Microbiota Flashcards
Holobionts Def
Ecological unit: assembly of different species. Survival benefit to all species involved
Symbiosis Def
2+ different species living in close association to the advantage of both. Eg nutrition, transport and protection
Hologenome Def
Human and bacterial genome. 30% microbiome and 70% unique to individual
Relationship between microbiome diversity and health
More diverse microbiome = better health
Microbiota Function
Digests fiber to short chain fatty acids, barrier function, mucus secretion, defensin production, tight junction permeability and epithelial proliferation and death, hormone secretion and nutrient transport
Microbiota Extra-intestinal Functions
Fat + sugar metabolism, immune function, cardiovascular function, cognition and mood
Effects of an absence of microbiota
Poor intestinal barrier function, poor immunity, abnormal gut development, increased stress hormones and decreased weight gain
How is the composition of the microbiome
16S Ribosomal DNA sequencing. Gene V4
Most common bacteria in human microbiome
Firmicutes (determined by genetic make up) and Bacteroidetes (determined by diet)
Progression of Microbiome with age
Fetus-sterile, child- fully formed and diverse microbiome and elderly - diversity decrease (diet changes, medication and changes in transit time)
Intestinal lumen and it’s relationship to the microbiome
Contains extensive anaerobic bacteria
Outer Mucus Layer and it’s relationship to the microbiome
Some bacteria (most bacteria can enter this layer). Contains degenerating mucus and diluted antimicrobials
Inner Mucus Layer and it’s relationship to the microbiome
Microaerobic only (most bacteria stopped at 1st mucus layer). Firmly adherent and rich in antimicrobials. Form a crypt cell barrier to prevent migration to next layer
Colonic Crypts and it’s relationship to the microbiome
No bacteria. Filled with mucus, site of antimicrobial production and an epithelial cell barrier with underlying and intervening leukocytes
SCFAs function
Epithelial cell energy and binding to GPR receptors to regulate cell proliferation, transport, barrier function and immune cell activation
Bile Acids Function
Produced by liver to facilitate digestion and absorption
2 receptors for bile acids in colon
TGR5 and FXR
TGR5 Outline
Cell surface (hydrophilic molecules), G protein receptor. Activated by conjugated bile acids (eg TCDCA)
Farnesoid X Receptor (FXR)
Nuclear. Activated by deconjugated bile acids. Antagonised by UDCA
Functions of TGR5 and FXR
Motility, fluid transport, barrier function, lipid metabolism, glucose metabolism and energy expenditure
Dysbiosis Def
Imbalance of bacterial levels in microbiome. Measured by the ration of firmicutes to Bacteroidetes in stool (F/B ratio)
Low F/B ratio indications (decreased firmicutes and increased Bacteroidetes)
Antibiotic associated diahorrea, Crohn’s Disease, ulcerative colitis and type 2 diabetes
High F/B ratio indications (higher firmicutes and lower Bacteroides)
Obesity
How to tend to the microbiota in disease states
Drugs, diet (increased fibre and decreased fat), probiotics and fecal microbial transport
Fecal Microbial Transport Def
Transfer of fecal matter containing bacteria from a healthy donor to a diseased recipient. Stool collected, mixed with saline, strained and taken by patient as enema. 90% cure rate of C Diff
