Gut microbiota Flashcards
Give examples of some host modifying function of GM?
Changing the immune system
Gut motility and permeability
Hormonal regulation
Give examples on some metabolic functions of GM?
Synthesis of B & K vitamins
Fiber digestion
Production of SCFA as epithelial nutrients
Biotransformation of ingested compounds
What is a defencesystem of GM
bacterial antagonism
Detection of microbes:
the route
DNA - microbiota characterization (who’s there)
DNA - Metagenomics (what can they do?)
RNA - Transcriptomics (What are they doing?)
Proteins - proteomics (What have they done?)
Metabolites - metabolomics (what have they done?)
What is the most common sample type for gut microbiota analysis?
Fecal samples
Is fecal sample sufficient?
If it is an inflammation it is not sufficient. Doesn’t give a perspective on the GM in the mucosa either.
But in many cases it can be sufficient.
Which part of the GI tract has highest density?
The large intestine (colon)
Are samples in different parts of the colon homogenous or hetrogenous.
Pretty homogenous, good representation of entire colon.
Although more diversity to the end
How does the type of bacteria vary thorughout life?
In beginning facultative anaerobic bacteria then goes to strictly anaerobic bacteria
How does the birth affect GM?
Big affect at first depending on C-section of vaginally. But then it possibly disappears after a while.
What can enterotypes be used for?
To classifying individuals based on the gut microbiome.
Name three common enterotypes
Prevotella
Bacteroides
Ruminococcaceae
What are enterotypes?
An enterotype is a classification of living organisms based on its bacteriological ecosystem in the gut microbiome.
enterotypes are not dictated by age, gender, body weight, or national divisions
Why can e.g. prevotella be an “influences”?
might have other bacteria that benefit being close to it
What is colonization resistance?
Protection of the host intestines from exogenous pathogens by commensal bacteria — a phenomenon termed colonization resistance — was described more than five decades ago and was thought to result from microorganism-mediated direct inhibition. However, recent work has shown that commensal bacteria can also indirectly control invading pathogens by enhancing host immunity in the intestines (known as immune-mediated colonization resistance)
Give examples of colonization resistance?
Changing the local gut environment - Fermentation contributes to a lower pH Interaction between bacteria - competition for nutrient - Influence bioavailability of nutrients - Production of bacteriocins Influence on gut mucosa - Occupation of binding sites - Increased protection of the gut mucosa - Regulation of immune function
What are bacteriocins?
proteinaceous or peptidic toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s)
How does B. thetaiotaomicron modulate the virulence gene expression of EHEC?
By making fucose available to EHEC by cleaving it from the polymers in the mucus layer.
What is Gut-brain-axis?
The gut–brain axis is the biochemical signaling that takes place between the gastrointestinal tract (GI tract) and the central nervous system (CNS)
Which nerve is important in the communication between the GI and the brain?
Vagus nerve
What is the role of the vagus nerve?
The vagus nerve, the longest of the cranial nerves, controls your inner nerve center—the parasympathetic nervous system. And it oversees a vast range of crucial functions, communicating motor and sensory impulses to every organ in your body.
What is the relationship between B12 and the vagus nerve?
The vagus normally stimulates the stomach’s parietal cells to secrete acid and intrinsic factor. Intrinsic factor is needed to absorb vitamin B12 from food.
Positive and negative aspects of antibiotica treatments
Positive: Cure infections by killing harmful bacteria
Negative: Development of antimicrobial resistance (AMR)
killing of beneficial bacteria
Risk factor for new infections
How does GM affect bile acids?
GM is involved in the biotransformation of BA and therefore modified by GM which affect the metabolism. BA also has antimicrobial activity that can damage bacterial cell membranes and thus inhibit bacterial overgrowth and also regulate the overgrowth and composition of the intestinal microbiota to protect the liver and intestine against inflammation
Metabolic function of microbiome in the large bowel?
Microbial fermentation of complex carbohydrates
Metabolic function of microbiome in the small bowel?
Degradation and absorption of proteins, lipids and simple carbohydrates
What can happen with the protein and lipids that are not absorbed in the small intestine?
Reach large bowel where they can be formed into unwanted metabolites
Which dicarboxylic acids makes propionate?
Lactate and succinate
What is the role of saccharolytic bacteria?
Convert oligo-,monosaccharides to e.g. dicarboxylic acid that can later be converted to SCFs
What can be produced by the saccharolytic bacteria?
Saccharolytic bacteria can produce formate, acetate, butyrate, lactate, succinate and ethanol
A few hormones that are related to the GM?
GLP-1, GLP-2, PYY, GIP, FGF15
What is TMAO?
It is produced when gut bacteria digest choline, lecithin and carnitine, nutrients that are abundant in animal products such as red meat and liver and other animal products.
What defines alpha-diversity?
Alpha diversity refers to the average species diversity in a habitat or specific area. Alpha diversity is a local measure.
What is beta-diversity?
Beta diversity refers to the ratio between local or alpha diversity and regional diversity. This is the diversity of species between two habitats or regions. It is calculated by a equation
How is dietary fibers and prevotella related?
dietary fiber-induced improvement in glucose metabolism is associated with increased abundance of prevotella.
Prevotella also assocciated with lowering of cholesterol
What diseases can be caused by the GM?
Autoimmune disease Chronic inflammation (IBD) Behavioural disturbance Infections Cancer Liver disease Metabolic diseases Malnutrition
What is dysbios?
a skewed balance between good and bad bacteria
If too much enterobacteria – common link to gut disturbance.
Lack of butyrate producing bacteria and lactic acid bacteria not good.
What are a few consequenses of a disturbed microbiota?
Defect barrier function
or
Unwanter metabolites –> toxic compounds –> leaky gut –> inflammation disease development
What is the definition of a prebiotic?
”A selectively fermented ingredient that results in specific
changes, in the composition and/or activity of the GI
microbiota, thus conferring benefit(s) upon host health”
What are three criteria for prebiotics?
1) Resistance to: gastric acidity, hydrolysis by mammalian enzymes and GI absorption
2) Fermented by the intestinal microbiota
3) Selective stimulation of growth and/or activity of beneficial bacteria
One common product with prebiotic effect
Inulin
Does prebiotic work?
Some studies have shown positive results whereas other haven’t so need more research
What is probiotic?
“live microbes with a health benefit on the host
What is related to dysbiosis?
Enterobacter
What is synbiotics?
Probiotics with a little lunch pack (suitable prebiotics)
