Comparison of growth of yeast mutants - (Jul/07/2007 )

Hi there,

I`d like to compare the growth of 7 different yeast mutant strains in complete synthetic medium.
I`ll inoculate 20 ml liquid cultures, normalize the OD to 0.1 and measure the cell nrs. spectrophotometrically over time.
My question is about how many samples to chose per mutant. Is it sufficient to pick 3 colonies per mutant strain, let them grow in liquid culture, normalize the OD to 0.1 and measure the OD then over time (= 3 measurements per mutant strain and time point)?
If I divided each culture into 3 new cultures after normalizing the OD, I would end up with 7 x 3 x 3 = 63 cultures, which is really not feasible.
I need to obtain statistically significant values.
Thanks for your ideas!

Isabelle

such is the problem in biology. statistically significant data is hard to come by and you are in company with many others.

Do you have an optical plate reader, something that reads OD of 96 wells plates?

Hi Isabelle

Plate readers iare very good as thay can be automated and record OD for each of the wells every 30 min, so you just inoculate it and forget about it. Next day you come and print the result. However it will not show you the difference in lag phase as ODs go up during the lag phase when cell numbers are not changing. This is because the cells change in size during lag phase. If your cultures are stressed than ODs are not giving you the information you need. Also if you want to check the death curves ODs do not change when cells start to die.
As for replicates you do need biological triplicates. You can then plot the medians on the graph showing the standard error.