8-1: The Human Microbiome Flashcards
How many bacterial genes are there for every human gene?
~100
What is the human microbiota? What is another name for it?
Collection of microbes living in/on us. Also called “microbial flora”
What is the human microbiome?
Microbiota and the environment they live in.
What is dysbiosis?
Term used to describe microbiota that is unhealthy for the host. “out of balance” - loss of commensals, increase in microbes associated with disease.
What does the majority of our knowledge regarding the microbiome come frome?
16s DNA shotgun sequencing and animal models
What are some things we know very little about regarding microbiota?
Community dynamics, how microbes interact
Links between microbiota and disease: causal or correlative?
Mechanisms linking microbiota and disease
Ways to restore healthy microbiome to individuals with dysbiosis
How are microbiota of people similar? How are they different?
Similar at phylum level, but also unique in each individual at species level
Microbiota composition depends largely on which two factors?
Mostly environmental factors, some genetic component.
At what age is microbiota established? What’s interesting about this?
Established at a young age, and very resilient to changes.
What problems can microbiota resilience and loss of resilience lead to?
Loss of resilience can lead to dysbiosis, while resilience makes interventions in the microbiota difficult.
Where are the microbes in/on our bodies?
Gastrointestinal tract (stomach, small intestine, colon)
Skin
Oral cavity/upper respiratory tract (mouth, nose, throat)
Urogenital tract (urethra, vagina)
Most internal sites of the body are considered what?
Sterile - no bacteria
How does microbiome vary by location?
Different parts of the skin, saliva, urogenital tract and GI tract have very different compositions of organisms
Describe the composition of the stomach microbiota.
Low pH tends to keep numbers low, but a microbial community still exists
What part of the GI tract has the densest microbial population?
Density increases as you progress through the GI tract, so the large intestine
What factors vary throughout the GI microbiome?
pH, O2 and nutrients
What protects the epithelium that lines intestines of the GI tract?
Mucous layer
What is mucous?
Thick and slippery suspension that includes antimicrobial factors and mucin
What is mucin?
Gel-like glycoprotein substance that serves as a barrier
Where do most microbes remain in the GI tract?
Lumen and NOT in direct contact with host cells
What feeds the GI tract population?
Nutrients in food, some of which we can’t digest
What percent of fecal matter is made of bacteria?
30%!
How is the gut microbiota variable?
Person-to-person differences, where the abundance of different genera varies by orders of magnitude
Even most abundant genera are missing from some people
What are the three major phyla of the gut microbiota
- Bacteroidetes: g(-)
- Firmicutes: g(+)
- Proteobacteria: facultative anaerobes. Maintain anaerobic environment by consuming any O2 present
