MicroB-03-Lesson-3.pdf

MicroB 03: Mycology 27/08/2024...

MicroB 03: Mycology 27/08/2024 Objectives MicroB 03 Understand and describe the diversity and classification of fungus-like Mycology organisms under Kingdom Protista and Chromista, including their The Pseudofungi: Kingdom distinguishing characteristics and life cycles. Protista and Chromista Describe the structural adaptations and reproductive strategies, and Prince Nur-Hakeem N. Buisan, RMicro., MSc. their impact on ecosystems and human activities of fungus-like organisms. Analyze the biological and ecological significance of key fungus-like phyla. Evolution of Biological Classification Systems Review (1735-2015) = indicates placement of “fungi” in this course Linnaeus Haeckel Chatton Copeland Whittaker Woese Woese et al. Cavalier- Cavalier- Ruggiero (1735) (1866) (1925) (1956) (1969) & Fox (1990) Smith Smith et al. Fungi are heterotrophic eukaryotes Cell Wall Composition 2 Kingdoms 3 Kingdoms 2 Empires (1977) (1993) (1998) (2015) 4 Kingdoms 5 Kingdoms 6 kingdoms 3 Domains 8 Kingdoms 6 Kingdoms 7 Kingdoms that absorb their food through True fungi (Eumycota) have cell walls osmotrophy. They do not Eubacteria Bacteria Eubacteria Bacteria made primarily of chitin, a strong but photosynthesize and rely on organic flexible polysaccharide. In contrast, Prokaryota Mychota Monera Archae- Archaea Archae- Bacteria Archaea matter for nutrition. bacteria bacteria fungus-like organisms like Oomycota Not treated Protista Structure have cell walls containing cellulose. Archezoa Protozoa Protozoa Protozoa The fungal body, or thallus, typically Importance Protista Protista Protista Chromista Chromista Chromista consists of a network of fine, Fungi play critical roles in ecosystems branching tubes called hyphae, as decomposers, symbionts, and Vegetabilia Plantae which collectively form a mycelium. pathogens, making them essential Eukaryota Plantae Plantae Eucarya Plantae Plantae Plantae This structure allows fungi to explore for nutrient cycling and ecological Plantae and colonize substrates. balance. Animale Animalia Fungi Fungi Fungi Fungi Fungi Mycelium - collective form of hyphae Animalia Animalia Animalia Animalia Animalia Animalia MicroB 03: Mycology 27/08/2024 Classification of Fungus-like Organisms Protosteloid Amoeba (Phylum Amoebozoa) Kingdoms Protosteloid amoebozoans, formerly called protostelids, are a non-monophyletic assemblage Protista (Pseudofungi): of Amoebozoa one point in their development, an amoeba rounds up Phyla Myxogastria, Dictyostelida, Protostelids, Acrasids, on the surface of a substrate and develops into a subaerial fruiting body, or sporocarp Plasmodiophorida The sporocarp consists of a noncellular, Chromista (Pseudofungi): microscopic stalk-bearing one to a few terminal spores Phyla Hyphochytriomycota, Labyrinthulomycota, and Oomycota Amoeboid states of protosteloid amoebae vary considerably in morphology, and many species have life cycles that include both amoeboflagellates, a cell type that can reversibly transform from amoeba to flagellate, and obligate amoebae, a cell type that exists only as Protostelium mycophaga an amoeba Protosteloid Amoeba (Phylum Amoebozoa) Protosteloid Amoeba (Phylum Amoebozoa) Characteristics: Myxamoeba – uninucleate or multinucleate, with filose pseudopodia Plasmodium (in Ceratiomyxa & Ceratiomyxella) – diploid by fusion of biflagellate isogametes, then multinucleate by synchronous nuclear division; protoplasmic flow, if present, unidirectional Sporocarp – solitary, formed directly from a single myxamoeba, or in Ceratiomyxa & Ceratiomyxella, in aggregates if developed by fragmentation of a single plasmodium Spore – solitary-2-4-8-several to a sporocarp MicroB 03: Mycology 27/08/2024 General Life Cycle of Protostelids Simple Life Cycle: Protostelium Without Plasmodial Stage (A) Mature sporocarp