Lecture 43: Rumen Bacteria and Global Warming

Question 1

Ruminants = ?

They’re crucial for the human ____ economy.

Answer 1

• Cows, sheep, goats, etc.

- Food

Question 2

Ruminant Stomach includes (4):

Answer 2

• Rumen
• Reticulum
• Omasum
• Abomasum

Question 3

Ruminant Stomach facts:

Answer 3

• First 3 compartments do not secrete mucus, digestive enzymes or acid and digestion results from microorganisms living in the rumen, breaking things down
  Rumen: (Ground up) food churned in a rotary motion, and fermentation takes place ( 9 -12h )
• Bacteria need time to digest it (permanent exponential group, doubling time = 7 hours)
  Reticulum: Used for regurgitation of food “chewing the cud” to increase surface area
  Omasum: Acts as a filtering device to regulate the type of digesta that enters the Abomasum
  Abomasum: True acidic stomach. Secretes gastric juices. Protein is denatured. Site of bacterial protein assimilation by the animal.

Question 4

Unique features of the Rumen:

Answer 4

• Large size
• Position in alimentary canal so that ingested food goes there first
• High constant temperature 39 degrees, pH 6.5, control, selects for specialized bacteria
• Anaerobic environment

Question 5

How do we study rumen bacteria?

Answer 5

• Fistulated animals

Question 6

What microorganisms live in the Rumen?

Answer 6

• Bacteria: ~10^10 cells per gram of contents
  Cellulose degraders - fibrobacter succinogenes
  Starch degraders - bacteroides ruminocola
  Lactate degraders - megasphaera elsdenii
  Methanogens - methanobrevibacter ruminantium
• Protozoa: 10^3 - 10^6 cells per gram of contents
• Fungi

Question 7

The overall rumen fermentation process:

Answer 7

• Plant feed is hydrolysed
• Fermented
• End-products = acetic + propionic + butyric acids (short chain fatty acids)

Question 8

Symbiotic Relationship:

Answer 8

• Microbes produce enzymes and digest ruminant’s food

- Rumen microbes provide amino acids and vitamins (when they’re destroyed in small bowel)

Question 9

‘Inter-species hydrogen transfer’

Answer 9

• Ruminococcus albus
• When bacteria grow, redox reactions take place. If we take cellulose –> pyruvate, there’s an oxidation, therefore there must be a reduction. NADH = reducing power. 2NAD –> 2NADH constant recycling. Hydrogen gas is made to help recycling.
• In the rumen we don’t detect hydrogen gas, they make it but as fast as they make it it’s converted into methane
• Cows make biogas
• Methanogens are selected for, use hydrogen as electron donor, autotrophic, “mop up the hydrogen”
• Syntrophic relationship, one organism can’t survive without the other (codependent)
• Get rid of Methane by belching / farting it out

Question 10

The rumen community is metabolically ______ interactive.

Answer 10

• Highly

Question 11

Syntrophy:

Answer 11

• An interaction between two microbes that makes possible a reaction not energetically feasible for one of the microbes acting alone

Question 12

Methanogens keep partial pressure of H2 low, and therefore fermentations are directed towards the formation of organic acids. Give an example

Answer 12

• ACETATE used by animal

Question 13

Methane (CH4) = ?

Methane is over 21 times more effective in…

Answer 13

• Greenhouse gas that remains in the atmosphere for approximately 9-15 years.
• Trapping heat in the atmosphere than carbon dioxide (CO2)

Question 14

Where are all the greenhouse gases coming from?

Answer 14

• 50% agriculture

- This is a big problem for us

Question 15

How do you stop cows from producing so much methane?

Answer 15

• Gov. gave 15 million for research to see how to limit methane production
• Feed animals things to limit methane
• Vaccinate against methanogens
• Feed cows inhibitor to reduce methane, target methanogen, NO NEGATIVE EFFECT ON MILK PRODUCTION

Question 16

What’s important about the Tamar Wallaby?

Answer 16

• It’s a low methane emitter