1. Introductory Mycology – Cell Structures

2. What are fungi?
Eukaryotic, spore-bearing, heterotrophic organisms that produce extracellular enzymes and absorb their nutrition.

3. Body Plan unicellular (yeast), filamentous, or both (=dimorphic)
Hypha (pl. hyphae) is the basic “cellular” unit in filamentous fungi; they may be septate or coenocytic (aseptate); collectively a mycelium
limited tissue differentiation and division of labor
somatic & reproductive structures
plectenchyma: all organized fungal tissue, somatic & reproductive

4. Fungal nuclei
1--3 m diam
3--40 chromosomes
Up to Mb (million base pairs) DNA coding for 6,000 to 13,000 genes
Intranuclear division--nuclear envelope remains intact during mitosis (unlike plants and animals)

5. 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

6. Fungi as model organisms
Small genome relative to other eukaryotes
Many fungal genes are homologous to those in other eukaryotes
Easy to grow, short life cycles
Haploid genomes amenable to mutation
Sexual stage for analysis of segregation and recombination of genes; all products of meiosis can be retrieved in haploid spores
Asexual (clonal) reproduction

7. Beadle and Tatum
Using the common bread mold Neurospora crassa, in 1941 developed the classic concept of “one gene, one enzyme”
Awarded Nobel Prize in 1945

8. Nuclear Status Eukaryotic; uni, bi- or multinucleate
Haploid, diploid (less frequent)
Monokaryon
(1 nucleus per hyphal compartment)
Dikaryon
(2 nuclei per hyphal compartment)
Homokaryotic
Heterokaryotic

9. Mitosis
intranuclear: nuclear membrane doesn't breakdown during mitosis
centric in flagellated forms; typical centrioles of eukaryotes
noncentric in nonflagellated forms; possess spindle pole bodies (SPBs); differ from centrioles in lacking microtubular component

10. Organelles typical eukaryote assemblage of organelles
+ fungal specific ones
mitochondria
endoplasmic reticulum
Golgi equivalents
single cisternal elements
vacuoles
microbodies
funx in fatty acid degradation,
N metabolism

11. Other organelles
Mitochondria—flattened or plate-like mitochondrial cristae in Fungi (similar to animals)
Golgi bodies—consist of a single, tubular cisternal element (stacked, plate-like cisternae in animals and plants)
Other types:
ribosomes, endoplasmic reticulum, vacuoles, lipid bodies, glycogen storage particles, microbodies, microtubules, vesicles

14. Cell Wall Chitin well defined chitin 1-4 n-acetyal glucosamine
-glucans
polymers of glucose
1-3 glucose
cellulose in some
1-4 glucose
Cellulose
 1-3 glucan
chitin
-glucans

15. Fungal cell wall composition
Structural components:
chitin microfibrils [ß(1-4)-linked polymer of N-acetylglucosamine]
chitosan in Zygomycota [ß(1-4)-linked polymer of glucosamine]
ß-linked glucans
Gel-like components:
Mannoproteins (form matrix throughout wall

16. Other cell wall components
Antigenic glycoproteins, agglutinans, adhesions—on cell wall surface
Melanins—dark brown to black pigments (confer resistance to enzyme lysis, confer mechanical strength and protect cells from UV light, solar radiation and desiccation)
Plasma membrane—semi-permeable

18. fungal specific organelles involved in cell wall growth
Spitzenkorper or vacuole
associated with growing hyphal tips in septate fungi
chitosome
microvesicles transporting chitin synthases to growing cell wall

19. Nutrition Heterotrophic Secrete extracellular enzymes
Absorptive nutrition
Saprobes: decay dead organic matter
pathogens: biotroph, necrotroph
symbionts: parasites - commensals - mutualists

20. Spores - a minute propagative unit functioning as a seed, but differing from it in that a spore does not contain a preformed embryo
Fruiting body - any complex fungal structure that contains or bears spores; a sporocarp

21. Reproduction Sexual reproduction: spores meiotically derived nuclei
Homothallic (selfing)
Heterothallic (outcrossing)
Genetic mating system
MAT loci
1 to hundreds of “sexes”
Asexual reproduction
Spores with mitotically derived nuclei

