Find a favorite microorganism! Bacteria, Protist and Fungi

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The microorganism assignment will ask you to develop your knowledge, comprehension and analytical skills.You will search for your favorite microorganism, either bacteria, protist or fungi. To find and identify your favorite microorganism:

  1. Use the internet [ Knowledge skills ]. Make sure to reference your work
  2. Post of a video, picture or video link of your favorite microbe
  3. Explain why you make this selection by using content from the Bacteria and Archaea, Protists and Fungi lectures, indicating where in the lineage your organism falls and whether it has specific structural, reproductive or nutritional characteristics [ Application and Analysis Skills ]

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Bio 104 Protists Dr. Reut Friedrich Figure 28.1 Which of these Organisms are Prokaryotes and Which are Eukaryotes? Prokaryote 2 Most eukaryotes are single-celled organisms • Protists are eukaryotes. • Eukaryotic cells have organelles and are structurally more complex than prokaryotic cells. • It is important to bear in mind that: – the organisms in most eukaryotic lineages are protists. – most protists are unicellular. • Genetic and morphological studies revealed that some protists are closer to plants, fungi or animals than they are to other protists. • As a result, the kingdom in which all protists were once classified, Protista, has been abandoned. • We still use the name protist as a convenient way to refer to an eukaryotes that are not plants, fungi or animals. 3 Protists Are Nutritionally and Reproductively Diverse • Protists, the most nutritionally diverse of all eukaryotes, include – Photoautotrophs, which contain chloroplasts. – Heterotrophs, which absorb organic molecules or ingest larger food particles. – Mixotrophs, which combine photosynthesis and heterotrophic nutrition. • Protists exhibit different modes of reproduction, some reproduce asexually, while others reproduce sexually, or by the sexual processes of meiosis and fertilization. Four Supergroups of Eukaryotes • Our understanding of the evolutionary relationships among protist groups continues to change rapidly • Several hypotheses have been proposed and discarded • One current hypothesis divides all eukaryotes into four supergroups • Because the root of the eukaryotic tree is unknown, all four supergroups of eukaryotes are shown as diverging simultaneously from the common ancestor. We know it is not true, but we do not know which supergroup was the first to diverge from the others. • Not all four supergroups are equally established. 5 Figure 28.2 Exploring Protistan Diversity 6 Endosymbiosis in Eukaryotic Evolution • There is now considerable evidence that much protist diversity has its origins in endosymbiosis • Endosymbiosis is a relationship between two species in which one organism lives inside the cell or cells of the other organism (the host) 7 The First Eukaryotes • The oldest fossils of eukaryotic cells date back 1.8 billion years • Eukaryotic cells have a nuclear envelope, mitochondria, endoplasmic reticulum, and a cytoskeleton • Eukaryotes originated by endosymbiosis when a prokaryotic cell engulfed a small cell that would evolve into a mitochondrion • An endosymbiont is a cell that lives within a host cell 8 Serial Endosymbiosis • All eukaryotes have mitochondria or remnants of mitochondria, but not all have plastids (chloroplasts and related organelles). • Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events. • Mitochondria and plastids likely descended from bacterial cells; the original host is thought to be an archaean or close relative. Cytoplasm Infolding of plasma membrane DNA Plasma membrane Ancestral Prokaryote Probably an archaean or a close relative or the archaeans Engulfed aerobic bacterium Endoplasmic reticulum Nucleus Nuclear envelope 10 Engulfed aerobic bacterium Mitochondrion Ancestral eukaryote (a heterotroph) Engulfed photosynthetic bacterium Plastid Ancestral photosynthetic eukaryote 11 Key evidence supporting an endosymbiotic origin of mitochondria and plastids 1. The inner membrane of both organelles have enzymes and transport systems that are homologous to those found in the PM of living bacteria. 2. These organelles replicate by a splitting process that is similar to that of certain bacteria. 3. Each of these organelles contains circular DNA molecule that, like the chromosome of bacteria, are not associated with histones or large amounts of other proteins. 4. These organelles also have the cellular machinery (including the ribosomes) needed to transcribe and translate their DNA into proteins. 5. In terms of size, RNA sequences, and sensitivity to some antibiotics, the ribosomes of the mitochondria and plastids are more similar to bacterial ribosomes than they are to 12 cytoplasmatic ribosomes of eukaryotic cells. Plastid Evolution: A Closer Look • mtDNA sequence analyses indicated that the mitochondria of protist, animals, fungi and plants descended from a single common ancestor, suggesting that it arose only once in the course of evolution. • Mitochondria arose through descent from am alpha proteobacterium that was engulfed by a cell from an archaeal lineage. • Similar analyses provide d evidence that plastids also descended from a single common ancestor , from a photosynthetic cyanobacterium that was engulfed by a heterotrophic eukaryote . • Plastids came after the mitochondria, thus, all eukaryotic cells have mitochondria or reduced form of it. • The plastid-bearing lineage of protists evolved into two lineages of photosynthetic protists, red and green algae 13 Diversity of Plastids Produced by Endosymbiosis (Part 1: Primary Endosymbiosis) 14 Plastid Evolution: Supporting Evidence • Cyanobacteria are gram-negative, thus they have two cell membranes: an inner PM and an outer membrane that is part of the cell wall. • Like cyanobacteria, plastids of red algae and green algae surrounded by two membranes • Transport proteins in the membranes of red and green algae are homologous to those found in cyanobacteria Secondary Endosymbiosi On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis, in which they were ingested by a heterotrophic eukaryote Diversity of Plastids Produced by Endosymbiosis (Part 2: Endosymbiosis of Red algae) 17 Diversity of Plastids Produced by Endosymbiosis (Part 3: Endosymbiosis of Green Algae) Nucleomorph within a Plastid of a Chlorarachniophyte The chlorarachniophytes of the supergroup Rhizaria have a nucleomorph. Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids. Studies of the genomic organization and of the molecular phylogeny have shown that the nucleomorph of the chlorarchniophytes was the nucleus of a green alga that were engulfed by a larger eukaryote. 