Lecture 19

Question 1

How are microbes connected to their physical surroundings?

Answer 1

Microbial communities are affected by changes in:

• temperature
• rainfall/moisture
• pH
• salinity
• etc.

Question 2

How are microbes connected to climate change?

Answer 2

As the claim the changes, microbes will respond, adapt, and evolve in their surroundings.

Question 3

What are the 2 interconnected sub cycles that are included in the global carbon cycle?

Answer 3

1. Rapid carbon exchange among living organisms (fast cycles).
2. Long-tmr cycling of carbon through geological processes (slow cycles).

Question 4

What are long-term and rapid carbon cycles driven by?

Answer 4

Long-term: plate tectonics, weathering, eroding carbon from mountains - sequestration.

Rapid: living organisms - carbon is moving through different realms on a faster time scale.

Question 5

What is the role of microbes in the global carbon cycle?

Answer 5

Photosynthetic microorganisms (i.e. phytoplankton) drawdown CO2 from the atmosphere during photosynthesis.

Photosynthesis creates usable carbon for other organisms - creates organic matter that goes to the bottom of the ocean.

Bacteria in the ocean will decompose or eat the organic material produced by phytoplankton - consuming a carbon source = release of CO2 by bacteria.

This is a biological carbon pump.

Question 6

Why does microbial respiration and decomposition lead to the release of CO2?

Answer 6

Heterotrophs microbes break down organic carbon compounds for cellular growth and energy - gets released by bacteria that consume it.

Question 7

What is organic matter and where does it come from?

Answer 7

Organic matter is material that has come from a recently living organism.

It includes the remains of organisms, such as plants and animals and their waste products in the environment.

Question 8

Where does soil organic matter derive from?

Answer 8

Terrestrial environments.

On land almost all organic matter is derived from plants.

Question 9

Where does marine organic matter derive from?

Answer 9

Marine environments.

In the ocean most organic matter is derived from phytoplankton.

Question 10

What is a major constituent of organic matter?

Answer 10

Carbon.

Question 11

What determines the fate of organic matter?

Answer 11

The activity of microorganisms that live in the sediment.

If the carbon is degraded it is released as CO2, but if not it will be buried and sequestered for a long time.

Question 12

How is bioavailability determined?

Answer 12

By intrinsic chemical properties of the compound - its size and structure.

Size: low molecular wight (most bioavailable), high molecular weight (least bioavailable).

Structure: aliphatic (most bioavailable), highly aromatic (least bioavailable).

It is not always te case (e.g. lignin).

Question 13

Is bioavailability of organic matter only affected by chemical properties?

Answer 13

No lol.

Question 14

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

Answer 14

Monitor respiratory CO2 production and collect it sequentially for carbon isotope analysis.

Question 15

What can carbon isotopes tell us?

Answer 15

C13 signature: differences in source and where something came from.

C14 signature: tells us the age of something.

Question 16

Explain the “you are what you eat (and breathe) principle for microbes. How do we apply this idea?

Answer 16

Heterotrophic microbes show similar isotopic signature as carbon sources.

The isotopic carbon respirometer-bioreactor measure and collects CO2 for carbon isotope analyses.

It allows us to track the source, age, and sequences of carbon compounds that are degraded by microorganisms.

Question 17

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

Answer 17

The use of extra cellular enzymes.

Extracellular enzyme activity is a key step in organic matter degradation in the ocean.

Question 18

How do we use genomic characteristic to observe patterns of organic matter degradation?

Answer 18

We can count the total copy number of genes encoding for known extra cellular enzymes.

Organic matter degradation patterns are consistent with genomic characteristics for the two example species. .

Question 19

Explain the organic matter in the permafrost.

Answer 19

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.

Question 20

What is the positive feedback cycles happening in the arctic and what are its consequences?

Answer 20

Positive feedback cycle: less ice and snow causes more warming (less reflection of sun’s radiation) - more warming causes less ice and snow.

Thawing permafrost = microbes are making a shift from dormancy to activity.

When the claim the warms, the microbes become active and degrade organic matter leading to the release f greenhouse gases.

Question 21

What kind of microbes might become active when permafrost thaws?

Answer 21

Most bacteria release CO2 as a byproduct of their metabolism. Some microorganisms can release methane (more potent).