1. Molds, mildews, & mushrooms An introduction to fungi

2. Fungi Large monophyletic Kingdom – –Ca. 98,000 species described –Estimated to be 1.5 million species Significant group of organisms – both basic and applied biology Fungi play variety of roles – can be either destructive or beneficial

3. A number are plant pathogens Fungi are major pathogens of plants – cause great deal of damage to crops (losses of 20- 50% of yield) Example: Wheat rust –Major losses in yields of wheat –Romans had a god of rust - Robigus –In Southeastern US Wheat rust severe, can’t grow wheat Corn replaced wheat –cornbread, bourbon

4. Coffee rust epidemic in Ceylon

5. Irish potato famine Potato imported to Europe in 1500’s, became a staple Several years of favorable weather lead to epidemic of late blight of potatoes Caused the Irish potato famine – mid 1800’s

6. Late blight of potato Caused by Phytophthora infestans No longer considered a true fungus

7. Fungal diseases of animals & humans Generally less widespread than diseases caused by bacteria and viruses (exception – athletes foot), but can be severe Certain diseases endemic to geographic areas – e.g. valley fever caused by Coccidioides sp. in the desert SW Incidence of human mycoses is on the increase with use of immunosuppresant drugs and AIDS

8. Fungi as symbionts Mycorrhizal association is very common among plants Lichens

9. Fungi as decomposers Important agents in the flow of energy and cycling of nutrients in biosphere Decomposition particularly of plant litter Food for higher trophic levels

10. Fungi as agents of deterioration Cause deterioration of organics –food, wood, clothing, leather Variety of antifungal products developed

11. Food and food supplements Yeast – bread and alcohol Mushrooms Fermentation of plant products (soybeans) – soya sauce, tempeh, miso tofu,etc. Biotechnology – enzymes, antibiotics, statins, organic acid production

12. Mycotoxins Produced by microfungal species on different stored food products Aflatoxin produced by Aspergillus flavus

13. Allergens Spores present in outdoor & indoor air Sick building syndrome Stachybotrys

14. Myths & Religions Hallucigenic mushrooms

15. Used as model systems in biology Neurospora crassa – 1 gene – 1 enzyme Saccharomyces Aspergillus

16. Major characteristics of fungi Eukaryotic Heterotrophic Osmotrophs Modular organisms – indeterminate growth Multinucleate Generally surrounded by cell wall Generally nonmotile (some produce motile cells) Most form spores as reproductive units

17. Fungal biology Fungal body = thallus Vegetative (somatic) phase – absorbs and assimilates nutrients, grows Reproductive phase - all or part of thallus may differentiate to form reproductive structures – spores Asexual (mitosis) or sexual reproduction (meiosis, fertilization)

18. Vegetative thallus Variable – but most fungi form a branching network of multinucleate filaments Filament = hypha (pl. hyphae) Exceptions – yeasts, some lower fungi

19. Mycelium = filamentous fungal thallus All hyphae in a thallus form the mycelium

20. Largest mycelia Armillaria gallica – fungus humongous 30 acres, 10 tons, 1500 years old – now larger Armillaria species have been found

21. Hyphae Walled tubes that contain cytoplasm Eukaryotic – nuclei, mitochondria, ER, etc Grow at tip Form lateral branches that grow at tip

22. Basic types of hyphae Aseptate hyphae – lack crosswalls, found in lower fungi Septate hyphae – crosswalls divide hyphae into compartments, are incomplete, found in higher fungi

23. For filamentous fungi What is a cell? –Not typical with one nucleus controlling a defined volume of cytoplasm, many nuclei occur together –Have age transitions – tip is young with senescent cytoplasm away from the tip What is an individual? Hyphae from two individuals may fuse two or more  one Hyphal pieces may be separated from thallus one  two or more

24. Basic structure of hyphae Size – 2 μm to 1 mm in diameter, –5-10 μm most common Surrounded by cell wall – gives hypha shape and prevents it from bursting from osmotic pressure –Cell walls composed primarily of polysaccharides with less than 10% proteins and lipids –Microfibrillar polysaccharides embedded in an amorphous matrix

25. Cell walls Microfibrillar polysaccharides – in most fungi is chitin – polymer of N-acetyl glucosamine (  1,4) Chitin accounts for 5-60% of cell wall Amorphous matrix contains a variety of polysaccharides – glucans, mannans

26. Fine structure of hyphae Apical region of hyphal tip – typically 150- 500 μm long. Dense cytoplasm, rich in organelles, few vacuoles Extreme tip (1-5 μm) contains many small vesicles (the apical vesicle cluster, AVC) – with light microscope = spitzenkörper (in sepatate hyphae only); no other organelles Behind the apical region, vacuoles increase in number and size, lipid granules accumulate

