Cell concentration Question - (Sep/27/2009 )

hello all, for my microbio lab, I have some discrepancy for cell concentration calculations obtained from Turbidity readings and my plating experiments... from Turbidity readings I obtained 2.10 x 10^9 cells/mL and from pour plating I obtained 2.81 x 10^9 cells/mL, so quiet a bit of difference

what could be a cause for this discrepancy? is this type of thing normal? any insight would be greatly appreciated.

thank you!

Agree - this is a concern about nothing. The precision of your plate counts is probably not sufficient to separate these, much between techniques. you are also attempting an overly precise interpretation of turbidity data.

CellSpecific.com on Sep 27 2009, 06:47 AM said:

hi, i used
doubling dilutions (1/2, 1/4/ 1/8, 1/16, 1/32) to obtain the turbidity readings. to do this i added 3 mL Luria broth and 3mL of Bacteria successively.

decimal dilutions (10^-6, 10^-7, 10^-8) to pour plate and count the colonies. on to the final plate, i added 1mL of 10^-6 for 10^-6, 0.1mL of 10^-7 and 1mL of 10^-8 to obtain 10^-6, 10^-7, 10^-8 final plate dilutions, respectively.


so this kind of discrepancy is normal i assume? as long as they are in the same magnitude it is acceptable?
which method would you guys say is more reliable?

thank you!

CellSpecific.com on Sep 27 2009, 05:11 PM said:

thank you