Microbial Eukaryotes

Question 1

Oxygenic photosynthesis

Answer 1

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

Question 2

Non-oxygenic photosynthesis

Answer 2

Electron donor = Sulphide, Arsenite, etc.

Break down glucose (glycolysis) by fermentation –> gives less energy than cellular respiration

Question 3

Origin of oxygen rich atmosphere

Answer 3

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

Question 4

Origin of mitochondria

Answer 4

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

Question 5

Endosymbiotic origin of the mitochondria

Answer 5

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)

Question 6

Syntrophy

Answer 6

“Shared feeding” - the waste products of one organism become the food source for another organism

Question 7

Origin of chloroplasts

Answer 7

After primary endosymbiosis, eukaryotic cells with chloroplasts were engulfed by other eukaryotic cells

Question 8

Elements of a eukaryotic cell

Answer 8

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

Question 9

Origin of chloroplasts

Answer 9

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:

1. Cyanobacteria and chloroplasts have internal membrane folds
2. Peptidoglycan (bacterial structure) in glaucophyte chloroplast

Question 10

Photosynthesis origin

Answer 10

First occurred in bacteria - 4 groups of bacteria do photosynthesis

Question 11

Photosynthesis requirements

Answer 11

Carbon source
Electron donor
Light energy (photons) and something to harvest the energy (pigment)

Question 12

Agents of disease in Amicomplexa

Answer 12

Almost all parasites
Causes malaria (vector = mosquitos)

Question 13

Dinoflagellates as coral symbionts, free-living forms, causing food-borne illness (red tide)

Answer 13

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

Question 14

Stramenopiles as “algae”

Answer 14

Include giant photosynthesizers called brown algae or kelp + tiny photosynthetic diatoms, slime nets, and oomyctes

Question 15

Damage to golf course grass via slime nets

Answer 15

Labrinthulids (slime nets, Stramenopiles, but in their own group within this clade)

Invades the leaves of plants, builds slime tubes, feed and destroy plants

Question 16

Oomycetes in potato blight and Sudden Oak Death

Answer 16

Non-photosynthetic, absorptive heterotrophes, look like fungus

Question 17

Excavates (Giardia and Leishmania) that cause disease

Answer 17

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)

Question 18

Amoebozoans (Naegleria fowleri and Entamoeba histolytica) that cause disease

Answer 18

Naegleria fowleri amoebic meningitis (swimming pools) –> gets up nose and feeds on brain tissue

Entamoeba histolytica: causes ameobiasis, diarrheal disease

Question 19

4 different body plans (unicellular, colonial, multinucleate, multicellular)

Answer 19

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

Question 20

Conditions required for multicellularity

Answer 20

• cells specialize

- only some cells reproduce sexually

Question 21

Unicellular and multicellular phases of plasmodial and cellular slime molds

Answer 21

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

Question 22

Primary endosymbiosis

Answer 22

Occurs when a prokaryote is merged with a eukaryote

Chloroplasts in plantae result from a primary endosymbiosis

Question 23

Secondary and tertiary endosymbiosis

Answer 23

Occur when a eukaryote engulfs another eukaryote

Chloroplasts outside plantae were the result of secondary or tertiary endosymbiosis

Question 24

3 types of locomotion in microbial eukaryotes

Answer 24

Ciliate - covered in cilia, beat in coordinated waves
Amoeboid - can change shape
Flagellate - flagella beat