BIBC 120 Lecture Notes - Lecture 10: Inflammatory Bowel Disease, Gut Flora, Facultative Anaerobic Organism
24 May 2018
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week 4.1
MICROBIOTA
- Bacteria with Obligate Anaerobic Metabolism: Only carry out fermentation pathways
(no oxygen required) to produce energy (ATP), dot do as well whe there is ore
oxygen around.
- Bacteria with Facultative Anaerobic Metabolism: Can carry out either fermentation, or
respiration (which requires oxygen) to produce energy (ATP). can do well in the
presence or absence of oxygen
- What constitutes a healthy microbiota?
1. Diversity
2. More obligate anaerobes than facultative anaerobes
▪ The lumen of the colon is an anaerobic environment
▪ Higher oxygen levels in colon and occurrence of aerobic metabolism may
be associated with inflammation and disease states
- Beneficial Activities of Microbiota: SCFAs
o Bacterial fermentation of soluble fiber produces short-chain fatty acids (SCFAs)
▪ Butyrate (4C) CH3-CH2-CH2-COO-
▪ propionate (3C) CH3-CH2-COO-
▪ acetate (2C) CH3-COO-
o SCFAs are absorbed by the colon mucosa and metabolized by the host (this
provides up to 10% of daily energy intake)
o SCFAs may help to regulate inflammation in the GI tract
o differetiate these fro dietar short-chai fatt acids. I that cotet we are
referring to fatty acids less than 10 carbons in length
- Regulation of GI Immune Response
o Careful balancing act of immune function along intestinal mucosa
o Too little immune response—infection by pathogenic bacteria
o Too much immune response—inflammatory disease of intestine
- Inflammatory Bowel Disease (IBD)
o Immune inflammatory response impairs intestinal function (including absorption
of nutrients) and may damage the mucosa
▪ i.e. Irritable bowel syndrome—geerall ild sptos, Crohs Disease,
Ulcerative Colitis
o New evidence suggests a healthy gut microbiota may decrease susceptibility to
these diseases
- Gut microbiota affects host inflammatory response
o evidence from mouse models
o summary: Bacterial metabolites fight intestinal inflammation by metabolizing
fiber generating short-chain fatty acids which act on Treg cells to result in
immune suppressive properties
1) Regulatory T cells (Tregs): turn down inflammation/suppress immune
response
2) SCFA bind and initiate signal transduction through GPCR receptor (GPR43
and 41), Tregs have GPR43 (maybe 41), results in Treg secreting anti-
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Document Summary
Bacteria with obligate anaerobic metabolism: only carry out fermentation pathways (no oxygen required) to produce energy (atp), do(cid:374)(cid:859)t do as well whe(cid:374) there is (cid:373)ore oxygen around. Bacteria with facultative anaerobic metabolism: can carry out either fermentation, or respiration (which requires oxygen) to produce energy (atp). can do well in the presence or absence of oxygen. Regulation of gi immune response: careful balancing act of immune function along intestinal mucosa, too little immune response infection by pathogenic bacteria, too much immune response inflammatory disease of intestine. Immune inflammatory response impairs intestinal function (including absorption of nutrients) and may damage the mucosa i. e. irritable bowel syndrome ge(cid:374)erall(cid:455) (cid:373)ild s(cid:455)(cid:373)pto(cid:373)s, croh(cid:374)(cid:859)s disease, Ulcerative colitis: new evidence suggests a healthy gut microbiota may decrease susceptibility to these diseases. Potential mechanism for regulation of the immune inflammatory response by the colon microbiota: trompette, 2014: allergic asthma mouse model. A high fiber (4%: squirt dust mite extract into mouse causing lung inflammation.
