Eukaryotic Micro-organisms: Protists and Fungi PDF

Topic 7 Eukaryotic micro-organisms: Protists and Fungi Learning objectives (LOBs) Describe the different types and categories of protists and their role in human disease. Describe the different categories of fungi and their potential role in human disease. Reading: - Chapter 28 (Protists) - Chapter...

Topic 7 Eukaryotic micro-organisms: Protists and Fungi Learning objectives (LOBs) Describe the different types and categories of protists and their role in human disease. Describe the different categories of fungi and their potential role in human disease. Reading: - Chapter 28 (Protists) - Chapter 31 (Fungi) Domains of Livingorganisms Domain Eukarya includes 4 kingdoms: – Protists – Fungi – Plants – Animals Βasic categories of living organisms Prokaryotic Εukaryotic Μicroοrganisms Αrchaea Βacteria Protists Fungi Μacroοrganisms Do not exist Animals Plants Eukaryotic micro-organisms Protists: mostly unicellular eukaryotic microorganisms Protist types: - Protozoa (e.g. amoebas) - Algae (e.g. seaweeds) Fungi: unicellular or multicellular eukaryotic microorganisms Fungal types: - Yeasts: unicellular fungi (e.g. S.cerevisiae) - Multicellular fungi (e.g. mushrooms, molds) Eukaryotic micro-organisms Part I: Protists Protists Protist categories: 1. Protozoa: - Do not have cell wall or chlorophyll - Mostly unicellular - Includes several pathogenic species => eukaryotic parasites - Example: amoebas 2. Algae: - Have cell wall and chlorophyll - Photosynthetic organisms - Some species are multicellular - Example: seaweeds Protist types Amoeba (protozoon) Algae (seaweeds) Red algae Green algae Protists properties Most protists are unicellular, but some species are multicellular or can form multicellular colonies Motility: cilia or flagella Reproduction: asexual or sexual reproduction Various nutritional modes: – Photoautotrophs: contain chloroplasts, perform photosynthesis – Heterotrophs: absorb organic molecules or ingest larger food particles (by phagocytosis) – Mixotrophs: which combine photosynthesis and heterotrophic nutrition Four Supergroups of Eukaryotes Domain Eukarya (including protists) is divided into 4 supergroups These include the kingdoms of Animals, Plants, Fungi and several groups of Protists Four supergroups of Eukarya: 1. Excavates 2. SAR 3. Archaeplastids 4. Unikonts Parabasalids Euglenozoans Apicomplexans Ciliates Diatoms Stramenopiles Golden algae Brown algae SAR Oomycetes Forams Radiolarians Green algae Chlorophytes Charophytes Land plants Archaeplastida Red algae Rhizaria Cercozoans Domain Eukarya Chromalveolates Dinoflagellates Alveolates Animals, Plants, Fungi and several Protistgroups (yellow colour) Excavates Chromalveolata Diplomonads Excavata Four Supergroups of Eukaryotes Rhizarians Archaeplastids Gymnamoebas Entamoebas Nucleariids Opisthokonts Fungi Choanoflagellates Animals Unikonta Amoebozoans Slime molds Unikonts 1. Supergroup Excavates Parabasalids Euglenozoans Excavata Diplomonads 1. Supergroup Excavates The supergroup Excavates is characterized by the presence of a feeding groove in some members - Excavate subgroups: Diplomonads: e.g. Giardia intestinalis Parabasalids: e.g. Trichomonas vaginalis Euglenozoans: e.g. Trypanosomes I. Diplomonads: Giardia intestinalis (Giardia lamblia) Diplomonad characteristics: Flagellated protozoa with modified mitochondria (mitosomes) Pathogenic parasite: causes gastroenteritis (food poisoning) Transmission: food- borne disease Giardia intestinalis: a diplomonad parasite II. Parabasalids: Trichomonas vaginalis Parabasalid characteristics: Flagellated protozoa with modified mitochondria (hydrogenosomes) Pathogenic parasite: causes vaginitis in women, urethritis in men Sexually transmitted disease flagella nucleus Trichomonas vaginalis in a cervical smear Trichomonas vaginalis: a parabasalid parasite Trichomonas vaginalis