1. School of Sciences, Lautoka Campus BIO509 Botany Lecture 9: Kingdom Fungi

2. Fungi are heterotrophic organisms that were considered as primitive plants lacking chlorophyll. The only characteristic that fungi share with plants other than those common to all eukaryotes is a multicellular growth. They are so distinctive in life forms that they assigned to their own kingdom. Lets find out why?

3. Learning outcomes
Know in what ways do fungi differ from other kingdoms.
Distinguish major groups – Phylum Chytridiomycota, Phylum Basidiomycota, Phylum Ascomycota, Phylum Zygomycota and Phylum Deuteromycota.
Know the kinds of symbiotic relationships that exist between fungi and other organisms.
Understand and appreciate their importance.

4. Morphologically and ecologically diverse
100,000 species described, but may be as many as ~1.5 million un-described
A few are unicellular e.g. Yeasts
Mostly filamentous, the “typical” fungal body consists of many filaments stuck together

5. The filaments are called hyphae (singular hypha)
Septate hyphae, the hyphae are subdivided into cells that are multinucleate
Coenocytic hyphae consist of a continuous cytoplasmic mass that is multinucleate
Together all of the hyphae of a single organism is called the mycelium
Parasitic fungi usually have some of their hyphae as haustoria (nutrient absorbing tips)

7. Generalized life cycle of fungi

8. All fungi are heterotrophic
Saprophytes feed on non-living material
Parasites/disease-causing feed on living tissues
Some obtain energy from fermentation, produce ethyl alcohol from glucose

9. Fungi are important decomposers
Fungi and bacteria are the only organisms that can decompose lignin – the molecule that makes wood hard
Lignin must be broken down before further decomposition can occur

10. The rigid wall means fungi can not engulf food
Fungi have a rigid cell wall made of chitin, a polysaccharide that insects and arachnids use in their exoskeletons
The rigid wall means fungi can not engulf food
Secrete enzymes onto there food and absorb the released molecules

11. Basidiomycota – cap fungi ~22300 spp. Ascomycota – sac fungi
Several major groups
Basidiomycota – cap fungi
~22300 spp.
Ascomycota – sac fungi
~75000 spp.
Zygomycota – coenocytic true fungi
Deuteromycota – fungi imperfecti

12. Decompose almost everything; food spoilage
Negative impacts
Decompose almost everything; food spoilage
Disease causing, produce toxins
Human uses
Used in brewing, baking, cheese making and wine-making
Production of antibiotics and other medicines

13. Phylum Chytridiomycota- The chytrids
Majority of species are aquatic.
Simple, mostly one celled.
Parasites of protists, aquatic fungi, aquatic plants and algae.
Common chytrids consist of spherical cell with branching rhizoids.
Others may have coenocytic (multinucleate mycelia without crosswalls).
Asexual reproduction by production of zoospores.
Sexual reproduction by fusion of two motile gametes.
Chytrids are the only fungi with a flagellated stage.

14. Numerous parasitic chytrids attack the filament of a green alga
Sporangium
rhizoids
The thallus of a chytrid fungus, with a single round sporangium and rhizoids
Numerous parasitic chytrids attack the filament of a green alga

15. Life cycle of chytrids
Sexual reproduction
Asexual

16. One Chytrid species Batrachochytrium dendrobatidis is responsible for a recently discovered disease of amphibians.
This disease is known to kill amphibians in large numbers, and has been suggested as a principal cause for the worldwide amphibian decline.
A popular theory is the fungus hardens the skin of amphibians which hinders respiration.
Chytrids may also infect plant species – maize, alfalfa, potatoes

17. Phylum Zygomycota About 1,060 species with coenocytic hyphae.
Terrestrial fungi.
Some unicellular.
Most heterothallic
(require + and – strains
for fertilisation).
Include the common bread mold
Asexual and sexual reproduction

18. Life cycle of Rhizopus stolonifer
(n +n)
(n)
(2n)

19. The mycelium occur in two different mating strains (+ mycelium and – mycelium) although there is no visible difference between the two.
When a hypha of one strains encounters that of the opposite strain, the chemicals they produce create an attraction – producing swellings at the ends called progametangia.
The two progametangia fuse to form a gametangium and their contents (nuclei) fuse in pairs.

20. Some species produce spores externally on hyphae instead producing them in sporangium.
Dung-inhabiting fungi Pilobolus produces spores externally.
The fungus can only reproduce in fresh dung hence has special spore dispersal mechanism.

22. Ecological and Human Relevance of coenocytic true Fungi
One species of bread molds is used to produce a food (tempeh) in Asia from soybeans.
It consists of boiled, skinless soybeans that have been inoculated with the bread mold and allowed to stand for 24 hrs. The mycelium develops and holds the soybeans together. It produces several B vitamins and makes the soybean protein content even higher.
Tempeh is fried, roasted or cooked as soup.
Another species of bread mold is used with soybeans to produce Chinese cheese called sufu

23. Used commercially to produce birth control pills and anesthetics.
Also used to produce industrial alcohols and meat tenderizers.
Another species produces yellow pigment used for coloring margarine.

24. Two genera of zygomycetes cause disease in plants.
- Rhizophus causes soft rot of many flowers, fleshy fruits, seeds, bulbs and corms.
- Choanephora causes a soft rot of squash, pumpkin, okra and pepper.

25. How do cells of fungi differ from those of other organisms?

26. Phylum Ascomycota More than 30,000 species.
Most diverse phylum being significant decomposers, agricultural pests (e.g., Dutch elm disease, powdery mildews of crops) and pathogens of humans and animals.
Called cup or sac fungi because of the shape of their reproductive structures.
Have septate hyphae.
Asexual reproduction by production of conidia. In yeast is by budding.
Sexual reproduction through formation of asci.
Has well developed dikaryotic stage (pairs of nucleus in cells, each derived from a different parent).

