Measuring OD for a bacteria culture
Posted 09 February 2009 - 07:48 AM
First off, I read in a paper which mentioned "culture from the log phase (OD600=0.8)...". I'm not sure if that reading was a diluted reading or one measured directly.
I cultured my bug for about 28 hours to obtain the growth profile. I wanted to measure the dry cell weight but since I'm waiting for the freezing to complete, I took the OD reading directly. The mid log phase is about 14 hours with an OD600nm of about 1.9...
Did I do anything wrong? Do I have to dilute the culture before taking a reading?
When we say we "standardize" our inoculum for a batch culture, it's standardized ad libitum right? I mean, I can set the inoculum size as I wish and maintain it for every flask? Does 2 mL of culture at OD600nm= 2.0 sound like a standardized inoculum for my batch culture?
I know it's a loaded one. Thanks very much.
Posted 09 February 2009 - 09:07 AM
what do you blank against? it should be against un-inoculated medium.
also keep in mind that there may be some differences in the readings with different spectrophotometers (for various reasons).
also keep in mind pathlength. most cuvettes have a 10mm path.
Edited by mdfenko, 09 February 2009 - 09:11 AM.
genius does what it must
i do what i get paid to do
Posted 09 February 2009 - 09:14 AM
OD readings pass 1.0 aren't accurate anymore (it has passed the linear phase of the spectrophotometer), and you need to dilute the culture to calculate readings of that density.
Posted 09 February 2009 - 09:32 AM
Posted 10 February 2009 - 05:12 AM
For the record, I'm using a Hitachi U-1900
Edited by dreamchaser_jc, 10 February 2009 - 05:22 AM.
Posted 16 March 2009 - 01:45 AM
I would dilute already from 0,6-0,7 on 1:10 because I saw in my experiments that already from this density there is a mistake in the measurement when you do not dilute...
Posted 27 August 2009 - 05:30 AM
Edited by Ivanov_br, 27 August 2009 - 05:30 AM.
Posted 27 August 2009 - 10:49 PM
Should I use a blank (medium) before measure the OD?!
yes you have to