Calculating Population doublings in yeast - (Dec/08/2010 )
I've just finished an experiment where I measure the cell density of yeast cultures by spectrophotometer to find out how the doubling time changes as an inducible protein begins to disappear in order to figure out at what point after protein knockdown I can perform further experiments related to cell cycle (for example FACS analysis) I can tell by my data at what point in time the culture doubling time changes, but I also want to know after how many population doublings this change takes place but I can't figure out how to calculate that. Any ideas?
I didnít really get the question, but anyway, using spectrophotometer to measure OD of yeast culture is not very specific. Every strain divides at different speed. If you are after something reliable these culture would preferably be synchronised prior to the experiment, and synchronizing yeast is pretty much waste of time unless you have proper equipment.
Another thing that will increase your accuracy is hemocytometer. Once you find out how much time it takes, on average for yeast cell to divide the calculation will be straight forward.
I think it takes about 90 minutes for S. cerevisiae to complete one cell division, but in selection media it takes longer (at least my yeast took longer).