Human Microbiome Flashcards
What is commensal bacteria?
Supplies the host with essential nutrients and protects host against opportunisitic pathogens without causing harm to our health. They form part of the normal microbial flora
What is a microbiome?
Community of bacteria
Which commensal bacteria is present in the gut microbiome?
Lactobaccilius and escherischia coli
How does the gut microbiome develop?
Babies are sterile until delivery when they travel through the birth canal where the vagina is rich in lactobaccilius bacteria and gain maternal bacteria, alongside breastfeeding. It changes in composition and becomes more diverse during development
What affects composition of gut microbiota?
Diet, medication like antibitoics, chronic inflammation, hygeine and lifestyle
How does the density of bacteria change?
Greatest in the large intestine, specifically, the proximal transverse colon
Which type of bacteria is present in gut microbiome?
Gram positive, anaerobic.
What is the difference in microbiota between infants born vaginally vs C-section?
Vaginally: commensal bacteria such as prevotella, sneathius and lactobaccilius
What is the microbiota of infants born by C section?
Harmful bacteria such as streptococcus, corynebacterium and propionibacterium
Where is the majoirty of serotoinin produced?
Intestines
What is the role of the gut microbiome?
Protection against pathogens, immune system development, modulation of CNS
What prevents interaction between gut microbiota and intestinal cells?
Thick layer of mucus on top of enterocytes contaning IgA antibodies
Which vitamins are produced by the gut microbiome?
Production of vitamin K and B12/folate, and B2.
How does the gut microbiome affect metabolism?
It increases metabolism of xenobiotics and drugs, by promoting absorptive capacity of enterocytes through increasing intestinal angiogenesis. Increases adiposity. It increases fermentation and lipogenesis
Why are the metabolites of the gut microbiome important?
Signalling molecules for biochemical communication between enteric system and CNS.
What provides majority of energy to colon cells?
Fermentation of dietary fibre/ non-digestable carbohydrates -> short chain fatty acids such as butyrate
How does gut microbiome affect lipid levels?
Increases lipid storage and adiposity by promoting lipogenesis
How does gut microbiome affect the morphology of the gut?
It increases mucus thickness, levels of IgA antibodies, development of lymphoid tissue.
It increases intestinal angiogenesis, lipogenesis, production of short chain fatty acids by metabolsim of dietary fibre.
How does the gut microbiome protect against pathogens?
Via colonisation resistance. Bacteria which survive low stomach pH establish colonisation through replication and resist peristalsis. Gut promotes immune defences through metabolic products, nutrient competition, direct toxicity and immune induction
How do metabolic products provide protection against pathogens?
Bile salts disrupt bacterial membranes; short chain fatty acids regulate virulence factors. These provide indirect protection against clostridium and e.coli
How does gut microbiome affect immune response?
Promotes production of defensins from epithelial cell lining of GI tract which inhibit bacterial growth of enterococcus and listeria. This is indirect.
How does gut microbiome provide direct protection against pathogens?
Nutrient competition with pathogens for sialic acid and fucose in intestinal mucus. Gut microbiota produces the toxin bacteriococcilin and uses type VI secretion.
What is type VI secretion?
Mode of transport of toxins from gut microbiota into target cell membrane/cyptoplasm/
How can commensal bacteria cause infection?
Spread into sterile areas of the body or replicate if normal numbers are disturbed and increase in population
What causes increase in population of commensal bacteria?
Immune deficiency, pH imbalance, decrease in mucus. This can lead to infection because population must be low to prevent harm
What is clostridium dificile?
Gram positive anaerobic Bacteria which composes a small proportion of commensal flora when in low levels. It forms spores and transmitted from faecal to mouth causing bowel infection.
How does antibiotic treatment affect gut microbiome?
Non discriminatavely eliminates both commensal and harmful bacteria
What is antibiotic selective pressure?
Use of antibiotics leaves only bacteria with mutation for resistance to survive
What is pseudomembranous colitis?
Inflammation of colon with elevated yellow-white plaques on mucosa, caused by clostridium dificle when antibitoic selective pressure increases their population. This causes diarrhoea
What is fecal microbial transplant?
Transfer of healthy bacteria from processed stool of healthy donor to intestine via a tube. This is to restore gut bacteria and control infection from clostridium dificile.
What is dysbiosis?
Imablance in gut microbiome associated with disease due to changes in micorbe abundance which cause harm to the host.
What are prebiotics?
Non digestable food ingredient as dietary fibre which promotes activity/growth of colonic bacteria by providing nutrients, improving host health without being destroyed during digestion
What are probiotics?
Living non- pathogenic organisms in food to improve host health
