Topic 8- L1 - Human Microbiome

Question 1

Human microbiota:

Answer 1

collection of microbes living in/on us

Question 2

Human microbiome:

Answer 2

Microbiota and the environment(s) they live in

Question 3

Dysbiosis:

Answer 3

a term used to describe an altered microbiota that is unhealthy for the host. Typically thought of as being “out of balance” – loss of important commensals, increase in microbes associated with disease

Question 4

Most members of human microbiota are not culturable in the lab – vast majority of our knowledge comes from

Answer 4

DNA sequencing

16S, shotgun

Question 5

similarities in microbiota of different people

Answer 5

(similarities at phylum level), but the microbiome composition in each
individual is unique (very different at species level)

Question 6

Microbiota composition more about

Answer 6

environmental factors than genetic

factors…but some genetic component

Question 7

Microbiota (esp. in gut) established at young age & is remarkably

Answer 7

resilient. Microbiota changes with different conditions…but generally
returns to original composition

Question 8

Gastrointestinal tract:

Answer 8

Stomach, small intestine, large intestine (colon)

Question 9

Stomach microbiota :

Answer 9

Low pH keeps numbers low,

but a microbial community exists here

Question 10

Large intestines contain

Answer 10

Dense population of anaerobic microbes

Question 11

Throughout GI tract

Answer 11

pH, oxygen content (generally low) and nutrients availability varies – as does the composition of microbiota

Question 12

Epithelium that lines intestines protected by

Answer 12

mucus layer

Question 13

Mucus is a thick and slippery suspension that includes

Answer 13

antimicrobial factors & mucin (gel-like glycoprotein substance, serves a barrier function)

Question 14

Most microbes remain in

Answer 14

lumen, don’t directly contact host cells (there are important interactions…but there is a barrier to prevent routine, direct
physical interactions with epithelium)

Question 15

Remarkable person-to-person variation

in the

Answer 15

gut microbiota

Question 16

Bacteroidetes are

Answer 16

Gram-negative bacteria
– masters of complex carbohydrate
metabolism

Question 17

Firmicutes is a very diverse

Answer 17

phylum of

Gram-positive bacteria

Question 18

Proteobacteria are generally

Answer 18

facultative anaerobes – rapidly consume any oxygen present. Important for maintaining anaerobic environment. High proportions of can be a sign of dysbiosis.

Question 19

In the guy, O2 and other common terminal electron acceptors

Answer 19

absent or present at low levels –

tiny bit of aerobic respiration (proteobacteria), some anaerobic respiration, but a lot of fermentation

Question 20

Primary fermenters (many species, but
especially Bacteriodetes)

Answer 20

can break down (ferment) diverse carbohydrates from food (or mucin)

• some of their products absorb short chain fatty acids

Question 21

Many fermentation products feed a

Answer 21

range of other organisms (syntrophy)

Question 22

The gut microbiota is very important for human health:

Answer 22

• Compete with potential pathogens – prevent/inhibit colonization
• Digest food for us. E.g. ferment fiber to short-chain fatty acids that we then absorb
• Produce nutrients (amino acids, vitamins) we can’t make – get absorbed in the colon
• Promotes a healthy immune system, “trains” immune system &
  promotes immune tolerance

Question 23

An example of a relatively well

established causal relationship is

Answer 23

Helicobacter pylori in stomach appears

to be cause of stomach ulcers

Question 24

Disruptions to microbiota early in life

(e.g. antibiotics) that

Answer 24

reduce microbiota diversity linked to asthma and allergies

Question 25

Much of the growth in oral cavities is as

Answer 25

biofilms (highly complex communities), especially on teeth (dental plaque)

Question 26

On the skin, Some common members of microbiota are opportunistic pathogens, notably

Answer 26

Staphylococcus aureus, enters through cuts. Can be life threatening

Question 27

Lactobacilli benefit host by

Answer 27

lowering vaginal pH (~5) via fermentation end products (lactic acid) – helps prevent infection by pathogens

Question 28

In the vaginal microbiota, yeast (e.g. genus Candida) are part of a

Answer 28

healthy microbiome, but found at low levels.

Question 29

Disruption of microbiome (reduced Lactobacilli, increase pH) allows these yeast to bloom, leading to a

Answer 29

“yeast infection”

Question 30

Probiotic:

Answer 30

Live microorganism(s) that, when administered, have a beneficial affect on host. Consuming “good bacteria”

Question 31

Prebiotic:

Answer 31

A substance that when consumed promotes the growth of beneficial microbes. Can be simple and effective (e.g. fiber in diet to promote healthy microbiota)

Question 32

Fecal transplants:

Answer 32

Fecal matter from health donor transplanted into a patient - attempt to reintroduce a normal/healthy microbiota into a patient experiencing dysbiosis causing significant health issue

Question 33

Fecal transplants cure to

Answer 33

Clostridoides difficile infections, which are highly resistant to antibiotics