Microbiota of the GI tract (not done)

Question 1

How does the population of bacteria change as you move down the GI tract?

Answer 1

Trend of increasing population

Question 2

How do the living conditions for bacteria change as you move down the GI tract?

Answer 2

• Becomes increasingly anaerobic
• Increasing bacterial density
• Increasing dominance of obligate anaerobes

Question 3

What is the difference between a Facultative anaerobe and an obligate anaerobe?

Answer 3

Facultative = Can live with and without oxygen (although some grow poorly with oxygen)

Obligate = Can only live in the abscence of oxygen

Question 4

What are the dominant bacteria in the mouth?

Answer 4

Streptococcus, Actinomyces, Veillonella, Fusobacterium, Porphromonas, Prevotella, Treponema

Question 5

What are the dominant bacteria in the stomach?

Answer 5

Lactobacillus

Candida

Streptococcus

H.pylori

Peptostreptococcus

Question 6

What are the dominant bacteria in the Duodenum?

Answer 6

Streptococcus

Lactobacillus

(not much lives in the duodenum as its so enzymey)

Question 7

What are the dominant bacteria in the jejunum?

Answer 7

Streptococcus

Lactobacillus

(same as duodenum)

Question 8

What are the dominant bacteria in the proximal ileum?

Answer 8

Streptococcus

Lactobacillus

(same as duod & jejunum but worth noting that the population is slightly larger)

Question 9

What are the dominant bacteria in the distal ileum?

Answer 9

Clostridium

Streptococcus

Bacteroides

Actinomycinae

Corynebacteria

(large increase in population compared to rest of small intestine)

Question 10

What are the dominant bacteria in the colon?

Answer 10

Bacteroides

Clostridium groups IV & XIV

Bifidobacterium

Enterobacteriaceae

(10¹¹-10¹²)

Question 11

What factors affect how liveable a section of the GI tract is?

Answer 11

Transit time

pH

Oxygen concentration

Secretions etc

Question 12

How much bacteria is in the human body?

Answer 12

about 200g

up to 100 trillion bacteria

Question 13

How diverse is the bacterial population of the large intestine?

Answer 13

4 major phyla

>200 genera (genus)

>1250 species

Question 14

How does diet affect the diversity of gut bacteria?

Answer 14

High fibre diets have most bacterial diversity

Western diets = low diversity

Highest in Amerindians

Question 15

What does the GIT bacteria do?

Answer 15

• Metabolise foodstuffs
• Modify host secretions
• Defend against pathogens
• Produce essential metabolites for our health
• Develop our immune system
• Host signalling

Question 16

What secretions are modified by bacteria?

Answer 16

Mucin, bile + more

Question 17

What are the benefits of high fibre diets?

Answer 17

Improves faecal bulking, eases passage, results in shorter transit time

Contains important phytochemicals, anti-oxidants and vitamins

Bacterial fermentation provides essential nutrients

Question 18

Bacterial fermentation of fibre is beneficial for our health. Explain how

Answer 18

• It releases additional phytochemicals
• Maintains slightly acidic pH
• Increased commensal bacterial population and pH improves resistance to pathogens
• Supplies us with short chain fatty acids