Plaque assay is performed beggining with a 10 mL phage solution. The solution is serially diluted 4 times by taking 1 mL and adding it to 9 mL. 0.1 mL of the final dilution is plated & yields 21 plaques. What is the initial density of the starting phage solution?

 

So here's what I know. Density= (# of colonies formed/ mL plated) x Dilutionbefore plating

 

# of colonies formed is 21.

 

Now I'm assuming the mL plated is 0.1 mL?

 

And as for the the dilution I am stuck. Is there a way I can figure out how to calculate that?

You take 1 ml and fill it up to 10 ml. What amount of dilution is that?

So if we do that four times it becomes 10000 more dilute. Is that my dilution number I'm looking for?

Yupps.

Wow awesome.

 

 

So...

 

(21 plaques/ 0.1 mL plated) x 10^5

= 2.1x10^7 PFU/mL

 

So I did it perfect? 100%?

yeah, that's what I got when I did it on the assignment