Topic 7A: Protists ✅ Flashcards
Domain Eukarya’s kingdoms
- Protists
- Fungi
- Plants
- Animals
Protists are mostly..
Unicellular eukaryotic microorganisms
Protist types
Protozoa (e.g. Amoebas)
Algae (e.g. seaweeds)
Fungi are mostly
Unicellular or multicellular eukaryotic microorganisms
Fungal types
Yeasts
Eg unicellular fungi (S. cerevisiae)
Multicellular fungi
Eg mushrooms, molds
Protozoa
No cell wall
No chlorophyll
Mostly unicellular
Several pathogenic species → eukaryotic parasites
Eg amoeba
Algae
Cell wall
Chlorophyll
Photosynthetic organisms
Some are unicellular (eg seaweeds)
Properties of protists
Most unicellular
Some multicellular or can form multicellular colonies
Motility: cilia or flagella
Reproduction: asexual or sexual
Various nutritional modes: photoautotrophs, heterotrophs, mixotrophs.
Photoautotrophs
Contain chloroplasts
Perform photosynthesis
Heterotrophs
Absorb organic molecules or ingest larger food particles (by phagocytosis)
Mixotrophs
Combine photosynthesis and heterotrophic nutrition
Supergroups of Eukarya
- Excavates
- SAR
- Archaeplastids
- Unikonts
SAR has..
Chromalveolates
Rhizarians
Excavata
Characterized by presence of feeding groove in some
Diplomonads (Giardia intestinalis)
Parabasalids (Trichomonas vaginalis)
Euglenozoans (Trypanosomes)
Diplomonads example
Eg Giardia intestinalis (Giardia lamblia)
Characteristics: flagellated Protozoa with modified mitochondria (mitosomes)
Pathogenic parasite: causes gastroenteritis (food poisoning)
Transmission: food-borne disease
Parabasalipids example
Eg Trichomas vaginalis
Characteritistics: flagellated Protozoa with modified mitochondria (hydrogenosomes)
Pathogenic parasite, causes vaginitis in women, urethritis in men
Sexually transmitted disease
Euglenozoans example
Eg Trypanosomes
Morphological characteristic: spiral or crystalline rod inside their flagella
Euglenozoa:
Kinetoplastids- includes pathogenic species, have a single mitochondrion
Euglenids- non-pathogenic
Trypanosoma brucei
Pathogenic
Causes sleeping sickness in humans (African trypanosomiasis)
-transmitted by the tsetse fly (genus Glossina)
-CNS infection -> lethargy, coma death
Trypanosoma cruzi
Pathogenic
Causes Chagas’ disease (American trypanosomiasis)
-transmitted by triatomine bugs (genus Triatoma)
-symptoms: chronic myocardiopathy
SAR
Stramenopiles & Alveolates, Rhizaria
Chromalveolates
Alveolates
Stramenopiles
Alveolates
Have membrane-bounded sacs (alveoli) underneath their plasma membrane
Include:
Apicomplexans: contains pathogenic species
Dinoflagellates
Ciliates
Apicomplexans
Pathogenic parasites, some cause serious human diseases
Spread through host cell as infectious cells called sporozoites
Apex contains organelles specialized for penetrating host cells and tissues
Require 2+ different host species for completion of life cycle
Eg Plasmodium malariae (causes malaria) and Toxoplasma gondii (causes toxoplasmosis)
Plasmodium malariae
Apicomplexan (pathogenic parasite)
Causes malaria
Transmitted by mosquitoes
-> reproduced in the RBC leading to haemoglobin digestion
->natural secretion favored selective survival of the thalassaemia allele carriers in areas with high prevalence of malaria
900,000 deaths/year
Ongoing efforts for vaccine development
Toxoplasma gondii
Apicomplexan
Causes toxoplasmosis
Transmission:
1. Oral-faecal route:
-by consuming contaminated raw/undercooked meat
-by ingesting anything contaminated with cat or other animal faeces
- Trans-placental transmission:
-from mother to foetus
-can cause abortion , hydrocephalus, mental retardation
Sporozoites
Infect liver cells
Merozoites
Infect RBC
Ciliates
Use cilia to move and feed
Eg paramecium- ciliated protozoon
Ciliates morphology
Cilia
Oral groove
Cell mouth
Food vacuoles
Macronucleus
Micro nucleus
Contractile vacuole
What are stramenopiles characterized by?
Presence of smooth or hairy flagella
Stramenopiles ->
Diatoms
Golden algae
Brown algae
Oomycetes
Dinoflagellates and Diatoms
Dinoflagellates: 2 flagella (in Alveolates)
Diatoms: photosynthetic protists, unicellular (in Stramenopiles)
Major components of phytoplankton
Golden algae and Brown algae
Golden: unicellular (form multicellular colonies)
Brown: multicellular algae
Oomycetes
Stramenopile
Water molds and their relatives
Initially considered fungi, based on morphological studies
-phylogenetic analysis categorized the under Parasites
Most are decomposers or parasites
Eg Phytophthora infestans: causes potato blight
Phtophthora ramorum: causes oak death
Rhizaria ->
Cercozoans
Forams
Radiolarians
Rhizaria
Includes several types of amoebas with threadlike pseudopodia
Eg Globigernina
Pseudopodia
Cytoplasmic projections
-role in motility and phagocytosis
Archaeplastids
Includes plants and some protists groups
Protist groups:
-Red algae and
-Green algae - Chlorophtes and Charophytes
Archaeplastids ->
Red Algae
Green Algae:
-Chlorophtes
-Charophytes
-Land plants
Red Algae
Red colour due to phycoerythrin pigment
Eg tropical seaweeds
Bonnemaisonia hamifera, Dulse (Palmaria palmata), Nori.
