Microbial Ecology #8

Question 1

Describe the general role of microorganisms in decomposition of plant and animal material, including the role of specific exoenzymes, how decomposition differs under aerobic and anaerobic conditions, and why organic matter tends to accumulate under water-saturated conditions.

Answer 1

1: Leaves fall.
2: nutrients are either
- Taken up and broken down quickly by microbes, contributing to microbial biomass then leaving as CO2
- More difficult to digest, made of Lignin, or surrounded by it. Ends up forming humus in the soil, which autochthonous organisms live off of.
3: Under water saturated conditions O2 diffuses slowly and will be practically absent in deep water (little that makes it will be consumed)
4: Lignin and octane fuels cannot be broken down without O2.
5: biomass will accumulate because Lignin and octane will not break down, and will surround material which could be broken down. Given time, this slow accumulation and compacting of organic material will cause the formation of fossil fuels.

Question 2

Humus:

Answer 2

Key quality of quality soil. It is a layer of hard to digest organic matter that microbes will live off of slowly. It will grow and shrink as more is deposited and more is slowly broken down.

Question 3

2. Distinguish between autochthonous and zymogenous soil microbial communities.

Answer 3

Autochthonous: Grow on humus material. They grow slowly, because less nutrients are received. Analogous to the growth of oligiotrophs

Zymogenous: Use all material and nutrients from freshly fallen leaves as fast as possible. Analogous to copiotrophs.

Question 4

Phyloplane:

Answer 4

The surface of leaf. Microbes on the phyloplane will begin breakdown before the leaf hits the ground. (probably before it leaves the tree)

Question 5

Anaerobic respiration in the ocean:

Answer 5

Reduction of Nitrate leads to production of nitric oxide, a greenhouse gas.

Question 6

3. Describe the two mechanisms by which methane is produced.

Answer 6

Method 1:
CO2 H2
H+ CH4
CO2 H20

One organism pulls e-‘s from Fatty acids and uses that to reduce hydrogen (H2).
Methanogens take H2 and oxidize it to H+, producing CH4 in the process.
CH4 is then oxidized further to CO2, reducing O2 –> H20 in the process.

Mechanism two acetate –> CH4

Question 7

Name four different environments that are important global sources of biologically-produced methane.

Answer 7

Cow pastures
Termites
Rice Patties
Marshes/swampland
Landfills
Oceans/lakes

Question 8

Distinguish between the terms methanogenesis and methanotrophy (i.e. which occurs under aerobic conditions and which occurs under anaerobic conditions; what are the e- donors and acceptors in each process?).

Answer 8

Methanogenesis: Is anaerobic process. Generates CH4. H2 is the e- donor, CO2 is the e- acceptor. Occurs in access H2 to make the reaction more favorable.

Methanotrophy: Breakdown of CH4, often done aerobically, but can also be done anaerobically. CH4 is the e- donor (forming CO2), O2 is the e- acceptor (forming H2O)

Question 9

Explain the causes of the annual oscillations in atmospheric CO2 concentrations, and provide reasons why concentrations have increased each year.

Answer 9

“Respiration” of the forests causes oscillation of CO2 levels.
Human production of CO2 from fossil fuel burning has increased CO2 concentrations.

Question 10

Anthropogenic pollutants:

Answer 10

Pollutants arising due to human influence.

Question 11

Name at least four important greenhouse gases. Be able to rank them in order of potency. Identify three that are microbial products, and describe in detail how they are produced.

Answer 11

Most potent
1: Chlorofluorocarbons (1000-10000x)
2: N20 nitrous oxide (300x)
3: CH4 (30x)
4: CO2 (1x)
Least potent

Microbial products:

1: N20 nitrous oxide (anaerobic respiration utilizing glucose, the ocean is an example)
2: CH4 (methanogens)
3: CO2 (methanotrophs/most bacteria/us)

Question 12

Describe how the presence of greenhouse gases increases the amount of heat trapped in the earth’s atmosphere.

Answer 12

Light that enters the is predominately shortwave (UV, Visible)
shortwave light enters and passes through the greenhouse gasses.
The earth absorbs shortwave and produces infrared light
Greenhouse gasses absorb infrared light, and equally redistribute it. Some is aloud to return to space. But probably >50% of infrared light. This causes heating.

Question 13

Bioremediation:

Answer 13

Degradation of pollutants utilizing microbial populations.

Question 14

Biogeochemistry:

Answer 14

Cycling of nutrients largely done by microbes.

Question 15

recalcitrant:

Answer 15

Someone who resists authority or control; not obedient or compliant; refractory. Hard to convince