Hello,
I know that the Fisher peptone precipitation has been addressed before, but I am seeing a precipitate form after I add calcium chloride to my PYCa agar. After I autoclave the media and cool it down to 60 degrees C, I add 40% dextrose and 1M calcium chloride. The media is completely clear even after adding the dextrose, but it goes cloudy after adding the calcium chloride and I can see a precipitate forming when it is stirring on the hot plate. I am not using Fisher brand peptone and it does not seem to be affecting our ability to isolate phage. We have phage plaques forming just fine. I was just wondering if anyone else had seen this.

I appreciate any insight.

Anne Davenport