Taxonomy Eukaryotes Part 1

Question 1

Endosymbiosis theory and secondary endosymbiosis

How phylogenetics differs in eukaryotes to prokaryotes?

Answer 1

Endosymbiosis theory states that mitochondria engulfed by early archaea became the LUCA of eukaryotes and then later chloroplasts were engulfed by early ancestor of plants/algae

Secondary endosymbiosis theory is red or green algae being incorporated into another branch of eukaryotes
- red and green contain same chloroplasts indicating this happened later in time

Phylogenetics is less sensitive with SSU rRNA 18S sequencing than with 16S so more MLST is used for taxonomy

Question 2

Red algae

Answer 2

AKA rhodophytes

Mostly marine, some fresh water and terrestrial
- multicellular, except for Galdieria living in acidic hot springs

Phycoerythrin pigment –> red color
- lower depth –> more phycoerythrin produced

Question 3

Green algae

Answer 3

AKA Chlorophytes

Closely related to plants - mostly freshwater, some marine or terrestrial
- unicellular or multicellular

Can reproduce sexually or asexually

Question 4

Amitochondriate eukaryotes

Organelles

Answer 4

Primitive eukaryotes without mitochondria - lost them due to lack of use living in anaerobic environment

Mitosome: reduced form of mitochondria without TCA enzymes or ETC
- Center of maturation for Fe-S clusters

Hydrogenosome: oxidation of Pyruvate –> H2, CO2 + acetate
- present in eukaryotes who do strict fermentation
*Endosymbiotic methanogens sometimes also present and feed off H2 produced by hydrogenosome fermentation (secondary endosymbiosis)

Question 5

Cysts

Answer 5

Cysts are like endospores for eukaryotes

Hardy protection against deleterious environmental conditions, starvation, desiccation, infection by prokaryotes

Question 6

Diplomonads and parabasalids

Answer 6

Both: unicellular, flagellated, no chloroplasts, anoxic living

Displomonads: ex. Giardia
- 2 nuclei
- contain mitosomes

Parabasalids: ex. Trichomonas vaginalis
- contain parabasal body to structurally support golgi complex
- contain hydrogenosomes but no mitochondria

Question 7

Giardia lambia

Trichomonas vaginalis

Answer 7

Giardia lambia - type of Diplomonad, grows in colon and release cysts which get into the water supply through sewage and cause diarrhea
- Contain mitosomes and 2 nuclei

Trichomonas vaginalis - Type of Parabasalid, STD most common in developed countries
- adapted to sexual transmission and does not survive well outside host
- contain hydrogenosomes and parabasal body

No chloroplasts

Question 8

Euglenozoans

Answer 8

Phylum of unicellular flagellated eukaryotes which include kinetoplastids and euglenids

Question 9

Kinetoplastids

Kinetoplast

Example

Answer 9

Kinetoplastids type of euglenids which feed on bacteria
- Aquatic living, some species can cause serious disease

Kinetoplast - mass of DNA present in the single large mitochondria of some euglenozoans

Ex. Trypanosoma brucei
- African sleeping sickness (chronic + fatal)
- lives and grows in blood, infects CNS
- transmitted by tsetse fly
- single flagellum enclosed in membrane flap

Question 10

Euglena

Answer 10

Type of euglenids

Nonpathogenic and phototrophic
- contains chloroplasts (green algae secondary symbiosis) and can exist as heterotroph
- can feed on bacteria by phagocytosis

Question 11

Alveolates general

Types

Answer 11

Contain alveoli: sacs under cytoplasmic membrane
- may function to maintain osmotic balance
- contractile vacuole in Paramecium (water filter feeding)

Some contain red algae chloroplasts by secondary endosymbiosis

Can be:
1) Ciliates (Paramecium)
2) Dinoflagellates
3) Apicomplexans (Plasmodium)

Question 12

Alveolates: Ciliates

Answer 12

Ciliates: cilia used for motility and feeding, and contain 2 nuclei (macro and micronuclei)
- micronuclei exchanged during conjugation/sexual reproduction
- can be parasitic or symbiotic in animals

Question 13

Alveolates: Dinoflagellates

Answer 13

Dinoflagellates: marine/freshwater phototrophic organisms
- free living or symbiotic with corals
- 2 flagellum: transverse (direction) and longitudinal (forward)

Can secrete neurotoxins:
- In warm, polluted waters can cause red tides associated with human poisoning (paralytic shellfish poisoning) especially in mussels

Question 14

Alveolates: Apicocomplexans

Answer 14

Apicocomplexans contain apicoplasts
- obligate parasites of animals

Apicoplasts: degenerate chloroplasts without pigments but have anabolic metabolic function

Complex life cycle:
Sporozoite (transmission), gametocyte (sexual reproduction), other stages

Causes severe diseases such as toxoplasmosis (Taxoplasma) and malaria (Plasmodium falciparum)