Chapter 31 - Fungi
Metagenomics
a huge study of genetic material recovered directly from environmental samples
Body structure of Fungi
- mostly multicellular - some are single - yeasts Many grow as both, but most grow as only as filaments; relatively few grow as yeasts Hyphae - a filament that collectively moves up the body of the fungus. Networks of tiny filaments. Tubular cell walls strengthened with chitin Chitin - a strong but flexible polysaccharide that makes up the cell wall of fungi (structural polymer) •Chitin-rich walls prevent cells from lysing (bursting) due to the osmotic pressure that builds up during nutrient absorption mycelium - the branched network of hyphae that allows for feeding
Fungi diversity in the ecosystem?
-Decomposers break down and absorb nutrients from nonliving organic material -Parasitic fungi absorb nutrients from living hosts -Mutualistic fungi absorb nutrients from hosts and reciprocate with actions that benefit the host (their relationship is mutual)
What are the two types of mycorrhizal fungi?
-Ectomycorrhizal fungi form sheaths of hyphae over the root surface and extend into the extracellular spaces of the root cortex -Arbuscular mycorrhizal fungi extend arbuscules through (penetrates) the root cell wall and into tubes formed by invagination of the root cell plasma membrane •Most vascular plants depend upon mycorrhizae •Mycorrhizal fungi colonize soils by the dispersal of haploid cells called spores
•Fungi may have colonized land as early as ______ million years ago
505
Fungi Phylums
Cryptomycetes microsporidians chytrids zoopagomycetes mucoromycetes ascomycetes basidiomycetes
how does fungi feed?
Fungi are heterotrophs that feed by absorption. They use hydrolytic enzymes to break complex molecules into smaller organic compounds there are no internal digestive system. Despite their diversity, fungi share key traits, most importantly the way in which they derive nutrition
What kind of species are mushrooms?
heterotroph, multicellular, unicellular
after karyogamy
Fungi undergo meoisis, where the haploid nuclei fuse, a diploid cell, such as a zygote, is produced
Asexual reproduction in fungi
Hyphae breaks off & grows on its own or Sporangia release spores that scatter & grow
How does hyphae grow?
Hyphae grow primarily in length—not girth—using cytoplasmic streaming to move materials to the tips
pheromones
Many fungi use sexual signaling molecules called pheromones to communicate their mating type
How does fungi colonize new territory?
Multicellular fungi are not motile, but can colonize new territory through the growth of their hyphae
Does fungi on reproduce asexually or sexually?
No, some use both reproduction, others use on or the other
Stages of fungi reproduction
Plasmogmy, heterokaryote, meosis - zygote, spores, mycelium
How does fungi digest and absorb their food?
To begin their extracellular digestion, fungi must first release many digestive enzymes, these enzymes decompose complex molecules, like cellulose, rna, proteins and fat into simple subunits like glucouse, nucleic acid, amino acids, and fatty acids. Once these smaller monomers are produced the fungal cell absorbs them into a cytoplasm, where they are used for energy for the fungal cell or as building blocks for fungal macromolecules
dikaryotic
Referring to a fungal mycelium with two haploid nuclei per cell, one from each parent.
How does reproduction in Fungi produce asexually?
Reproduction occurs through simple cell division or pinching of small "bud cells" off a parent cell
Arbuscules
Specialized branching hyphae that are found in some mutualistic fungi and exchange nutrients with living plant cells.
What is the ancestor of fungi?