19 Nucleomorphs Serves as Evidence to Secondary Endosymbiosis Because the nucleomorph lies between two sets of membranes, nucleomorphs support the endosymbiotic theory and are evidence that the plastids containing them are complex plastids; Having two sets of membranes indicate that the plastid, a prokaryote, was engulfed by a eukaryote, an alga, which was then engulfed by another eukaryote, the host cell, making the plastid an example of secondary endosymbiosis. The unique combination of host cell and complex plastid results in cells with four genomes: two prokaryotic genomes (mitochondrion and plastid of the green alga) and two eukaryotic genomes (nucleus of host cell and nucleomorph). Endosymbiosis - Eons 20 Excavata 21 Excavates include protists with modified mitochondria and protists with unique flagella • The clade Excavata was originally proposed based on morphological studies of the cytoskeleton. • Some members have an “excavated” feeding groove on one side of the body. • The excavates include three monophyletic groups: the diplomonads, parabasalids, and euglenozoans. • Recent genomic studies support the monophyly of the excavated supergroup. 22 Diplomonads and Parabasalids These two groups: ➢ lack plastids ➢ have modified mitochondria ➢ most live in anaerobic environments 23 • Diplomonads – have reduced mitochondria called mitosomes. These are not used in ATP synthesis the way mitochondria are, but are potentially involved in the maturation of iron-sulfur proteins. – derive energy from anaerobic biochemical pathways. – have two equal-sized nuclei and multiple flagella. – are often parasites, for example, Giardia intestinalis The common intestinal parasite Giardia lamblia (Giardia intestinalisis) Parabasalids: ➢This group also have reduced mitochondria called hydrogenosomes that generate some energy anaerobically, releasing H2 gas as a byproduct. ➢Most of these organisms form a symbiotic relationship in animals, other species within this group are known parasites, and include human pathogens, like Trichomonas vaginalis, a sexually transmitted parasite. Trichomonas vaginalis 25 Trichomonosis could have killed some tyrannosaurs The lesions of tyrannosaurid specimens are consistent with those caused by an avian parasitic infection (Trichomonas allinae that harm modern birds of prey) and would have made swallowing difficult and eventually led to starvation of the dinosaur. 1371/journal.pone.0007288 26 Euglenozoans • Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, mixotrophs, and parasites. • The main feature distinguishing them as a clade is a spiral or crystalline rod inside their flagella. • Eukaryotic flagella are extensions of the cytoplasm, consisting of bundles of microtubules (component of the cytoskeleton) covered by the cell’s PM. • This clade includes the kinetoplastids and euglenids. 27 Figure 28.6 Euglenozoan Flagellum 28 Kinetoplastids • Kinetoplastids have a single mitochondrion with a kinetoplast, a network of circular DNA (kDNA) that contains many copies of the mitochondrial genome. • Free-living species are consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems. • Some species parasitize animals, plants, and other protists - For example, kinetoplastids in the genus Trypanosoma cause sleeping sickness in humans. 29 Figure 28.7 Trypanosoma, the Kinetoplastid that Causes Sleeping Sickness 30 Kinetoplastids: Trypanosoma • Trypanosomes evade host immune responses by producing cell-surface proteins with different molecular structures in each generation. • These frequent changes prevent the host from developing immunity. • About third of the Trypanosoma’s genome is dedicated to producing these surface proteins. Euglenids • Euglenids have one or two flagella that emerge from a pocket at one end of the cell. • Some species are mixotrophs; they can be autotrophic or heterotrophic depending on the environmental conditions. • Many other euglendis engulf prey by phagocytosis. 32 Figure 28.8 Euglena, A Euglenid Commonly Found in Pond Water 33 The SAR Clade Based on a whole-genome DNA sequence analyses it is currently suggested that three major clades of protists the Stramenopiles, Alveolates, and Rhizarians form a monophyletic group. 34 Stramenopiles Stramenopiles includes some of the most important photosynthetic organisms on Earth. Their name (from Latin stramen=straw, pilos=hair) refers to their characteristics flagellum, which has numerous fine hairlike projections. In most stramenopiles, this “hairy” flagellum is paired with a shorter “smooth” flagellum. Stramenopiles include diatoms, golden algae, and brown algae. 35 Diatoms Diatoms are unicellular algae with a unique two-part, glass-like wall of silicon dioxide embedded in an organic matrix. Diatoms are a major component of phytoplankton and are highly diverse (estimated 100,00 living species). 36 The Effect of Diatoms on CO2 Level Diatoms are widespread and abundant thus their photosynthethic activity affects the global CO2 Level. When ample nutrients are available, there is a rapid growth of the population known as bloom. Usually, diatoms are eaten by a variety of invertebrates and other protists, but during blooming periods, many escape this fate. When these diatoms die, their bodies sink to the ocean floor but their decomposition takes centuries. As a result, the carbon stay cooped in their bodies and not released immediately as CO2 as the decomposers respire. The overall effect of these events is that CO2 absorbed by diatoms during photosynthesis is transported or “pumped” to the ocean floor. 37 Golden Algae • Golden algae are named for their color, which results from their yellow and brown carotenoids • The cells of golden algae are typically biflagellated, with both flagella near one end • All golden algae are photosynthetic; some are mixotrophs that can dissolve organic compounds or ingested particles, including live cells by phagocytosis. • Most are unicellular, but some are colonial. 38 Figure 28.11 Dinobryon, A Colonial Golden Alga Found in Fresh Water (LM) 39 Brown Algae The largest and most complex algae are brown algae. All are multicellular, and most are marine. They are brown because of the carotenoids in their plastids. Brown algae include many species commonly called “seaweeds” Kelps are large brown algae 40 Brown Algae, Continued Brown algal seaweeds have plantlike structures: the rootlike holdfast, which anchors the alga, and a stemlike stipe, which supports the leaflike blades. Morphological and DNA data show that these similarities to plants evolved independently and are analogous structures and not homologous. Some have gas-filled, bubble-shaped floats to keep their photosynthetic structures near the water surface. r_Wrack_(Fucus_vesiculosus) Seaweeds: Adapted to Life at the Ocean’s Margins 42 Alternation of Generations • A variety of life cycles have evolved among the multicellular algae. • The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid generations. • Some species have heteromorphic, structurally different, generations; others have isomorphic, structurally similar, generations. 