with (A) Mature fruiting body with spore solitary uninucleate spore siting atop non-cellular stalk (B) Amoeba from germinated (B) Spore spore (C) Spore germination into an amoeba (C) Early prespore cell (D) Encystment of amoeba (D) Prespore cell just prior (E-F) Amoeba rounds up, becomes ellipsoid, and elevates itself by to stalk formation formation of a basal stalk. At stalk maturity, cell body gets walled as (E) Culminating sorogen a spore shot off Complex Life Cycle: Ceratiomyxella spore spores apophysis (A) Mature sporocarp stalk (B) Spore germination to release multinucleate protoplast, which may develop into a plasmodium (K) (C) Or the multinucleate protoplast becoming a zoocyst with only one nucleus surviving Protostelium mycophaga Nematostelium ovatum Protostelium nocturnum spore sways in air current; stalk tip refractive along entire height; spore ballistosporous, entire stalk no longer (D-F) Zoocyst undergoes 3 mitotic swells after spore discharge (arrows) ovate; apophysis distinct visible right after spore release nuclear divisions (G-H) Zoocyst germinating into 8 or fewer biflagellate cells (I-J) Amoebomastigote stages (K) Amoeboid stage transformed into multinucleate plasmodium (L) Plasmodium may fragment into zoocyst (C) Protostelium pyriformis Endostelium zonatum Protostelium arachisporum (M) Or plasmodium cleaving into spore freely swings in air current; stalk noticeably widens above basal disc; attached spore swings in air current, prespore cells distinctly pyriform stalk beaded spore slightly constricted at middle (N) Rising sporogen MicroB 03: Mycology 27/08/2024 A Cavostelium apophysatum Echinostelium bisporum Tychosporium acutostipes short stalk with cup-like apophysis; 1-spored short stalk; 2-spored long stalk tapered to point tip; spore single SIMPLE LIFE CYCLE, UNI-BISPORED, NON-DECIDUOUS B B A C D Ceratiomyxa fruticulosa Ceratiomyxa hemisphaerica Ceratiomyxella (A) Endostelium zonatum, (B) Schizoplamodiopsis vulgare, stalked spores or sporangia on coralline white sporocarps several sporocarps arranged on a slime column or pad deposited by (A) sporocarps and (B) plasmodium (C) Echinosteliopsis zonatum, (D) Cavostelium apophysatum developed from single plasmodium one plasmodium prior to dividing into prespore cells COMPLEX LIFE CYCLE, MULTI-SPORED, DECIDUOUS Acrasid Slime Molds (Phylum Percolozoa: Class Heterolobosea) Heterolobosea is a group of ~150 described species of heterotrophs, almost all free living Many are “amoeboflagellates” with a three-phase asexual life cycle, centered on trophic amoebae that can reversibly transform into flagellates (some of which undertake phagocytosis and/or division) and cysts. Ceratiomyxa porioides The amoebae are usually lobose, with “eruptive” pseudopodia. Ceratiomyxa fruticulosa Lobose is having broad, thick pseudopodia Acrasis rosea MicroB 03: Mycology 27/08/2024 Life Cycle: Sappinia pedata (1-2) Binucleate cells (3-4) Amoebae standing (upright) and crawling on fungal hypha (3) and on agar (4) (A) Vegetative, binucleate (5) Bicellular cyst (above) and two amoebae adjoined prior to encystment amoeba (6) Unicellular cyst (B) Upright (standing) (7) Uninucleate amoebae (8) Trinucleate amoeba amoeba (C) Two amoebae coming Sappinia (9) Tetranucleate amoeba (10) Cluster of amoebae on agar together pedata (11) Standing amoeba on agar (12-13) Same amoeba in (11) has fallen (D) Encapsulation of and becomes active as trophic amoeba amoebae within common cell wall (E) Bicellular cyst (F) Unicellular cyst (may be sexual, but formation and fate not unknown) 11 12 13 Life Cycle: Fonticula alba Fonticula alba (A) Mature sorocarp with a mucoid spore mass (sorus) atop stalk made of extracellular matrix material. Not all spores incorporated into the spore mass. at maturity. Some sorogenic amoebae remain and do not become spores at bottom of sorocarp (A-D) Typical trophic (B-C) Spores germination to amoebae amoebae with filose with filopodia pseudopodia (bar = 10 (D) Encystment of amoebae; cyst similar morphologically to spore µm). (E) Multicellular (E) Amoebae aggregate and form a mound sorocarp, (F) Aggregate forms a common slime side view(bar = 100 sheath, and sorogenic amoebae secrete µm). (F) Mature extracellular matric of stalk material sorocarps on agar (G) Upper two-thirds of amoebae encyst in viewed from above (bar the stalk and become spores (H) At stalk maturity, a bulge forms at apex = 500 μm) and spores are mechanically forced upward into sorus, which expands as more spores are forced upward MicroB 03: Mycology 27/08/2024 Life Cycle: Copromyxa protea Copromyxa protea (A) Mature sorocarp solely consisting of A B C (A-B) Mature columnar (A) sorocysts or functional spores and arborescent (B) (B) Germination of sorocysts as amoebae sorocarps on dung (bar = (C) Trophic amoebae limax-type and 100 µm). (C) Mature uninucleate columnar sorocarp on agar (bar= 50 µm). (D-I, bar = (D) Encystment of amoeba to microcyst 10µm) (D) Sorocysts from (E) Amoebae may aggregate in which a sorocarp on dung; founder cell of sorocarp encysts and sorocysts germinate amoebae of aggregate crawl on top and leaving empty wall. (E) encyst to form sorocysts Uninucleate limax amoeba (F-I) Surrounding amoebae continue to crawl up the column of sorocysts and with anterior hyaloplasm encyst at apex and a posterior contractile D E F G H vacuole. (F) Uninucleate (J-L) Trophic amoebae may come together, the two presumably undergo plasmogamy amoeba with uroid (J), then karyogamy (K), and then form a consisting of adhesive thick-walled, diploid sphaerocyst (L) filaments. (G) Amoeba I with secondary uroid pseudopodium (H) Copromyxa protea is the first slime mold found to be in the Microcyst. (I) Sphaerocyst. class Tubulinea of the supergroup Amoebozoa (A) Two sorocarps fruiting in close proximity; both are Life Cycle: Acrasis rosea Acrasis rosea branched and have an amorphous spore mass at the (A) Mature arborescent sorocarp with apex of the stalk, from which D E F chains of spores (dark tone = stalk branches emanate. Scale bar G cells, light tone = distal spore cells) = 100 μm. (B) Uniseriate B C (B-C) Spores germinate as limax sorocarp. Scaled to A. (C) amoebae; stalk cells do not germinate Tangled sorocarp structure (D) Amoebae may form microcysts common in agar culture. H that can germinate back to amoebae Scale bar = 100 μm. (D) (E) Aggregation of amoebae into a Pocheinoid sorocarp with a A simple stalk and globes spore small mound mass. Scaled to A. (E) (F) Aggregation stops Developing sorocarp, where (G) One cell in aggregation encysts to 2 stalked sorogens coalesced. become the first stalk cell; mass of Scale bar = 100 μm. (F) Same I-J amoebae (sorogen) remains on top of developing sorocarp as in E. stalk cell 30 min. after E was taken. (H-J) Cells in sorogen encyst to form Scaled to E. (G) Spore with 2 next basal stalk cells; sorogen elevates as stalk cells encyst prominent raised areolate hila. Scale bar = 10 μm. (H) L K (K-L) Cells of sorogen align into chains Uninucleate limax amoeba of amoeboid cells and then encyst as spores with an obvious uroid that has several trailing filaments. Scaled to G. (I) Two round cysts. Scaled to G MicroB 03: Mycology 27/08/2024 Life Cycle: Acrasis helenhemmesae Acrasis helenhemmesae (A) Mature sorocarp arranged as a uniseriate chain of spores. Sorocarp displays 2 basal elongate stalk cells with 7 distal spore cells (1-5) Mature sorocarps with (B) Spores germinate as amoebae, have unbranched or branched, uniseriate raised hila, and with the spore walls persisting spore chains (bars = 50µm). (6) after germination Spore with distal and proximal hila (arrows) at spore-to-spore (C) Trophozoites are limax amoebae connections. (7) Uninucleate (D) Amoebae may form microcysts, which can amoeba with central nucleolus. (8) germinate back to amoebae Three spores of a sorocarp, the middle germinated leaving an (E) Amoebae aggregate to form small mound empty spore wall. (9) Uninucleate (F) A cell in the aggregate encysts to become amoeba with a hyaloplasmic bulge the first stalk cell, with a mass of amoebae, the in direction of locomotion. (10) Amoeba with two prominent uroid sorogen, remaining on top of newly encysted filaments opposite the direction of stalk cell locomotion. (11-12) Microcysts. (G) A cell in the sorogen encysts to become (13) Two crescent-shaped the next basal elongate stalk cell, with the microcysts and wall of one other sorogen elevating by virtue of stalk cell uroid germinated microcyst (6-13, bars = encystment 10µm) (H) Cells of the sorogen align in a column and then encyst to become spores Acrasis takarsan Sorocarps: Acrasis spp. (A) Sorocarp with a simple uniseriate stalk and a complex basket-shaped spore mass (B) Spores with prominent hila (C-D) Uninucleate limax amoebae (E) Cysts (B-E, bars = 10 μm) A. helenhemmesae branching spore mass branching spore chains Acrasis kona (A-B) Mature sorocarps with highly complex branching of spore chains and thick-based stalks tapered to a globose spore uniseriate row of stalk cells spore mas(sorus) chain (C) Canopy of spores viewed from above A. takarsan (D) Sorocarps in various stages of development (A-C, bars = 100μm) A. kona A. rosea (E) Same developing sorocarps in (D) amorphous spore mass 30 min after (F) Uniseriate sorocarp (G) Spores with prominent hila (H) Amoeba (I) Cyst Sorocarps: Acrasis spp. MicroB 03: Mycology 27/08/2024 Cellular Slime Molds (Phylum Amoebozoa: Dictyostelids vs. Acrasids (Alexopolous et al., Class Dictyostelia) 1996) Characters Dictyosteliomycota Acrasiomycota Dictyostelia are common amoebae, mostly known from forest soil and litter. Pseudopodia of Filose Lobose The life cycle involves independent myxamoebae amoebae that aggregate in response to Mitotic apparatus Spindle pole body present Spindle pole body absent cyclic AMP (cAMP) to form a pseudoplasmodium, also known as a slug. Pheromone cAMP (cyclic AMP), others Unknown Dictyostelium discoideum is a model organism used to study cell differentiation Migration of “slug” Present Absent and signaling. When conditions become unfavorable, the Prespore vacuoles Present Absent slug forms a structure called a sorocarp, which produces spores. No germination of stalk Sorocarp differentiation Stalk cells germinate Dictyostelium is widely used in research on cells cell motility, chemotaxis, and the evolution Spore and cyst wall Cellulose Unknown of multicellularity. Flagella Non-flagellate Biflagellate cells in some Sexual reproduction Macrocyst formation ? Unknown Life Cycle: Dictyostelium discoideum Life Cycle: Developmental Cycle Dictyostelium discoideum. (A) Mature fruiting body consists of a stalk formed from sacrificed dead cells, with a spore mass sitting atop. (B) Spore germinates as an amoeba (C). (D-E) Amoebae aggregate. (F) The aggregate (pseudoplasmodium) forms a slug that can migrate. (G-H) The pseudoplasmodium then undergoes a complex process of fruiting. MicroB 03: Mycology 27/08/2024 Alternative Developmental Pathways Macrocyst Myxamoebae (n) Fruiting body (sorocarp) (n) binary (asexual) fission pseudoplasmodium (slug) in stalkless migration food ingestion multicellular and cell division (sexual) Myxamoeba Macrocyst (2n) Myxamoeba Microcyst (n) Induction of Microcyst Formation & Germination Germination: Spore to Myxamoeba  Microcyst formation is induced by high osmotic pressure (i.e., 0.2M sucrose) or high concentrations of ammonia. Each myxamoeba rounds up and forms a food cellulose-rich microcyst wall bacteria food vacuole  Microcysts (germination) remain dormant as long as stress