Eukaryotic Microbes – Innovations in Biology Flashcards
Protista were divided into:
- Monera (bacteria and blue-
green algae without a nuclear
membrane). - Eunucleata (unicellular
organisms with a nuclear membrane).
Evolutionary relationships are reconstructed from
study of reliable homologous characteristics.
Describe phylogenetic resolution across time
100 homologous characteristics in 1980’s, now >1000.
Describe the eukaryote cell structure
- typically much larger and more complex than prokaryote cells.
- membrane enclosed nucleus
- mitochondria
- hydrogenosomes and a strictly fermentative metabolism or mitosomes
- nucleus contains linear chromosomes
- DNA is wound around histones: Chromatin.
- chloroplasts present in phototrophic cells
- cell wall present in fungi, algae, plants and some protists
- some have cilia or flagella for movement
Describe some eukaryotes with hydrogenosomes and a strictly fermentative metabolism
- Trichomonas
- some fungi
- ciliates living in the rumen and animals
Who has mitosomes?
Giardia
histones
positively charged proteins
What are the six eukaryotic supergroups
- Archaeplastida
- Rhizaria
- Chromoalveolata
- Excavata
- Amoebozoa
- Opisthokonta
SAR phylogenetic cluster
- Stramenopiles
- Alveolata
- Rhizaria
Archaeplastida
Plants, red and green algae
Rhizaria
Mostly heterotrophic unicellular organisms
Chromoalveolata
Stramenopiles: unicellular flagellates and diatoms
Alveolata: widespread group predators and parasites (e.g. Paramecium)
Excavata
- Mostly heterotrophs
- includes pathogens
- many anaerobic
- e.g. Giardia, Trypanosoma
Amoebozoa
Many forms of amoeba including Dictyostelium, slime moulds.
Opisthokonta
Fungi, Animalia
Define protists
single-celled or very few celled eukaryotes that are not plants, animals or fungi.
Define protoctists
- single-celled and multicellular eukaryotes that do not fit into the other kingdoms
- largely historical term
Define protozoans
nformal term referring to unicellular, primarily “heterotrophic” eukaryotic organisms (“animals”)
Describe protist distribution and diversity
- between 1.4x10^5 and 1.6x10^6 species
- occupy every conceivable ecological niche
- parasitic forms challenge a wide range of hosts
Foraminiferans
calcium carbonate ‘tests’
Chlamydomonas
Unicellular green algae
Trypanosoma brucei
parasitic
List some niches occupied by protists
- marine trenches
- rainforests
- artesian and thermal springs
- salt lakes
- ice flows; glaciers
Dinoflagellates
‘red tide’
Plasmodium
parasitic
Describe the variable size of protists
- ## 5-500micrometres
Cryptosporidium
- Apicomplexan
- c. 5micrometres
Giardia
- Diplomonad
- c. 10micrometres
Trichonympha
- Parabasalid
- c. 100micrometres
Amoeba
150-400 μm
Describe protist nutrition
- aerobic and respire
- photosynthetic
- heterotrophic
- predatory
- parasitic
- intracellular and extracellular niches
Describe aerobic protists
- mitochondria
- mitosome
- hydrogenosomes
Describe heterotrophic protists
absorb extracellularly-digested food
Discuss a predatory protist
amoeba and some ciliates, such as Paramecium.
Why are protists underrepresented?
- bias towards species that are phototrophic, parasitic or economically important
- Archaeplastida and Stramenopila easier to culture
- pathogens Toxoplasma and Plasmodium within Alveolata/Apicomplexans
Describe Pneumocystis
- opportunistic pathogen causing pneumonia in immunocompromised patients.
- fungus
- treated with antifungal agents
Describe Phytophthora
- cause of potato blight
- Stramenopiles
Describe the Holozoa
- most closely related unicellular lineages to animals
- Choanoflagellatea closest
- Filasterea and Ichtyosporea also closely related
Describe the first animals
evolved from an unknown ancestor in the pre-Cambrian period.
In order to learn how animals evolved,
phylogenetic relationships are reconstructed from extant organisms.
Describe the multiple origins of multicellularity
16-22 times
Describe multicellularity in the tree of life
Metazoa and Embryophyta contain only multicellular organisms
Describe adhesion
- plants use pectin and hemicellulose
- fungi use extracellular glycoproteins
- animals use cadherins and integrins
Describe Pseudopodia
- temporary projections of the plasma membrane.
- extend and contract by the reversible assembly of actin subunits into microfilaments.
- Rhizaria have more threadlike pseudopodia than Amoebae.
- used for phagocytosis
phagocytosis
sensing and engulfing targets for ingestion.
Describe flagella
- rapid ‘whip like’ motion
- crucial for survival, cell feeding and reproduction
- ‘9+2’ microtubule axoneme.
- organelles associated with their own metabolism
- respond to and initiate signal- transduction cascades
Describe cilia
- hair-like structures,
- large numbers on the cell surface
- 0.25 microns in diameter
- 2-20 microns long.