43 Alternation of Generations, Continued The diploid generation is called a sporophyte; the haploid generation is called a gametophyte. The sporophyte produces haploid spores that move by means of flagella, called zoospores in the brown algae Laminaria. Spores develop into multicellular haploid male and female gametophytes, which produce gametes. Fertilization of gametes results in a diploid zygote, which grows into a new sporophyte. In Laminaria the generations are heteromorphic, meaning that the sporophyte and the gametophyte look different from one another (and differ in their chromosome number). The Life Cycle of the Brown Alga Laminaria: An Example of Alternation The sporophyes are usually found in of Generations water just below the line of the lowest tides, attached to rocks by branching holdfasts. Cells on the surface of the blade develop into sporangia Sporangia produce zoospores by meiosis All zoospores are structurally alike, but about half of them develop into male gametophytes and half into female gametophhytes. The gametophytes are short, branchedgrow on subtidal rocks. The zygotes grow into new sporophytes while attached to the remains of the female gametophyte. Sperm fertilizes the egg Male gametohpyte release sperm, and female gametophyte produces eggs, which remain attached to the female gametophye. Eggs secrete a chemical signal that attracts sperm to the same species, thereby increasing the probability 45 of fertilization in the ocean. Alveolates • Alveolates have membrane-enclosed sacs (alveoli) just under the plasma membrane. • The alveolates include – Dinoflagellates – Apicomplexans – Ciliates 46 Dinoflagellates The cells of many dinoflagellates are enforced with cellulose plates, creating an “armor”. Two flagella are located in grooves in this “armor” making the dinoflagellates spin as they move through the water. 47 Dinoflagellates Half of all dinoflagellates are heterotrophs and the rest are photosynthetic or mixotrophic. Dinoflagellates bloom cause “red tide” where the coastal waters appear brownish red because of the presence of carotenoids, the most common pigments in dinoflagellate plastids. Toxins produced by certain dinoflagellates have caused massive kills of invertebrates and fishes. Human who eat molluscs that have accumulated the toxins are affected as well, sometimes fatally. 48 Apicomplexans Nearly all apicomplexans are parasites of animals – and virtually all animal species examined so far are attacked by these parasites. They spread through their host as tiny infectious cells called sporozoites. The origin of their name comes from their structure: One end of the sporozoite cell, the apex, contains a complex of organelles specialized for penetrating host cells and tissues. Although apicomplexans are not photosynthetic they retain a modified plastid (apicoplast), most likely of red algal origin. 49 Plasmodium ▪ The life cycles of most apicomplexans have both sexual and asexual stages and require two or more different hosts. ▪ Plasmodium, the parasite that causes malaria lives in both humans and mosquitoes. ▪ Approximately 200 million people in the tropics are infected, and 600,000 die each year from malaria 50 The Two-host Life Cycle of Plasmodium, The Apicomplexan that Causes Malaria (Step 1) 1. An infected Anopheles mosquito bites a person, injecting Plasmodium sporozoites in its saliva 2. The sporozoiyes enter the person’s liver cells. After several days, the sporozoites undergo multiple divisions, and become merozoites, which use their apical complex to penetrate red blood cells. 3. The merozoites divide asexually inside the red blood cells. At intervals of 48 or 72 hours (species dependant), large numbers of merozoites break out of the blood cells, causing periodic chills and fever. Some of the merozoite infect other blood cells 4. Some merozoites form gametocytes. 51 The Two-host Life Cycle of Plasmodium, The Apicomplexan that Causes Malaria (Step 2) Fertilization occurs in the mosquito’s digestive tract, and a zygote forms. Another Anopheles mosquito bites the infected person and picks up Plasmodium gametocytes along with blood. Gametes form from gametocytes; each male gametocyte produce several slender male gametes 52 The Two-host Life Cycle of Plasmodium, The Apicomplexan that Causes Malaria (Step 3) An oocyst develops from the zygote in the wall of the mosquito’s gut. The oocyst release thousands of sporozoites, which migrate to the mosquito’s salivary gland. 53 Ciliates • Ciliates, a large varied group of protists, are named for their use of cilia to move and feed. • Most ciliates are predators of bacteria or other protists. • Ciliates have two different sorts of nuclei: – a tiny, diploid micronucleus passes its genetic material to offspring, but does not express its genes. – a large, polyploid macronucleus provides the nuclear RNA for vegetative growth. It is generated from the micronucleus by amplification of the genome and heavy editing. 54 Structure and Function in the Ciliate Paramecium Caudatum How Paramecium eats: Food vacuoles fuse with lysosomes (not shown). As the food is digested, the vacuoles follow a looping path through the cell. Wastes are released when the vacuoles fuse with specialized region of the PM that functions as an anal pore. Contractile vacuole collect water and expel it from the cell to maintain osmotic pressure Cilia along a funnel-shaped oral groove move food (mainly bacteria) into the cell mouth, where the food is engulfed into food vacuoles by phagocytosis. Conjugation and Reproduction ▪ Genetic variation results from conjugation, in which two individuals exchange haploid micronuclei. ▪ Conjugation is a sexual process and is separate from reproduction, which generally occurs by binary fission. 56 Conjugation and Reproduction Two cells of compatible mating strains align side by side and partially fuse. Meiosis of micronuclei produces four haploid micronuclei in each cell Three micronuclei in each cell disintegrate. The remaining micronucles in each cell divides by mitosis The cell swap one micronucleus The cells separate Conjugation and Reproduction Two rounds of binary fission yield two daughter cells. 4 micronuclei become macronuclei Three rounds of mitosis produce 8 micronuclei The two micronuclei fuse Rhizarians • Many species of rhizarians are amoebas. • Amoebas are protists that move and feed by pseudopodia, extensions of the cell surface. • As it moves, an amoeba extends a pseudopodium and anchors the tip; more cytoplasm then stream into the pseudopodium. • Amoeba are not a monophyletic group, and Rhizarian amoebas differ from amoebas in other clades by having threadlike pseudopodia. • Rhizarians include radiolarians, forams, and cercozoans. 59 Radiolarians • Radiolarians, mostly marine protists, have delicate, symmetrical internal skeletons generally made of silica. • Pseudopodia reinforced by microtubules radiate from the central body of radiolarians. • Cytoplasm covering the microtubules engulf prey that become attached to the pseudopodia. 60 Forams • Foraminiferans, or forams, are named for their porous shells, called tests. • Foram tests consist of a single piece of organic material that typically is hardened with calcium carbonate. • Pseudopodia extend through the pores in the test and are used for swimming, test formation, and feeding. • Some are also nourished by the photosynthetic activity of symbiotic algae living within their tests. • Both freshwater and marine forms are known. 61 Forams, Continued • Foram tests in marine sediments form an extensive fossil record. • Researchers can use measures of the magnesium content in fossilized forams to estimate changes in ocean temperature over time. Forams take up more magnesium in warmer water than in colder water. Cercozoans • Cercozoans are a large group of amoeboid and flagellated protists with threadlike pseudopodia. • This group was first identified in molecular phylogenetics. • They are common in marine, freshwater, and soil ecosystems. • Most are heterotrophs, including parasites and predators. 