microbiology

• What are the 3 different shapes of bacteria? (scientific names)

  Bacillus, Cocci, Spirline

  
• What are the 3 different shapes of bacteria? (normal names)

  Rod, Spherical, Spiral
• What do obligate aerobes require?

  require oxygen for metabolism

  
• What is an example of an obligate aerobe

  Mycobacterium tuberculosis
• What do facultative anaerobes require?

  grow best w O2 but can survive when oxygen is absent

  
• Example of a facultative anaerobe?

  E. Coli
• What do Obligate anaerobes require?

  Absence of oxygen

  
• Example of an obligate anaerobe

  Clostridium tetani ← this type of bacteria produce toxins or poisons in a wound. They destroy a condition called ‘moist gangrene’
• What is gram staining

  Used to identify the 2 types of bacteria- those with and those without an outer layer of lipid

  
• what is the process of gram staining

  1) Strain with crystal violet/iodine

  
  

  2) Decolorize with ethanol

  -Decolorization removes the outer membrane and thin peptidoglycan layer

  
  

  3) The crystal violet stays bound to gram positive cell walls

  
  

  4) Decolorized cells are counter stained with safranin
• What colour does gram negative stain

  Red/ pink
• What colour does gram positive stain?

  Purple (Not violet!)
• Gram positive bacteria


  Bacteria that have a thick peptido glycan cell wall, and no outer membrane.

  
• Gram negative bacteria


  Bacteria that have complex cell walls with less peptidoglycan but with lipopolysaccharides. Very toxic and hard to treat.

  
• Why are Gram-negative bacteria relatively more resistant to antibiotics?

  the outer lipopolysaccharide protects the peptidoglycan which makes gram neg bacteria resistant to penicillin and to protect themselves from lysozymes and other hydrolytic enzymes
• How are gram negative treated?

  they require a different class of antibiotics to control them which interfers with the cells ability to make proteins
• How does penicillin work against gram positive bacteria

  penicillin prevents the bonds between peptidoglycan molecules from forming it makes the cell walls structurally weak and prone to collapse which leads to water uptake by osmosis causing the cell to burst
• Why are animal cells not damaged by penicillin?

  they have no cell wall only a cell membrane
• Aseptic technique


  Laboratory practice that maintains sterility in apparatus and prevents contamination of the equipment and the environment
• How to prevent contamination from the bacteria in the experiment to the environment

  sterilise work surface before and after

  use correct handling technique to prevent contamination of personell and the immediate environmental organisms being cultured
• How do we sterilise equipment

  either by autoclave or radiation
• How doe we keep everything sterile during inoculation

  - Flame the neck of the bottle - pass loop through flame untile red hot and allow to cool
• Why do we not put tape all around the petri dishes

  could cause anaerobic conditions and cause pathogenic microorganisms to grow
• Why do we store upside down

  prevents condensation from diluting the bacteria