Green Algae
Chlorophtes, Charophytes
Eg
Ulva (sea lettuce)
Caulerpa (an intertidal chlorphyte)
Volvox (a colonial freshwater green algae)
Unikonts
Supergroup 4
2 groups:
Amoebozoans
Opisthokonts
Amoebozoans->
Slime molds
Gymnamoebas
Entamoebas
Amoebozoans
In Unikonts
Amoebas with lobe or tube shaped pseudopodia
Slime molds
Gymnamoebas: in aquatic environments
Entamoebas: includes pathogenic species
Opisthokonts
In Unikont supergroup
Animals, fungi, 2 Protist groups
Protist groups: Nucleariids, Choanoflagellates
Structure of an Amoeba
Pseudopodium
Cell membrane
Ectoplasm
Endoplasm
Nucleus
Food vacuole
Digestive vacuole
Contractile vacuole
Entamoebas
Amoebozoa group in Unikont Supergroup
Animal parasites (pathogens)
Eg Entamoeba histolytica: causes amebic dysentry
-3rd leading cause of human death due to eukaryotic parasites
-stomach ulcers
Acanthamoeba: contact lenses eye infection (keratitis), encephalitis
Role of protists in ecological communities: symbiotic protists
Dinoflagellates: role in development of reeefs
Wood-ingesting protists: digest cellulose in the gut of termites
Role of protists in ecological communities: Phtotsynthetic protists
Major energy producers in aquatic environments
Role of protists in ecological communities: Pathogenic Protists
Parasite protists
Plasmodium malaria: causes malaria
Pfiesteria shumwayae: dinoflagellate that causes fish kills
Eukaryotes (domain) -> ____ (Supergroups) -> ___ (groups)
Excavates -> Several protist groups (Parabasalids, Diplomonads, Euglenozoans)
SAR -> Several Protist groups (Stramenopiles, Alveolates, Rhizarians)
Archaeplastids -> 2 Protist groups (Red and Green algae) and Plant [Kingdom]
Unikonts -> Several Protist groups, Fungi and Animal [Kingdoms]
What are Chromalveolates and Rhizarians classified together as?
The supergroup SAR clade
Where may Chromalveolates have originated from?
By secondary endosymbiosis
Supergroup -> Major groups -> key morphological features -> specific examples
Excavates ->Diplomonads and parabasalids
-> modified mitochondria
-> Giardia, Trichomanas
Excavates -> Euglenozoans (Kinetoplastids, Euglenids)
-> Spiral or crystalline rod inside flagella
-> Trypanosoma, Euglena
SAR (Chromalveolates) -> Alveolates (Dinoflagellates, Apicomplexans, Ciliates)
-> Membrane-bounded sacs (alveoli) beneath plasma membrane
-> Pfiesteria, Plasmodium, Paramecium
SAR (Chromalveolates) -> Stramenopiles (Diatoms, Golden Algae, Brown Algae, Oomycetes)
-> Hairy and smooth flagella
-> Phytophthora, Laminaria
SAR (Rhizarians) -> Radiolarians
-> Amoeba with threadlike pseudopodia radiating from central body
-> Hexacontium
SAR (Rhizarians) -> Forams
-> Amoebas with threadlike pseudopodia and a porous shell
-> Globigerina
SAR (Rhizarians) -> Cercozoans
-> Amoebas and flagellated protists with threadlike pseudopodia
-> Paulinella
Archaeplastida -> Red algae
-> Phcoerythrin (accessory pigment)
-> Porphyra
Archaeplastida -> Green Algae
-> Plant-type chloroplasts
-> Chlamydomonas, Ulva
Archaeplastida -> Land Plants
-> ———————
-> Mosses, ferns, conifers, flowering plants
Unikonts -> Amoebozoans (Slime molds, Gymnamoebas, Entamoebas)
-> Amoebas with lobe-shaped pseudopodia
-> Amoeba, Entamoeba, Dictyostelium
Unikonts -> Opisthokonts
-> ———
-> Nucleariids, choanoflagellates, animals, fungi
Humans pathogenic Protists
Giardia Intestinalis (giardia lamblia) -> gastroenteritis (food poisoning)
-> diplomonad
Trichomonas vaginalis -> vaginitis (women) and urethritis (men)
-> Parabasalid
Trypanosoma brucei -> African tryptanosomiasis (sleeping disease) -> Kinetoplastid Euglenozoan
Trypanosome cruzi -> American trypanosomiasis (Chagas’ disease)
-> Kinetoplastid Euglenozoan
Plasmodium malariae -> Malaria
-> Apicomplexan Alveolate
Toxoplasma gondii -> Toxoplasmosis
-> Apicomplexan Alveolate
Entamoeba histolytica -> Amebic dysentry
-> Entamoeba amoebozoan
Acanthamoeba -> Eye infection, encephalitis
-> Entamoeba amoebozoan