- alternating power and recovery strokes
- ‘wave’ like motion
- generate force perpendicular to the cilia’s axis
- synchronised beats (coordinated by hydrodynamic linkage)
- generally faster
Describe binary fission
Division into two approximately equal parts where cytoplasmic division follows mitosis
Describe flagellate binary fission
longitudinal plane
Describe Amoeba division
- no fixed plane of division
- round up and divide into two basically equal halves
Describe ciliate binary fission
- equatorial or transverse plane
- maintain the correct number of cilia
- replication of the cytostome precedes the division of the cytoplasm
Describe endodyogeny
- each DNA replication cycle is followed by mitosis and budding
- e.g. T. gondii
Describe leukocyte transformation
- sporozoites infect leukocytes
- transforms them and divides by exploiting the mitotic and cytokinetic machinery of the host
- Theileria spp.
Describe Schizogony
- nuclei multiply by asynchronous rounds of mitosis
- last round is synchronous for all nuclei and coincides with budding at the parasite surface
- e.g. P. falciparum, Eimeria
Describe Endopolygeny
- DNA replicates without nuclear division, using multiple synchronous mitotic spindles
- final mitotic cycle coincides with budding and the emergence of a new generation of merozoites
- T. gondii in cats
Describe ciliate sexual reproduction
compatible mating types exchange genetic material
Describe ciliate conjugation
- two cells contact
- cytoplasmic bridge forms
- micronuclei undergo meiosis: four micronuclei per cell
- three micronuclei disintegrate; one mitoses
- micronuclei exchange
- cells separate, micronuclei fuse, micronuclei disintegrate
- new macronucleus forms in each cell from mitotic divisions in micronucleus
Describe gametogony and sporogony in Eimeria (Apicomplexa) spp.
- sporulated oocyst ingested
- sporozoites escape from the
sporocyst and invade epithelial cell - sporozoites under shizogony
- merozoites leave cell and infect another cell
- shizogony repeated until the final merozoites form into macrogametocytes and microgametocytes
- after fertilisation, oocyst is formed
- passes to the environment and undergoes meiosis and mitosis to form sporocysts containing sporozoites
Describe Eimeria
- > 1,000 described species
- infect fish, birds, reptiles and mammals
- important veterinary pathogen
schizogony basics
asexual multiple fission
Describe Excavata, Euglena gracilis
- free-living aquatic unicellular protist
- model organism
- photoautotrophic
- heterotrophic
- mixotropic
- swim using flagella
- creep using metaboly
- covered by a pellicle
- natural tolerance to acidic growth conditions and ionizing radiation
- sequesters heavy metals
- uniquely reserve the carbohydrate Paramylon for use as a Carbon source under Carbon starvation conditions
metaboly
a peculiar type of “inching” locomotion
pellicle
- flexible coat
- allows the cell to change shape
Describe the bioproducts from Euglena gracilis
- nutrition
- nutraceuticals and biomedicine
- biofuels and biomaterials
- large-scale cultivation
Describe E. gracilis nutrition
- dietary protein
- (pro)vitamin A, C, E
- polyunsaturated fatty acids
- dietary fibre
Describe E. gracilis nutraceuticals and biomedicine
- beta-1,3-glucan paramylon
- paramylon derivatives
Describe E. gracilis biofuels and biomaterials
- lipids (wax esters)
- fermentable sugars
- biogas and bio-oil
- bioplastics and nanofibres
Describe large-scale cultivation by E. gracilis
- outdoor cultivation
- (photo)bioreactors
Describe Alveolata, Paramecium
- unicellular ciliate
- model organism
- widespread in freshwater, brackish water and marine environments
- most are heterotrophs feeding on bacteria
- some are mixotrophs, using nutrients from chlorella in the cell cytoplasm
- cilia used for motility and to move food along a groove towards the cell mouth
- food phagocytosed and enclosed in the vacuole, where it is broken down by enzymes
- reproduce asexually by binary fission
- conjugation can be induced by food shortage
chlorella
endosymbiotic algae
List some protist diseases
- Malaria
- Leishmaniosis
- Cryptosporidiosis
- Amoebiasis
- Chagas disease
- African Trypanosomiasis
- Schistosomiasis
Describe Giardiasis
- Giardia intestinalis (Excavata)
- two nuclei of equal size
- flagellated
- heterotrophic (low oxygen environments)
- no mitochondria; mitosomes
- asymptomatic to severe diarrhoea and malabsorption
Describe the symptoms of Giardiasis
- diarrhoea
- abdominal pain
- bloating
- nausea, and vomiting
Describe Entamoeba (Amoebozoa)
- parasites of vertebrates and invertebrates
- several species infect humans
- anaerobic (mitosomes)
- cysts in free-living dispersal stage
List some free-living Amoebozoans
Gymnamoebas & slime molds
Describe Amoebozoans
free-living (fresh water, soil)
Describe Entamoeba gingivalis
oral cavity
Describe Entamoeba coli
intestinal tract
Describe Entamoeba histolytica
- trophozoite causes dysentery, ulceration, bloody diarrhoea, liver abscess
- readily killed in the environment
Describe Entamoeba cysts
excreted in the host’s faeces and survive in water or the soil
Eimeria spp. on livestock
- infect almost all vertebrates
- particularly young
- farmed animals (esp. poultry)
Describe Cryptosporidium spp.
wide impact on young animals
Describe Toxoplasma gondii
- infection of cats
- can cause severe disease in other animals (incl. foetal
damage)
Describe Giardia intestinalis
persistent problem for many animals
Describe Leishmania spp.
- zoonosis with a reservoir of infection in dogs
- transmission to dogs by infected sandfly
Describe Trypanosoma brucei
- cattle
- transmitted by Tsetse fly in areas of Africa
