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Drop plate technique


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#1 ultraman

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Posted 18 July 2012 - 05:14 AM

After making serial dilution and the solution will be plated out.

For example, I prepare dilution like this.

10^-1
10^-2
10^-3
10^-4
10^-5

Change pipette tip when transferring mixtures to the next dilution in each step.
However, I'd like to know that Can I use the same pipette tip when plating out from high to low dilutions or not (from 10^-5 to 10^-1)? The number of bacteria will be the real number or not?

Thanks for answer.

#2 bob1

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Posted 18 July 2012 - 01:58 PM

In theory, yes, the addition of small amounts of diluted sample to a much more concentrated (10x in your case) shouldn't make much, if any difference to the more concentrated sample.

#3 pito

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Posted 19 July 2012 - 04:48 AM

A general rule I always learned: from diluted to not diluted => same tip (goes for everything, not just microbiology)
From not diluted to diluted: change..

Its pretty easy to understand.

If you go from 10^-6 cells/ml to 10 cells/ml then why change a tip? You are not going to "add" cells in the 10 cells/ml

Other way around....

Same goes for chemical dilutions etc..

If you don't know it, then ask it! Better to ask and look foolish to some than not ask and stay stupid.





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