Hi,

I too was wondering about the 2X 7H9 Top Agar as we have always prepared it as a 1X solution. We are currently working with smeg and have a reoccurring issue with our top agar appearing grainy while working with it in the lab. I thought perhaps the students were letting the top agar cool down (leaving it on the bench for too long), but I myself poured a couple of plates and found the same problem - grainy top agar. We prepare a 1X 7H9 top agar, autoclave and keep in the fridge until we need it. We then microwave the 1X 7H9 top agar and add the CaCl2 after warming and right before our lab.

To clarify, these plates were for our first plaque assay where we added a direct (soil) isolation phage sample with our smeg. We are currently testing our smeg directly added to our L-agar plates (no top agar) to see if any grainy particles appear, in which case the grainy texture would be from our smeg.

Has anyone had any similar problems with the 7H9 Top Agar? Thanks!

Elena