Module 1 Summary

• define micro-organism

  • organism with typically cellular features too small to be seen without a microscope
• why does immersion oil improve resolution

  • it increases the numerical aperture
• 3 domains of life

  1. bacteria - no nucleus
  2. archea - no nucleus
  3. eukary
• ways micro-organisms have influenced life

  1. food industry
  2. medience
  3. water quality
  4. disease
• compare prokaryotes and Eukarytoes

  pros: bacteria and archea, no nucleus or organelles and circular chromosomes, size and complexity

  euk: protozoa (animal like charcteristics, uni cell), fungi (uni and multi cell) and algea (uni and multi cell), nucleus and organelles and linear chromosomes
• Why is it necessary to Stan before visualisation

  • helps with contrast between bacteria and background
  • helps to determine morphology
• why is phase contrast and fluorescence more superior

  • it has better contrast with the bacteria and the background compared to bright field where there is a lack of contrast
• TEM vs SEM

  TEM: transmission electron micro: internal structures

  SEM: scanning electron micro: external structures
• advantages of electron microscopy compared to light

  1. better contrast
  2. can see internal structures
  3. high magnification and resolution
  4. can see viruses
• what is the step that can be omitted in gram staining

  • safrianin

  remember: gram -ve: colourless and gram +ve: pink/purple
• key events in evolution

  • life 3.86 billion
  • Cyanobacteria —> oxygenation: 3 billion
  • eukaryotic: 2 billion
  • atm oxy: 1 billion
  • multi cell: 650 million
• most likely the early cellular process

  • hyperthermophilic anerobic respiration
• define endosymbiosis hypothesis

  • development of organelles in eukaryotes
• chronometer

  • measures changes in organisms over time
  • measures evolutionary time and changes that occur over time
  • sequence genes like rRNA and fossils like stromatolities
• best describes Cyanobacteria

  • carry out oxygenic photosynthesis
• Give 2 reasons why viruses are not 4th domain in tree of life

  1. they are non-cellular particles
  2. the tree of life is categorised based on ssu rRNA gene seq which viruses do not have
• Why is there no temperate bacteriophages with RNA genomes

  NA of temperate bacteriophages integrate into host cell genome which is DS DNA and therefore they need to be dis DNA viruses
• how does entry into and out of host cell differ from animal cells and e.coil

  animal cells: viruses attaches to cell surface receptors and the complete virus enters the host cell mostly be endocytosis or occasionally by membrane fusion.

  • they enter either by: budding (envelope), lysis (non-envelope) or lysis

  e.coli: bacteriophages attaches to cell surface receptors and only the viral genome enters the host cell. when viral particles are produced, the bacterial cell is lysed and viruses are released