Lecture 14 - Microbiome 1 Flashcards Preview

MIIM20002 - Microbes, Infections, Responses > Lecture 14 - Microbiome 1 > Flashcards

Flashcards in Lecture 14 - Microbiome 1 Deck (38):
1

Where are microbes found on the body?
Which area has the most?

Gut - the most
Vagina
Skin
Throat

2

Why are microbiota important?

Associated with:
• Health
• Disease

3

What is the Human Microbiome?

Project to sequence all of the genes associated with the microbiota

4

Compare the bacteria at the different colonisation sites in the body?

Different phyla, depending on the location

5

How many phyla are represented in the human microbiota?

Only a few

6

What is meant by 'humans are superorganisms'?

Humans have evolved to collaborate with microbiota, giving us properties that we would not have on our own

7

What are the general benefits of microbiota?

• Enhanced digestion
• Intestinal deelopment
• Protection

8

How do commensals aid digestion?

Degrade polysaccharides
Vitamin K

9

How do commensals aid development of our gut?

Epithelial cell maturation
Angiogenesis
Lymphocyte development

10

How do commensal protect us from pathogens?

• Occupy a niche
• Competition for nutrients
• Stimulate the immune system

11

What are the main phyla found in the microbiome?

Bacteroidetes
Firmicutes
Actinobacteria

12

Which phylum is only rarely found in the microbiome?

Proteobacteria (E. coli)

13

Which is the most common phylum in the gut?

Firmicutes

14

Which phylum commonly colonises the skin?

Actinobacteria

15

Are most of the bacterial phyla represented in the human microbiome?

No - relatively few phyla are found in the human microbiome

16

Describe the distribution of bacteria within the gut

More bacteria as we progress down the GIT

17

Describe the changes in the microbiome over one's lifetime

When we are healthy, are microbiome is stable

At the extremities of life, our microbiome can be unstable

18

What factors influence the microbiome?

• Age
• Diet
• Mode of delivery during childbirth
• Breast feeding
• Antibiotics

19

What is the effect of fever on the human microbiome?

Changes the makeup of the microbiome

Increase in number of actinobacteria

20

Over the first 2.5 years of life, what brings about the major changes in the microbiota in the gut?

The introduction of solid foods into the diet

Onset of Bacteroidetes

21

Compare microbiota in twins

Monozygotic twins: less than 50%

Unrelated people: even less

22

What is the greatest site of antigenic challenge in the body?

The gut

23

Where do microbiota sit in the gut?

Above the mucin and glycocalyx

24

How does the microbiota help the innate immune system?

Direct:
• Produce antimicrobials

Indirect
• Interact with PRRs to induce tolerogenic responses
• Produce compounds that maintain the epithelium

25

Does the microbiota bring about inflammation?

We call it physiological inflammation

26

What does the interaction of microbiota with PRRs brings about?

• Induction of regulatory cytokines
• Induction of antibacterial compounds, defensins

27

How does the gut epitehlium distinguish between invading pathogens and gut commensals?

Proximity:
• gut commensals are held at arms length
• pathogens bind tightly to the gut epithelium

PRRs:
• PRRs detect invasion on basolateral surface
• Commensals bind poorly to PRRs

28

Compare the types of Th induced by commensals and pathogens

Commensals: Treg, Th2 (tolerogenic)

Pathogens: Th17, Th1 (inflammatory)

29

What is the effect of commensals of DCs?

• Induce tolerogenic Th cells
• Indues more effective sampling by the DCs

30

What are the effects of the microflora on the adaptive immune system?

How do we know this?

• less IgA
• poorly developed Peyer's Patches
• fewer IELs
• more susceptible to infection
• prone to allergies

We know this from studies of Germ-free mice

31

What is the effect of commensals on IgA?
Why is this good?

• Induce low levels of IgA

IgA cross reacts with pathogens

32

What is a term for physiological inflammation?

Mucosal homeostasis

33

Which cytokine is really important for mucosal homeostasis?
What does it do?

TGF-beta

It is really important for skewing towards Treg and Th2

34

What is it called when the makeup of the intestinal microbiota is altered?

Dysbiosis

35

How is dysbiosis directly associated with disease?

• infectious disease due to gut microbiota
• nutritional (malabsorption)

36

What are the indirect assocations of dysbiosis with disease?

• Obesity (metabolic syndromes)
• Inflammatory bowel disease
• Allergies
• Autoimmune diseases

37

What is a common cause of dysbiosis?

Antibiotic use

38

Describe the expression of PRRs on the gut epithelium

Why is this so?

Apical: low expression
In endosomes: TLR 3, 7, 9
Basolateral: TLR 5

Don't want to have much of a response to commensals in the gut

We only want to have a response if bacteria penetrate further