Microbio

• Microbial growth

  • increase number of cells
  • dependent on nutrients of the culture
• Growth curve

  • lag
  • log
  • stationary
  • death
• Microbial counts

  • determine how microorganisms grow
  • indicator of spoilage
• Serial dilution

  • bacterial suspension
• Counting methods

  • direct count
  • viable count
  • pour plate
  • spread plate
• Plate count

  • pour plating: 1ml
  • Spread plating: 0.1 ml
• Direct count

  • living and dead cels are counted
• Superior marienfeld chamber

  • one of the grid 5 squares
• Cells per ml = ( ave no. of cells / 5 ) ( 1/4 nl) ( dilution factor ) ( 10 ^6 )
• Viable counting

  • colony forming units are considered
  • represents viable cell
  • spread or pour plate
  • more reliable
• Cfu per ml = # of colonies x DF / Volume plated
• Pour plating

  • anaerobic to facultative
  • volume plated: 1ml to 0.1 ml
  • lower count than spread plating
• Spread plating

  • aerobic to facultative anaerobe
  • volume plate: 0.1 ml
• Measuring microbial population provide valuable information
• Direct and viable count are methods used in microbial counts
• Direct count is the number of cells present without any manipulation