structure Trichomonas vaginalis 5 m Flagella Undulating membrane III. Euglenozoans Morphological characteristic: spiral or crystalline rod inside their flagella Euglenozoa: - Kinetoplastids: include pathogenic species e.g. Trypanosomes - Euglenids: non-pathogenic Euglenozoans Flagella 0.2 m 8 m Crystalline rod (cross section) Ring of microtubules (cross section) Euglenozoans: Kinetoplastids Kinetoplastids: have a single mitochondrion Pathogenic species: Trypanosoma brucei: which causes sleeping sickness in humans (African trypanosomiasis) - transmitted by the tsetse fly (genus Glossina) - CNS infection => lethargy, coma, death Trypanosoma cruzi: causes Chagas’ disease (American trypanosomiasis) - transmitted by triatomine bugs (genus Triatoma) -Symptoms: chronic myocardiopathy Trypanosoma brucei: a kinetoplastid 9 m Red blood cells Trypanosoma brucei Trypanosoma brucei presence in blood Trypanosomes Τrypanosomes in blood Blood smear 2. Supergroup SAR SAR= groups Stramenopiles, Alveolates,Rhizaria Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Stramenopiles Brown algae Forams Radiolarians Rhizaria Oomycetes Cercozoans Rhizaria Chromalveolata Alveolates A. Alveolates Alveolates have membrane-bounded sacs (alveoli) underneath their plasma membrane The alveolates include: – Apicomplexans: contain pathogenic species – Dinoflagellates – Ciliates Alveolates Flagellum Alveoli 0.2 m Alveolate Alveolates: alveoli sacs underneath the plasmamembrane I. Apicomplexans Apicomplexans are pathogenic parasites => some cause serious human diseases They spread through their host as infectious cells called sporozoites Their apex contains organelles specialized for penetrating host cells and tissues Require 2 or more different host species for completion of their life cycle Pathogenic species: - Plasmodium malariae => causes malaria - Toxoplasma gondii => causes toxoplasmosis Apicomplexans: Plasmodium malariae Plasmodium malariae: causes malaria Transmission: by mosquitoes - Reproduction in the RBC => haemoglobin digestion  Natural selection favoured selective survival of the thalassaemia allele carriers (heterozygotes) in areas with high prevalence of malaria 900,000 deaths/ year from malaria Ongoing efforts for vaccine development Red blood cells (RBC) Plasmodium malariae in a blood smear Blood smear Inside mosquito Inside human Plasmodium lifecycle Merozoite Sporozoites (n) Liver Liver cell Apex Oocyst MEIOSIS Red blood cell Merozoite (n) Zygote (2n) Red blood cells 0.5 m Infectious cells: Sporozoites: infect liver cells Merozoites: infectRBC FERTILIZATION Gametes Gametocytes (n) Key Haploid (n) Diploid (2n) Apicomplexans: Toxoplasma gondii Toxoplasma gondii: causes toxoplasmosis Transmission: (a) Oral-faecal route - by consuming contaminated raw or undercooked meat - by ingesting anything contaminated with cat or other animalfaeces (b) Trans-placental transmission: from mother to fetus => can cause abortion, hydrocephalus, mental retardation of the fetus Toxoplasma gondii Toxoplasmosis II. Ciliates Ciliates: use cilia to move and feed Example: Paramecium Paramecium: ciliated protozoon Ciliates: morphology Oral groove Contractile vacuole 50 m Cell mouth Cilia Micronucleus Macronucleus Food vacuoles (a) Feeding, waste removal, and water balance B. Stramenopiles Characterised by presence of smooth or hairy flagella Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Stramenopiles Brown algae Oomycetes Chromalveolata Alveolates III and IV. Dinoflagellates and Diatoms Dinoflagellates: have 2 flagella (belong to Alveolates) Diatoms: photosynthetic protists (belong to Stramenopiles) Major components of the phytoplankton Flagella A dinoflagellate Diatoms: unicellular algae V and VI. Golden algae and Brown algae Golden algae Unicellular algae (form multicellular colonies) Brown algae (seaweeds) Multicellular algae VII. Oomycetes Oomycetes: water molds and