Thursday, 04 Jul 2013


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7/04/13 Milk Agar Plates

  • The purpose of milk agar plates is often to detect protease activity, including the activity of keratinases.
  • A measurement of any baseline protease activity of our parent B. subtilis strain (WB700), which does not endogenously express any keratinases, is desired.
  • Excess protease activity of our parent B. subtilis strain may prevent our use of milk agar plates as an assay for keratinase expression of our future transformants with the kerA gene.
  • Therefore, the parent B. subitilis strain (WB700) was streaked on the milk agar plates to observe baseline protease activity that could prevent us from detecting keratinase expression after transformation.
  • [Milk Agar Plates] (in LB):
    • Total volume of 600 ml (makes 20-25 plates)
    • 20g (30*.6) nonfat dry milk powder
    • 500mL 2X [LB medium]
    • 250mL 2X [agar]
  • Ideally, there should be a minimal zone of clearing around our B. subtilis colonies.
  • Next Steps:
    • Observe the results of our milk agar plates with B. subtilis colonies