1
Q
What is the microbiome?
A
-consists of microbes (native bacteria) that are both helpful and harmful
- symbiotic (both human and microbiota benefit)
- can be pathogenic
2
Q
If a disturbance in the microbiome occurs, what can happen?
A
dysbiosis
3
Q
What are two dominant divisions of the Gut Microbiota?
A
- Firmicutes
- Bacteriodetes
4
Q
How does the gut microbiota vary?
A
- intestine anatomical regions
5
Q
How does the gut microbiota vary in each intestinal anatomical region (x5)?
A
- physiology
- pH and O2 tension
- digesta flow rates
- substrate availability
- host secretions
6
Q
Does each person have a unique gut microbiota profile?
A
Yes
7
Q
When is each human’s gut microbiota developed?
A
In early life!
depends on infant transitions and external factors (ex antibiotic use)
8
Q
Does healthy core native microbiota remain relatively stable in adulthood?
A
YES
9
Q
Is there a unique optimal gut microbiota composition?
A
NO! this is because it is different for each individual
- However, a healthy host-microorganism balance must be respected in order to optimally perform metabolic and immune function and prevent disease development!
10
Q
What are the 7 roles of the gut microbiome?
A
- protect against pathogens
- synthesis of vitamins
- develop the immune system
- promote intestinal angiogenesis (formation of new blood vessels)
- promote fat storage
- produce SCFA by fermentation of dietary fiber
- Modulation of the CNS
11
Q
How does the gut microbiome “protect against pathogens”?
A
- produces products with antimicrobial effects
- causes the bacteria to compete for nutrients present in the gut –> important for colonization resistance
12
Q
What 3 products are produced by the gut microbiome that have antimicrobial effects?
A
a. SCFAS
b. secondary bile acids
c. bacteriocins
13
Q
What do bile acids do to protect against pathogens in gut microbiome?
A
- antimicrobial properties
- produced in liver
- excreted into intestinal tract to aid in DIGESTION OF DIETARY LIPIDS
14
Q
What are bacteriocins and what is one mechanism they use?
A
- short, toxic peptides
- inhibit the colonization and growth of other species
- mechanism: can disturb RNA and DNA metabolism and kill cells through pore formation in cell membrane
15
Q
What composition factor of the gut microbiota acts as a physical barrier function?
A
inner mucus layer!
16
Q
What does the gut’s inner mucus layer do?
A
- impenetrable and firmly attached to epithelium
- stops bacteria from interacting with epithelium to cause an inflammatory response
17
Q
What are 4 competition processes that can occur in the gut microbiome to prevent pathogenic colonization?
A
- nutrient metabolism
- pH modification
- antimicrobial peptide secretions
- effects on cell signaling pathways
18
Q
How does the gut microbiome “synthesize vitamins”?
A
- cross-feeding between gut microbes allows for essential vitamins growth!
19
Q
What are the 2 main vitamins synthesized by the gut microbiota?
A
- Vitamin K
- B group vitamins (ex: folates, biotin, riboflavin, etc..)
20
Q
How does the gut microbiome “develop the immune system”?
A
trains and develops major components of the host’s innate and adaptive immune system
21
Q
Does the immune system orchestrate the maintenance of key features of host-microbe symbiosis?
A
YES!
22
Q
What is one important tissue that the gut microbes important for maturation of?
A
GALT (Gut Associated lympathic tissue)
23
Q
What does GALT mediate (x2)?
A
- immunity
- immune oral tolerance
24
Q
What 3 gut bacteria induce GALT formation?
A
1, Bacteroids fragilis
2. Bacillus subtilis
3. PSA
25
What happens if you are exposed to microbes early in life?
- prevents development of T lymphocytes associated with allergies and IBS
- enhances T - helper cells (GOOD!!!)
26
Are microbes required for full complement of T cells and development of B cells in mucosa?
YES
27
What gut microbe bacteria and the type of cell "promote intestinal angiogenesis" and capillarization?
- Bacteriaoides thetaiotaomicron
- paneth cells
28
What was seen in germ freee mice and mice with a convention microbiota in regards to fat storage?
Germ free = leaner and lower body fat
mice with conventional gut microbiota = higher body fat levels, higher levels of leptin, higher levels of fasting glucose and insulin
29
How are SCFAs produced?
by bacteria through fermentation of nondigestable carbs
30
What are the 3 main SCFAs?
1. acetate
2. propionate
3. butyrate
31
What do the SCFAs do in the intestinal mucosa?
All of them...
