The Kingdom Fungi

1. The Kingdom Fungi • These morels are a type of fungus prized by many people for their distinctive flavor • Unlike the violets, fungi are not plants and do not produce their own food

2. The Kingdom Fungi

3. The Kingdom Fungi • In spring, if you know where to look, you can find one of the most prized of all foods—the common morel—growing wild in woodlands throughout the United States • Its ridged cap is often camouflaged by dead leaves that collect in abandoned orchards or underneath old oaks or tulip poplars • Some morels grow alone, but others grow in groups • They appear suddenly, often overnight, and live for only a few days • What are these mysterious organisms? • How do they grow so quickly?

4. KINGDOM FUNGI • Diverse group of over 65,000 species • Most fungi are saprophytic or parasitic, and a few are predatory • Saprophyte: • Is an organism that feeds on dead organic matter • Recycling the nutrients • Referred to as decomposers • Without decomposers, nutrients would not be reused and life could not continue on earth • Parasite: • Derives its nutrients from a living host organism at the host’s expense • Cause many plant and animal diseases • Predatory: • Captures prey for food • Example: Pleurotus ostreatus capture roundworms

5. What Are Fungi? • Like mushrooms and molds, morels are fungi • The way in which many fungi grow from the ground once led scientists to classify them as nonphotosynthetic plants • But they aren't plants at all • In fact, fungi are very different from plants

6. What Are Fungi? • Fungi are eukaryotic heterotrophs that have cell walls • The cell walls of fungi are made up of chitin, a complex carbohydrate that is also found in the external skeletons of insects • Recall that heterotrophs depend on other organisms for food • Unlike animals, fungi do not ingest their food • Instead, they digest food outside of their bodies and then absorb it • Many fungi feed by absorbing nutrients from decaying matter in the soil • Others live as parasites, absorbing nutrients from the bodies of their hosts

7. FUNGAL EVOLUTION • Precambrian fossils about 900 million years old • Late Carboniferous period, fossils indicate that all modern divisions of fungi had evolved • Most are terrestrial • Indicates adaptive radiation shortly after plants and animals colonized the land • Like all eukaryotes, arose from prokaryotes • Arose from other heterotrophs • Present theory is that they evolved from red algae

8. Structure and Function of Fungi • Except for yeasts, all fungi are multicellular • Multicellular fungi are composed of thin filaments called hyphae (singular: hypha) • Each hypha is only one cell thick • In some fungi, cross walls divide the hyphae into cells containing one or two nuclei • In the cross walls, there are tiny openings through which the cytoplasm and nuclei can move • Other hyphae lack cross walls and contain many nuclei

9. CHARACTERISTICS • Hypha: vegetative filament of the fungus • Types: • Septate: • Filaments with internal cross walls (septum) • Individual cells have nuclei • Coenocytic: • Filaments without internal cross walls (septum) • Filament contains many nuclei that move through the cytoplasm • Grows at the tip where new membrane material is added by the action of Golgi bodies • A mat of interwoven hyphae is called mycelium • Cell wall composed of chitin (not cellulose) • Complex polysaccharide also found in the exoskeleton of insects and other invertebrates • Store food as glycogen (like animals) • Reproduce asexually (spores)(fragmentation) and sexually (gametes) • Heterokaryotic hypha: genetically different nuclei coexist within a hypha • Homokaryotic hypha: genetically similar nuclei coexist within a hypha

10. STRUCTURE OF FUNGI

11. Structure of Two Types of Hyphae • Fungi are eukaryotes that have cell walls made of chitin • Most fungi are made up of filaments called hyphae • In some fungi, the hyphae are divided by cross walls • These cells may contain one or two nuclei • In other fungi, the hyphae lack cross walls and contain many nuclei

12. Structure of Two Types of Hyphae

13. HYPHAE TYPES

14. STRUCTURE OF FUNGI

15. Fungus Structure  • The bodies of multicellular fungi are composed of many hyphae tangled together into a thick mass called a mycelium • The mycelium (plural: mycelia) is well suited to absorb food because it permits a large surface area to come in contact with the food source through which it grows

16. Structure of a Multicellular Fungus • The body of a mushroom is part of a mycelium formed from many tangled hyphae • The major portion of the mycelium grows below ground • The visible portion of the mycelium is the reproductive structure, or fruiting body, of the mushroom

17. Structure of a Multicellular Fungus

18. Fungus Structure • What you recognize as a mushroom is actually the fruiting body of a fungus • A fruiting body is a reproductive structure growing from the mycelium in the soil beneath it • Clusters of mushrooms are often part of the same mycelium, which means that they are part of the same organism

