Lecture 21 - Microbiota And Human Health Flashcards
(49 cards)
What is microbiota?
The microorganisms found associated with normal healthy people
Where is microbiota found?
Surface tissue - skin, gastrointestinal tract, respiratory tract, urogenital tract
What does microbiota vary with?
Age, diet and environment
Parasitism
One species lives at cost of other
Mutualism
Both species benefit
Commensalism
One species benefits without harm to other
What are microbial pathogens?
Parasites
What are normal flora often called?
commensals
Why does normal microbiota matter to clinicians?
Surgery breaks physical defences of body allowing normal flora into sterile sites Treatment damage normal immune defences, allowing normal flora to become opportunistic pathogens Isolation of potential pathogens for diagnosis dependent on distinction from normal flora Role of microbiota in health and disease
What are the benefits of microbiota?
Nutrition protection - “colonisation resistance” Maturation of the gut priming of the immune system
Nutrition
Breakdown of complex polysaccharides Production or useful metabolites e.g. vitamin K
Protection
Occupy niche to prevent access by pathogens produce bacteriocins to inhibit other species disruption of normal flora by antibiotic treatment can cause problems “thrush and pseudomembranous colitis”
Priming of the immune system
Presence of low level antibodies against normal flora may enhance immunity against pathogens Immune system abnormal in germ-free animals
What is the acquisition of the microbiota?
Microbiota acquired rapidly after birth, mostly from mother composition changes depending on age and environment Tests on individuals training for space flights show flora shared, become uniform
How to investigate the microbiota?
Culture bacteria from biopsy or faeces Apply molecular techniques
What is the cast of characters
Differences in: cell wall, surface antigens, secreted proteins, respiration, metabolites, genome sequence
How to identify species?
Use 16SrRNA genes Extract total DNA PCR with universal 16S primers Clone and sequence products.
Identify species present
What is the gut?
Highly anaerobic - organisms that have never been exposed which find that oxygen is toxic in nature - hard to culture
More related species have more similar what ?
Similar 16SrRNA gene sequence
What does sequence allow?
Identification of species
What are new sequences assigned to?
genus or higher phyla
What is next generation sequencing?
Takes an array and spreads them out on a glass dish so each spot has a sequence on it. Can be amplified in situ Sequencing can determine the sequence from each spot on this plate AKA massively parallel sequencing technologies
Metagenomics
Extract total DNA Sequence fragments (cloned or direct).
Identify species present Identify metabolic functions encoded
What is the diversity of human intestinal microbial flora?
3 individuals (great diversity) 6 sites in colon + stool (little diversity Total 12,000 sequence gave 395 phylotypes