- exert anti-inflammatory effects by histone deactylases (HDACs)
- role in microbiota-gut-brain cross talk
- beneficial effect for intestinal epithelial cells and immune cells (via intra and extra celllular processes)
32
What 2 things does the SCFA "butyrate" do?
1. promote the epithelial barrier function
2. main energy source for colonocytes
33
How does the gut microbiome modulate the CNS?
symbiotic bacteria may stimulate postnatal development of mammalian brain
- regulate anxiety-like behaviours and emotion behaviour via vagus nerve-dependent regulation of GABA receptors
- important for social behaviour (decreases risk of autism)
- gut-brain communication
34
could the gut microbiota cause some psychological conditions potentially?
YES? --> anxiety (bacteria changed metabolites in blood)
35
Is the intrauterine environment sterile? if not, why?
NO!
- there is non-pathogenic bacteria present in amniotic fluid and placenta of healthy infants found
Therefore, showing a maternal-fetal exchange of microbes
36
What alters the development of the human microbiome?
early-life environmental exposures
--> puts immune system into a hypersensitive and hyperinflammatory state
37
Is an early life microbiome a crucial factor for proper immune development and long term health?
YES
38
What in pregnancy is considered a "sterile organ" based on the conventional paradigm?
placenta
39
How do adverse pregnancy outcomes occur in relation to microbiome?
from microbes that originate from the vaginal tract, ascend to the cervix which then colonizes in the placenta
40
What is another route of transmission of microbes in the placenta of pregnant women that has recently showed interest?
Oral cavity! --> may be a reason why women with periodontal disease are at risk of pregnancy complications!
41
Do changes in a woman who is pregnant change the microbiota of her gut, oral cavity, and vagina?
YES, though data is not consisent
42
The gut microbiota does not shift throughout pregnancy and increased in richness for both alpha diversity and beta diversity. true or false
False
- it DOES shift
- decreased richness of alpha
- increased beta diversity
43
What is the difference between alpha and beta diversity?
alpha = measure of microbiome diversity in a single sample
beta = measure of similarity or dissimilarity of two communities
44
what are the 4 ways that the gut microbiota contribute the the necessary weight gain of pregnancy?
1. enhanced absorption of glucose and fatty acids
2. increased fasting-induced adipocyte factor secretion
3. induction of catabolic pathways
4. stimulation of the immune system
45
What are 3 roles that the microbiome has during pregnancy?
1. maintenance of a healthy pregnancy
2. contribution of fetal development
3. acquisition of necessary bacteria by the neonate for first days outside the womb
46
What are 4 health problems that are associated with gestational dysbiosis?
1. prepregnancy obesity
2. IBS
3. gestational diabetes
4. preeclampsia
47
What are 3 maternal exposures that could alter the maternal gut microbiota composition, function and availability of microbiota-derived metabolites during pregnancy?
1. diet
2. stress
3. infection
48
If there are changes in the availability of the microbiota-derived metabolites from mom, what could happen?
cause programmatic effects on placenta and fetal compartment
49
What does stress in the first trimester do to the mother and fetus?
alters microbes in vagina
- changes are passed to newborns during birth --> cause changes in their gut microbiome and brain development
50
How does maternal diet have an effect on the microbiota?
-having a high fat diet can effect the offspring microbiome
- alter the immune response in offspring
- shapes the composition and diversity of breast milk microbiota
51
Does gestational fruit and vegetable consumption have an effect on the infant gut microbiome?
YES
52
What are 7 factors affecting the gut microbiome of fetus/neonate?
1. maternal gut microbiome
2. maternal skin
3. mode of feeding --> breastfeeding better than bottle
4. maternal conditions
5. early environmental exposure
6. gestational age
7. mode of birth
8. maternal vaginal microbiota
53
What is a well-known component of human milk that favours gut infant colonization with beneficial bacteria called?
lactoferrin
54
What are 5 bacteria present during pregnancy in the microbiome?
1. fermicutes
2. proteobacteria
3. bacteroides
4. fusobacteria
5. actinobacteria
55
What is dysbiosis?
where the gut bacteria becomes imbalanced
56
What are some factors that can lead to dysbiosis (x6)?
1. excessive or wrong use of antibiotics
2. excessive alcohol consumption
3. increased intake of sugar or protein
4. frequent use of antiacids
5. exposure to pesticides
6. chronic stress
57
What is the "Gut-brain axis"?