19. Fairy Rings  • Some mycelia can live for many years • As time goes by, soil nutrients near the center of the mycelium become depleted • As a result, new mushrooms sprout only at the edges of the mycelium, producing a ring • People once thought fairies dancing in circles during warm nights produced these rings, so they were called “fairy rings” • Over many years, fairy rings can become enormous—from 10 to 30 meters in diameter

20. Reproduction in Fungi • Most fungi reproduce both asexually and sexually • Asexual reproduction takes place when cells or hyphae break off from a fungus and begin to grow on their own • Some fungi also produce spores, which can scatter and grow into new organisms • Recall that a spore is a reproductive cell that is capable of growing into a new organism by mitosis alone • In some fungi, spores are produced in structures calledsporangia(singular: sporangium) • Sporangia are found at the tips of specialized hyphae called sporangiophores

21. Reproduction in Fungi • Sexual reproduction in fungi usually involves two different mating types • Because gametes of both mating types are about the same size, they are not called male and female • Rather, one mating type is called “+” (plus) and the other “−” (minus)

22. Reproduction in Fungi • When hyphae of opposite mating types meet, they start the process of sexual reproduction by fusing, bringing plus and minus nuclei together in the same cell • After a period of growth and development, these nuclei form a diploid zygote nucleus • In most fungi, the diploid zygote then enters meiosis, completing the sexual phase of its life cycle by producing haploid spores • Like the spores produced asexually, these spores are also capable of growing, by repeated rounds of mitosis, into new organisms

23. How Fungi Spread • Fungal spores are found in almost every environment • This is why molds seem to spring up in any location that has the right combination of moisture and food • Many fungi produce dry, almost weightless spores • These spores scatter easily in the wind • On a clear day, a few liters of fresh air may contain hundreds of spores from many species of fungi

24. How Fungi Spread • If these spores are to germinate, they must land in a favorable environment • There must be the proper combination of temperature, moisture, and food so that the spores can grow • Even under the best of circumstances, the probability that a spore will produce a mature organism can be less than one in a billion

25. How Fungi Spread • Other fungi are specialized to lure animals, which disperse fungal spores over long distances • Stinkhorns smell like rotting meat, which attracts flies • When they land on the stinkhorn, the flies ingest the sticky, smelly fluid on the surface of the fungus • The spore-containing fluid will pass unharmed out of the flies' digestive systems, depositing spores over many kilometers

26. FUNGI CLASSIFICATION • Four Divisions: • Based primarily on the structure of hyphae or on the type of reproduction

27. Classification of Fungi • The kingdom Fungi has over 100,000 species • Fungi are classified according to their structure and method of reproduction • The methods by which fungi reproduce are unlike those of any other kingdom • The four main groups of fungi are: • Common molds (Zygomycota) • Sac fungi (Ascomycota) • Club fungi (Basidiomycota) • Imperfect fungi (Deuteromycota)

28. CLASSIFICATION OF FUNGI

29. The Common Molds • The familiar molds that grow on meat, cheese, and bread are members of the phylum Zygomycota, also called zygomycetes • Zygomycetes have life cycles that include a zygospore • A zygospore is a resting spore that contains zygotes formed during the sexual phase of the mold's life cycle • The hyphae of zygomycetes generally lack cross walls, although the cells of their reproductive structures do have cross walls

30. DIVISION ZYGOMYCOTA • Approximately 600 species • Mostly terrestrial organisms • Commonly found in soil and dung • Coenocytic hyphae • Example: Rhizopus Stolonifer • Bread mold • Three different types of hyphae: • Rhizoids: • Anchoring hyphae that penetrate the bread • Produce digestive enzymes, and absorb nutrients • Stolons: • Hyphae that grow across the surface of the bread • Sporangiophores: • Upright hyphae that produce sporangia at their tips which produce spores

31. Structure and Function of Bread Mold • Black bread mold, Rhizopus stolonifer, is a familiar zygomycete • Expose preservative-free bread to dust, and you can grow the mold • Keep the bread warm and moist in a covered jar, and in a few days dark fuzz will appear • With a hand lens, you can see delicate hyphae on moldy bread • There are two different kinds of hyphae: • The rootlike hyphae that penetrate the bread's surface are rhizoids • Rhizoids anchor the fungus to the bread, release digestive enzymes, and absorb digested organic material • The stemlike hyphae that run along the surface of the bread are stolons • The hyphae that push up into the air are the sporangiophores, which form sporangia at their tips • A single sporangium may contain up to 40,000 spores

