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Michaelmas Term 1 > The Social Microbe > Flashcards

The Social Microbe Flashcards

1
Q

What is LUCA?

A

An inferred cellular organism

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2
Q

Where does the inference for LUCA arise from?

A

The shared fundamental biochemical and genetic characteristics of all known life

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3
Q

LUCA hypotheses

A
  • anaerobic
  • CO2-fixing
  • H2-dependent
  • N2-fixing
  • thermophilic
  • dependent on transition metals
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4
Q

What setting are the LUCA hypotheses consistent with?

A

Hydrothermal

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5
Q

What are the competing hypothesis for the origin of life location:

A
  • surface origin hypothesis
  • subsurface origin hypothesis
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6
Q

Madigan model for the origin of cellular life

A
  • RNA World
  • DNA becomes genetic repository; RNA adopts a more transitory role in genetic inheritance
  • three part system (DNA, RNA, protein) evolve and become universal amoung cells
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7
Q

What is the RNA World theory?

A

That the first self-replicating systems must have been RNA-based

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8
Q

What would make RNA a good first self-replicator?

A
  • can bind small molecules (ATP, other nucleotides)
  • catalytic activity (autocatalysis?)
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9
Q

Describe the world in which life arose

A
  • hot
  • anoxic
  • inorganic
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10
Q

How did the origin of life change the earth?

A
  • organic chemical synthesis
  • CO2 fixation
  • oxygenic photosynthesis
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11
Q

What did oxygenic photosynthesis facilitate?

A
  • O2-based respiration
  • much more energy available
  • evolution of super-energy expensive lifestyles (large, multicellular)
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12
Q

Describe the evolution of oxygenic photosynthesis

A

~2.7GYA cyanobacteria evolved a photosystem using H2O rather than H2S

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13
Q

How can we measure O2?

A
  • it reacts spontaneously with oceanic iron minerals
  • abundant iron oxides visible in geological record (banded iron formations)
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14
Q

What did O2 accumulation in the atmosphere result in?

A
  • formation of the ozone shield
  • toxic oxygen radicals
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15
Q

Describe the endosymbiosis eukaryogenesis theory

A

mitochondrion of present-day eukaryotes arose from the stable incorporation of an aerobic bacteria into early eukaryotic cells

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16
Q

What did endosymbiosis allow?

A

increased early cell’s respiratory capacity, allowing early mitochondria-containing cells with o becomes the ancestors of all extant Euakarya

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17
Q

Describe chloroplast endosymbiosis

A
  • stable incorporation of a Cyanobacterium-like cell into the cytoplasm of a eukaryotic lineage
  • plant evolution
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18
Q

What is common between prokaryotes, mitochondria and chloroplasts relative to size and shape

A
  • smaller
  • similar in size and shape
  • generally lack membrane bound organelles
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19
Q

What is common between prokaryotes, mitochondria and chloroplasts relative to ribosomes

A
  • smallest
  • 60S-75S
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20
Q

What is common between prokaryotes, mitochondria and chloroplasts relative to the initiation of protein synthesis

A
  • initiation amino is N-formyl-methionine (not methionine)
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21
Q

What is common between prokaryotes, mitochondria and chloroplasts relative to chromosome

A

Mostly circular, not linear

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22
Q

What is common between prokaryotes, mitochondria and chloroplasts relative to rifampicin action

A

Inhibits RNA polymerase (does not in eukaryotes)

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23
Q

Rifampicin

A

Ah inhibitor of RNA polymerase

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24
Q

What is common between prokaryotes, mitochondria and chloroplasts relative to chloramphenicol

A

Inhibits protein synthesis (doesn’t in eukaryotes)

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25
Q

Chloramphenicol

A

Protein synthesis inhibitor

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26
Q

What about mitochondria and chloroplast are consistent with the endosymbiotic hypothesis

A

Their physiology, metabolism and genome structure

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27
Q

Compare and contrast mitochondria and chloroplasts relative to their function

A

Mitochondrion: oxidative phosphorylation, beta oxidation and photorespiration
Chloroplast: photosynthesis and photorespiration

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28
Q

Compare and contrast mitochondria and chloroplasts relative to their metabolism

A

Mitochondria: break down glucose to CO2 and H2O, consumes oxygen, generates ATP
Chloroplasts: synthesise glucose from CO2 and H2O, libérâtes oxygen

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29
Q

Compare and contrast mitochondria and chloroplasts relative to their shape

A

Mitochondria: oblong or bean shaped
Chloroplast: ellipsoid disc

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30
Q

Compare and contrast mitochondria and chloroplasts relative to their structure

A

Mitochondria: double membrane; inner membrane folded into cristae
Chloroplast: double membrane; inner membrane contains thylakoid stacks, grams

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31
Q

Compare and contrast mitochondria and chloroplasts relative to their size

A

Mitochondria: 0.75-3 micromètres
Chloroplasts: 0.5-10 micromètres x 2.5 micromètres

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32
Q

Compare and contrast mitochondria and chloroplasts relative to their distribution

A

Mitochondria: universal, most eukaryotes
Chloroplasts: restricted; plants, green algae, some unicellular eukaryotes

33
Q

Compare mitochondria and chloroplasts

A
  • both have small circular genomes
  • both replicate independently of the rest of the cell
  • in both the outer membrane has proteins that enable permeability
  • in both the inner semi-permeable membrane is the site of metabolic activity
34
Q