The ancestor of fungi was an aquatic, single-celled, flagellated protist •Fungi and animals are more closely related to each other than either group is to plants or most other eukaryotes
Life Cycle of mushroom-forming basidiomycte
The life cycle of a mushroom-forming basidiomycete Long Description: The cycle is as follows. 1.Two haploid mycelia of different mating types undergo plasmogamy. 2.A dikaryotic mycelium forms, growing faster than, and ultimately crowding out, the haploid parental mycelia. 3.Environmental cues such as rain or change in temperature induce the dikaryotic mycelium to form compact masses that develop into basidiocarps (mushrooms, in this case). 4.The basidiocarp gills are lined with terminal dikaryotic cells called basidia. 5.5). Karyogamy in each basidium produces a diploid nucleus, which then undergoes meiosis. 6.Each diploid nucleus yields four haploid nuclei, each of which develops into a basidiospore (SEM). 7.When mature, the basidiospores are ejected and then dispersed by the wind. 8.In a suitable environment, the basidiospores germinate and grow into short-lived haploid mycelia.
after the zygote is produced
The short-lived diploid cell undergoes meiosis, producing haploid spores
What is the function of the hyphae?
absorb nutrients by secreting enzymes that break down organic matter than releases nutrients than other organisms surrounding the fungi will absorb that nutrient
•Fungi likely originated in _______ habitats, but the oldest widely accepted fossils are of terrestrial species from ___ million years ago
aquatic, 440
Microsporidians
are unicellular parasites of protists and animals, including humans -For example, Nosema ceranae is a parasite of honeybees that may contribute to Colony Collapse Disorder •Microsporidians can synthesize a chitin-rich cell wall •They have highly reduced mitochondria and small genomes with as few as 2,000 genes •Instead of flagellated spores, they produce spores that infect host cells via a harpoon-like organelle
How do structure and function in fungi relate to their role in ecosystem?
as they grow, the fungi extends filaments called hyphae into their surroundings by absorbing and releasing nutrients back into the environment - decomposers in the ecosystem of almost any organic molecule. -spores enable fungi to colonize new environments.
A mycelium that contains coexisting, genetically different nuclei is called a
heterokaryon unfused nuclei from different parents
•Animals are most closely related to a different group of protists called ______________.
choanoflagellates
•In most fungi, fusion between the haploid nuclei of the parents is ______
delayed. before sexual reproduction can move forward.
In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be
dikaryotic
•Molecular clock analysis indicates that animals and fungi ________ more than a billion years ago
diverged
•Multicellularity likely evolved independently in _______ and animals
fungi, animals
Hyphae cell walls, there are two differences what are they?
in most fungi, hyphae are divided into cells by cross-walls, or septa (separations) with pore (the pores allow micro organelles (cytoplasm and nutrients through out mycelium) to move through the different compartments) Septa have pores large enough to enable cell-to-cell movement of organelles Coenocytic fungi lack septa; they have hundreds or thousands of nuclei in a continuous cytoplasmic mass
What paired processes produces fungi variation?
karyogamy and meiosis
dotted phylogeny branch means
scientist does not know where to put those particular group
Fungi produce spores through ?
sexual or asexual life cycles •Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually •Spores are carried long distances by wind or water •If they land in a moist place with food, they will germinate and form new mycelia
Fungi reproduces?
sexually and asexually by producing spores which are dispersed by wind. which lands and begin to germinate and grow into long branching hyphae, a tangled network of hyphae is called mycelium that can cover hundreds of acres As mycelia grows they release nutrients into their surroundings. these enzymes break down decaying matter, liberating sugar and amino acid
where is the top portion of the fungi?
they are spore producing structures
Yeasts
unicellular fungi Yeasts inhabit moist environments with plentiful soluble nutrients, such as sugars or amino acids
•Mutualistic fungi have specialized branching hyphae for?