63 Cercozoans’ Nutrition Most cercozoans are heterotroph, both parasite and predators. The chlorarachniophytes that were discussed in slides 20-21 are mixotrophs: ingest smaller protist and bacteria as well as perform phtosynthesis. Paulinella chromatophora is noteworthy because it contains two unique photosynthetic, cyanobacterial – derived organelles called chromatophores. DNA evidence indicate that chromatophores are derived from different cyanobacterium than the plastids of other photosynthetic eukaryotes. 64 A Second Case of Primary Endosymbiosis? Paulinella chromatophora 65 Archaeplastida 66 Red Algae and Green Algae are the Closest Relatives of Plants • Plastids arose when a heterotrophic protist acquired a cyanobacterial endosymbiont. • The photosynthetic descendants of this ancient protist evolved into red algae and green algae. • Plants are descended from the green algae. • Archaeplastida is the supergroup that includes red algae, green algae, and plants. 67 Red Algae • Red algae are reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll. • The color varies from greenish-red in shallow water to dark red or almost black in deep water. • Red algae are usually multicellular. • Red algae are the most abundant large algae in warm coastal waters of the tropics. • Red algae reproduce sexually and have diverse life cycles in which alternation of generations is common. Yet, their sperm is not flagellated and they rely on water currents to bring gametes together for fertilization. 68 Red Algae 69 Green Algae Green algae are named for their grass-green chloroplasts Molecular systematics indicate that plants and green algae are closely related. Green algae are a paraphyletic group. Viridiplantae is an “expanded” plant group that includes both plants and green algae, creating a clade. The two main groups are the charophytes and the chlorophytes. Charophytes are most closely related to plants. 70 Evolution of Archaeplastidae 71 Chlorophytes The chlorophytes include more than 7,000 species. Most live in fresh water but some are marine and even terrestrial. The simplest chlorophyte are unicellular organisms such as Chlamydomonas. Most chlorophytes have complex life cycles with both sexual and asexual stage. Alternation of generations developed in some, like the Ulva. 72 Larger Size and Complexity Evolved in Green Algae Larger size and greater complexity evolved in green algae by three different mechanism: 1. the formation of colonies from individual cells (e.g., Zygnema) 2. the formation of true multicellular bodies by cell division and differentiation (e.g., Ulva) 3. the repeated division of nuclei with no cytoplasmic division (e.g., Caulerpa) Zygnema Caulerpa Chlamydomonas Chlamydomonas is a genus of green algae consisting of unicellular biflagellates. Although it is a photosynthetic organism it can also absorb nutrients directly through the cell surface. 74 The Life Cycle of Chlamydomonas, A Unicellular Chlorophyte These daughter cells develop flagella and cell walls and then emerge as swimming zoospores from the parent cells. The zoospores develop into mature haploid cells. Mature cells are haploid and contain a single cup-shaped chloroplast In response to environmental stress, cells develop into gametes. Gametes of different mating types fuse (sygamy) The zygote secretes a durable coat that protects the cell from harsh conditions. When a mature cell reproduces asexually, it resorbs its flagella and then undergoes two rounds of mitosis, forming 4 cells. After a dormant period, meiosis produces 4 haploid cells (two of each 75 mating type) that emerge and mature The Volvocine Series ❖ The volvocine green algae are a model system for the evolution of simple multicellularity and cellular differentiation. ❖ Complex multicellular organisms are the dominant form in our naked eyes: Plants, animals, and macroscopic fungi. ❖ Complex multicellularity arose during the Ediacaran Period (635 Mya-541 Mya), more than 3 billion years after microbial life began to diversify. ❖ The first evidence of simple multicellularity is from cyanobacteria-like organisms that lived 3–3.5 billion years ago. 76 Simple Multicellularity ❖Simple multicellular organisms include filaments, clusters, balls, or sheets of cells that arise via mitotic division from a single progenitor. ❖ These organisms have the capacity to divide into a multicellular organism with a predictable shape from one cell. ❖They exhibit only basic pattern of differentiation: Reproductive cells and Somatic cells. ❖Adhesive molecule connects the cells in a coherent and reproducible fashion. ❖Communication between cells and the transfer of resources from one cell to another is commonly limited. 77 Figure 1. Rough outline of phylogenetic relationships in volvocine green algae [9], [10], [15]. In these organisms a very important developmental principle has been worked out: the ordered division of one cell to generate a number of cells that are organized in a predictable fashion. Arakaki Y, Kawai-Toyooka H, Hamamura Y, Higashiyama T, Noga A, et al. (2013) The Simplest Integrated Multicellular Organism Unveiled. PLoS ONE 8(12): 78 e81641. doi:10.1371/journal.pone.0081641 Figure 1. Rough outline of phylogenetic relationships in volvocine green algae [9], [10], [15]. The next two genera of the volvocacean series exhibit another important principle of development: the differentiation of cell types within an individual organism. The reproductive cells become differentiated from the somatic cells. In all the previous genera, every cell can, and normally does, produce a complete new organism by mitosis. In the genera Pleodorina and Volvox, however, Arakaki Y, Kawai-Toyooka H, Hamamura few Y, Higashiyama T, Noga A, et al. (2013) The Simplest Integrated Multicellular Organism Unveiled. PLoS ONE 8(12): relatively cells can reproduce. 79 e81641. doi:10.1371/journal.pone.0081641 Unikonta 80 Unikonts include protists that are closely related to fungi and animals • The supergroup Unikonta includes animals, fungi, and some protists • This group includes two clades: the amoebozoans and the opisthokonts (animals, fungi, and related protists) • The root of the eukaryotic tree remains controversial • It is unclear whether unikonts separated from other eukaryotes relatively early or late 81 Amoebozoans • Amoebozoans are amoebas that have lobe- or tubeshaped, rather than threadlike, pseudopodia • They include slime molds, tubulinids, and entamoebas • Slime molds, or mycetozoans, were once thought to be fungi due to their spore-producing fruiting bodies • This resemblance between slime molds and fungi is a result of convergent evolution • Slime mold descended from unicellular organism and are an example of independent origin of multicellularity in eukaryotes. • Slime molds include two lineages, plasmodial slime molds and cellular slime molds 82 Plasmodial Slime Molds • Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange • They form a unicellular feeding mass called a plasmodium (Do not confuse with the malarial Plasmodium) • Despite its size, the Plasmodium in not multicellular but a single mass of cytoplasm, undivided by PM with many diploid nuclei • This “supercell” is a product of mitotic nuclear divisions that are not followed by cytokinesis Life Cycle of Plasmodial Slime Mold The feeding stage is a multinuclear plasmodium When food becomes scarce, the plasmodium erects stalked fruiting bodies (sporangia). 