Karteikarten
Lecture 28 & 29 PMB
Karten in diesem Stapel (35)
- 1sterile sites of human bodybloodstream, CSF, heart, liver, kidneys
- 2Human Microbiome Projectgoal was to acquire a “reference” microbiome of healthy adult humans
samples from 250 people, analyzed by 16S rRNA sequencing --> community metagenomes obtained, genes and biological pathways can be guessed - 3conclusions of human microbiome project1) NO reference microbiome exists for healthy adult humans
2) One body site is more likely to be similar to an identical body site on another person than a different body site on same person
3) No virulent pathogens just waiting around, just opportunistic pathogens
4) At a given site there are different phylogenies for each individual BUT same metabolic pathways still represented - 4How might different microbial communities perform the same functions at a given site?--> distinct groups of microbes can provide roughly the same set of metabolites as each other
- 5How to compare two colonies from two different individualsdo metagenomics, then BLAST, then predict all the different functional genes for each community
- 6What areas of the skin can microbes occupy?can occupy sweat glands, sebaceous glands, hair follicles, epidermal surface
--> NOT a uniform environment depending where on the body the skin is! - 7different skin environmentssurface = cool, dry, salty, acidic (gram positive S. epidermis love this)
axilla, scalp, ear, genital = more humid
face, chest, back = more sebaceous glands - 8P. acneslives in sebaceous glands, digests triglycerides in sebum --> stimulates immune system --> produce inflammatory fatty free acids --> clog pores, create ACNE!
lots of diversity at the strain level = metagenome sequencing shows diversity, not 16S - 9oral cavity microenvironments: below the gum lineanoxic, microbes digest proteins secreted by host & catabolize amino acids
healthy state: streptococci, actinomyces, veillonella
diseased state: P. gingivalis dominates! --> gum detachment + tooth loss - 10oral cavity microenvironments: above the gum linebacteria must be able to withstand antibacterial factors in saliva (lysozymes)
streptococci are most abundant, ferment carbohydrates to acids (lactate, formate, acetate) --> sugars abundant, pH drops --> enamel dissolution
when carbohydrates are exhausted, pH rises and enamel dissolution stops - 11What happens with poor oral hygiene?acid-loving S. mutans and lactobacilli dominate and produce more acids through fermentation --> destroy enamel, more grow with increase in acids
is a positive feedback loop - 12Stages of enamel decay1) Healthy, only a few commensals
2) Healthy, more commensals pack in
3) Damaging, acid-tolerant fermenters enter and alter environment
4) Damaging, acid-tolerant fermenters completely outcompeting commensals and taking over biofilm - 13Microbiome of vaginally born babies vs Cesarean sectionvaginally born babies have higher species diversity 3 days after birth
babies of CS in prospective studies found to have greater instances of asthma and allergies --> early exposure to microbes can influence immune system? - 14microbiome pH going down the human gutstomach pH = 2
small intestine pH = 4-5
large intestine pH = 7 - 15alpha diversitythe average human's diversity in the GI (about 1000 species)
- 16beta diversityALL GI microbiota sampled to date (about 10,000)
- 17in general, what AFFECTS the GI microbiome?host genes; birth procedure (C section vs vaginal); early diet; early microbial exposure; antibiotic perturbation
- 18in general, what is the EFFECT of the GI microbiome?--> digestion
--> nutrient processing
--> immune system
--> nervous system - 19How do we tolerate billions of commensals?we NEED these microbes for the development of an immune system
- 20Experimental evidence of gut microbiome's important role in the immune systemGerm free mice: accumulate a lot of iNKT T-cells in GI mucosa --> more susceptible to CHEMICALS that cause IBD + asthma
IF production of iNKT cells blocked --> germ free mice get less sick!
Non-sterile mice: imbalance of T-cells balanced by transfusion of microbes NEONATALLY (as babies), not not as adults - 21TH17 cells vs Treg cells in segmented filamentous bacteria (SFB)TH17 helper cells ramp up infection, while Treg dampen inflammation
If balanced: healthy microbiome
If imbalanced: disease (IBD, asthma, eczema OR lack of protection from pathogens) - 22Gut microbiome link to obesity/metabolic disease: antibiotics and weight gainfeed constant low level antibiotics to healthy mice with no change in diet --> gain weight faster
GI microbiome changes how the body stores/metabolizes food? - 23Gut microbiome link to metabolic disease: H. pylori and hormonestest humans with or without H. pylori in stomachs after eating --> those WITH had much lower hormone ghrelin (hormone which stimulates us to eat) --> alters our behavior
*H. pylori can help us to stop eating* - 24CHO diet effect on microbiome (diet --> GI)germ free mice fed (plant carbohydrates) CHO diet --> after twelve weeks were colonized with non-sterile mice fed same diet --> half stay on CHO diet, half fatty western diet --> 16S sequencing shows GI microbiomes between diets are diff! --> more species diversity for CHO + gain less body fat
- 25Microbiome effect on fat accumulation (GI --> body)donor mice NOT sterile, half raised on CHO diet and half on Western --> both donors GI microbes transplanted to GF mice raised on CHO diet --> no change in diet for recipients!! --> GF mice who got microbes from Western donor had a larger body fat increase than from CHO diet
(donors genetically obese --> same result) - 26disbiosissweeping changes in population of microbes that produce an imbalance in your GI microbes
- 27gnotobiotic micegerm free mice, easier to study than humans
- 28Bacteriodes fragillis and Clostridiae in Human MicrobiomeSFBs that grow in GI, you need a balance of these to end up with a balance of TH17 and Tregs or else disbiosis will cause disease!
- 29effect of human fecal transplant on GF micetake obese human twins, and lean human twins --> inoculate fecal samples into GF mice --> feed mice same LF-HPP diet --> measure fat mass after 35 days
*microbes from obese twins led to greater fat gain than from lean twins* - 30results of cohousing mice with "lean" microbiota and "obese" microbiota (fed on same diet)Lean + obese = obese mice gain some fat mass but not much, lean don't change
Obese + obese = obese mice gain the most fat mass
Lean + Lean = no change
GF + Lean + Obese = GF LOSE fat mass - 31results of cohousing mice with "lean" microbiota and "obese" microbiota (fed on different diets)"lean" microbes protect mice with "obese" microbes IF diet is low in saturated fats + high in fruits and veggies (LoSF-HiFV)
NOT protected if fed opposite: HiSF-LoFV
--> change in microbiome must be accompanied by change in diet to be healthy! - 32signaling pathways that most affect metabolic outcomes--> fermenting bacteria production of short-chain fatty acids
--> small intestine microbes modification of bile salts - 33What happens when you disturb the GI ecosystem?antibiotics --> reduction in species diversity
"weed" species C. difficile can survive and become dominant --> painful antibiotic-resistant diarrhea (AWFUL)
occurs NOT from exposure but from killing off its competition - 34treatments for recalcitrant C. difficileFecal microbial transplant: harvest stool from healthy patient --> transplant to patient through colonoscopy
- 35probiotics effect on healthprovided in food or capsules
can help people but negative side effects occur from adding dominant species to gut in high numbers