Mitochondria late scenario

A
  • Posits endosymbiosis uptake by phagocytosis
  • requires evolution of phagocytosis first
35
Q

Mitochondria early hydrogen hypothesis

A
  • metabolic symbiosis of a methane producing bacterium
  • complex membrane structures and molecules and phagocytosis evolve after endosymbiosis
36
Q

Both mitochondria late and mitochondria early envisage

A
  • extensive gene transfer from bacterium to host
  • system evolution is to transfer nuclear-encoded proteins to organelle
37
Q

Syntrophic communities

A
  • cross-feeding
  • one species lives off of the products of another species
  • highly nutritional, interdependent communities of eubacteria and archaea
  • anoxic environments
38
Q

Describe gene exchange in syntrophic communities

A
  • patterns
  • suggests community above independent evolution
39
Q

Relationship between mitochondria early hypothesis and syntrophy

A
  • eukaryogenesis from bacterial and archaea syntrophic interactions
  • supported by chimeric eukaryotic genomes
40
Q

Examples of intracellular bacteria

A
  1. Pleurocapsa spp
  2. Pseudomonas fluorescens, Bdellovibrio bacteriovorus
  3. Pseudococcidae
41
Q

Describe Pleurocapsa spp.

A

Nitrogen-fixing, spore-forming marine cyanobacterium showing intracellular bacteria

42
Q

Describe Pseudomonas fluorescens and Bdellovibrio bacteriovorus

A

Bdellovibrio bacteriovorus infects Pseudomonas fluorescens periplasm

43
Q

Describe mealybug Pseudococcidae

A
  • TEM shows bacteriome containing betaproteobacterial Trembleya endosymbionts
44
Q

Describe Trembleya symbionts

A

Contain gammaproteobacterial Morganella endosymbionts

45
Q

What are Acanthamoeba?

A

Ubiquitous, free-living amoebae

46
Q

Describe Acanthamoeba:

A
  • important predators of microbial communities
  • ~25% contain obligate intracellular bacterial symbionts
47
Q

Which two endosymbionts are present in one Acanthamoeba?

A
  • Candidatus procabacter
  • Candidatus parachlamydia
48
Q

Where are mitosomes found?

A

In some unicellular anaerobic/micro aerophilic eukaryotes

49
Q

Give a genus in which mitosomes are found

A
  • Giardia
  • parasitic diplomondad
50
Q

Describe mitosomes

A
  • double membrane
  • lack DNA
  • reduced metabolic capacity (no ECT/TCA enzymes)
51
Q

What are hydrogenosomes?

A

Energy-yielding mitochondria alternatives present in some anaerobic protists

52
Q

Give an example of a species containing hydrogenosomes

A
  • Nyctotherus ovalis
  • ciliate
53
Q

Where are hydrogenosomes found?

A
  • trichomonads
  • hypermastigotes
  • euglenids
54
Q

What are hydrogenosomes thought to have evolved from?

A

Mitochondria

55
Q

Describe hydrogenosomes

A
  • double membrane
  • DNA present (reduced due to gene loss)
56
Q

How do hydrogenosomes generate energy?

A
  • Partial oxidation of pyruvate to acetate
  • pyruvate fermentation
57
Q

Give an example of a genus that exists without mitochondria

A

Monocercomonoides

58
Q

Describe the amitochondrial status of Monocercomonoides

A
  • Thought that they once had them, but we’re lost over time
  • evidence of LGT of bacterial sulfur mobilisation genes
59
Q

Give an example of primary endosymbiosis

A

Uptake of a Cyanobacteria by a non-photosynthetic organism

60
Q

Give an example of secondary endosymbiosis

A

Plastid-containing algae ingested by non-photosynthetic eukaryote

61
Q

Describe diatoms

A
  • abundant microscopic algae
  • contribute ~20% to global photosynthesis
  • important in biogeochemical cycles
62
Q

What are diatoms predominantly associated with?

A
  • proteobacteria
  • bacteriodetes
63
Q

How have bacteria contributed to diatom genomes?

A
  • through HGT
  • recruitment of metabolic capacity
64
Q

What are the metabolic interactions of diatoms?

A
  • parasitism
  • synergism
  • competition
65
Q

Describe the Asgard superphylum lineage

A

Thought to be ancestral to, or sister group of, Eukarya

66
Q

All cellular life has a

A

Common ancestor

67
Q

The first metabolic processes arose in an

A

Oxygen-free, microbial world

68
Q

How did eukaryotes aquire during endosymbiosis?

A

Nutritional versatility and oxygen-based metabolism

69
Q

What did gene exchange post-endosymbiosis result in

A

Increasing interdependence

70
Q

OILRIG

A
  • oxygen is the most oxidising agent
  • hydrogen is the most reducing agent
71
Q

Oxygen =

A

Toxic

72
Q

H2O is a

A

Much more efficient energy system than H2S

73
Q

Eukaryotes can

A

Compartmentalise

74
Q

LGT occurs from

A

Organelle to nucleus

75
Q

HGT occurs from

A

Bacteria to eukaryote

76
Q

Diatomic carbons in the sea are not

A

Locked up

77
Q

Most eukaryotes are still

A

Microbes

78
Q

List some mitochondria-related entities

A
  • mitosomes
  • hydrogenosomes

Michaelmas Term 1 (42 decks)

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