84 Life Cycle of Plasmodial Slime Mold The motile haploid cells are either amoeboid or flagellated; the two forms readily convert from one to the other The resistant spores germinate in favorable conditions, releasing motile cells. In the sporangia, meiosis produces haploid spores, which disperse through the air. 85 Life Cycle of Plasmodial Slime Mold Repeated mitotic divisions of the zygote’s nucleus, without cytoplasmic division, form the plasmodium The cells fuse, forming a diploid zygote 86 Cellular Slime Molds During the feeding stage of this organism they function individually, as solitary cells Once the food is depleted, the cells form a slug-like aggregate that functions as a unit Still, the cells remain separated by their individual PM and form asexual fruiting bodies Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity 87 The Life Cycle of Dictyostelium, A Cellular Slime Mold Spores are released Other cells crawl up the stalk and develop into spores In favorable conditions, amoebas emerge from the spore coats and feed In the feeding stage, solitary haploid amoebas engulf bacteria; these solitary cells periodically divide by mitosis When food is depleted, hundreds of amoebas congregate in response to a chemical attractant and form a slug-like aggregate The aggregate migrate for a while and then stops. Some of the cells dry up after forming a stalk that supports an asexual fruiting body. 88 The Life Cycle of Dictyostelium, A Cellular Slime Mold During sexual reproduction 2 haploid amoebas fuse and form a zygote The wall ruptures, releasing new haploid amoebas The zygote becomes a giant cell by consuming haploid amoebas. After developing a resistant wall, the giant cells undergoes meiosis followed by several mitotic divisions. 89 Nobody Likes Cheaters ➢ Mutation in a single gene, can turn individual Dictyostelium into a “cheater”, that never becomes part of the stalk, thus, never die. ➢ This mutation give a strong reproductive advantage over the “noncheaters”, so why don’t all Dictyostelium cells cheat? Cheating cells lack certain surface protein that noncheating cells can identify; Noncheating cells prefer to aggregate with other noncheating cells, preventing the cheaters from exploiting them. 90 Tubulinids • Tubulinids are a diverse group of amoebozoans with lobe- or tube-shaped pseudopodia • They are common unicellular protists in soil as well as freshwater and marine environments • Most tubulinids are heterotrophic and actively seek and consume bacteria and other protists 91 Entamoebas • Entamoeba are parasites of vertebrates and some invertebrates • Entamoeba histolytica causes amebic dysentery, the third-leading cause of human death due to eukaryotic parasites 92 Opisthokonts • Opisthokonts include animals, fungi, and several groups of protists • Choanoagellates are more closely related to animals than they are to other protists. • Nucleariids are more closely related to fungi than they are to other protists. • The nucleariids and the choanoflagellates illustrates why scientists abandoned the concept of kingdom protistsa: A monophyletic group that include all protists would also have to include the multicellular animals and fungi that are closely related to them. 93 Slime Mold: A Brainless Blob that Seems Smart .com/watch?v=mOIJlNcDVs 94 Creeping, seeping, spitting spores Fungi link the forest’s floors Living fountains, shifting webs, Feed the living, eat the dead. “The Forest’s Floor” by Luke Heaton Dr. Reut Friedrich Fungi Bio 104, Spring 2018 1 Hidden Networks • The mushrooms you see on the forest floor are just the aboveground parts of a vast network of underground filaments • Fungi are diverse and widespread • They are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients • About 100,000 species of fungi have been described • It is estimated that there are as many as 1.5 million species of fungi • Despite their diversity, fungi share key traits, most importantly the way in which they derive nutrition 2 In Fungi, Digestion precedes Ingestion ▪ Fungi are heterotrophs but unlike animals, they do not ingest their food but absorb nutrients from the environment to their body (absorptive heterotrophy). ▪ They excrete enzymes (therefore named exoenzymes) that can degrade many types of substances to smaller organic compounds that can be absorbed through the large surface area of the mycelium. ▪ There are many different kinds of enzymes including hydrolytic enzymes and enzyme that can penetrate cell walls, enabling the fungi to directly absorb nutrients from the cell. ▪ The versatility of these enzymes contributes to fungi’s ecological success 3 Fungi Exhibit Diverse lifestyles • Fungi exhibit diverse lifestyles: decomposers, parasites, and mutualists • 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 4 Body Structure • The most common body structures are multicellular filaments and single cells (yeasts) • Some species grow as either filaments or yeasts; others grow as both, but most species are filamentous and only a few are yeast. 5 The Morphology of Multicellular Fungi Enhances Their Ability to Absorb Nutrients • The bodies of fungi form a network of tiny filaments called hyphae (singular, hypha). • Hyphae consist of tubular cell walls surrounding the plasma membrane and cytoplasm of cells. • The cell walls are strengthen by chitin, strong and flexible polysaccharide. • The cell wall protects the fungi cells from bursting: As the fungus absorbs nutrients from its environment, the concentration of those nutrients in its cells increases, causing water to enter the cells via osmosis. This movement of water could have ended with burst of the fungi cells, but the protection of the rigid cell wall prevents it. •The mass of hyphae is a mycelium . 6 Figure 31.2 Structure of a Multicellular Fungus The mushroom and its subterranean mycelium are a continuous network of hyphae © 2017 Pearson Education, Inc. Mycelium ▪ The mycelium (plural mycelia), maximizes its surface-to-volume ratio, making feeding very efficient. ▪ Just 1 cm3 of rich soil may contain as much as 1 km of hyphae with total surface area of 300 cm3 in contact with the soil! ▪ A fungal mycelium grows rapidly, as proteins and other materials synthesized by the fungus move through cytoplasmic streaming to the tips of the extending hyphae. ▪The fungus grow in length and not girth, thus increasing its overall absorptive surface area. 8 Fungi’s morphology ▪ Most fungal hyphae are divided into separate cells by end walls called septa (singular, septum). ▪ In most phyla of fungi the septa is perforated meaning they have tiny holes that allow for the rapid flow of nutrients and organelles from cell to cell along the hypha. ▪ Some Fungi lack septa, and are termed coenocytic hyphae; they have continuous cytoplasmic mass with hundreds or thousands of nuclei. 9 Specialized Hyphae Some fungi have specialized hyphae that allow them to feed on living animals. Nematode Hyphae 25 µm In Arthrobotrys, a soil fungus, portions of the hyphae are modifies as hoops that can constrict around a nematode (roundworm) in less than a second. The growing hyphae then penetrate the worm’s body, and the fungus digests its prey’s inner tissues. 