Calculating yeast cell numbers using OD values?

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MikeWestUSA
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Calculating yeast cell numbers using OD values?

Post by MikeWestUSA » Fri Oct 22, 2010 9:41 pm

I've got 4 different strains which i need to measure the OD value of in order to calculate cell number - how do i do this?

Also, once calculated, how do i make each strain comparable if i were to use to 2ml of each, but they had differing cell numbers?

Thanks

Mike

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alchilito
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Re: Calculating yeast cell numbers using OD values?

Post by alchilito » Sat Oct 23, 2010 12:37 am

Grow all 4 strains under standard conditions until you reach log phase by plotting time vs OD

Take samples during mid log phase, smear them evenly in appropriate culture plates, ideally performing serial dilutions of samples until a countable number of colonies grow.

Hope this helps.

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canalon
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Post by canalon » Sat Oct 23, 2010 7:58 pm

And for the second part, instead of using the same volume, just pipette enough cells (measure OD. calculate cell number/ml, adjust volume), centrifuge and resuspend in 2ml of your buffer/medium of choice.
Patrick

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any proof. (Ashley Montague)

MikeWestUSA
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Re: Calculating yeast cell numbers using OD values?

Post by MikeWestUSA » Sat Oct 23, 2010 8:43 pm

alchilito wrote:Grow all 4 strains under standard conditions until you reach log phase by plotting time vs OD

Take samples during mid log phase, smear them evenly in appropriate culture plates, ideally performing serial dilutions of samples until a countable number of colonies grow.

Hope this helps.


CAn you please expand on that - how do i calculate cell numbers from the OD read out of the log phase?

What part do the serial dilutions play in relation to the OD value?

Sorry if this seems dim - but i've no experience of spectrometers etc

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canalon
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Post by canalon » Mon Oct 25, 2010 1:31 am

Measure the OD.
Now take the same culture and plate to count the number of cells.
You can then estimate that X cells per ml give an OD of Y in your medium, and the relation being more or less linear, you will be able to estimate the number of cells per unit of volume in the same medium in the future just by reading OD.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

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