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"Plaque forming units per ml"

Im hoping Ros is around to help me here, i done a dilution series on an e.coli broth that was infected with some phage, ive plated them out and counted the plaques but im getting confused about how to calculate plaques per ml.

Im hoping Ros is around to help me here, i done a dilution series on an e.coli broth that was infected with some phage, ive plated them out and counted the plaques but im getting confused about how to calculate plaques per ml.

Phew... thought you were going to say you ate it.

Damn... thought you were going to say you ate it.

This isnt helping me people.

*waves*

how may I help

Rosalind wrote:
> *waves*
>
> how may I help

Great, thanks, lets see if you can.

Ok, lets say i made a dilution series that ranged from 10 to the power 0 (i.e undiluted) to 10 to the power -8 of this e.coli broth. I plated these dilutions at varying times (every 10 mins for 70 mins) and left plaques to form on the bacterial lawn.

I went to count the plaques and say i found 70 plaques formed on the plate which was the 10 to the power -4 dilution, how would i calculate this as plaques per ml?

Im thinking its 70 divided by the dilution factor (0.001) to get the number of plaques in 0.750ml (this is the volume of e.coli broth we actually used for the dilutions after spinning a 1ml in the centrifuge) i then have to adjust the number i get to make it up to the 1ml.

I hope that makes sense, or im screwed. :D

first of all you need to know how much you plated out i.e did you plate out 100ul then you would have to x10 to get to 1ml.

so your 70 plaques would become 700/ml

then x0.75 to negate your concentration of 1ml to 0.75ml

then muliply by 1x10 to the 4 (or divide by dilution factor) = 5.25x10 to the 6

not many phage!!!! :p

hope this helps

Edit:
If you want to get in touch with me again my msn/e-mail is [email protected]

OMG.

You are a young man with biological weaponry.

CALL THE PAPERS! LET THEM SAVE US!