10 Arbuscules Mutualism is an ecological interaction that benefits each of the interacting species. Some mutualistic fungi have specialized hyphae called arbuscules that they use to exchange nutrients with their plant hosts. Mycorrhizae (“fungus roots”) are mutually beneficial relationships between fungi and plant roots. Mycorrhizal fungi (fungi that form mycorrhizae) are more efficient than plant’s roots in acquiring phosphate ions and other minerals from the soil using their mycelial networks. They supply these minerals to the plants that reward them with organic nutrients. 11 There are two types of mycorrhizal fungi: • Ectomycorrhizal fungi form sheaths of hyphae over a root and typically grow into the extracellular spaces of the root cortex • Arbuscular mycorrhizal fungi extend arbuscules through the root cell wall and into tubes formed by invagination of the plasma membrane Arbuscular mycorrhizal fungi 12 Almost all vascular plants have mycorrhizae and rely on their fungal partners for essential nutrients With mycorrhizae Without mycorrhizae Many studies have shown the significance of mycorrhizae by comparing the growth of plants with and without them. Mycorrhizal fungi colonize soils by the dispersal of haploid cells called spores. 13 Fungi produce spores through sexual or asexual life cycles • Most fungi propagate themselves by producing vast numbers of spores, either sexually or asexually • Spores can be carried long distances by wind or water; they will germinate if they land in moist conditions with available food What is a spore in fungi? 1. Spore is a haploid cell, produced either sexually or asexually, that produces a mycelium after germination. 2. Sporangium is a multicellular organ (fungi/plants) in which meiosis occurs and haploid cells develop. 3. Sporocyte is a diploid cell within a sporangium that undergoes meiosis and generates haploid spores; also called spore mother cell. 14 Figure 31.5_3 Generalized Life Cycle of Fungi © 2017 Pearson Education, Inc. Sexual Reproduction • Fungal hyphae and spores are normally haploid, with the exception of transient diploid stages formed during the sexual life cycles • Sexual reproduction requires the fusion of hyphae from different mating types • Fungi use sexual signaling molecules called pheromones to communicate their mating type • If the mycelia are of different mating types, the pheromones from each partner bind to the receptors on the other, and the hyphae extend towards the source of the pheromones. • When the hyphae meet, they fuse. 16 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 fused part of the mycelium, called a heterokaryon • In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic • As a dikaryotic mycelium grows, the two nuclei in each cell divide in tandem without fusing. Hours, days, or in some fungi centuries, may pass before they will progress to the next phase, the Karyogamy 17 Sexual Reproduction, Continued • Karyogamy is the fusion of the two haploid nuclei to produce a diploid cell • The diploid phase is short-lived and undergoes meiosis, producing haploid spores • The paired processes of karyogamy and meiosis produce genetic variation • Spores produce in this way are termed “sexual spores” 18 Asexual Reproduction Many fungi can reproduce both sexually and asexually but about 20,000 species can reproduce only asexually. Molds produce haploid spores by mitosis and form visible mycelia Mold typically grow very fast producing many asexual spores, enabling fungi to colonize new sources of food. Yet many of these species are capable of sexual reproduction. Penicillium mold 19 Asexual Reproduction, Continued • 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 filamentous mycelia The yeast Saccharomyces cerevisiae 20 Duteromycetes • Many molds and yeasts have no known sexual stage • Mycologists traditionally classified fungi based on their sexual structures called these types of fungi deuteromycetes (second fungus) • These fungi are reclassified if their sexual stage is discovered • Mycologists can now also use genomic techniques to classify fungi 21 The Origin of Fungi Ɀ The ancestor of fungi was an aquatic, single-celled, flagellated protist Ɀ Fungi and animals are more closely related to each other than they are to plants or other eukaryotes Ɀ Fungi, animals, and their protistan relatives form the opisthokonts clade Ɀ Opisthokonts evolved from a unicellular flagellated ancestor and the name refers to the posterior (opistho) position of the flagellum 22 The Origin of Fungi, Continued • DNA evidence suggests that • Fungi are most closely related to unicellular protists called nucleariids • Animals are most closely related to unicellular protists called choanoflagellates • This suggests that multicellularity arose separately in animals and fungi 23 Nuclearids are the Closest Group of Organisms Related to Fungi. They are Unicellular, Amoeboid Protists With Filose Pseudopodia. 24 Fossil Fungal Hyphae and Spores from the Ordovician Period (About 460 Million Years Ago) The oldest undisputed fossils of fungi are about 460 million years old and terrestrial © 2017 Pearson Education, Inc. Basal Fungal Groups • Genomic studies have identified chytrids in the genus Rozella as an early diverging fungal lineage • Furthermore, one metagenomic study place Rozella in a previously unknown clade of unicellular fungi tentatively named “cryptomycota”. • Rozella and other members of the unicellular group cryptomycota have flagellated spores and lack chitin-rich cell walls • This suggests that chitin strengthen cell walls, a key structural feature of most fungi, arose after the cryptomycota diverged from the rest of the fungi. 26 The Move to Land • Fungi were among the earliest colonizers of land • Fossil evidence indicates fungi formed mutualistic relationships with early land plants • This evidence includes fossils of hyphae that have penetrated within plant cells and formed structures that resemble the arbuscules formed today by arbuscular mycorrhizae. • The earliest plants lacked roots, limiting their ability to extract nutrient from the soil; the extensive mycelia formed by the fungi transfer these nutrients from the soil to the plants. Transverse section of fossilized Aglaophyton (405 mya) major axis showing tissue preservation. Arrow indicates zone of arbuscule-containing cells. Remy et al ; PNAS 1994 27 The Genetic Basis of Mycorrhizae For a mycorrhizal fungus and its plant partner to establish a symbiotic relationship, certain genes must be expressed by the fungus and other genes must be expressed by the plant. Three genes are expressed in plants, called sym genes are required for the formation of the mycorrhizae. Interestingly, these genes were present in all major plant lineages including basal lineages like liverworts. A flowering plant, that had a mutated sym gene, couldn’t form mycorrhizae, yet when it was transferred with a sym gene from livewort, it regained this ability. These findings suggests that the mycorrhizae interactions were present in early plant lineages and their function were conserved for hundreds of millions of years as plants