is present. Simply washing the cells can lead to germination, with each cyst releasing a single myxamoeba. Germination involves a controlled nucleus sequence of events beginning with swelling and followed by emergence of the myxamoeba spores C cyst (c) myxamoebae filose pseudopodia m m nucleus dormant cells washed swollen release of myxamoebae (m) MicroB 03: Mycology 27/08/2024 Microcyst Germination Macrocyst Formation dormant swollen emergent microcyst microcyst myxamoeba Enzyme Enzyme System I System II A B C cyst wall the polyvesicular bodies swell; polyvesicular bodies shrink; protein protein synthesis started but not synthesis required; RNA synthesis required; ER dilates; cell wall starts but is not required; ER loosens decreases in size; cell wall digested A B C Sorocarp Morphotypes Sorocarp Morphotypes (A) Acytostelium – A B C typical dictyostelid sori, fresh as slime drops with unicellar spores (inset); the stalks are acellular. (B) Dictyostelium polycephalum – coremiform sorocarp compressed consisting of as many cellular stalks as many as laterally compressed sorus number of cellular stalks as number terminal sori of stalked sori. (C) Reticulum of cell walls of dead (“sacrificed”) stalked acellular stalk cells within cellulose cylinder in stalks of Dictyostelium and spores Polyspondylium species. MicroB 03: Mycology 27/08/2024 cream-white Phylogeny All known species can be subdivided into four major sorus violet sorus groups based on phylogenetic analysis of their small subunit ribosomal RNA sequences. Group 1 (red) is most closely related to solitary amoebozoan ancestors. acropetal formation of whorls of Groups 1-3 retains the small, lateral Dictyostelium-like sorocarps from posterior of the ancestral survival strategy of terminal sorogen encystment of individual myxamoebae. This strategy is lost in Group 4 (purple), the most recently diverged group (includes the model organism D. discoideum). Group 4 species also show other features, e.g., use of cAMP as a chemoattractant and cellular supports for the fruiting body, that are not (or Dictyostelium seldom) displayed by species in rosarium mucoroides purpureum Polysphondylium violaceum Groups 1-3 Plasmodial Slime Molds (Phylum Amoebozoa: Types of Life Cycles Class Myxogastria) The myxomycetes (class Myxogastria), also Apogamic Life Cycle commonly known as plasmodial slime molds or The condition of a myxomycete having a nonsexual life cycle without acellular slime molds, are the most species-rich ploidy variation and, therefore, no fusion of haploid gametes group within the Amoebozoa with approximately 1,000 morphologically Heterothallic Life Cycle recognizable species having been described. The life cycle features a macroscopic, slimy, Describes a sexual reproductive system with mating-types controlling amoeboid plasmodium phase. amoeboflagellate fusion to produce a diploid plasmodium. These organisms are commonly found in soil, This requires two genetically compatible sexual gametes controlled by decaying wood, and other organic matter. a one-locus, multiple allelic mating system. Myxomycetes can be kept as "pets" in laboratories, feeding on bacteria and small These sexual systems are found in Physarum polycephalum, organic particles, making them interesting Didymium iridis, and Physarum pusillum models for studying cellular processes. MicroB 03: Mycology 27/08/2024 Morphology of Fruiting Bodies Heterothallic Life Cycle Apogamic Life Cycle Types of Plasmodia Phaneroplasmodium: multinucleate, diploid, acellular mass of A B F protoplast, the veins prominent and with rapid bidirectional protoplasmic streaming; common and readily seen in nature Aphanoplasmodium: also acellular and In vitro on water agar and fed with bits of raw oatmeal multinucleate; formed in C D E G film of water; transparent and inconspicuous; the veins with slow