22. Fungal Reproduction
Many fungi have the ability to reproduce by asexual and sexual means

23. Asexual Reproduction in Fungi
Fragmentation – hyphae simply break off.
Budding – small outgrowth of hyphae pinches off
Formation of spores
Sporangiospores: produced in sporangia (sac-like structures) located on a sporangiophore.
Conidiospores: produced at the tips of specialized hyphae

25. Fungal reproduction Anamorph= asexual stage Teleomorph= sexual stage
Mitospore=spore formed via asexual reproduction (mitosis), commonly called a conidium or sporangiospore
Teleomorph= sexual stage
Meiospore=spore formed via sexual reproduction (e.g., resulting from meiosis), type of spore varies by phylum

27. Kingdom Fungi Zygomycota Form asexual spores called sporangiospores
Phyla:
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

28. Fungal life cycles
The vegetative thallus predominates in the life cycle of a fungus
The thallus may 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)

29. Misc. Life cycle: simple to complex; wide variety
Sporocarps: microscopic or macroscopic, limited tissue differientiation
Habitat: ubiquitous
Studied by mycologists!!!!!!

31. Fungal life cycles mitosis Life cycle is predominantly haploid (n)
Plasmogamy
n n+n
Karyogamy
n+n n
2n n
Meiosis

33. Fungal life cycles mitosis
Life cycle is predominantly dikaryotic (n + n)
Karyogamy
n + n n
Meiosis
2n n
n n + n
Plasmogamy

34. Fungal life cycles mitosis Life cycle is predominantly diploid (2n)
Meiosis
2n n
Plasmogamy
n n + n
n + n n
Karyogamy

40. What are fungi?
Eukaryotic, spore-bearing, heterotrophic organisms that produce extracelluar enzymes and absorb their nutrition.

41. Fungi vs. "fungi"
Based on the phenotypic definitions or traits attributed to fungi, fungi do not comprise a single monophyletic group of organisms
more than one evolutionary origin
not all "fungi" are members of the Kingdom Fungi

42. Some characters that separate the
the Kingdom Fungi from “protistan fungi”
Kingdom Fungi Protistan fungi
mitochondria: cristae flattened cristae tubular
motile cells: no motile cells or motile cells with anterior
posterior flagellum or lateral
heterokont flagella
cell wall
carbohydrate: glucans, chitin glucans, cellulose
lysine biosynthesis: alpha-aminoadepic acid (AAA) diaminopimelic (DAP)
storage compound glycogen mycolaminarins
sterols ergosterol fucosterol
Phyla: Chytridiomycota Oomycota
(emphasized Zygomycota Myxomycota
in class) Glomeromycota Dictyosteliomycota
Basidiomycota
Ascomycota

43. General characteristics of the Phyla of the Kingdom Fungi
basal lineages
Zygomycota: (1000)
generally coenocytic mycelium
production of zygosporangia & zygospores
no sporocarp production

44. Basidiomycota: (22500)
septate mycelium
clamp connections
complex dolipore septa
dikaryotic, haploid mycelium
production of exospores (basidiospores) on a basidium
production of complex sporocarps
Ascomycota: (35000)
simple septa
monokaryotic, haploid mycelium
production of endospores (ascospores)
in an ascus
often dominant asexual reproduction

45. Nomenclature Amanita muscaria Kingdom - Fungi Phylum - Basidiomycota
Class - Hymenomycetes
Order - Agaricales
Family - Amanitaceae
Genus - Amanita
Species - A. muscaria

46. Medically important fungi are in four phyla:
Ascomycota - Sexual reproduction in a sack called an ascus with the production of ascopspores.( Aspergillus, Blastomyces dermatidis, Histoplasma capsulatus)
Basidiomycota -Sexual reproduction in a sack called a basidium with the production of basidiospores.( Cryptococcus neoformans)
Zygomycota - sexual reproduction by gametes and asexual reproduction with the formation of zygospores.( Rhizopus, Mucor)
Deuteromycota(Fungi Imperfecti \Mitosporic Fungi) - no recognizable form of sexual reproduction. Includes most pathogenic fungi ( Sporothrix, Coccidioides immitis, Candida, Pneumocystis).

47. Introductory Mycology- Cell Structure