Microbial Eukaryotes Flashcards
Oxygenic photosynthesis
Water is used as the electron donor in photosynthesis –> products oxygen as waste product (released into atmosphere)
Origin: cyanobacteria use water as an electron donor and chlorophyll a to harvest light energy –> buildup of oxygen in atmosphere
Break down glucose (glycolysis) by cellular respiration –> gives more energy than fermentation
Non-oxygenic photosynthesis
Electron donor = Sulphide, Arsenite, etc.
Break down glucose (glycolysis) by fermentation –> gives less energy than cellular respiration
Origin of oxygen rich atmosphere
Origin: cyanobacteria use water as an electron donor and chlorophyll a to harvest light energy –> buildup of oxygen in atmosphere
Evidence + dating event: The oxygen reacted with iron in seawater which precipitated as banded iron –> can date event at 2.5 bya by looking at rock formations
Shifted relative fitness of bacterial types
Origin of mitochondria
Hypothesis: The ancestors of mitochondria were once free-living bacteria that formed a symbiosis with another organism that could not use oxygen. The new organism was the first eukaryotic cell. Aerobic bacteria could be the ancestors of mitochondria.
Evidence: phylogeny of genes from mitochondria and bacteria –> similar genes
Hypothesis: Mitochondria may have originated through syntrophy. The host cell belonged to Lokiarchaeota. It was hydrogen-dependent and formed a mutually beneficial syntrophic relationship with the hydrogen-producing bacterium.
Haploid
Endosymbiotic origin of the mitochondria
A cell encounters an aerobic bacterium. This bacterium was brought into the host cell by phagocytosis or endocytosis and formed a symbiotic relationship with the host.
Supporting evidence:
1. Mitochondrial size (right size for bacteria - v small)
2. Mitochondrial structure and the presence of mitochondria DNA
Mitochondria DNA is similar in structure, size and shape to bacterial DNA
4. Membranes around mitochondria (multiple membranes around mitochondria - from being engulfed by host membrane)
Syntrophy
“Shared feeding” - the waste products of one organism become the food source for another organism
Origin of chloroplasts
After primary endosymbiosis, eukaryotic cells with chloroplasts were engulfed by other eukaryotic cells
Elements of a eukaryotic cell
There is DNA in the nucleus of the cell, the mitochondria, and the chloroplasts (if they have) –> 2-3 distinct genotypes
Mitochondria: the cell’s power plants
Cytoskeleton: composed of microtubules, intermediate filaments, and microfilaments supports the cell and is involved in cell and organelle movement
Plasma membrane: separates the cell from its environment and regulates traffic of material into and out of the cell –> bacteria filamentous actin homologous to actin eukaryotes
Origin of chloroplasts
After primary endosymbiosis, eukaryotic cells with chloroplasts were engulfed by other eukaryotic cells
Hypothesis: the ancestors of chloroplasts were once free-living bacteria that formed a symbiosis with a eukaryotic cell. Cyanobacteria could be the ancestors of chloroplasts.
Genetic evidence: Phylogeny of chloroplast and bacterial genes cluster –> chloroplasts came from cyanobacteria
Morphological evidence:
- Cyanobacteria and chloroplasts have internal membrane folds
- Peptidoglycan (bacterial structure) in glaucophyte chloroplast
Photosynthesis origin
First occurred in bacteria - 4 groups of bacteria do photosynthesis
Photosynthesis requirements
Carbon source Electron donor Light energy (photons) and something to harvest the energy (pigment)
Agents of disease in Amicomplexa
Almost all parasites Causes malaria (vector = mosquitos)
Dinoflagellates as coral symbionts, free-living forms, causing food-borne illness (red tide)
Some dinoflagelletes are endosymbionts in coral and other vertebrates –> coral opens up and exposes dinoflagellete to sunlight –> they do photosynthesis and release excess carbon back to host
Red tide caused by dinoflagellates: saxitonin (neurotoxin made by cyanobacteria) accumulates in filter feeders, eaten by fish that accumulate toxin
Stramenopiles as “algae”
Include giant photosynthesizers called brown algae or kelp + tiny photosynthetic diatoms, slime nets, and oomyctes
Damage to golf course grass via slime nets
Labrinthulids (slime nets, Stramenopiles, but in their own group within this clade)
Invades the leaves of plants, builds slime tubes, feed and destroy plants
Oomycetes in potato blight and Sudden Oak Death
Non-photosynthetic, absorptive heterotrophes, look like fungus
Excavates (Giardia and Leishmania) that cause disease
Giardia is a human/animal gut parasite –> host = animals, poops in water, humans drink water, get infected (don’t have mitochondria)
Leishmania: sand fly vector –> two forms: 1) skin - lesions of skin 2) attacks the organs (esp spleen)
Amoebozoans (Naegleria fowleri and Entamoeba histolytica) that cause disease
Naegleria fowleri amoebic meningitis (swimming pools) –> gets up nose and feeds on brain tissue
Entamoeba histolytica: causes ameobiasis, diarrheal disease
4 different body plans (unicellular, colonial, multinucleate, multicellular)
Unicellular
-single cell
Multinucleate
-body plan can form by karyokinesis without cytokinesis or by fusion of cell membrane
Colonial
- cells connect together but no specialization (everyone can reproduce)
Colonial and multicellular body plans:
- multiple cells
- secrete an extracellular matrix (ECM)
- cells attach to each other or ECM
- Cells communicate
Multicellular body plans only:
- cells specialize
- only some cells reproduce sexually
- formed by cell division or by aggregation of cells
Conditions required for multicellularity
- cells specialize
- only some cells reproduce sexually
Unicellular and multicellular phases of plasmodial and cellular slime molds
Plasmodial slime mold
Individual motile diploid cell undergoes mitosis to form single, enormous multinucleate cell (plasmodium)
Harsh conditions - make diploid resting stage or goes thru meiosis to form spores –> spores germinate to make swarm cells which can be asexual or fuse to make a new diploid cell
Feeding stage - multinucleate plan
Cellular slime molds
Amoeboid stages called myxamoebae and are haploid
When food runs out, myxamoebae make a slug body (multicellular) that moves to a new habitat where it makes spores
When slug makes a fruiting structure, releases spores that are dormant until food is available
Primary endosymbiosis
Occurs when a prokaryote is merged with a eukaryote
Chloroplasts in plantae result from a primary endosymbiosis
Secondary and tertiary endosymbiosis
Occur when a eukaryote engulfs another eukaryote
Chloroplasts outside plantae were the result of secondary or tertiary endosymbiosis
3 types of locomotion in microbial eukaryotes
Ciliate - covered in cilia, beat in coordinated waves
Amoeboid - can change shape
Flagellate - flagella beat
