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BSCI 2150 > Origin of Microbial Life > Flashcards

Origin of Microbial Life Flashcards

1
Q

What did prebiotic earth look like?

A

Inorganic compounds
Very little free oxygen
Lots of water (oceans)
Hot
Lots of ionizing radiation from space (no ozone layer)
Frequent electrical storms due to an unstable atmosphere
Volcanic and thermal vent activity

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2
Q

Miller-Urey Experiment

A

-created the primordial soup
-showed that the mixture of heat, water, lightning, and inorganic gases could produce the first organic compounds on earth
-water turned dark, revealed complex molecules (amino acids)

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3
Q

Chemical composition of cells

A

7% ions and small molecules
23% macromolecules (carbohydrates, proteins, lipids, nucleic acids)
70% H2O

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4
Q

What are the major nucleic acids in cells?

A

DNA and RNA

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5
Q

Common building blocks of DNA/RNA

A
  1. sugar (deoxyribose or ribose)
  2. phosphorus group
  3. nitrogenous base
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6
Q

Types of nitrogenous bases

A

pyrimidines and purines

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7
Q

Pyrimidines

A

one ring
“Y” in their names
Cytosine and Thymine (DNA)/Uracil (RNA)

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8
Q

Purines

A

multiple rings
energy storing molecules (ATP/GTP)
Adenine and Guanine

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9
Q

First nucleic acid oligomers and tidal pools

A
  1. High tide to tide goes out: Evaporation/concentration of nucleotides (mineral-rich ocean floor)
  2. Low tide to dry tidal pool: polymerization (dehydration synthesis)
  3. Tide comes back/high tide (cooling): H bond formation and polymers dissolve
  4. Repeat
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10
Q

Advantages of RNA over DNA

A

-self-replicate
-catalytic
-can form ribozymes

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11
Q

RNA World Hypothesis

A

Self-replicating RNA in cell membranes (protocells) were the precursors to modern life by storing genetic information and catalyzing the chemical reactions in these primitive cells

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12
Q

Evidence for RNA World

A

-RNA invovled in ancient, cellular processes (mRNA, rRNA)
-conserved ribosomes from all taxa have catalytic and structural RNAs
-catalytic ribozymes can be self-splicing and self-cleaving
-RNA genomes known in viruses

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13
Q

What are the seven major groups of viruses?

A
  1. DNA virus: dsDNA (+/-)
  2. DNA virus: ssDNA (+)
  3. RNA: dsRNA (+/-)
  4. RNA: ssRNA (+)
  5. RNA: ssRNA (-)
  6. Reverse transcribing virus: ssRNA (+)
  7. Reverse transcribing: dsDNA (+/-)
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14
Q

dsRNA

A

rotavirus (inflamed intestine/abdominal pain)

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15
Q

ssRNA (+)

A

SARS-CoV-2

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16
Q

ssRNA (-)

A

Measles

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17
Q

RT ssRNA (+)

A

HIV

18
Q

What are the two possible models for the evolution of viruses and modern cells?

A
  1. virus-first
  2. escape
19
Q

Virus-first model

A

-hypothesis that viruses preceded cellular life
-selfish replicons > viruses > protocell > modern cell

20
Q

Escape model

A

-modern cells evolved then viruses evolved from escaped transposable elements
-protocell > modern cell > viruses from escaped elements

21
Q

Panspermia Hypothesis

A

I. An impact on a “donor planet” produced a shock wave which forces a surface rock into space at high speed.
II. Organisms on the surface rock then survived space
III. Organisms on the surface rock survived atmospheric entry and impact

22
Q

Evidence for Panspermia

A
  1. Organic compounds and amino acids in meteorites
  2. Bacteria can survive harsh environment of space
  3. Over half a ton of Mars lands on Earth every year
23
Q

Microbes are subjected to these conditions in space

A

-extreme desiccation
-low temperatures
-cosmic UV radiation
-vacuum conditions
-microgravity

24
Q

Thermophilic

A

optimal growth at 45ºC or greater
ex: sulfolobus solfataricus (archaea) and thermus aquaticus (bacteria)

25
Q

Hyperthermophilic

A

optimal growth at temperatures above 80ºC

26
Q

Mesophilic

A

optimal growth from 20-45ºC
ex: Salmonella spp. (bacteria)

27
Q

Psychrophilic

A

optimal growth at temperatures of 15ºC or lower
ex: Colwellia psychrerythraea (bacteria) and Chlamydomonas nivalis (eukaryote)

28
Q

Obligate Anaerobe

A

only grows in environments devoid of oxygen, bottom of tube
ex: C. diff

29
Q

Aerotolerant Anaerobe

A

cannot perform aerobic respiration but can tolerate oxygen, dispersed throughout tube

30
Q

Facultative Anaerobe

A

can perform aerobic or anaerobic metabolism, clustered at surface of tube and dispersed throughout
ex: E. coli

31
Q

Microaerophilic

A

cannot perform anaerobic metabolism but poisoned by large amounts of oxygen, clustered at top of tube but not on the surface
ex: Campylobacter jejuni

32
Q

Obligate Aerobe

A

can only perform aerobic metabolism, all microbes are clustered at surface
ex: Mycobacterium tuberculosis

33
Q

Autotrophic

A

-Can produce its own food
-photosynthesis or chemosynthesis
-photoautotroph: Prochlorococcus marinus
-chemoautotroph: Nitrososphaera gargensis

34
Q

Heterotrophic

A

-Derive energy from organic compounds
-most bacteria
-Staphylococcus aureus

35
Q

Halophilic

A

-Optimal growth w/ HIGH salt concentrations
-are also Alkaliphiles
-Haloferax volcanii (archaea in Dead Sea)

36
Q

Acidophilic

A

-Optimal growth at pH 3 or below
-Picrophilus torridus (archaea) in vents for volcanic vapor

37
Q

Alkaliphile

A

-Optimal growth at pH 9 or above
-Natronomonas Pharaonis (archaea) in soda lakes

38
Q

LUCA

A

Last Universal Common Ancestor

39
Q

Likely characteristics of LUCA

A

-strict anaerobe
-thermophilic
-autotroph

40
Q

What are the 3 domains of life?

A
  1. Archaea
  2. Eukaryotes
  3. Bacteria
41
Q

How did Carl Woese resolve the tree of life (phylogenetic tree)?

A

Compared the similarity of 16S and 18S rRNA across a number of organisms. 16S and 18S are homologous sequences.

BSCI 2150 (11 decks)

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