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Flashcards in Eukaryotic Microbes 1 Deck (25):
1

Give the step by step process of the development of the mitochondria and photosynthesizing cell!

1. ancestral prokaryote -> infolding of plasma membrane -> cell with nucleus and endomembrane system -> engulfing of aerobic heterotrophic prokaryote -> mitochondrion development in cell= ancestral heterotrophic eukaryote
2. ancestral heterotrophic eukaryote engulfs a photosynthetic prokaryote = ancestral PS eukaryote containing plastids

2

Compare prokaryotes and eukaryotes with respect to cell size, nucleus , DNA, ribosomes, organelles, plasma membrane and cell wall.

1. Eukaryotes:
- 10-100um
- the nucleus with nuclear membrane
- multiple linear chromosomes with histone arrangements
- Ribosomes: 80S (40S and 60S with 18S rRNA)
-membrane enclosed, lysosomes, golgi complex, ER, mitochondria, chloroplasts
-sterols and carbohydrates make up the plasma membrane
- when a cell wall is present it is chemically simple
2. Prokaryotes:
-0.2-2um
-nucleoid
-singular chromosomes, no histones
-Ribosomes: 70S (50S and 30S with 16S rRNA)
- no organelles
-Plasma membrane has no carbohydrates and generally lacks sterols
- cell wall is usually present and is chemically complex

3

List some structures some eukaryotes have!

- chloroplasts (plants, algae and some protists)
- cell walls ( entirely different from prokaryotic cell walls)
- smaller membrane bound compartments (lysosomes, peroxisomes etc)
- cilia and flagella ( which are entirely different from prokaryotic flagella)

4

With respect to the diversity of eukaryotes what groups are actually classified as euk? (4)

1. Plants and Animals
2. Fungi (yeast, moulds and mushrooms)
3. Red and green algae
4. Protists

5

Explain the basic characteristics of the fungi!
L> polyphyletic or monophyletic?
L> number of species known?
L> how do they acquire energy?
L> what very important roles do they have?

- monophyletic group (all have a similar origin aka evolved from a common ancestor)
L> polyphyletic would mean groups have similar characteristics but are not evolving from a common ancestor
- 100 000 species known, total probably > 1.5 million
- they are all chemoorganotrophs aka derive energy by the breakdown of organic material
- they play an important role as decomposers, in biotechnology and as disease agents, especially in crops.

6

Explain the running theory of dinosaurs and fungi!

- collision event caused large deforestation
- this caused the environment to be extremely nutrient rich for vegetation decaying fungi
- there was an increase in fungal biomass
- increase in fungal spores
- fungal infections in dinosaurs which caused them to die off
**** this is a case of secondary succession - do you remember anything from ecology, bro?

7

Fungi in the tree of life:
- oldest fossils were found approx how many years ago?

- 460 million years ago
L> coincides with rapid expansion of multicellular organisms

8

Describe the fungal cell.

- typical eukaryotic cell structure except:
- ergosterol instead of cholesterol in plasma membrane (NB also n some protists)
- very rarely flagellated with some exceptions
- they have a cell wall which is VERY COMPLEX

9

What do antibiotics typically target with respect to fungal infections?

- ergosterol
- they usually target the molecule directly or its synthesis
- they target this since it will result in the lack of viability in the fungal cells while not harming the host eukaryotic cells that lack this characteristic
AKA a targeted drug

10

Describe the fungal cell wall.

- composed of chitin
L> these are a long chain polymer of N-acetylglucosamine
L> beta 1,4 linkages which animals cannot break down
- synthesised by chitin synthase and usually there are multiple paralogues in genome

11

Paralogous genes?

Paralogous genes are homologous genes that occur within one species and have diverged after a duplication event. Unlike orthologous genes, a paralogous gene is a new gene that holds a new function. These genes arise during gene duplication where one copy of the gene receives a mutation that gives rise to a new gene with a new function, though the function is often related to the role of the ancestral gene.

12

Orthologous genes?

