BIOL 172 4 Fungi Fall 2024.pdf

Fungi BIOL 172  Diplomonads Excavata Parabasalids Euglenozoans...

Fungi BIOL 172  Diplomonads Excavata Parabasalids Euglenozoans Stramenopiles Diatoms Golden algae Brown algae “SAR” clade Dinoflagellates Alveolates Apicomplexans Ciliates Forams Rhizarians Cercozoans Radiolarians Archaeplastida Red algae Chlorophytes Green algae Charophytes Land plants Amoebozoans Slime molds Tubulinids Entamoebas Unikonta The supergroup Unikonta Nucleariids Opisthokonts Fungi includes animals, fungi, Choanoflagellates Animals and some protists  What Are Fungi? Fungi are single-celled or multicellular heterotrophic eukaryotes. To date, over 100,000 species of fungi have been discovered, but there’s probably over one million. Fungi can live in many habitats including the arctic, tropical rainforest, fresh and salt water. However, most fungi live in soil.  What Are Fungi? Fungi have a cell wall, like plants do, but it is composed of chitin, the same material that covers insects. Fungi are non-vascular: they have no internal pipes to distribute nutrients. Fungi are non-motile (they don’t move).  Eukarya Land plants Dinoflagellates Green algae Forams Ciliates Diatoms Red algae Amoebas Cellular slime molds Euglena Trypanosomes Animals Leishmania Fungi Fungi are more closely related to animals than to plants. Over 70 species of fungus are bioluminescent What is the biggest organism ever? Apatosaurus? Blue whale? Redwood? A single clone of the “honey mushroom” Armillaria can cover more than 1800 football fields. The main “body” of the fungus is made up of thin, thread-like filaments that are called hyphae. A mass of hyphae is called a mycelium. Hyphae Reproductive structure Spore-producing structures 60 m Mycelium Most fungi have hyphae divided into cells by septa, with pores allowing movement of organelles. Coenocytic fungi lack septa and have a continuous cytoplasmic mass with hundreds or thousands of nuclei. Cell wall Nuclei Cell wall Pore Septum Nuclei (a) Septate hypha (b) Coenocytic hypha  Fungi obtain food by extracellular digestion and absorption: secrete digestive enzymes into the environment, then absorb the nutrients released. Most fungi are decomposers: live on decaying organisms. Some fungi are parasites: extract food from living organisms. Few are predators: paralyzing prey “Ringworm” and athlete’s foot are caused by parasitic fungi that feed on the keratin in skin cells. Some unique Nematode Hyphae 25 m predatory fungi have specialized hyphae for capturing prey. (a) Hyphae adapted for trapping and killing prey Fungi can extract or Fungal hypha Plant exchange nutrients cell wall with plants with specialized hyphae called haustoria that Plant cell penetrate the tissues Plant cell plasma Haustorium of their host. (b) Haustoria membrane  Mycorrhizae Mycorrhizae are mutually beneficial relationships between fungi and plant roots. Mycorrhizal fungi either grow into the extracellular spaces of the root or extend hyphae directly through the cell walls of the root. Most plants have mycorrhizae and rely upon the fungi to obtain phosphate ions and minerals. Soybean Soybean treated with with fungicide mycorrhizae  Lichens A lichen is a symbiotic association between a photosynthetic protist (algae) or bacteria and a fungus. The algae provide carbon compounds, bacteria also provide organic nitrogen, and fungi provide the environment for growth. Millions of algae or bacteria occupy an inner layer below the lichen surface. The symbioses are so complete that they are given single Fungal species names. hyphae Algal layer Fungal hyphae Algal cell  Fungi Life Cycles Fungi reproduce by means of spores, which can be sexual (the products of meiosis) or asexual (the products of mitosis). Asexual reproduction is more common than sexual. Fungi are haploid for most of their life cycle, becoming diploid only for the purpose of meiosis.  Key Haploid (n) Heterokaryotic stage Heterokaryotic PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures SEXUAL Zygote REPRODUCTION Spores ASEXUAL Mycelium REPRODUCTION MEIOSIS GERMINATION GERMINATION Spore-producing structures Spores  Fungi Sexual Reproduction Plasmogamy is the union of cytoplasm from two parent mycelia. In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon. If the nuclei pair off two to a cell the fungus is dikaryotic. Karyogamy is the fusion of nuclei to produce diploid cells.  Fungi Asexual Reproduction Molds are fungi that produce visible mycelia and produce haploid spores through mitosis.  Fungi Asexual Reproduction Other fungi that can reproduce asexually are yeasts, which are single cells. Instead of producing spores, yeasts reproduce asexually by simple cell division and the pinching of “bud cells” from a parent cell. Some fungi can grow as yeasts and as mycelia.  Hyphae 25 m Chytrids Chytrids are widespread in lakes Zoopagomycetes and soils and include decomposers and parasites. Fungal hypha 25 m Mucoromycetes Zoopagomycetes include parasites and commensals Ascomycetes (>90,000 species) Mucoromycetes Include molds and Basidiomycetes form mycorrhizae (>50,000 species)  Ergot of rye is caused by an ascomycete, and produces toxins More than 40,000 people died from an epidemic of ergotism during the Middle Ages Ergotism could include gangrene, nervous spasms, burning sensations, and hallucinations Ergots contain lysergic acid, the raw material for LSD Saccharomyces cerevisiae is an ascomycete used to make beer!  Shelf fungi Basidiomycetes include mushrooms, puffballs, and shelf fungi, mycorrhizae, and plant parasites. Many basidiomycetes are decomposers of wood Puffballs emitting spores Maiden veil fungus (Dictyphora)  Dikaryotic Key PLASMOGAMY mycelium Haploid (n) Dikaryotic (n + n) Mating Diploid (2n) type (−) Mating type (+) Haploid mycelia Gills lined with basidia SEXUAL Basidiocarp REPRODUCTION (n + n) Dispersal and germination Basidiospores (n) Basidium with Basidia Basidium four basidiospores (n + n) Basidium containing four haploid nuclei KARYOGAMY MEIOSIS When conditions are right the 1 m Diploid dikaryotic mycelium produces Basidiospore nuclei spore-bearing structures called basidiocarps (mushrooms).