Chapter 24 Flashcards
Define microbiome
a functional collection of different microbiota. Ex: human microbiome
Define microbiota (aka microhabitat)
All microbes in an environmental habitat.
Different microhabitat support different microbes.
Ex: skin microhabitat is diff from mouth microbiota. Both are part of human microbiome.
Benefits of understanding human microbiome
1) Development of biomarkers (can predict predisposition to diseases- before symptoms show)
2) design of therapy targeting (select and modify specific microbe in specific body site)
3) personalized drug therapy and probiotics
PS: about 10^13-14 microbes present in human microbiome
Host and microbiota interactions
Complex, cause and effect relationship (microbiota can affect host; host affect microbiota through activities, diet, and health)
host-microbiota relationships not always immediately obvious/identifiable
Experimental investigation on microbiome
It’s difficult because most microbes cannot be cultured in labs
advanced sequencing techniques can identify different microbiota (of different body sites)
What are some microbiome trends, you dummies?
1) No single microbial species most abundant at ALL body sites (species A is abundant in mouth; species C is abundant on your hair, etc.)
2) no single microbial species is most abundant in all individuals (ed has species A more than vivi does; vivi has more species C)
3) However, certain microbial groups do dominate. In taxonomic levels, there are some pattern of domination depending on individuals and at body sites. (Ex: Propionibacterium dominates skin microbiome, while Lactobacillus dominates urogenital tract.)
Effects of Human Gastrointestinal microbiota
gastrointestinal microbiota affect: 1. early development (colonization of gut begins at birth); 2. health, and 3. predisposition to disease.
Human gastrointestinal organs review for dummies & microbe density of the organs
About 400 m^2 of surface area (organs 3 to 5 combined)
1 - esophagus
2- liver (pH = 7 secrete bile)
3- stomach (pH =2 secrete HCl to digest macromolecule)
4- duodenum, jejunum, ileum (ph = 4-5absorb monosaccharides, aa, FA, H2O)
5- large intestine + appendix (useless like u jk) (pH = 7 absorb bile acids, vit B12)
Microbe density increases as u go down (ex: jejunum has 10^3 cells, ileum has 10^8, colon has 10^11)
Roles of Gastrointestinal microbiota
1) digest food
2) absorb nutrients
3) produce nutrients (ex: some vitamins body cant make)
Characteristics of stomach microbiota
pH is 1-2 in lumen but 6-7 in mucus layer of wall. Density is about 10^4 cells
Difference between Lumen & Mucosa microbiota
Lumen microbes are firmicutes, bacteroidetes, and actinobacteria
Mucosa microbes are firmicutes and proteobacteria (esp. Helicobacter pylori - in 50% of human population)
Characteristics of duodenum microbiota
microbiota similar to stomach since it’s close to stomach and has similar pH as stomach
Characteristics of ileum microbiota
Less acidic with 10^8 cells.
Microbiota competes with host for absorption of rapid small carbohydrate
Characteristics of large intestine microbiota
pH = 7 and 10^10-12 cells
known as fermentation vessel
Major large intestine microbes are firmicutes and bacteroidetes.
Most of them are in lumen
Other trace organisms in large intestine
In trace amounts:
Archae - ex: methanogens like Methanobrevibacter smithii
Fungi - ex: Candida albicans
Other eukaryotic microbes NOT present