27. Fungal hypha

28. Hyphal tip

29. Nuclei Small (1-2 μm) Nuclear envelope does not break down during division, chromosomes not distinct In apical region there are 1-50 nuclei Fungal DNA less complex than other eukaryotes - fewer repeated DNA segments compared to other eukaryotes (less than 10% compared to 35% in mammals)

30. Nuclei

31. Organelles Mitochondria – elongate with platelike cristae Endoplasmic reticulum – narrow membrane bound channels Golgi – ringed cisternae not flattened stacks

32. Hyphal growth Growth occurs at the tip Grow in pulse of radiolabelled wall precusor Vesicles also concentrated at tip – few other organelles in tip

33. Hyphal growth Not the same as cellular growth Filamentous fungi do not undergo cell division after cell has doubled in size Duplication cycle (analogous to cell cycle) Apical compartment grows to a particular length, nuclear division followed by formation of 1 to several septa

34. Hyphal branching

36. Carbon nutrition of fungi All fungi are heterotrophic – obtain C from organic sources In this regard, they are like animals, but Absorb nutrients from environment, do not ingest food

37. Three modes of heterotrophy Saprotrophs (saprophytes)– obtain C from non-living organic matter Biotrophs – obtain C from living organic matter –Parasites –Symbionts Necrotrophs – kill organisms and use C of dead bodies –Parasites Facultative or obligate

38. Fungi and Plants Originally fungi were classified with plants – nonmotile, have cell wall Are also similar to plants in that they are modular organisms not unitary like animals Modules in plants – buds and branch; in fungi – hyphal tips Comparison of characteristics of modular with unitary organisms

39. Unitary vs modular organisms CharacteristicUnitaryModular Growth patterndeterminateIndeterminate, iterative SizeAdults vary littleVaries greatly Mobilitymobileimmobile Acquisition of resources Use mobilityGrow to resources Reproductive capability Increases with age, decreases Can increase indefinitely

40. Unitary vs modular organisms Clonal reproduction UnusualCommon Internal age structure AbsentPresent LongevityDefinite life span Indefinite life span Local damageSeriousUnimportant

41. Vegetative phase  Reproductive phase After period of growth, differentiation may occur Reproduction can be sexual or asexual Functions of reproduction –Recombination of genetic information –Propagation and dispersal of fungus –Dormancy – dispersal through time

42. Asexual reproduction Fragmentation of thallus Production of asexual spores (two main types) –Sporangiospores – develop within a sporangium Lower fungi –Conidium (pl. conidia) – formed externally at the tips of specialized hyphae Higher fungi

43. Sporangiospores

44. Conidia

45. Sexual reproduction Three events occur in sexual life cycle –Plasmogamy – union of two cytoplasms –Karyogamy – union of two nuclei –Meiosis – reduction division (In most organisms plasmogamy and karyogamy occur close together – called syngamy or fertilization

46. Sexual life cycle The three events lead to three phases based on nuclear condition –Haploid (1n) – one set of chromosomes per nucleus –Diploid (2n) – two sets of chromosomes per nucleus –Dikaryotic (n+n) – two sets of chromosomes in separate nuclei Vegetative phase may be any of the above

47. Sexual life cycle

48. Sexual reproduction Spores are typically produced May be produced after plasmogamy & karyogamy – diploid (zygospores) May be produced after meiosis – haploid (meiospores)

49. Reproductive phases Fungi may carry out sexual reproduction, asexual reproduction or both types The sexual reproductive phase is the teleomorph (perfect phase) The teleomorph is used in phylogenetic classification system No problem for those species that reproduce sexually or both sexually and asexually – can identify and classify based on teleomorph

50. Reproductive phases Asexual reproductive phase = anamorph (imperfect phase) For those fungi that only produce anamorph, there is a problem – can’t classify in the phylogenetic classification system for fungi Sometimes difficult to connect anamorph and teleomorph - holomorph Separate artificial classification scheme set up for anamorphs

51. Phylogeny of fungi Traditionally fungi were classified with plants Theories that fungi evolved from algae Today, considered that fungi did not evolve from algae and are not very closely related to plants – more closely related to animals

52. Evidence for phylogeny of fungi A number of lines of evidence that fungi are not closely related to plants Most compelling evidence comes from recent work comparing base sequences of rDNA and other genes among organisms

53. Kindom Fungi “lower fungi” –Zoosporic fungi – Chytridiomycota -706 spp, Blastocladiomycota –179 spp, Neocallimastigomycota -20 spp –“Zygomycota” – four subphyla –Glomeromycota – 169 spp. “higher fungi” –Ascomycota – 64,163 spp. –Basidiomycota – 31,515 spp.

54. Fungal phyla – lower fungi Zoosporic fungi Chytridiomycota Blastocladiomycota Neocallimastigomycota “Zygomycota”

55. Fungal phyla – higher fungi AscomycotaBasidiomycota

56. Classification Endings for major taxa of fungi –-mycota = phylum (division) –-mycotina = subphylum –-mycetes = class –-ales = order –-aceae = family