used to exchange nutrients with their plant hosts -For example, arbuscules are specialized hyphae found in mutualistic fungi, that penetrate plant cell walls, but not the cell membrane (the cell membrane is forming around this structure, but not able to penetrate inside of the cell)
Life cycle Basidiomycetes
•A mushroom results from a concentrated growth of hyphae that forms from the dikaryotic mycelium •The cap of the mushroom supports and protects a large surface area of dikaryotic basidia on gills •Karyogamy occurs within the basidia, immediately followed by meiosis •Sexually produced basidiospores are ejected and dispersed by wind
Ascomycetes (phylum Ascomycota)
•Ascomycetes are often called sac fungi, named for the saclike asci, in which spores are produced •During the sexual stage, ascomycetes produce fruiting bodies called ascocarps •The ascocarps contain the spore-forming asci
Ascomycetes (phylum Ascomycota)
•Ascomycetes include plant pathogens, decomposers, and symbionts •More than 25% of all ascomycete species form lichens, symbiotic associations with green algae or cyanobacteria •Some form mycorrhizae with plants; others live within plant leaves and produce compounds toxic to insects
Ascomycetes (sac fungi) reproduction
•Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia •Conidia are produced at the tips of specialized hyphae called conidiophores
What role does basidiomycetes play?
•Basidiomycetes are important decomposers of wood •Certain basidiomycetes are the best at decomposing lignin, a complex polymer abundant in wood
Basal fungal lineage
•Cryptomycetes (phylum Cryptomycota) and microsporidians (phylum Microsporidia) form a sister group and are a basal fungal lineage
Fungi Sexual Reproduction
•Fungal nuclei and spores are usually haploid •Some species have transient diploid nuclei formed during the sexual life cycles •Sexual reproduction requires the fusion of hyphae from different mating types •Many fungi use sexual signaling molecules called pheromones to communicate their mating type
How do structure and function in fungi relate to their role in ecosystems?
•Fungi are diverse, widespread, and essential for the well-being of most ecosystems •Some are single-celled, though most are complex multicellular organisms
Fungi are most closely related to several groups of ___________ _____ protists
•Fungi are most closely related to several groups of single-celled protists -For example, nucleariids are closely related amoebas that feed on algae and bacteria
The move of fungi to land
•Fungi were among the earliest colonizers of land •Fossil evidence supports the formation of mutualistic relationships between fungi and early plants •Molecular analysis indicates that sym genes required for mycorrhizal formation were present in early plants
Mucoromycetes (Zygomycota)
•In deteriorating conditions—for instance, most of the food is consumed—sexual reproduction may occur •Fusion between mycelia of different mating types (plasmogamy) produces a zygosporangium •Nuclei fusion (karyogamy) and then meiosis occur within the zygosporangium
Ascomycetes (sac fungi) reproduction
•In sexual reproduction, conidia fuse with the hyphae of a mycelium from a different mating type •Dikaryotic cells are formed, each containing two haploid nuclei, one from each parent •Asci form at the tips of dikaryotic hyphae, and karyogamy and meiosis occur within the asci •Ascospores develop and are discharged from the ascocarp after they are formed on the inside
What fungi produces asexually?
•Molds produce haploid spores asexually by mitosis, and form visible, "furry" mycelia WILL BE ON TEST: Molds are one of the few of fungi that reproduce ASEXUALLY. •Single-celled yeasts reproduce asexually without producing spores
Fungi have radiated into a diverse set of lineages
•Molecular analyses have helped clarify evolutionary relationships among fungal groups •Metagenomic studies have led to the discovery of entirely new groups
Mycorrhizae
•Mutually beneficial relationships between fungi and plant roots are called mycorrhizae ("fungus roots") -Mycorrhizal fungi deliver phosphate ions and minerals to plants •In exchange, plants supply organic nutrients to the fungi
Ascomycetes (phylum Ascomycota)
•Neurospora crassa, a bread mold, is a model research organism •Its entire genome was published in 2003 •Neurospora has about three-fourths as many genes as the fruit fly Drosophila and about half as many as a human
Crytomycetes
•Only 30 species are known, but genetic data suggest cryptomycetes are a large, diverse group •They are found globally in soils, and marine and freshwater habitats •There are both aerobic and anaerobic species •Many species are parasites of protists and other fungi •Cryptomycetes are unicellular and have flagellated spores •Like other fungi, they can synthesize a chitin-rich cell wall
Mucoromycetes
•Phylum Mucoromycota also includes an arbuscular mycorrhizae-forming clade of fungi called glomeromycetes •About 85% of all plant species have mutualistic partnerships with arbuscular mycorrhizae
Some fungi has specialized hyphae, what are they and what do they do?
