Role of PBS in cell culturing - (Dec/02/2005 )

Hi all!

I am fairly new to the world of cell culturing. I would appreciate if someone could tell my what PBS actually does.
Today I was subculturing and completely forgot to do the PBS wash, added the trypsin in directly. My cells didnt bugde. Then realised about the PBS, did the wash and added trypsin, and the cells came off easily.
I just cant figure out what the actual role of PBS is....
Can anyone enlighten me?

Thanks

PBS is just a buffer solution. The washing step is included because after removal of medium, you will still have some medium in your flask. As your medium contains serum, you will not be able to trypsinise your cells, as serum inhibits trypsin.

So, you add PBS to remove traces of your serum/old medium. You could also do this with serum-free medium, but that would be more expensive.