continued to adapt to life on land. 28 Fungi Have Radiated Into a Diverse Set of Lineages © 2017 Pearson Education, Inc. Figure 31.UN02 In-text Figure, Chytrids Mini-tree, P. 658 © 2017 Pearson Education, Inc. Chytrids Chytrids (1,000 species) • Chytrids (phylum Chytridiomycota) are found in terrestrial, freshwater, and marine habitats including hydrothermal vents • They can be decomposers, parasites, or mutualists • Molecular evidence supports the hypothesis that chytrids diverged early in fungal evolution • Chytrids are unique among fungi in having flagellated spores, called zoospores 31 Video: Phlyctochytrium Zoospore Release Figure 31.11 Flagellated Chytrid Zoospore (TEM) 32 Figure 31.UN03 In-text Figure, Zygomycetes Mini-tree, P. 660 © 2017 Pearson Education, Inc. Zygomycetes • The zygomycetes are named for their sexually produced zygosporangia • Zygosporangia are the site of karyogamy and then meiosis • Zygosporangia, which are resistant to freezing and drying, can survive unfavorable conditions 34 Zygomycetes • The zygomycetes (phylum Zygomycota) include fastgrowing molds, parasites, and commensal symbionts • The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum Zygomycetes (1,000 species) • The life cycle of Rhizopus stolonifera serves as an example for zygomycetes reproduction. 35 The Life Cycle of the Zygomycete Rhizopus Stolonifer (Black Bread Mold) Neighboring mycelia of different mating types form hyphal extensions (gametangia), each of which encloses several haploid nuclei Mycelia have various mating types. A zygosporangium forms, containing multiple haploid nuclei from two parents The zygosporangium develops a rough thick-walled coating that can resist harsh conditions for months. © 2017 Pearson Education, Inc. The Life Cycle of the Zygomycete Rhizopus Stolonifer (Black Bread Mold) The sporangium disperse genetically diverse haploid spores The sygosporangium germinates into a sporangium on a short stalk © 2017 Pearson Education, Inc. When conditions are favorable, karyogamy occurs, then meiosis Figure 31.12 The Life Cycle of the Zygomycete Rhizopus Stolonifer (Black Bread Mold) The spores germinate and grow into a new mycelia Mycelia can also reproduce by forming sporangia that produce genetically identical haploid spores © 2017 Pearson Education, Inc. Glomeromycetes © 2017 Pearson Education, Inc. Glomeromycetes • The glomeromycetes (phylum Glomeromycota) were once considered zygomycetes • Molecular analyses indicate that glomeromycetes form a separate clade • Nearly all species of glomeromycetes (200 known species) form arbuscular mycorrhizae Glomus mosseae bulging into a root cell by pushing in the membrane (cytoplasm removed for the SEM), branching into tiny treelike arbuscules 41 Ascomycetes © 2017 Pearson Education, Inc. Ascomycetes • Ascomycetes (phylum Ascomycota) contain 65,00 known species that live in marine, freshwater, and terrestrial habitats • Ascomycetes produce sexual spores in saclike asci (singular, ascus) contained in fruiting bodies called ascocarps • Ascomycetes are commonly called sac fungi • Ascomycetes vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels Orange peel fungus (Aleuria aurantia) Morchella esculenta Tuber 43 melanosporum Ascomycetes, Continued • Ascomycetes include plant pathogens, decomposers, and symbionts • More than 25% of all ascomycete species form symbiotic associations with green algae or cyanobacteria called lichens • Some ascomycetes form mycorrhizae with plants. • Yeast are also ascomycetes. 44 The Life Cycle of Ascomycetes • Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia • Conidia are produced at the tips of specialized hyphae called conidiophores • Conidia may also participate in sexual reproduction by fusing with the hyphae of a mycelium from a different mating type 45 The Life Cycle of Neurospora Crassa, An Ascomycete Ascomycete mycelia can reproduce asexually by producing pigmented haploid spores (conidia) © 2017 Pearson Education, Inc. The Life Cycle of Neurospora Crassa, An Ascomycete Neurospora can also reproduce sexually by producing specialized hyphae. Conidia of opposite mating types fuse to these hyphae. The dikaryotic hyphae that result from plasmogamy produce many dikaryotic asci The ascospores are discharge forcibly from the asci through an opening in the ascocarp. Germinating ascospores give rise to new mycelia Each haploid nucleus divides once by mitosis, yielding 8 nuclei. Cell walls and PM develop around the nuclei, forming ascospores © 2017 Pearson Education, Inc. Karyogamy occurs within each ascus, producing a diploid nucleus Each diploid nucleus divides by meiosis, yielding 4 genetically different haploid nuclei Figure 31.16 The Life Cycle of Neurospora Crassa, An Ascomycete © 2017 Pearson Education, Inc. Basidiomycetes © 2017 Pearson Education, Inc. Basidiomycetes • Basidiomycetes (phylum Basidiomycota) include mushrooms, puffballs, and shelf fungi • Some basidiomycetes form mycorrhizae, and others are plant parasites (rusts & smuts) • The phylum is defined by a structure called a basidium, a cell in which karyogamy occurs, followed immediately by meiosis. • The club-like shape of the basidiumalso gives rise to the common name: “club fungi” • Many basidiomycetes are decomposers of wood; some basidiomycetes excel at lignin break down. Amanita muscaria 50 Figure 31.17 Basidiomycetes (Club Fungi) © 2017 Pearson Education, Inc. Basidiomycetes, Life Cycle • The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium • The mycelium can reproduce sexually by producing fruiting bodies called basidiocarps • White mushrooms found in the supermarket are examples of basidiocarps • The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores 52 The Life Cycle of a Mushroom-forming Basidiomycete Two haploid mycelia of different mating types undergo plasmogamy In a suitable environment, the basidiospores germinate and grow into short-lived haploid mycelia © 2017 Pearson Education, Inc. A dikaryotic mycelium forms, growing faster than, and ultimately crowing out, the haploid parental mycelia Environment cues such as rain or change in temperature induce the dikaryotic mycelium to form compact masses that develop into basidiocarps The Life Cycle of a Mushroom-forming Basidiomycete When mature, the basidiospores are ejected and then dispersed to the wind The basidiocarp gills are lined with terminal dikaryotic cells called basidia Each diploid nucleus yields 4 haploid nuclei, each of which develops into a basidiospore © 2017 Pearson Education, Inc. Karyogamy in each basidium produces a diploid nucleus, which then undergoes meiosis Figure 31.18 The Life Cycle of a Mushroomforming Basidiomycete © 2017 Pearson Education, Inc. Morphological characteristics of the five Fungal Phylum 57 Fungi play key roles in nutrient cycling, ecological interactions, and human welfare 58 Fungi as Decomposers • Fungi are efficient decomposers of organic material including cellulose and lignin • In fact, almost any carbon-containing substrate – even jet fuel and house paint – can be consumed by at least some fungi and bacteria. • As a result, fungi and bacteria are primarily responsible for keeping the ecosystems stocked with inorganic nutrients essential for plant growth • They perform essential recycling of chemical elements between the living and nonliving world • Without these critical decomposers, life as we know it would cease 59 Fungi as Mutualists • Fungi form mutualistic relationships with plants, algae, cyanobacteria, and animals • Mutualistic fungi absorb nutrients from the host organism and reciprocate with actions that benefit the host • A classic example is the mycorrhizal association that fungi form with most plants. 