protoplasmic streaming Protoplasmodium: microscopic, diploid, uninucleate (A-F) Phaneroplasmodia; (C) network of veins & veinlets enlarged Aphanoplasmodium MicroB 03: Mycology 27/08/2024 Sclerotia Types of Sporocarps Sporangium Aethelium Pseudoaethelium Plasmodiocarp - Stalked or sessile - large, sessile, mound or - Fusion of many - sessile, elongated, worm-like, - Often with round-shaped sporangia packed branched network, or ring- spherical spore - Formed from a single together shaped case plasmodium multiple sclerotia formed in water - Fuligo and Lycogala agar plate with bits of oatmeal 7 days after seeding at center with one part of x-section of sclerotium; spherules with sclerotium variable number of 2n nuclei (darkened) Sporocarps of Common Local Myxogastrids fruiting on grass blades Fuligo septica Arcyria cinerea Ceratiomyxa fructicola Stemonitis axifera Arcyria ferruginea immature mature Ceratiomyxa fructicola enlarged Stemonitis axifera Didymium sp. Trichia sp. Fuligo septica MicroB 03: Mycology 27/08/2024 Metatrichia vesparium Arcyria denudata Hemitrichia serpula Diderma sp. Diderma hemisphaericum Dictydiium cancellatum Tubifera ferruginosa Physarum nutans Physarum pusillum Physarum bogoriense Arcyria cinerea: Sequential Fruiting A B C D E F Leocarpus fragilis (immature mature) MicroB 03: Mycology 27/08/2024 Stemonitis fusca: Sequential Fruiting Badhamia utricularis: Sequential Fruiting A B C A B D E F C D (1) environmentally resistant resting spore Phytomyxids (Class Phytomyxea) Life Cycle (2) biflagellate primary zoospore (3) location of host cell by zoospore and commencement of encystment – for many plasmodiophorids, primary infection occurs in root hairs Endoparasites of Plantae or heterokont hosts Two Orders: Plasmodiophorida (soil/freshwater) (4) cell penetration by Stachel (bullet-like structure) via a Rohr (tubular cavity) followed by zoospore contents and Phagomyxida (marine) (5) development of multinucleate plasmodium Obligate parasites of plants, these organisms (6) multilobed structure containing zoosporangia produce biflagellate zoospores that infect plant roots. (7) secondary zoospore – reinfection of host cells occurs by encystment as in 3 and 4, or via a myxamoeboid Persist in the environment as thick-walled, phase (dashed lines to 8) uninucleate resting spores (8) secondary plasmodium Plasmodiophora brassicae causes "club root" (9) resting spores or aggregates in cabbages and other cruciferous plants. Note: Dashed lines - indicate uncertainty about direct The infection leads to root swelling and significant progression to secondary infection mediated via primary crop damage. zoospores or generation of new cycles of primary infection by secondary zoospores Clubroot on cauliflower MicroB 03: Mycology 27/08/2024 Life Cycle: Plasmodiophora brassicae Spongospora subterranea zoosporangia in trypan blue stained potato roots. (a) root with heavily infected root hairs; (b) infected root epidermal cells; (c) root hair with zoosporangia; (d) And (e) root hair and epidermal cells containing empty zoosporangia following zoospore release. left column, Plasmodiophorida; right column, Phagomyxida. (a) Sorosphaerula viticola: hollow sporosori in the roots of Vitis sp. (b) Woronina pythii: resting spores in Pythium sp. (c) W. pythii in Pythium sp.: lobose plasmodium, just starting to develop into resting spores (arrow); right mature resting spores. Phagomyxa bellerocheae infecting the diatom (d) Ligniera junci: resting spores in the root hairs of Juncus Plasmodiophorid plant infections Bellerochea malleus effusus. (e) Maullinia sp. resting spores in Durvillaea antarctica. (f) Plasmodiophora diplantherae: resting spores in enlarged cells of Halodule sp. Arrow: starch grains. (g) Maullinia ectocarpii: hatching zoospores (arrow) from an enlarged infected cell of the host Ectocarpus fasciculatus. Maullinia