19 December 2008

Date: 19 December 2008; Time: 0930; Agenda: Quantification of 24hr biofilm at 3 temperatures and results of plating of serial dilutions done on 18 December.

• Proceeded to quantify the biofilm formed by carrying out CV staining and measuring the absorbance using the microplate reader.

Results for plating of serial dilutions done on 18 December.

• For LB McFarland Standard:
  • 10^-10: TOO MANY TO COUNT
  • 10^-12: 269
  • 10^-14: 165
  • 10^-16: 8
  • 10^-18: 3
  • 10^-20: NONE

• For M9 sample (with the same starting number of cells as LB McFarland Standard)
  • 10^-6: 94
  • 10^-8: 70
  • 10^-10: NONE

• Results of plating seems inaccurate as the starting number of cells in M9 and LB medium should be theoretically similar assuming the centrifuging was done properly. If the starting number of cells are the same, the LB agar plates (at a certain dilution) should contain similar number of colonies for both M9 and LB media. However, the number of colonies vary by a lot (compare at 10^-10: for LB: TOO MANY TO COUNT; for M9: NONE). Hence, the centrifuging may have been inaccurate!