their relatives They were initially considered fungi based on morphological studies Phylogenetic analysis categorized them under Protists Most oomycetes are decomposers or parasites Example: - Phytophthora infestans: causes potato blight - Phytophthora ramorum: causes oak death Potato blight C. Rhizaria Forams Radiolarians Rhizaria Cercozoans C. Rhizaria Includes several types of amoebas with threadlike pseudopodia Pseudopodia: cytoplasmic projections - role in motility and phagocytosis E.g. marine, freshwater amoebas Globigerina: a foram in the supergroup Rhizaria Threadlike pseudopodia 3. Supergroup Archaeplastids Includes Plants and some Protists groups Protist groups: - Red algae - Green algae: Chlorophytes and Charophytes Green algae Chlorophytes Charophytes Land plants Archaeplastida Red algae Figure 28.20 Bonnemaisonia hamifera 20 cm I. Red algae - Red colour due to phycoerythrin pigment - E.g. tropical seaweeds 8 mm Dulse (Palmaria palmata) Nori II. Green algae Ulva (sea lettuce) Caulerpa, an intertidal chlorophyte Volvox: a colonial freshwater green alga 4. Supergroup Unikonts Slime molds Amoebozoans Gymnamoebas Nucleariids Fungi Opisthokonts Choanoflagellates Animals Unikonta Entamoebas 4. Supergroup Unikonts Includes 2 groups: I. Amoebozoans: amoebas with lobe or tube shaped pseudopodia Slime molds Gymnamoebas: in aquatic enviroments Entamoebas: includes pathogenic species II. Opisthokonts: Animals, Fungi, and 2 Protist groups - Protist groups: Nucleariids Choanoflagellates I. Amoebozoa: lobe-shaped pseudopodia A unikont amoeba pseudopodia Entamoebas Entamoebas: animal parasites (pathogens) Pathogenic species: - Entamoeba histolytica: causes amebic dysentery -3rd leading cause of human death due to eukaryotic parasites - Acanthamoeba: contact lenses eye infection (keratitis), encephalitis Intestinal ulcers due to infection with Entamoeba histolytica Role of protists in ecologicalcommunities Symbiotic protists: – Dinoflagellates: role in development ofcoral reefs – Wood-digesting protists: digest cellulose in the gutof termites Photosynthetic protists: - Major energy producers in aquaticenvironments Pathogenic protists: parasitic protists – Plasmodium malaria: causes malaria – Pfiesteria shumwayae: a dinoflagellate that causes fish kills Classification of Eukaryotes Eukaryotes (domain) Excavates (supergroup) SeveralProtist groups (Parabasalids, Diplomonads, Euglenozoans) SAR (supergroup) Several Protist groups (Stramenopiles Alveolates, Rhizarians) Archaeplastids (supergroup) 2 Protist groups (Red algae and Green algae) and Plant (kingdom) Unikonts (supergroup) SeveralProtist groups, Fungi and Animals (kingdoms) Figure 28.UN06a Summary (part I) SAR clade Figure 28.UN06b Summary (part II) SAR clade Note: Chromalveolates and Rhizarians are now classified as one supergroup called the SARclade Summary: human pathogenic Protists Protist name Disease Protist group Giardia intestinalis (Giardia lamblia) Gastroenteritis (food poisoning) Diplomonad (Supergroup Excavates) Trichomonas vaginalis Vaginitis (women), urethritis (men) Parabasalid (Supergroup Excavates) Trypanosoma brucei African trypanosomiasis (sleeping disease) Kinetoplastid Euglenozoan (Supergroup Excavates) Trypanosome cruzi American trypanosomiasis (Chagas’ disease) Kinetoplastid Euglenozoan (Supergroup Excavates) Plasmodium malariae Malaria Apicomplexan Alveolate (Supergroup SAR) Toxoplasma gondii Toxoplasmosis Apicomplexan Alveolate (Supergroup SAR) Entamoeba histolytica Amebic dysentery Entamoeba amoebozoan (Supergroup Unikonts) Acanthamoeba Eye infection, encephalitis Entamoeba amoebozoan (Supergroup Unikonts) SBA example Which eukaryotic supergroup does Acanthamoeba belong to? A. B. C. D. E. Amoebozoans Archaeplastids Excavates SAR Unikonts SBA example What does Trichomonas vaginalis cause? A. B. C. D. E. Botulism Gastroenteritis Meningitis Tetanus Vaginitis