sp. gall-like structures on infected Durvillaea antarctica fronds MicroB 03: Mycology 27/08/2024 Labyrinthulomycota (Class Schematic Life Cycles Labyrinthulomycetes) Labyrinthulomycetes are unique in forming spindle-shaped cells that move within a network of tubular, polysaccharide sheaths. They cause diseases in marine plants, such as the eelgrass wasting disease caused by Labyrinthula. They play a role in marine ecosystems, especially as parasites of algae and seagrasses, influencing coastal Cell with network of ectoplasmic environments. filaments (Aplanochytrium sp.) Two main clades: Thraustochytrids and Labyrinthulids Hyphochytriomycota and Oomycota Both feature osmotrophic nutrition and have traditionally been considered as zoosporic “fungi,” but are unrelated to organisms in the monophyletic kingdom Mycota Hyphochytriomycota Uniflagellate Have simple nonmycelial, holocarpic thalli 3 families: Anisolpidiaceae, Hyphochytriaceae, Rhizidiomycetaceae Most are saprotrophs or parasites, infecting the resting spores of Oomycota and Glomeromycota MicroB 03: Mycology 27/08/2024 Hyphochytriomycota and Oomycota Oomycota Biflagellate Holocarpic organisms that lack mycelial organization Zoospores have two flagella: one tinsel, one whiplash, and these arise from the side of the cell rather than at the front or the rear, as in other groups. General Phylogeny The zoospores swim with their tinsel flagellum pointing forward, while the whiplash flagellum is directed backward. 2 major clades: Saprolegniomycetes and Peronosporomycetes Oomycota Order Saprolegniales Example: Saprolegnia parasitica, a common water mold, attacks fish and their eggs, leading to significant losses in aquaculture. Life Cycle: Asexual reproduction through mitosporangia that produce biflagellate zoospores. The spores encyst and germinate to produce new mycelium. Asexual Reproduction Saprolegniales Peronosporales Environmental Role: These fungi are decomposers in aquatic systems but can also act as pathogens in fish populations. in Oomycota Order Peronosporales Example: Phytophthora infestans caused the Irish Potato Famine, devastating crops and leading to mass emigration and death. Historical Significance: The famine illustrates the profound impact of plant pathogens on human history and agriculture. Control Measures: Modern agriculture uses fungicides, resistant crop varieties, and forecasting systems to manage such pathogens. MicroB 03: Mycology 27/08/2024 Life Cycles of Animal Pathogenic Saprolegniales: Oomycota Saprolegnia Plant Pathogenic Oomycota Damping-off Disease (Pythium spp.) Mechanism: These soilborne pathogens infect seedlings at the Plant Pathogenic base, causing them to collapse due to enzymatic degradation of cell walls. Oomycota Control Methods: Include soil sterilization, fungicide application, water molds and white rusts, downy and careful management of mildews, and damping-off watering practices. Impact on Agriculture: Affects a wide variety of crops, especially during the early stages of growth. MicroB 03: Mycology 27/08/2024 Plant Pathogenic Oomycota Downy Mildew Diseases Examples: Plasmopara viticola (grape downy mildew) and Life Cycles of Peronospora tabacina (blue mold of tobacco). Peronosporales: Economic Importance: Grapevine Pythium diseases led to the development of Bordeaux Mixture, a critical fungicide in viticulture. Life Cycle: These fungi produce mitosporangia that disperse via air or water, causing widespread infections. Conclusion Fungi and fungus-like organisms display various forms, life cycles, and ecological roles. Life Cycles of They are indispensable in natural ecosystems, agriculture, and Peronosporales: industry. Plasmopara viticola Advancements in mycology can lead to better management of fungal diseases and harnessing fungi for sustainable practices. Causes downy mildew on grapes