Microbiology of Animals

Question 1

Commensals

Answer 1

Microorganisms routinely found on the bodies of most healthy individuals

Question 2

Animals as microbial habitats

Answer 2

• Provide a warm, wet and potentially highly nutritious environment

Question 3

What factors influence microbial abundance and richness

Answer 3

• Temperature
• pH
• nutrient supply
• the immune system

Question 4

Where are the vast majority of microorganisms in animals found?

Answer 4

GI tract

Question 5

Purpose of microorganisms in GI tract

Answer 5

• Animals lack the enzyme required to degrade cellulose
• Microorganisms present in the GI tract of herbivores are able to degrade cellulose and provides the host with nutrients

Question 6

2 digestive strategies in herbivores

Answer 6

• Foregut fermentation (ruminants):
• Hindgut fermentation:

Question 7

Foregut fermenters (Ruminants)

Answer 7

• Fermentation chamber = rumen
• Precedes acidic stomach

Question 8

Hindgut fermenters

Answer 8

• Fermentation chamber = Cecum/large intestine
• After acidic stomach

Question 9

Ruminants: Food Pathway

Answer 9

1. Food is chewed minimally, swallowed, and passed into the rumen
2. Cellulolytic microbes digest cellulose to sugars
3. Sugars are fermented, producing volatile fatty acids (VFAs), CH4, & CO2
4. VFAs go into the bloodstream and are the main energy source
5. After several hours of microbial digestion, small portions of the rumen contents are regurgitated, well chewed and then swallowed again
6. Food particles are collected by the reticulum and moved to the omasum, where excess water is collected
7. The material then goes into the stomach (abomasum) and from there, to the intestines
8. The mass of microbial cells are subjected to digestion and serves as a major source of amino acids and vitamins

Question 10

Rumen microorganisms

Answer 10

• Ruminococcus
• Methanogens

Question 11

Ruminococcus

Answer 11

• Major group that do cellulose degradation in rumens
• Contain protein complexes (cellulosomes) which grab & cleave the cellulose

Question 12

Methanogens

Answer 12

• Convert H2 + CO2 –> CH4/Acetate –> CH4
• Up to 10% of the energy value of the feed can be lost as CH4

Question 13

Monensin

Answer 13

Inhibits methanogenesis

Question 14

Non-ruminant herbivores

Answer 14

• Fermentation takes place in the caecum
• Provides organic acids absorbed by the animal
• The microbial mass that grows on cellulose and other polysaccharides are not digested, & are excreted
• Higher dietary requirement for amino acids & vitamins

Question 15

Coprophagy

Answer 15

• consuming faeces
• Adaptation to get around higher dietary requirements of non-ruminants

Question 16

Termites

Answer 16

• Decompose cellulose and hemicellulose
• Contain a diverse community of anaerobes (including ruminococcus)