Lecture 2: Microbial Evolution and Diversity Flashcards
Friday 4th October 2024
How long ago did bacteria and archaea appear on the earth?
3.6 to 3.8 billion years ago
What is the surface origin hypothesis?
- 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.
What protects us from UV radiation?
The ozone layer, which is made up of oxygen.
Why can early life be described as hostile?
- There were high levels of UV radiation in the atmosphere.
- There were many meteor strikes.
- There was a lot of volcanic activity.
Why is the surface origin theory unlikely?
Because there were high levels of UV radiation, many meteor strikes, and high levels of volcanic activity.
What is the subsurface origin hypothesis?
- 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).
Can life begin without light?
yes
What’s more stable RNA or DNA?
DNA
Can RNA act as an enzyme?
Yes, but DNA can’t
What was early life very dependant on?
H2 and CO2
What did H2 and CO2 react together in the early atmosphere to make?
Methane
Is it true that bacteria made acetate and archaea made methane in the early atmosphere?
Yes
As the planet began to cool, what was there a lesser reliance on?
There was a lesser reliance on chemical energy.
What did purple and green bacteria use for anoxygenic photosynthesis?
Hydrogen sulfide
When the cyanobacteria evolved, what did they use for photosynthesis?
Water, this produced Oxygen and Hydrogen
Initially, why was the oxygenation of the atmosphere problematic?
Because oxygen is highly reactive. So, the oxygen started oxidising everything it touched.
What happened as the amount of oxygen in the atmosphere increased?
An ozone layer was produced. This reduced the amount of UV light reaching the earth.
Is it true that before the use of molecular biology, we didn’t know that Archaea existed?
Yes
Describe the properties of marker molecules that are used in phylogenetic analysis
- Must be universal
- Must contain variable and conserved regions
- Must not be subject to horizontal gene transfer
- Must be truly homolgous
Why are ribosomal RNA genes a universal molecular marker?
Because they’re present in all forms of life
Name some molecular markers
- Ribosomal RNA genes
- ATPase subunits
- EF-Tu
- RecA
Did the 3 domain tree of life arise due to comparative ribosomal RNA sequencing?
Yes
Describe the first theory in the potential chain of events in the evolution of Eukaryotes
- 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
Describe the the more widely accepted theory in the potential chain of events in the evolution of Eukaryotes
- A nucleus was created inside a eukaryotic cell.
- The mitochondria appeared
- The chloroplast appeared
What is the alternative to the endosymbiont theory?
The hydrogen hypothesis
What is the hydrogen hypothesis?
The idea that an archaea fused with a bacterial cell using Hydrogen as an energy source to produce hydrogen as a’waste’ product.
what is the scientific name for Aquifex?
Aquifex aeolicus
Describe aquifex
- 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
What is the scientific name for Deinococcus?
Deinococcus radiodurans
Describe Deinococcus
- 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
Describe cynobacteria and plastids
- 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
describe Actinobacteria
- 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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Name an actinobacteria
Streptomycetes, which are major producers of antibiotics
What are the pathogens of actinobacteria?
Mycobacterium leprae , which causes leprosy
M. tuberculosis, which causes tuberculosis
Corynebacterium diphteriae, which causes diptheria
describe the firmicutes
- Low G+C Gram positives
- Mostly heterotrophs
- Some form spores i.e Bacillus and Clostridium
- Medically and industrially important
what are the firmicutes Lactobacillus and Lactococcus are used in
food processing and probiotics
what do the firmicutes Listeria and Staphylococcus cause?
Infections
what firmicute causes botulism?
Clostridium botulinum
what firmicute causes tetanus?
Clostridium tetani
describe Chlamydia
- 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
Describe Spirochaetes
- 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
Describe proteobacteria
- 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.
What are most archaea?
Methanogens
Describe the methanogens
- 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
Describe the halophilic archaea
- 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”