32. Life Cycle of Molds  • The life cycle of black bread mold is shown in the figure • Its sexual phase begins when hyphae from different mating types fuse to produce gamete-forming structures known as gametangia ( singular: gametangium) • Haploid (N) gametes produced in the gametangia fuse with gametes of the opposite mating type to form diploid (2N) zygotes • These zygotes develop into thick-walled zygospores, which may remain dormant for months • When conditions become favorable, the zygospore germinates, then undergoes meiosis, and new haploid spores are released • The significance of this sexual process—zygote formation followed by meiosis—is that it produces new combinations of genetic information that may help the organism meet changing environmental conditions

33. ZYGOMYCOTARHIZOPUS STOLONIFER

34. Life Cycle of a Black Bread Mold • Zygomycetes have life cycles that include a zygospore • During sexual reproduction in the bread mold Rhizopus stolonifer, hyphae from two different mating types form gametangia • The gametangia fuse, and zygotes form within zygospore • The zygospore develops a thick wall and can remain dormant for long periods • The zygospore eventually germinates, and a sporangium emerges • The sporangium reproduces asexually by releasing haploid spores produced by meiosis

35. Life Cycle of a Black Bread Mold

36. DIVISION ZYGOMYCOTAASEXUAL REPRODUCTION • Hormonal action causes upright sporangiophores to form • Sporangia form at the tips of sporangiophores producing spores (sporangiospores) that are dispersed by the wind

37. SEXUAL AND ASEXUALREPRODUCTIONOF ZYGOMYCOTA

38. ZYGOMYCOTALIFE CYCLE

39. DIVISION ZYGOMYCOTASEXUAL REPRODUCTION • Called Conjugation • Two filaments line up next to each other • Hyphae of two mating strains come close together • Each hyphae encloses haploid (1N) nuclei • Hormones cause short branches to form on each hypha and grow outward until they touch • Septa form near the tip of each branch • Resulting cell is a gametangium (1N) that contains several nuclei • Gametangia fuse; then nuclei fuse in pairs (2N) • Each pair contains one nucleus from each mating strain (2N) • Zygote contains many diploid (2N) nuclei • Wall surrounding the zygote (2N) thickens forming a protective, temporary structure called a zygospore (2N) • Meiosis occurs when the zygospore germinates forming new hyphae (1N)

40. SEXUAL AND ASEXUALREPRODUCTIONOF ZYGOMYCOTA

41. ZYGOMYCOTALIFE CYCLE

42. ZYGOMYCOTASEXUAL REPRODUCTIONCONJUGATION

43. ZYGOTE

44. DIVISION ZYGOMYCOTAASEXUAL/SEXUAL REPRODUCTION • Provide adaptive advantages • Asexual Reproduction: • During periods when the environment is favorable • Rapid formation of spores ensures the quick spread of the species • Sexual Reproduction: • In periods of environmental stress • Ensures genetic recombination before the hyphae die

45. The Sac Fungi • Sac fungi, also known as ascomycetes, belong to the phylum Ascomycota • The phylum Ascomycota is named for the ascus, a reproductive structure that contains spores • There are more than 30,000 species of ascomycetes, making it the largest phylum of the kingdom Fungi • Some ascomycetes, such as the cup fungi, are large enough to be visible when they grow above the ground • Others, such as yeasts, are microscopic

46. DIVISION ASCOMYCOTA • Sac fungi • Approximately 30,000 species • Largest Division of Fungi • Live in a variety of habitats, including freshwater and saltwater • Morels, powdery mildews, yeast, and cup fungi

47. ASCOMYCETEEDIBLE MOREL

48. Life Cycle of Sac Fungi  • The life cycle of an ascomycete usually includes both asexual and sexual reproduction • The life cycle of a cup fungus is shown in the figure at right

49. Life Cycle of an Ascomycete • The life cycle of ascomycetes includes both asexual and sexual reproduction • During asexual reproduction, spores called conidia are formed at the tips of specialized hyphae called conidiophores • Duringsexual reproduction, hyphae of two mating types fuse to form hyphae with two haploid (monoploid) nuclei (N + N) • The N + N hyphae then form a fruiting body, which eventually releases ascospores • Ascomycetes are named for the ascus, the reproductive structure that contains ascospores

50. Life Cycle of an Ascomycete