle



Spindle Pole Body







Animal Cell Plant Cell



G. T. Cole. 1986. Microbiol. Rev. 50: 95 132

Fungal reproduction



g p

• Anamorph= asexual stage– Mitospore=spore formed via asexual

reproduction (mitosis), commonly called aconidiumor sporangiospore

• Teleomorph= sexual stage

– Meiospore=spore formed via sexualreproduction (e.g., resulting from meiosis),

type of spore varies by phylum

Kingdom Fungi; Phyla



g g ; y

• Chytridiomycota– Form motile spores called zoospores

– Meiosis occurs in resting sporangium

• Zygomycota

– Form asexual spores called sporangiospores

–

Meiosis occurs in zygospore• Ascomycota(including Deuteromycetes)

– Form asexual spores called conidia

– Meiosis occurs in ascus

• Basidiomycota

–

Meiosis occurs in basidium

Concept of fungal holomorph



p g p

• Fungi may reproduce through asexualand/ or sexual means

•Asexual and sexual reproduction may beseparated in timeandspace

•

The holomorph is the entire fungus—including asexual and sexual stages if bothare formed

Fungal life cycles



g y

• The vegetative thalluspredominates in the lifecycle of a fungus

• The thallusmay be haploid (1n), dikaryotic

(n+n) or diploid (2n) in different groups of fungi• Ploidy of thallus is determined by the timing of

these events in the life cycle:– Plasmogamy (cell fusion)

– Karyogamy (nuclear fusion)

– Meiosis (reduction division)

Fungal life cycles



2n n

Plasmogamy

n n+n

Karyogamy

n+n 2n

Life cycle is

predominantly

haploid (n)

mitosis

Meiosis

Fungal lifecycles



n n + n

Fungal life cycles

Karyogamy

n + n 2n

Meiosis

2n n

Life cycle is

predominantly

dikaryotic (n + n)

mitosis

Plasmogamy

Fungal lifecycles



n + n 2n

Fungal life cycles

Meiosis

2n n

Plasmogamy

n n + n

Life cycle is

predominantly

diploid (2n)

mitosis

Karyogamy

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1 Mycology & K Fungi