27. Asexual Reproduction in yeast
In yeast , it is through budding. Nucleus divides and a small part balloons out from the cell.
One daughter nucleus moves into this bud which pinches off

30. Human and ecological significance
Morels and truffles are edible and priceless delicacies.
The ergot fungus can sometimes infect wheat and cause a disease called ergotism if bread contaminated with this fungus is eaten. It causes hysteria, convulsions, and sometimes death.
In controlled doses the ergot drugs can have medicinal use in childbirth, treatment of migraine headaches.

31. Yeast is used in baking, alcohol preparation.
Enzymes produced by yeast aid in fermentation producing alcohol and CO2.
Trapped CO2 in bread dough gives bread its texture.
Yeast is used to ferment fruits and grains to flavor alcoholic beverages.
yeast is rich source of vitamin B.
Yeast is high in protein and makes a nourishing feed for livestocks.

32. Fungi in this Division also cause a number of plant diseases
Peach leaf curl
Oak wilt disease
Chestnut blight

33. One interesting sac fungi the parasitic fungi of genus Cordyceps.
Have over 400 described species.
Their hosts are usually insects.
One species parasitizes ants and can change its victim's behaviour.
The fungus makes the ant to climb up a plant where it dies.
High up on the plant the fungus's fruiting body grows out of the victim's body, allowing the spores to be more widely distributed by the wind.
Some species, such as the caterpillar fungus, are considered to have medicinal properties in China and Tibet.

34. Phylum Basidiomycota About 22,300 species of most familiar fungi.
Includes mushrooms, toadstools, stinkhorns, puffballs and shelf fungi.
Includes smuts and rusts that are plant pathogens.
Septate perforated hyphae.
Sometimes have clamp connections.
Produce basidia (swollen hypal tips) during sexual reproduction resembling clubs.

35. Clamp connections form as a result of a unique type of mitosis so that each cell has one nucleus of each original mating type within it.

36. Asexual Reproduction
Less common in club fungi compared to the other Divisions.
Can occur either through conidia or buds (like in yeast). Some have hyphae that fragment into individual cells. These form new mycelia.

37. Sexual Reproduction
When a spore falls on suitable ground (moisture, and organic matter) it germinates and produces mycelium just beneath the surface.
The cells of the hyphae which form contain haploid nucleus. These are known as monokaryotic mycelium
When two compatible mycelia come close together they unite to form dikaryotic mycelium.
The dikaryotic mycelium develops into a button which pushes above the ground and forms a basidium (mushroom).

38. Most mushrooms have a cap (pileus) and stalk (stipe)
Most mushrooms have a cap (pileus) and stalk (stipe). Some have rings on the stalk called annulus.
Thin, fleshy looking plates on the underside of the cap are called the gills.
Fertilization occurs inside the gills in basidia forming zygotes
This is followed by meiosis and basidiospores are formed.
These are forcibly discharged into the air around the gills from where they discharged.

39. Life cycle of a typical mushroom
(n + n)
(n)
(2n)

40. Stink horns
Earth stars

41. Mushrooms
Bracket or shelf fungi

42. Giant puffballs
Bird’s nest fungi

43. Fairy Ring The mushroom appear periodically toward the edge of a dykaryotic mycelium that grows out from a point where the first diakaryotic cell was initiated

44. Smuts and Rusts do not form basidia
Smuts damage corns, wheat and other grain crops.
In corn smut mycelium grows between the cells of the host, absorb nutrients and form tumors.
Tumors break open to release spores.

45. Rusts attack a wide range of crops.
Most rusts are heteroecious - require two or more different hosts to complete their life cycle.

46. Puccinia graminis causes black stem rust in wheat
Puccinia graminis causes black stem rust in wheat. It reproduces on asexually on wheat.
For sexual reproduction to take place, the rust must spend part of their life cycle on barberry and part on wheat.

47. If all rusts had one host, would they be easier to control?

48. Human and Ecological Relevance of the Club Fungi
Of the 25,000 species known 75 are poisonous
It is sometimes difficult to distinguish between the edible ones from the poisonous ones
Inky cap mushroom
Shiitake mushroom
Commercial mushroom farm

49. The inky cap and shaggy mane mushrooms are edible but can make one very ill if consumed with alcohol.
Shiitake mushrooms are high in calcium, phosphorus and iron and grown in China and Japan for consumption.
Lentinacin, a cholesterol lowering substance has been found in Shiitake mushrooms

50. Phylum Deuteromycota – the Imperfect fungi.
Fungi for which the sexual stage has not been observed are known as imperfect fungi.
They reproduce by means of conidia asexually.
One species grows on dead leaves and debris, at the bottom of streams.

51. Another group parasitizes protozoans and other small animals.
Some enter the victims’ bodies and absorb nutrients through haustoria until the host dies.
Some well known members include Aspergillus and Penicillium where sexual state is known but they resemble Deutromycetes.

52. Human and Ecological Relevance of Imperfect Fungi
The fungi Penicililum mold which secretes penicillin is used as a source of antibiotic.
It prevents bacterial growth another drug from a group of imperfect fungi is used during organ transplant since it suppresses reactions which cause rejection of transplanted organs.
Antibacterial action of Penicillium

53. The fungi Aspergillus is used in flavoring foods, the development of photographic dyes, inks.
Aspergillus is also used to produce artificial flavoring and perfume substances.
One species of Aspergillus is used in Asia to produce soy sauce.

54. These fungi also cause a number of human diseases
These fungi also cause a number of human diseases. They attack the respiratory tracts, human ears, athletes' foot, etc.
Aspergillus flavus which grows on moist seeds secretes aflatoxin that is the most potent carcinogen known.

55. Questions??