Flashcards in The Gut Microbiome in Metabolic Disorders Deck (36):
What is the microbiome?
Collection of microorganisms and their genes and proteins living within our mucosae, skin, and secretions
What is the exposome?
What are the two most dominant phyla in the colons of healthy adults?
What are the Firmicutes mainly made of?
Gram positive Clostridia
What are the Bacteroidetes mainly made of?
Gram negative Bacteroides
Are the less important phyla functionally important?
What are the two approaches to sequencing the microbiome?
16S ribosomal sequencing
Metagenomic shotgun sequencing
How does 16S ribosomal sequencing work?
Takes areas common to most bacteria in 16S ribosomal subunit gene and amplifies it
Those areas that are different are also amplified
On this basis, bacteria can be separated
What is the speed and ease of 16S ribosomal sequencing?
Straightforward to analyse
What does 16S ribosomal sequencing report?
Operational taxonomic units, not sequences of species
Does 16S ribosomal sequencing resolve well at the species level?
What are the shortcomings of 16S ribosomal sequencing?
May fail to resolve substantial fraction of diversity
Not ID novel/highly diverged microbes
Can't resolve biological functions associated with taxa
How does metagenomic shotgun sequencing work?
Microbial and human DNA separated
Microbial DNA randomly sheared into short segments > sequenced > re-assembled
Does metagenomic shotgun sequencing reveal microbial genes that are active?
No, only those that are present
What is alpha diversity?
Measure of species diversity within sample
What is beta diversity?
Measure of diversity between samples
What is dysbiosis?
Disturbance/imbalance in biological system
How is a newborn baby seeded with microbiota?
What are the dominant species in the vagina with which the baby is seeded?
What does a healthy microbiome do in a baby?
Induces maturation and maintains integrity of
- Immune system
- Neurological system
Protects against infection
Produces nutrients and vitamins
Utilises energy > regulates metabolism and weight
What happens to the breast milk microbiome after elective C-section?
What childhood diseases is C-section associated with?
Type 1 diabetes
What evidence is there to show that the microbiome regulates development of type 1 diabetes?
Incidence of T1D in wild mice very low
More than half of mice reared in specific pathogen free environments developed T1D
All mice reared in germ-free environment, and had no microbiome, developed T1D
What does diet protection against autoimmune diabetes need?
What is the relationship between gut microbial diversity and seroconversion to clinical type 1 diabetes?
Decrease in diversity with seroconversion
Significant decrease in diversity with diagnosis T1D compared to controls
How does the gut microbiome change in children with type 1 diabetes?
Actinobacteria and Firmicutes decreased
Butyrate-producing species within Clostridium decreased
How are short-chain fatty acids, such as butyrate, produced?
Bacteria ferment undigested starch
What do short-chain fatty acids do?
Maintain epithelial integrity
Absorbed > go to
- Bind and activate GTRs
- Inhibit histone deacetylases
How does a fast food diet change the gut microbiome?
Has many additives affecting microbiome
What is the gut microbiome like in type 2 diabetes?
Fewer butyrate-producing bacteria
More opportunistic pathogens > can cause infections
What is a better predictor of insulin resistance than BMI?
Is there evidence that a faecal microbiota transplant cures anything?
No clear evidence that it cures anything except recurrent C difficile infection
How did things change in people with metabolic syndrome with the transfer of gut microbiota from lean donors?
Increased insulin sensitivity
Increased diversity in faecal microbiome
Butyrate-producing bacteria increased
Is obesity transmissible by gut bacteria?
What are the issues with probiotics?
Contain only few bacteria
Evidence for passage to large bowel
Varying resistance to acid and bile across species and strains
Lack of randomised clinical trials