Practical exam Anna

• Growth means an increased in the


  Number of cell
• generation time (doubling time)=

  the time taken for a population to double
• binary fission steps

  1. DNA replication
  2. cell elongation
  3. septum formation
  4. formation of distinct wall
  5. cell separation
• cell cycle =


  time taken for a newly cell to replicate DNA elongate and divide
• two phases of cell cycle

  C phase -replication to form 2 identical daughter DNA

  D- separation cytoplasmic membrane
• C phase takes approx

  40 min for one round of replication
• D phase takes approx

  20 min between termination of DNA and cell division
• population of growth is estimated by

  change in cell number or biomass per unit time
• growth rate is 


  change in cell number or cell mass per unit time
• Four phases of typical growth curve

  1. Lag
  2. Exponential
  3. Stationary
  4. death
• lag phase 


  cell synthesising essential constituents for growth
• exponential phase log phase

  cell number double with each generation
• equation for exponential growth

  Nt=No(2n)

  Nt= cell number after n generation

  No=starting cell number
• population expressed as log 10

  on logarithmic scale
• stationary phase 


  no net increase pr decreases
• death phase 


  death rate > rate of reproduction
• requirement for microbial growth physical

  • temp
  • ph
  • osmotic effect
  • oxygen
  • pressure
• physical growth and affect

  • Extended lag phase
  • decreased log phase
  • premature stationary
• Temperature

  rapid growth lead to protein denature

  
• psychrophiles 0-20

  mesophiles 12-45

  thermophiles 40-80

  extreme thermophiles 65-113
• acidophiles PH 


  grow at 0-5

  helicobacteria
• neutrophiles PH


  grows at 5-8

  microbes
• alkalophiles 


  grows at 9-11

  spda lake
• osmotic effects 


  environment with high solute concentration water flows out the cell
• osmotolerant 


  grows of wide rage of osmotic conc
• osmophiles 


  live on high sugar solute
• halophiles 


  high salt conc
• halotolerant 


  don’t require salt but can grow with
• nonhalophiles 


  can’t do with salty environment
• xerophiles 


  very dry enviroment
• obligate aerobes 


  requires o2
• obligate anaerobes 


  inhibited by o2
• facultative anaerobes 


  grows with or without o2
• microaerophiles 


  requires low o2
• aerotolerant anaerobes 


  don’t use o2 but tolerate it
• pressure barophiles 


  adapted to high pressure
• pressure barotolerant 


  grow on high but not very high
• barosensitive 


  die at high pressure
• Phototrophs 


  Energy from light
• chemotrophs 


  energy from oxidation and reduction of chemical