biology question

kelxx

Twenty five colonies grew in nutrient agar from 1.0 ml of sample withdrawn from a solution diluted to 10-5 in a standard plate count procedure. How many cells were in the original sample?

Anyone no how to work this out?
thanks!

Capt'n Midnight

by 10-5 do you mean 10E-5 / 1 in 100,000 dilution ?


No idea since the cells could be clumped
but you could count the colony forming units by multiplying back the dilutions

if there are 25 per ml then at the previous 1:10 dilution there were 250 per ml

Kevster

She must mean 10^-5? In that case, the answer would be 2,500,000 cells? If it was a 10^-5 dilution, that's 1-in-100,000. You just multiply this by 25 to get the answer I think.

Kevin

GLaDOS

Kevster wrote: »

She must mean 10^-5? In that case, the answer would be 2,500,000 cells? If it was a 10^-5 dilution, that's 1-in-100,000. You just multiply this by 25 to get the answer I think.

Kevin

Yeah, it's 25 x 10^5 = 2,500,000. However that's not cells, it's colony forming units per ml (cfu/ml) as Capt'n said.