W10 GI microbiota: balance and alteration

Question 1

What are examples of defences to prevent GI infections? (5)

Answer 1

• Mucous secretion
• Secretory IgA (the most abundant in the GI)
• Peristalsis
• Fluids with antimicrobial properties (lysozyme in saliva; low pH in the stomach; bile salts)
• Gut-associated lymphoid tissue (GALT) that works as the immune system in the gut

Question 2

What are Normal flora?

Answer 2

Microorganisms that live
stably in the GI tract, establishing commensal or mutualism symbiotic relationship

Question 3

What is symbiosis and the 3 types?

Answer 3

Symbiosis is the relationship between normal microbiota and the host
* Commensalism: one organism benefits, and the other is unaffected
* Mutualism: both organisms benefit
* Parasitism: one organism benefits at the expense of the other (e.g. pathogen
causing infectious diseases)

Question 4

What are the functions of the normal flora in the gut?

Answer 4

Structural
Metabolic
Protective

Question 5

Structural functions of the normal flora in the gut?

Answer 5

• Enhance the epithelial barrier
  (located above the mucous layer)
• Activation of villi micro
  vascularisation
• Tight junction regulation

Question 6

Metabolic function of the normal flora in the gut:

Answer 6

• Synthesis of essential B-group vitamins (e.g. folic acid) and vitamin K
• Dietary fibre fermentation (insensible to host enzymes) into Short Chain Fatty Acids
  (source of energy)
• Absorption facilitation of dietary minerals
• Bile acids biotransformation and metabolising sterols, and xenobiotic