60 Fungus-Plant Mutualisms: Endophyte • Along with mycorrhizal fungi, all plant species studied to date appear to harbor symbiotic endophytes, fungi or bacteria, that live inside leaves or other plant parts without causing harm. • Some endophytes make toxins to help defend the host plant; others help the plant tolerate heat, drought, or heavy metals • Most endophytes are ascomycetes 61 Fungus-Animal Mutualism • Some fungi share their digestive services with animals • These fungi help break down plant material in the guts of cows and other grazing mammals • Many species of ants use the digestive power of fungi by raising them in “farms” 62 Fungus-Animal Mutualism ▪ Leaf-cutter ants search for leaves they cannot digest in the tropical forests and bring them back to their nests where they feed it to the fungi. ▪ As the fungi grow, they develop specialized swollen tips that are rich in proteins and carbohydrates. ▪ The ants feed primarily on these nutrient-rich tips. ▪ The fungi also detoxifies compounds from the plants that might be harmful for the ants. ▪ The co-evolution of farming ants and fungal crop have been tightly linked for over 50 million years. In many case, the fungi cannot survive without their care takers and vice versa. 63 Lichens • A lichen is a symbiotic association between a photosynthetic microorganism and a fungus • The photosynthetic component is green algae or cyanobacteria • The fungal component is most often an ascomycete, although one glomeromycete is known and 75 basidiomycete • The symbiosis between the two organisms is so complete, that they are given names as though they were a single organism • To date, there are 17,000 lichen species described 64 Figure 31.22 Variation in Lichen Growth Forms © 2017 Pearson Education, Inc. Lichens, Structure • Millions of photosynthetic cells are held in a mass of fungal hyphae • Algae or cyanobacteria occupy an inner layer below the lichen surface • Asexual reproduction as a symbiotic unit is common and happen either by fragmentation or by the formation of soredia (singular, soredium), small clusters of hyphae with embedded algae. • The fungi of many lichen can also reproduce sexually. 66 Figure 31.23 Anatomy of an Ascomycete Lichen © 2017 Pearson Education, Inc. What’s in it for me?? • The algae provide carbon compounds, cyanobacteria also fixes nitrogen and provides organic nitrogen compounds. • The fungi provide the environment for growth; the physical structure of the hyphae allows for gas exchange, protects the photosynthetic partner and retains water and minerals which are mostly airborne. • The fungus also secretes acids, which aids in the uptake of minerals. 68 Lichens Pave the Way for Plants • Lichens are important pioneers on new rock and soil surfaces: • They physically break the surface by penetrating it and chemically attacking it • They also trap windblown soil • Lichens were on land 420 million years ago; these early lichens may have modified rocks and soil much as they do today, helping pave the way for plants 69 Fungi as Parasites • Like mutualistic fungi, parasitic fungi absorb nutrients from the cells of living hosts, but they provide nothing in return. • About 30% of known fungal species are parasites or pathogens, mostly of plants 70 Chestnut Blight Fungi as parasite The plant pathogen Cryphonectria parasitica, is ascomyccte fungus that causes chestnut blight. It was accidentally introduced on tree imported from Asia in early 1900s, spores of the fungus entered cracks in the bark of American chestnut trees and produced hyphae, killing many trees. Today, only sprouts from stumps of former trees are surviving in once chestnuts forest. 71 Some fungi that attack crops produce compounds that are toxic to humans Fungi as parasite The ascomycete Claviceps purpurea grow on rye plants, forming purple structure called ergots. When infected rye consumed by humans, it can cause ergotism, characterizes by gangrene, nervous spasms, burning sensations, hallucinations and temporary insanity. One compound that have been isolated from ergots is lysergic acid, the raw material which hallucinogen LSD is made. Painting by Matthias Grünewald of a patient suffering from advanced ergotism from approximately 1512–16 CE 72 Fungi as parasite Batrachochytrium dendrobatidisor (Bd) • Animals are much less susceptible to parasitic fungi than are plants • The chytrid Batrachochytrium dendrobatidis has been implicated in the decline or extinction of about 200 species of amphibians worldwide Bd: Amphibian Plague juDb60KM 73 Fungi as parasite Animal Infection By Fungi • The general term for a fungal infection in animals is mycosis (plural, mycoses) • Ringworm and athlete’s foot (ascomycetes) are examples of human mycoses • Systemic mycoses spread through the body • For example, coccidioidomycosis produces tuberculosis-like symptoms • Some mycoses are opportunistic • For example, Candida albicans, which causes yeast infections 74 Fungi have many practical uses • Decomposer and recyclers of organic matter. • Mycorrhizae increase productivity of farming. • Human consumption (mushrooms, morels, truffles). • Used to ripen cheese (Roquefort and other blue cheese). • Yeast for food and alcohol production. • Medical usage (drug produced from ergot is used to lower blood pressure, antibiotics, cyclosporine that is used to suppress the immune system after transplants). Staphylococcus Penicillium Zone of inhibited growth 75 Practical Uses of Fungi, Continued • Genetic research on fungi is leading to applications in biotechnology • For example, scientists are using Saccharomyces to study homologs of the genes involved in Parkinson’s and Huntington’s diseases • For example, insulin-like growth factor can be produced in the fungus Saccharomyces cerevisiae • For example, Gliocladium roseum, a fungus that produces hydrocarbons similar to diesel fuel, could be used to produce biofuels 76 Entomopathogenic Fungus 77
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Explanation & Answer


Running head: Yeast


Yeast (Fungi)


Yeast is a unicellular eukaryotic microbe that belongs to the Fungi Kingdom together with

the mold and the mushrooms. A key characteristic that differentiates the Fungi from other
kingdoms such as plants is the presence of a structural component found in their cell walls known
as the chitin. As Gherbawy & Voigt (2010) indicates, the rigidity of the cell is attributed to this
chitin. Most of us are aware that yeast is an important microorganism with respect to the brewing
of alcoholic beverages, bioremediation, production of non-alcoholic drinks, baking, probiotics,
genetic engineered biofactories, and industrial production. It is an important microbe to study
because its DNA can be manipulated by biological processes as well a...

Great study resource, helped me a lot.


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