- bidirectional communication between the CNS and gut microbiota
- communicate via endocrine, immune, and humoral links
- hormones, neurotransmitters, and immunological factors are released from gut and send signals to brain directly or via autonomic neurons
58
What does the vagus nerve do?
regulates internal organ functions, vasomotor activity and certain reflex actions (coughing, sneezing, swallowing, vomiting)
59
Does the vagus nerve control communication of microbiota with brain?
YES
60
What two neurotransmitters connect the gut and the brain?
1. serotonin
2. GABA
61
What does GABA do?
control feelings of fear and anxiety
62
What is another gut microbe produced that affects brain functioning?
SCFAs! (by digesting fiber)
63
What is two thing sthat an SCFA does to brain function?
reduces appetite
forms blood brain barrier
64
What is another system that the gut-brain axis is connected to?
The immune system!
65
What does the gut microbes role with the immune system?
control what is passed into the body and what is excreted
66
What is one inflammatory toxin made by bacteria that can cause inflammation if too much is passed from gut into the blood?
Lipopolysaccharide (LPS)
67
How could LPS pass into the blood?
from a gut barrier becoming "leaky"
68
What has inflammation and high LPS been associated with?
Brain disorders (severe depression, dementia, schizophrenia)
69
What was present in obese people in terms of microbiome?
lower bacterial diversity
decreased fecal microbial gene richness
70
What type of diety causes changes in gut microbiome?
high fat diet
71
What are the 6 mechanisms of gut microbiota dysbiosis promote induced obesity and metabolic complications ?
1. immune dysregulation
2. altered energy regulation
3. altered gut hormone regulation
4. proinflammatory mechanisms (ex:LPS crossing gut barrier and entering blood)
5. higher production of SCFAs
6. use of antibiotics during first 6 months
72
There are well-known co-morbidities of COVID-19 associated with dysbiosis. True or false
TRUE
73
What can influence the severity of COVID
- variety and volume of bacteria in gut
- magnitude of immune response
74
can dysbiosis cause long covid? if so why?
YES --> cause a persistent inflammatory symptoms
75
When people had covid, what happened to gut microbiome?
loss of commensal gut microbes
76
what are commensal gut microbes?
benefical
directly act on host immune system to prevent invasion and colonization of pathogenic microbes
77
What are 6 reasons IBS occurs?
1. gut flora changes
2. prior infection
3. psychological stress
4. gut-brain axis
5. diet/food sensitivity
6. pre-post natal factors
78
Once the barrier is breached by influx of inflammatory mediators, pathogens or
any agents that provoke intense immune reactions, severe inflammation occurs
and this will affect the intestinal environment, and changes the gut microbiota
composition. True or false
TRUE
79
low grade mucosal inflammation + visceral hypersensitivity + impaired bowl motility = what?
IBS!!!
80
What reduction of type of food reduces symptoms of IBS?
foods high in fermentable carbohydrates (FODMAP) - short chain carbs that are fermented by gut bacteria into methane and hydrogen gasses but DO NOT GET ABSORBED WELL
81
What could be a fix for IBS with Clostridium difficile infection to restore intestinal homeostasis?
Fecal microbial transplant (FMT)
82
What is the "hygiene hypothesis" with IBD?
lack of early microbial exposure may reduce tolerance of the adaptive immune response
- we live cleaner, more urbanization, more antibiotic use
83
gut microbiota composition is altered in
patients suffering from T2D, but it is not clear whether these changes are a
cause or simply a consequence of the disorder. true or false
TRUE
84
What is the difference between probiotics and prebiotics?
Probiotics are foods or supplements that contain LIVE bacteria to maintain or improve the "good bacteria"
Prebiotics, are foods typically HIGH IN FIBERS that are fermented by your gut
bacteria, and act as food for your microflora (may also affect brain health --> could also reduce cortisol levels in body)
85
What are 3 other things known to cause dysbiosis in gut microbiome?
1. sucralose, asparatame, and saccharin
2. food additives (ex; emulsifiers)
3. certain restrictive diets (vegan, raw food or clean eating, gluten-free, low FODMAP)
86
What is IBS divided into 2 categories?
1. Crohns disease
2. Ulcerative colitis
87
Is dysbiosis greater in patients with Crohns or Ulcerative colits?
Chrons disease!
- more reduced diversity
- a less stable microbial community
88
What is the difference between Chrons and Ulcerative Colitis
- Crohn's disease can cause inflammation anywhere in the gastrointestinal tract from the mouth to the anus.
- Ulcerative colitis can cause inflammation and ulceration in the large intestine
89
HSS4102
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