8-1: The Human Microbiome Flashcards
How many bacterial genes for every human gene
~100
3.8x10^13 bacteria
Collection of microbes living in/on us
Human microbiota
Microbiota and the environment they live in
Human microbiome
Microbial flora is…
Used same way as microbiota
What is dysbiosis
Term used to describe microbiota that is unhealthy for the host. “out of balance” - loss of commensals
Things we know little about with regards to the microbiome:
community dynamics, how they interact
Links btw microbiota and disease: causal or correlative?
Mechanisms linking microbiota and disease
How are microbiota of similar people similar? How are they different?
Similar at phylum level, but also unique in each individual at species level
Microbiota composition depends largely on
Environmental factors, some genetic
Loss of resilience in composition leads to
Dysbiosis
About the (gut) microbiota…
Established at a young age, remarkably resilient
Where are the microbes in/on our bodies
Gastrointestinal tract (stomach, SI, LI)
Skin
Oral cavity/upper respiratory tract (mouth, nose, throat)
Urogenital tract (urethra, vagina)
Major players of microbiome in various locations
Lactobacillus (vagina)
Streptococcus (saliva)
Bacteroidetes (GI)
Propionibacterium (skin)
What part of the GI tract has the densest microbial population
Large intestine (increases as progress down GI tract)
Does the stomach have lots of microbes? Why/why not
No, low pH keeps numbers low, but still some
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, serves as barrier
Where do most microbes remain in the GI tract
Lumen
What feeds the GI tract population
Nutrients in food, some of which we can’t digest
How is the gut microbiota variable?
Person-to-person differences
Even most abundant genera missing from some ppl
Three major phyla of the gut microbiota
- Bacteroidetes: g(-)
- Firmicutes: g(+)
- Proteobacteria: maintain anaerobic environment by consuming any O2 present
Major metabolism of the gut
Fermentation
What breaks down (ferments) diverse CHO from food
Primary fermenters (Bacteriodetes)
How is the gut microbiota important for human health
- compete with pathogens to prevent colonization
- digest food
- Produce nutrients we can’t make (vitamins, aa)
- promote healthy immune system
Fibers are fermented to
short-chain f.a.
Symbiotic relationship with gut flora is…
mutualistic
When helicobacter pylori is in the stomach…
Stomach ulcers
What causes dental plaque
Formation of biofilms over bacteria on teeth
Staphylococcus aureus is on the skin, it is an…
opportunistic pathogen
What leads to s. aureus infections
Cuts/wounds
Release potent virulence factors
What dominates vaginal microbiota? What do they do?
Lactobacillus species
Lower vaginal pH (~5) via fermentation end products (lactic acid)
What does low vaginal pH prevent? What happens when it is high?
Infection with pathogens
Reduced lactobacillus increases pH allowing yeast to bloom = yeast infection
What is a prebiotic
Substance that when consumed promotes growth of beneficial microbes (e.g. fiber)
Explain fecal transplants
Fecal from healthy donor transplanted into dysbiosis patient, reintroduce normal/healthy microbiota
What infection can fecal transplants cure
Clostridoides difficile infections
