Lecture 37: Gut microbiome II Flashcards
How does the North American gut microbiome compare to the microbiome of indigenous populations? Why?
The composition is extremely different because the diets are different. The North American diet is more processed and meat-heavy, which changes the microbiome present.
How does obesity impact the gut microbiome?
Obese individuals have higher proportions of Firmicutes:Bacteroidetes than lean individuals.
What method was used to determine how the gut microbiome differs between obese individuals and lean individuals? Why?
Because there are several confounding factors that affect humans (diet, genetics, environment), mice models are used instead, as their genetics and diet and can be controlled.
As opposed to a normal lean mouse, how is an obesity-prone mouse different genetically?
The obesity-prone mouse will be lacking in leptin, which is a hormone made by fat cells that regulates the amount of fat stored in the body (the satiety hormone)
Describe how it was proven that obese organisms have a different gut microbiota than lean organisms.
Lean mice and leptin-mutant mice were fed the same diet. The 16S rDNA method was used to look at what type of gut microbiota was present in each. It was found that obese mice had a significantly higher proportion of firmicutes:bacteriodetes in their gut.
Describe how it was proven that the difference in gut microbiota between lean and obese individuals is the cause of the weight difference.
Two mice were transferred microbiomes from a lean human and an obese human respectively, and they confirmed that the bacterial ratios were as expected. The two mice were fed identical diets and quantities of food, but the obese mice still had more body fat despite this.
Explain why the difference in gut microbiomes between obese and lean individuals causes a difference in weight gain when put into mice. Also explain how this was determined.
The microorganisms from the obese system caused more genes involved in carbohydrate metabolism to be expressed. So, for the same amount of food, obese mice were getting more energy out of it vs losing it in the feces. This was shown by fecal calorimetry, with obese mice having less energy left in their feces.
What is the role of diet in the establishment of lean vs obese microbiota?
A bad diet cannot be cancelled out by having a “lean” microbiome. Lean microbiota still can’t colonize well if exposed to a high fat and lower fiber diet.
What impact do antibiotics have on gut microbiota diversity?
It vastly reduces microbiota diversity, even in strains that are not targeted by the antibiotics.
In what stage of life are antibiotics particularly disruptive?
During early childhood.
At sub-therapeutic doses, antibiotics can promote […]
Weight gain
How do antibiotics affect bacterial abundance before and after exposure?
They decrease abundance during exposure, but the numbers usually bounce back afterwards (although the diversity does not)
What is a pathobiont expansion?
This is an unintended effect of antibiotics whereby they can promote the establishment of pathogens in healthy hosts. This doesn’t always cause disease, but sometimes can.
Give an example of a pathobiont expansion (drug and pathobiont)
Drug: clindamycin
Pathobiont: C. difficile
Why does taking clindamycin promote the establishment of C. difficile?
Because the abundance of other bacteria in the system decrease, so it gives C. difficile the chance to colonize.
