1

• universal phylogenetic tree shows evolutionary relationship based on rRNA sequencing so does not represent all life (viruses and prions)
• infectious microbial agents with no rRNA

  prions and viruses
• prokaryotic infectious microbial agents

  bacteria and archea
• eukaryotic infectious microbial agents

  protozoa (single cell parasites), fungi, multicellular parasites
• parasites

  a eukaryotic organism that has a parasitic relationship with their human or animal host
• prokaryotes features

  thick cell wall, no nucleus or membrane bound organelles
• eukaryote features

  membrane bound organelles, membrane bound nucleus
• prions


  a large protein that changes conformation of normal proteins to abnormal form, no NA, replicate using host machinery
• prion example - PrP^sc


  causes mad cow disease and dementia, brain has normal form of protein, comes into contact with abnormal form of same protein and changes to abnormal and replicates
• viruses definition 


  no cellular structure, can't replicate themselves, use machinery of host cell, can't cause disease outside of human cell (DNA or RNA but not both)
• bacteria def


  prokaryotes, usually free living can intracellular, DNA and RNA
• fungi (mould + yeast)


  eukaryotes, usually free living, moulds and multicellular version of fungus, yeast single cell
• protozoa def


  single cell parasites, DNA and RNA
• prokaryote DNA


  single, circular chromosome of DS DNA
• prokaryotes site of respiration

  cell membrane
• gram positive bacteria stain


  purple
• gram negative bacteria stain


  pink
• gram positive cell envelope structure


  inner plasma membrane, thick layer of cell wall peptidoglycan outside
• gram negative cell envelope structure

  inner plasma membrane, thin layer peptidoglycan, outer plasma membrane
• functions of plasma membrane bacteria

  retain cytoplasm, selectively permeable, ATP synthesis (respiration)
• pleomorphic bacteria


  has multiple forms
• flagella 


  helical protein structure that mediates bacterial motility on some bacteria
• polar flagella


  at one or both ends of cell
• peritrichous 


  spread over whole surface of cell
• directed v tumbling motility

  directed rotates in one direction, tumbling looking for signal
• pili and fimbriae


  hair like protein structures, fimbriae are shorter
• pili and fimbriae function

  help bacteria attach to surfaces of host cells, adhesions on pilus attach to receptor molecules on host cell surface
• sex pili


  mediate transfer of DNA from cell to cell, conjugation to enable rapid spread of genes, extend from 1 bacteria to another
• capsule layer function


  helps pathogenic bacteria resist phagocytosis and mediates attachment of bacteria to surfaces
• slime layer


  variant of capsule, unorganised and easily removed
• S-layer


  2D crystalline protein lattice enclosing cell envelope, stabilise membrane
• endospores


  resistant, dormant spores formed in some bacteria when in harsh conditions
• which bacteria in particular form spores

  clostridium botulinum, c.tetani, c.difficile, bacillus anthrax
• endospores may germinate if water, nutrients present and start growing again
• how kill endospores 


  autoclave at high pressure, temp
• role of cell envelope in infection

  maintains cell shape and protects bacterial cell from osmotic lysis
• peptidoglycan 


  helical structure alternating polysaccharides NAM and NAG, peptide side chains cross linked with other strands
• teichoic acid


  in gram positive peptidoglycan, mediates adhesion of bacteria to host cells
• LPS


  on outer membrane of gram negative, mediates clinical effects of infections, O specific side chains (trigger specific immune response)
• Lipid A component 


  endotoxin causes fever, septic shock and death, actives immune cell, is an O LPS side chain