•Some fungi have specialized hyphae for feeding on live animals •Others have specialized hyphae called haustoria that allow them to extract nutrients from plants
Mucoromycetes
•Some mucoromycetes, such as Pilobolus, can "aim" and shoot their sporangia toward bright light
Mucoromycetes (Zygomycota)
•The life cycle of Rhizopus stolonifer (black bread mold) is fairly typical of mucoromycetes •Coenocytic hyphae spread and penetrate the surface, absorbing nutrients from the rotting food •Sporangia develop at the tips of upright hyphae, and asexually produce hundreds of air-dispersed spores
Life Cycle of Basidiomycetes
•The life cycle of a basidiomycete usually includes a long-lived dikaryotic (2 karyotes present) mycelium •The mycelium can reproduce sexually by producing fruiting bodies called basidiocarps -For example, the common white mushrooms found in supermarkets are basidiocarps
What clad does fungi belong to?
•The opisthokonts clade includes fungi, animals, and their protistan relatives •Opisthokonts evolved from a unicellular flagellated ancestor, meaning the fungi lost the flagellated feature
Basidiomycetes (phylum Basidiomycota)
•The phylum is named for the basidium, a cell in which karyogamy and meiosis occur •The club-like shape of the basidium gives rise to the common name club fungus
Fungi
•There are 145,000 known species of fungi; estimates of the actual number lie between 2.2 and 3.8 million
Basidiomycetes aka club fungi
•There are about 50,000 known species of basidiomycetes (phylum Basidiomycota) including mushrooms, puffballs, and shelf fungi •Some are mutualists that form mycorrhizae •Others are destructive plant parasites: rusts and smuts
Chytrids (Chytridiomycota)
•They are found in lakes, soil, and marine habitats including hydrothermal vents •They include species that function as decomposers, parasites, and mutualists •Nearly all chytrids have flagellated spores, called zoospores •Like other fungi, the cell walls are made of chitin •Some are single-celled; others form colonies
Zoopagomycetes
•They live as parasites or commensal symbionts of animals, or as parasites of other fungi or protists •Zoopagomycetes form filamentous hyphae and reproduce asexually via nonflagellated spores •Some species induce behavioral changes in the insects they parasitize
Ascomycetes (phylum Ascomycota)
•They live in a variety of marine, freshwater, and terrestrial habitats •They vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels
Zoopagomycetes
•Those that reproduce sexually form a durable structure called a zygosporangium •The zygosporangium houses and protects the zygote •This structure is also produced by some mucoromycete species
Zoopagomycetes
•Unlike more basal species, zoopagomycetes and their close relatives have nonflagellated, wind dispersed spores •This change was likely associated with the transition from aquatic habitats to life on land
What fungi do not have any known sexual stage?
•Yeasts and filamentous fungi that have no known sexual stage form a group called deuteromycetes •They are reclassified if a sexual stage is discovered •Genomic techniques are also used to classify fungi
Mucoromycetes
•Zygosporangia are metabolically inactive and resistant to freezing and drying •When conditions improve, meiosis occurs and the zygosporangium germinates into a sporangium •The sporangium releases genetically diverse haploid spores
karyogamy
•a process where it can take hours, days, or even centuries before the nuclei fuse
Plasmogamy
•is the union of cytoplasm from two parent mycelia
Mucoromycetes
•mucoromycetes (phylum Mucoromycota) •Molds in this group include important decomposers -For example, Rhizopus stolonifer is the mold responsible for breaking down bread •Many others live as parasites, pathogens, or mutualists with plants (including some mycorrhizae)
