L24 - Microbes on a Changing Planet

Question 1

What are microbial communities affected by?

Answer 1

• Changes in…
  
  • temperature
  • rainfall/moisture
  • pH
  • salinity
    
    • will respond, adapt, and evolve very quickly

Question 2

Rapid cycling of carbon VS long-term carbon cycling ??

Answer 2

Rapid (biological): carbon exchange among living organisms
- Photosynthesis, respiration, decomposition
Long-term: cycling of carbon through geologic processes
- Driven by plate tectonics (will change how carbon moves through atmosphere despite whether or not humans are there)

Question 3

How do microbes play a key role in the carbon cycle?

Answer 3

• Photosynthetic microorganisms (i.e. phytoplankton) drawdown CO2 from the atmosphere during photosynthesis
• Creates usable carbon for other organisms
• Ex: Bacteria in the ocean will decompose or eat the organic material produced by phytoplankton
  
  • Bacteria consume a carbon source, and re- release CO2
    **Phytoplankton produce half the oxygen we breathe

Question 4

Microbial respiration and decomposition leads to the release of CO2

Answer 4

• Heterotrophic microbes break down organic carbon compounds for cellular growth and energy
• Heterotrophic microbes need organic material like us, breathe in O2 and release CO2

Question 5

What is organic matter and where does it come from?

Answer 5

• Material that has come from a recently living organism
• Includes the remains of organisms such as plants and animals and their waste products in the environment

Question 6

What are different types of organic matter?

Answer 6

• Soil: derived from decomposed plants
• Marine: derived from phytoplankton (photosythesizing microscopic organisms either bacteria or eukaryotes)

Question 7

What determines the fate of organic matter?

Answer 7

• The activity of microorganisms that live in the sediment.
• If the carbon is degraded it is released as CO2
• If not, it will be buried and sequestered for a long time.

Question 8

How is bioavailability of organic matter determined?

Answer 8

• Intrinsic chemical properties of the compounds
• Most bioavailable: active, low in molecular weight, aliphatic
• Least bioavailable: stable, high molecular weight, highly aromatic
  
  • Not it’s only contributing factor however. Oxygen, temperature, and mineral availability affect bioavailability

Question 9

What is the goal of the bioreactor system that probes organic matter degradation?

Answer 9

• Carbon isotope analysis through the monitoring and collection of CO2 production
• We can use carbon isotopes signatures of respired CO2 to estimate the contribution of different types of organic matter to respiration.

Question 10

What are the 3 carbon isotopes?

Answer 10

• C12: Stable (very abundant)
• C13: Stable
• C14: Radioactive (half life is 5730 years)

Question 11

What can carbon isotopes tell us?

Answer 11

• C13 signature: differences in source and where something came from.
• C14 signature: tells us the age of something.

Question 12

Define half life

Answer 12

The time required for half of the original population of radioactive atoms to decay

Question 13

For the degradation of most organic matter, what do they require?

Answer 13

The use of extra-cellular enzymes (especially in marine environments)

Question 14

Explain the organic matter in the permafrost.

Answer 14

• Permafrost contains large stores of organic matter that have been locked for thousands of years.
• Microbial organisms are seasonally frozen and preserved within the permafrost.
• Thawing of permafrost: microbes become active and degrade organic matter, leading to the release of GHGs

Question 15

What kind of microbes might become active when permafrost thaws?

Answer 15

• Methanogens: produce methane as a byproduct of their metabolism
• Require anaerobic environments - extremely oxygen sensitive