Fungi Notes Fungi Fungi are more closely related to animals than plants. Mycology is the study of fungi. Opisthokonta Includes fungi, choanoflagellates, and animals. Earliest Fungus Last common ancestor with animals at least 1.2 billion years ago. Potential specimens as old as 2.4 billion years. Fossil fungus from 715 MYA. Florescent dye binds to chitin. Major Fungi Groups Seven major groups:Blastocladiomycota Zygomycota Neocallimastigomycota Chytridiomycota Glomeromycota Basidiomycota Ascomycota Blastocladiomycota Only fungi with a haplodiplontic lifecycle. Neocallimastigomycota Group of fungi found within the digestive tract of animals to break down cellulose. Chytridiomycota Many pathogenic species, targeting both plants and animals. Glomeromycota Plant symbionts. Require plant hosts to survive. Basidiomycota Mushrooms! Most familiar fungal group. Ascomycota Yeasts, molds, and morels are members of this group. General Characteristics of Fungi Four shared characteristics:Presence of hyphae Cell walls made of chitin Multinucleated cells Closed mitosis Heterotroph decomposers Hyphae Filaments, strings of cells. Underground, and often has continuous cytoplasm among all cells. Septa with pores separates individual cells. Able to rapidly share nutrients throughout an individual → Leads to rapid growth Mycelium Mass of connected hyphae. Capable of growing into different materials and leads to digestion of adjacent organic material. Produces above-ground reproductive structures in some groups (Mushrooms!). Cell Walls Cell walls made of chitin à Same protein made by animals. Plant and protist cell wall protein à Cellulose Multinucleated Cells A single cell can have two or more nuclei:Monokaryotic = One nucleus Dikaryotic = Two nuclei, usually two haploid nuclei Dikaryotic cell differs from diploid cell because haploid nuclei are separate and both undergo transcription. Dikaryotic Cells Two types of dikaryotic cells:Heterokaryotic = Two nuclei from genetically distinct individuals Homokaryotic = Two nuclei from genetically similar individuals Closed Mitosis Linked nature of cells à Cell is not relevant unit of reproduction Nuclear envelope does not break down à spindle apparatus forms within Reproduction Can undergo asexual and sexual reproduction. Sexual reproduction:Two haploid hyphae fuse à Forms heterokaryotic stage, which forms spores. Spores Can form from either sexual or asexual reproduction, typically forms from an above-ground structure. Spores are spread via wind and germinate to form new mycelium. Heterotroph Decomposers Does not undergo photosynthesis, and absorbs nutrients directly from the environment. External digestion à Hyphae secrete digestive enzymes into surrounding environment and absorb broken down organic material. Wood Decomposers Fungi are the only major organism capable of breaking down lignin à Major organic molecule within plant cell walls that forms wood. Also efficient at breaking down cellulose in plant cell walls. Fungi are capable of breaking down nearly every organic molecule, so are an important tool in bioremediation! Fungi Ecology Principle decomposer in the biosphere. Three major roles:Breakdown organic materialBreaks down all types of organic material. Even insoluble material such as cellulose and lignin. Return substances to circulate in ecosystemEspecially important for carbon, nitrogen, phosphorous Ecological interactions à Symbiotic relationshipsMany types of interactions, including beneficial and costly interactions Commensalism and Mutualism Recall commensalism and mutualism Endophytes Live within plants, produce toxins to prevent herbivory Lichens Symbiosis between fungi and photosynthetic organism Mycorrhizae Fungal association with plant roots Animal Mutualism Live within animals to help breakdown plant material Endophytes Live within plants, produce toxins to prevent herbivory Lichens Symbiosis between fungi and photosynthetic organism à Typically green algae or cyanobacteria. Provides nutrients to fungus. Fungus protects photosynthetic organism from desiccation à Capable of living in extreme environments Mycorrhizae Fungal association with plant roots that functions as an extensive root system. Two types:Arbuscular mycorrhizae à Fungus penetrates outer cell wall of plant Ectomycorrhizae à Surrounds roots, but does not penetrate cell walls Animal Mutualism Live within animals to help breakdown plant materialRuminant mammals à Capable of breaking down cellulose Termites à Capable of breaking down lignin Pathogenic and Parasitic Fungi Fungus gains resources from host, may cause disease Zombie-ants Cordyceps fungus from The Last of Us based on a real fungus! Fusarium Wilt Gros Michel banana major cultivar from the 18th century until the 1950s. The entire crop died due to Fusarium wilt à Fungal infection! Cavendish banana was created to replace the Gros Michel because of its immunity to Fusarium wilt New Mutations Threaten Cavendish Banana All Cavendish bananas are genetically identical because they reproduce via vegetative reproduction rather than sexual reproduction. Increasingly susceptible to Fusarium wilt due to lack of genetic variation. No variable immune response! Chytridiomycosis Deadly fungal disease affecting amphibian populations worldwide. Grows within the skin, and affects the ability of amphibians to breathe, thermoregulate, and osmoregulate à Leads to 100% death rate in many amphibian species Global decline in amphibian populations linked to the chytrid fungus Initially spread through the wildlife trade in the 1980s. Nearly 30% of amphibians may have already gone extinct! Knowt Play Call Kai