Orthologous genes are homologous genes that diverged after a speciation event. The genes generally maintain a similar function to that of the ancestral gene in which they evolved from. In this type of homologous gene, the ancestral gene and its function is maintained through a speciation event, though variations may arise within the gene after the point in which the species diverged.

13

Describe fungal lifestyles with respect to the following example species:
1. Saccharomyces cervisiae
2. Agaricus bispora
3. Candida albicans
- Also explain reproduction in general.

1. always yeast
2. always hyphal - example = normal mushroom
3. mixture of both yeast and hyphal -> transition between hyphal and yeast forms = how it spreads pathogenically. When pH is low they switch to filamentous form and it forms a biofilm and can infiltrate tissue.
THEREFORE the lifestyles do not have to be an either or depending on the species
- reproduction is often asexual done via hyphal spread, single cell budding and asexual spores

14

Explain classical mating.

- classical mating involves two mating types (alpha and a, or minus and plus) which can sometimes switch aka can choose either mating types ...alpha can switch to a...or minus can switch to plus.
L> fusion results in diploid cell that undergoes meiosis to generate haploid recombinants

15

Explain sexual reproduction in fungi. (Good luck bro, it's not as straight forward as the dirty deed in mammals)

- for many fungi, the sexual states are not known
- often diploids and haploids are BOTH stable
- the morphology of mating is HIGHLY variable
- mycologists give different names to the two states:
L> Anamorphs (asexual/imperfect) and teleomorphs (sexual/perfect) ...these can have different binomials eg
Ex of anamorph = cryptococcus neoformans (yeast) = Filobasidiella neoformans (hyphal) = teleomorphs
L> It is the SAME fungus

16

Algae:
- What are the three groups of algae?

- red, green and brown

17

Algae:
- Explain what brown algae are.

- multicellular (seaweed), highly derived species that arose through secondary endosymbiosis.

18

Algae:
- are blue-green algae really algae?

- NOPE haha fucking with you
- they are actually bacteria - more appropriately they are cyanobacteria

19

Algae:
-Describe Red algae!

- some unicellular, many are multicellular
- often but not always, red due to phycoerithrin (an accessory pigment)
- typically marine but some are freshwater

20

Algae:
- Describe green algae.

- some unicellular but many are multicellular
- typically freshwater but some marine
- Evolutionarily they are very important as the ancestor of plants and they offer insight into the evolution of multicellularity (volvox = model organism)

21

Algae:
- Multicellularity insight?

- Chlamydomonas is a single celled flagellate green algae
- volvox is a colonial alga --> up to 50 000 flagellate cells in a gelatinous hollow ball.
L> daughter colonies bud into the middle
**read abstract of paper to get better idea..

22

Algae:
- An aside: explain lichens.

- lichens are symbiotic organisms
- partner one is a fungus, that typically cannot live independently
- partner two is a cyanobacterium (eg Peltigera) or a green alga (eg Cladonia --> we've examined this in the field in Ecology last term)

23

Protists:
- describe the characteristics of the group, protists.

- polyphyletic group
- loosely defined as unicellular eukaryotes without a cell wall but no shared defining feature
- protozoa is sometimes used interchangeably but sometimes as a subgroup (the most animaly protists...lol what?)

24

Protists:
- describe their features.

- no unifying morphological or biochemical feature for all protists
- within the protists, different groups are frequently characterized by a unique, shared character
- Ex: Cortical alveoli (Alveolates) -> vesicles, forming pellicle
Ex: Kinetoplast (eg Trypanosoma) -> mass of DNA inside mitochondria

25

Explain endosymbiosis!
L> what two things developed from this
L> which came first?
L> time line?

- eukaryotes arose from this
- approx 2 billion years ago, symbiotic acquisition of an alphaproteobacterium by early eukaryote (nucleated) or Archaea (followed by nucleation) created the mitochondrion
- approx 1.5 billion years ago, symbiotic acquisition of a cyanobacterium produced the chloroplast