M4: topic 1: human microbes

• Endosymbiont


  Live in the tissue of the host
• Ectosymbiont


  Live on the surface of the host
• Different pathogens


  • Microbial parasites
  • Minority
  • Opportunistic pathogens
• Opportunistic pathogens


  Disease only in absence of normal host resistance
• Characteristics of pathogens


  • Adherence to host
  • Invasion of host
  • Toxigencity - how they produce toxin
  • Ability to invade host immune system
• Human microbiome


  • Favourable environment as it's a constant physical conditions
  • Colonises all exposed to environment ie. Skin, oral cavity, respiratory tract, gasp-instrial and urogential tract
  • Advanced sequence tehcniques allow for ID of different micro bacteria
• 16s RNA


  What the human microbiome is compared with
• Genetic/environmental factors influencing human microbiome


  • Diet
  • Race
  • Age
  • Climate and surrounds
• Skin microbiome


  • Impermeable to microbes
  • Distribution depends on local skin environment - oily, dry, moist
  • Dominated by gram -ve bacteria
  • Staphylococcus, propioni, coryenbacteria
  • Composition influenced by environment and host
• Oral cavity microbiome


  • Heterogenous and complex due to smoot, crevices and saliva
  • Microbes adapt and grow from plaque (biofilm)
• Common diseases in oral cavity


  • Periodontal = plaque tooth jaw interface
  • Strept mutants
• Respiratory tract microbiome


  • Upper: Pathogens are opportunistic - controlled by host defence, many bacteria is s.epider, normal flora adhere to epithial cells of the mucous membrane
  • Lower: No normal flora, transient microbes, infections occur here - macrophages
• Plaque formation


  1. Attachement and growth = biofilms on tooth surface

  2. Acidic glycoproteins from saliva

  3. Streptococci colonise a film

  4. Extensive growth = thick bacterial layer

  5. Anerobes = increase [] of acid = decalifcation
• Upper respiratory tract diseases


  • Pharyngitis
  • Laryngitis
  • Tonsilist
• Lower respiratory tract diseases


  • Bronchitis
  • Pneumonia
• Penicillin would not work with mycoplasma as an antibiotic due to no cell wall and thus no peptidoglycan to prevent beta-lactate chains
• Stomach and small intestine microbiome


  • Both have a pH of 2!
  • Low levels of microbes but high numbers of acid tolerant l.acid bacteria
• GI tract microbiome


  • SI: Low number in the duodenum due to bile and acidity, high number in ileum due to less acidic
  • LI: Complex anaerobic
• Commonly found in the gastric fluid


  • Firmicutes
  • Bacteriodetes
  • Actinobacteria
• Found in mucus layer of the stomach


  • Firmicutes
  • Proteobacteria
• GI microbiota


  • 2 main components
  • 98% of all gut phyla fall into 3 phyla: Firmicutes, Bacteriodetes, Proteobacteria
  • All regulate metabolism and host propensity for obesity
• Gut enterotypes


  Where individuals vary in their gut microbiota, influenced on drug therapy, diet, ethnicity, and community, can contribute to health
• 3 gut enterotypes


  • Bacteroides
  • Prevotella
  • Ruminococcus
• Products of intestinal microbiota


  • Vitamins
  • Mods of steroids
  • Amino acid biosynthesis
• Gut microbiota and birth


  • Colonisation begins at birth with the transfer from mother to child which is a source of vitamin "Faculative"
  • Variables determine nature of gut biome: Vag - biome similar to mother, Breast - increase commensal bac due to oligosaccharides and thus promote colonisation
• Probiotics


  Live organisms with confer health benefits to the host, species of bidiobacterium and lactobacillus in yogurts, work by taking space and nutrients and limiting ability of pathogen to colonise gut
• Prebiotics


  Carbohydrates and provide nutrition from fermentative gut bacteria, added to promote growth and colonisation