Lecture 8 - Microbiota Flashcards Preview

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Flashcards in Lecture 8 - Microbiota Deck (36):

decrease in diseases such as mumps, measels over the years has been paralleled by what?

increase in autoimmune diseases - e.g type 1 diabetes


What does the hygene hypothesis say?

inverse correlation of the types of allegies and the size of the families.

Therefore, reduced exposure to infectious agents caused a dysregulated immune response


What are the problems with the hygene hypothesis?

Some bugs stimulate autoimmune response by molecular mimicry

not the same in all countries i.e Japan


What does the old friends hypthesis say?

humankind has been exposed to bugs throughout history and this microbiota is training our immune system to respond to things that it needs to not just everything that it sees.


Diet hypthesis has been added to this, what does it stipulate?

diet drives changes in the microbiota and directs the development and function of the immune system

germ-free mice will have dysfunctional immune responses


What are the factors of nutritional transition?

economic factors

demographic - death/birth rates in society

epidemiological - societies with less infectious disease, good healthcare causing reduction in disease outcomes


Is diet the basis of increased "western world" disease?

high fat high sugar diets, less fibre which influences our microbiota


A change in microbial composition can lead to ...



The gut microbiota contains approx how many micro-organisms?

10 trillion

lots of genetic potention at least 5 million genes (500 different species)


There is species specific segreation along the different...

segments of the GIT


What is the significance of germ free mice?

They have different genetic backgrounds, can selectively restore microbiotas


Taxonomic and metabolic classification of microbiota can be achieved with...

High through-put DNA sequencing


what was the first and second phase goals for the human microbiome project/

First phase: chracteristed composition and diversity (nose, moth, skin etc)

evaluate genetic metabolic potential

second phase:
creation of the first integrated dataset of biological properties from both the microbiome and host from cohort studies of microbiome associated diseases


What is a healthy microbiome?

Each persons microbiome is unique

Two people may have different microbioal communitites but still be healthy


Certain communities can be used to predict characteristics, what are some examples

whether they were breastfed, education


True or false

There are related species in different communities in the same body e.g skin GIT



What are the major groups of phylum in the gut?

firmicutes, bacteroidetes

but - no core microbiome, at least at the species level


True or false

Diet is more important in shaping gt microbiota than ethnicity, sanitation, hygene, geography and climate



What are the functional classes of non-pathogenic members of microbiota/

probiotics - transient - can confer health benefit and affect beneficial bacteria

autobionts: permanent - symbiotic, direct influence on host immune function

pathobionts: permanent, parasitic, do not cause disease in presence of autobionts - but can when there are alterations


What adaptations have the autobionts made to adapt to life in the gut?

They express plysaccharide utilisation loci (PUL
- digest plant polysaccarides that make up dietary fibre


Bacteria produce what important end products?

Short chain fatty acids (SCFA)


these can be used by other bacteria and our own endothelium


What is the role of SCFAs, generated by autobionts, have what role in gut health?

Sensed by epithelial cells - increased mucous production - gut protection

Stimulates B-cells to produce IgA

stimulates tissue repair

regulate other immune cells


To summarise what is the importance of gut microbiota?


production of vitamins

gut epithelial development (and nutrition)

immune system development


combat infections (barrier function, competitive exclusion)


The increase in obesity underlies the worldwide increase in ..

type 2 diabetes - insulin resistance occurs in parallel


What is the role of gut bacteria in obesity and type 2 diabetes?

There are changes in gut microbiota of obese and t2d patients

There is a decrease in gut diversity assoc with weight gain - a less complex popuation

Theres also a reduction in certain SCFAs including butyrate, which decreases the protection against opportunistic pathogens


cohousing oexperiements shwoed that obese phenotype in mice could be overcome by precense of mice with..

lean microbiota


Why is gut microbiota changed during pregnancy?

weight gain, insulin insensitivity

changes in immunity and dysbiosis reinforce each other

transfer of microbiota from pregnant women to germ-free mice leads to weiht gain/ insulin insensitivity


what is involved in the modulation of host metabolism by SCFA?

GPC-R respond to specific metabolites -


PYY which regulated gut motility

GLP-1 - increase insulin sensitivity

IGN - SCFAs are converted to glocse

Fiaf - inhibits lipproteinlipase and fat accumulation in adipocytes


GPR43 deficient mice tend to be...

obese on a lean diet

with a high fat diet they are susceptible to


Diet induced gut dysbiosis also causes changes in what else?

balance of T-cells and CD4+ helps - SCFAs influence this

abundance of pathobionts and release of endotoxin

breakdown in gut barrier function and increase in gut bacteria and antigensin blood


The balance between Th17 and Tregs is important for...

the balance between immunosuppression and inflammatory responses


How does dysbiosis affect the balance of th17 and tregs?

Butyrate promotes formation of t regs and suppresse activation of th17s

cd4+ are activated by pathobionts (which are more active when the balance is lost)


Dysbiosis can also influence other organs including

bowel disease
behavioural problems


what are the ways to treat microbiota problems?

diet - less fat, more fibre

pro/prebiotics introduction

fecal transplantation


The risk of immunoallergic disorders is greater..

the earlier a migrant moves from region of low risk to region of high risk

The two way interaction between microbiota and immune sysmte is established early in life


Do prebiotics work? (yakult)

yes, but they require long term use - are cleared very quickly