The microbacteria in the GI tract Flashcards
Understand why there are differences in bacterial communities throughout the GI
• Transit time
• Anaerobic conditions increase
- Facultative anaerobes (with and without O2)
- Obligate anaerobes (cannot live with O2)
Understand the activities of different bacterial species
- Immune defences
- Metabolism of dietary components
- Production of essential nutrients to maintain health
- Developing the immune system
- Host signalling
- Modification of secretions: mucin, bile, gut receptors…
How do bacteria help with immune defences?
- Barrier effect: win out with their numbers which creates a barrier (also mucous layer)
- Competition: have strategies to get rid of other bacteria
- pH inhibition: generally grow over 6 but in the ascending colon the pH is lower than that
- Competition: have strategies to get rid of other bacteria
How do bacteria develop the immune system?
Immune priming
What are the essential nutrients that bacteria produce?
- SCFAs
- Photochemicals
- Gases
- BCFA
- Other metabolites
- Minerals
How does eating junk food affect bacteria?
Doesn’t feed microbes
How does a healthy diet with lots of fibre affect bacteria?
- Feeds the gut microbes
- Faecal bulking, eases passage
- Contains important anti-oxidants and photochemicals
- Bacterial fermentation
What does bacterial fermentation do?
- Releases additional photochemicals
- Maintains slightly acidic pH
- Increases population of commensal bacteria and improves resistance to bacteria
- Essential supply of SCFAs
Explain the effect of different diets on bacterial activity
- Better diet= better diversity= healthy (lots of products)
- Activities driven by what we eat
- Different gut microbes have different activities
Explain the effects of antibiotics on gut microbacteria
- Can result in a loss of diversity
- Kills off locals as well as visitors
- Provides opportunity for pathogens to colonise and dominate
- Can result in antibacterial resistant pathogens
What is causation with respects to microbes and disease?
It’s the bacteria’s fault
What is correlation with respects to microbes and disease?
- Bacteria in GI increase but are not the cause of the problem
- It is hard to tell the difference
- Symptoms can affect microbiota e.g.: inflammation, diarrhoea, host genotype
- Actions can affect the microbiota e.g. antibiotics or diet
What is microbial dysbiosis?
Microbial dysbiosis is a general imbalance in bacteria
Give examples of diseases the correlate with microbial dysbiosis
• IBD
- Dysregulated host immune response to gut microbria (likely)
- Inflammation
- Reduced bacterial diversity
- Typically manifests in a non-uniform manner
• Ulcerative colitis= reduced firmicutes
• Crohn’s disease= slightly elevated enterobacteria
What are probiotics? What are their actions?
- Microorganisms that when taken in an adequate amount can be beneficial
- The actions that probiotics take are: competition; barrier affect; competitive exclusion; vitamin production; decreases inflammation; Bioconversions; immune stimulations and direct antagonisms (pathogens)
- Certain probiotics will work in some cases (but not all) and others will work in some other cases
