Microbiota (what I think is important) Flashcards
When does colonization of microoganisms occur?
during birth
Why can the microbiome be viewed as an organ?
Develop during birth, and undergoes maturation and aging like other organs
What does dysbiosis mean?
“abnormal” microbiota
Composition of microorganism?
1 % - viruses, archaeons, eukaryotes
99% - bacteria
How does diet affect composition of miccroorganism?
Less diverse microorganism with processed food
Describe the microflora distribution
- no microflora in stomach (reason why people doubted H. Pylori existed)
- majority of microflora are located in the colon (most of these bacteria in the colon are anaerobes because there is little oxygen in colon - most O2 was already reabsorbed)
- the mouth is the location with the second most amount of microflora (all the microflora are aerobes and facultative anaerobes - utilize oxygen)
What is commensalism?
microbes benefit from the ineraction, but the human hoests are not affected either positively or negatively (based on traditional understanding of colonic microbes)
What are metagenomics?
Metagenomics is the study of genetic material recovered directly from environmental samples.
What are gnotobiotic animals?
A gnotobiotic animal is an animal in which only certain known strains of bacteria and other microorganisms are present. Technically, the term also includes germ-free animals, as the status of their microbial communities is also known.
** How is this possible? Gnotobiotic animals are born in aseptic conditions, which may include removal from the mother by Caesarean section and immediate transfer of the newborn to an isolator where all incoming air, food and water is sterilized. **
Benefits for microbes to live in gut?
(1) supply of food (indigestible food, shed epithelial cells)
(2) stable, protected environment
Benefits to humans to having microbes living in gut (there are many but he mentioned 4 new examples - specific to the layers of the gut)
(1) Thickening muscle wall
(2) Stimulating gut-associated lymphatic tissue (GALT) proliferation
(3) Stimulating epithelial cell generation and turnover
(4) Increasing lamina propria cellularity (may enhance functional coordination)
Why doesn’t size matter for bacteria?
Despite having a smaller genome compared to homo sapiens, they have a greater number of enzymes and have enzymes that are not present in humans (ex. enzymes that digest otherwise indigestible polysaccharides - supplies short chain fatty acids for reabsorption by the host)
How do bacteria increase the efficiency of nutrition reabsorption?
(1) break down indigestible polysaccharides into bacteria-derived short chain FA
(2) digest and recycle shed intestinal cells
(3) supplying essential amino acids
(4) supplying vitamins (K, B12, biotin, folic acid, and pantothenate)
(5) aiding in bile acid recycling in the colon (converting bile salts to bile acids)
(6) altering the intrinsic metabolic machinery of host cells, resulting in more efficient nutrient uptake and utilization
What disease can dysbiosis be linked to?
(1) Type II diabetes
(2) Obesity
(3) Metabolic syndrome - such as a knock of Toll like receptor 5 which is essential for innate immunity
(4) Malnutrition
(5) Type 1 diabetes populations in humans
What are the consequences of dysbiosis in type II diabetes patients?
- decrease in butyrate-producing bacteria
- increase in opportunistic pathogens
- restoration of microbita profile after gastric bypass surgery
Connection between obesity and microorganisms
Obese-prone mice stay lean when microbiota is removed, but become obese once again after reintroduction of microbiota
( shows that obesity - a metabolic syndrome - is regulated by host-microbiota interaction)
Connection between toll like receptor 5 and microbiota
- Transfer of microbiota of TLR5-null mice to germ-free wild type confers features of metabolic syndrome
- Antibiotics treatment reverses metabolic syndrmoe in TLR5-null mice
Connection between gut microbiota and malnurition/kwashiorkor
-Significant difference in microbiota composition between healthy cotwins
and kwashiorkor (severe malnutrition) co-twins in Malawi
- Microbiota in kwashiorkor co-twins do not mature as microbiota in healthy cotwins.
(Main idea: Dysbiosis can cause malnutrition and malnutrition can cause dysbiosis)
How does gut microbiota contribute to immunity?
(1) competition (for nutrients and adhesion sites)
(2) secrete antimicrbial factors
(3) degrade toxins
(4) stimulate immune factions
What is antibiotics-induced dysbiosis?
antibiotics introduced to fight off an infection which simultaneously kills helpful microorganisms
Why give antibiotics for viral infections?
Kill bacteria because bacteria in the gut can act as pathogens’ helper which means they worsen viral infections
What is mechanic cleaning?
The fact that the gut secretes and moves in itself serves as protection. Mice treated with opium, an inhibitor of motility and secretion require 1000x lower salmonella bacteria to develop bacteremia (more susceptible to disease)
