Lecture 2: Microbial Evolution and Diversity

Question 1

How long ago did bacteria and archaea appear on the earth?

Answer 1

3.6 to 3.8 billion years ago

Question 2

What is the surface origin hypothesis?

Answer 2

• The idea that life evolved in warm little ponds on the surface of the planet, with a primordial soup of a mixture of chemicals that allowed organisms to form.

Question 3

What protects us from UV radiation?

Answer 3

The ozone layer, which is made up of oxygen.

Question 4

Why can early life be described as hostile?

Answer 4

• There were high levels of UV radiation in the atmosphere.
• There were many meteor strikes.
• There was a lot of volcanic activity.

Question 5

Why is the surface origin theory unlikely?

Answer 5

Because there were high levels of UV radiation, many meteor strikes, and high levels of volcanic activity.

Question 6

What is the subsurface origin hypothesis?

Answer 6

• The idea that life formed from hydrothermal vents in the ocean floor.
  (energy, heat, reduced compounds, organic compounds form)
• More stable conditions than conditions on the surface
• Constant source of energy, from reduced inorganic compounds produced inside the planet, which produce chemical energy).

Question 7

Can life begin without light?

Answer 7

yes

Question 8

What’s more stable RNA or DNA?

Answer 8

DNA

Question 9

Can RNA act as an enzyme?

Answer 9

Yes, but DNA can’t

Question 10

What was early life very dependant on?

Answer 10

H2 and CO2

Question 11

What did H2 and CO2 react together in the early atmosphere to make?

Answer 11

Methane

Question 12

Is it true that bacteria made acetate and archaea made methane in the early atmosphere?

Answer 12

Yes

Question 13

As the planet began to cool, what was there a lesser reliance on?

Answer 13

There was a lesser reliance on chemical energy.

Question 14

What did purple and green bacteria use for anoxygenic photosynthesis?

Answer 14

Hydrogen sulfide

Question 15

When the cyanobacteria evolved, what did they use for photosynthesis?

Answer 15

Water, this produced Oxygen and Hydrogen

Question 16

Initially, why was the oxygenation of the atmosphere problematic?

Answer 16

Because oxygen is highly reactive. So, the oxygen started oxidising everything it touched.

Question 17

What happened as the amount of oxygen in the atmosphere increased?

Answer 17

An ozone layer was produced. This reduced the amount of UV light reaching the earth.

Question 18

Is it true that before the use of molecular biology, we didn’t know that Archaea existed?

Answer 18

Yes

Question 19

Describe the properties of marker molecules that are used in phylogenetic analysis

Answer 19

• Must be universal
• Must contain variable and conserved regions
• Must not be subject to horizontal gene transfer
• Must be truly homolgous

Question 20

Why are ribosomal RNA genes a universal molecular marker?

Answer 20

Because they’re present in all forms of life

Question 21

Name some molecular markers

Answer 21

• Ribosomal RNA genes
• ATPase subunits
• EF-Tu
• RecA

Question 22

Did the 3 domain tree of life arise due to comparative ribosomal RNA sequencing?

Answer 22

Yes

Question 23

Describe the first theory in the potential chain of events in the evolution of Eukaryotes

Answer 23

• On the archaeal line before the eukarotes and archaea diverged from each other, a mitochondrion appeared.
• The nucleus formed inside the eukarya.
• A cyanobacteria entered a eukaryotic cell and became a chloroplast

Question 24

Describe the the more widely accepted theory in the potential chain of events in the evolution of Eukaryotes

Answer 24

• A nucleus was created inside a eukaryotic cell.
• The mitochondria appeared
• The chloroplast appeared

Question 25

What is the alternative to the endosymbiont theory?

Answer 25

The hydrogen hypothesis

Question 26

What is the hydrogen hypothesis?

Answer 26

The idea that an archaea fused with a bacterial cell using Hydrogen as an energy source to produce hydrogen as a’waste’ product.

Question 27

what is the scientific name for Aquifex?

Answer 27

Aquifex aeolicus

Question 28

Describe aquifex

Answer 28

• Is Isolated from a hot spring
• Is Hyperthermophilic, so can grow in areas that are up to 90 degrees celcius.
• One of the deepest branching bacterial phyla
• Is a Chemolithoautotroph, so oxidises H2 to water using O2 as e- acceptor
• Autotrophic: C-fixation

Question 29

What is the scientific name for Deinococcus?

Answer 29

Deinococcus radiodurans

Question 30

Describe Deinococcus

Answer 30

• Extremely radiation resistant, including ionising radiation
• Isolated from canned meat that was sterilised by gamma irradiation
• Very rapidly reassembles radiation damaged DNA
• Interest in using organism for bioremediation as it remaining viable in radiation contaminated sites

Question 31

Describe cynobacteria and plastids

Answer 31

• Blue green algae
• Plastids (chloroplasts in plants) were originally cyanobacteria
• Morphologically diverse
• Widely distributed
• Oxygenic phototrophs, use light to fic carbon and release oxygen
• Important in carbon cycle
• May cause nuisance and toxic blooms

Question 32

describe Actinobacteria

Answer 32

• They’re High GC Gram positives
• They have varied morphology and varied metabolism
• They’re heterotrophs, so use organic carbon as they’re energy source, so they eat food and don’t make their own food.

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Question 33

Name an actinobacteria

Answer 33

Streptomycetes, which are major producers of antibiotics

Question 34

What are the pathogens of actinobacteria?

Answer 34

Mycobacterium leprae , which causes leprosy

M. tuberculosis, which causes tuberculosis

Corynebacterium diphteriae, which causes diptheria

Question 35

describe the firmicutes

Answer 35

• Low G+C Gram positives
• Mostly heterotrophs
• Some form spores i.e Bacillus and Clostridium
• Medically and industrially important

Question 36

what are the firmicutes Lactobacillus and Lactococcus are used in

Answer 36

food processing and probiotics

Question 37

what do the firmicutes Listeria and Staphylococcus cause?

Answer 37

Infections

Question 38

what firmicute causes botulism?

Answer 38

Clostridium botulinum

Question 39

what firmicute causes tetanus?

Answer 39

Clostridium tetani

Question 40

describe Chlamydia

Answer 40

• All pathogens
• Obligate intracellular parasites that live inside eukaryotic cells
• C. trachomatis cause sexually transmitted disease, can lead to infertility
• Also can infect the eye

Question 41

Describe Spirochaetes

Answer 41

• Helically shaped, motile, gram negative
• Unuusual flagellum, on inside of cell
• Heterotrophs
• Contains free living, symbiotic and parasitic species
• Can cause syphilis and lyme disease

Question 42

Describe proteobacteria

Answer 42

• Subdivided in alpha, beta, gamma, delta and epsilon Proteobacteria
• Extremely metabolically diverse and include: Phototrophs, chemolithoautotrophs, heterotrophs
• Include many important pathogens like Vibrio cholerae, which causes cholera and salmonella, which causes food poisoning.

Question 43

What are most archaea?

Answer 43

Methanogens

Question 44

Describe the methanogens

Answer 44

• Produce methane as a waste product
• Are at the very bottom of the food chain
• Turn simple compounds into non-organic compounds, finish off the carbon cycle
• Anaerobes
• Grow slowly
• Produce methane as a waste product

Question 45

Describe the halophilic archaea

Answer 45

• grow in a saturated salt solution that is 20 times saltier than seawater
• Salt lakes and ponds and salt crystals in subsurface
• Can take very strange shapes and colours
• Walsby square “bacterium”