Hi All,
I have just experienced the first problem with Malmgrens Media I have ever had. I have been using Malmgrens Modified (From Phytotech) for 3 years, but I have always sterilized in the Oven. I switched to a Pressure cooker 2 months ago, and I've made many successful batches of T839, T842 and T849 with it.

However, I just tried Malmgrens and the ones I did in the Pressure cooker turned into liquid, while those that I did in the oven turned out not liquidy enough! I thought that It must have been bad mixing or something. So I dumped the sterilized flask contents into a measuring cup, reheated and repoured. I put 8 flasks into the pressure cooker to sterilze, and 4 wouldn't fit, so I left them out to do the next day. The 8 that were cooked were liquid again! But the 4 that weren't cooked had cooled and gelled into perfect, but non-sterile, medium.

Has anyone had this problem? Can anyone explain this phenomenon? I suppose I will have to just do all my Malmgrens in the Oven from now on. :(

Best,
Ross

I had a simular problem once useing Western 3 Media. My problem was that the flasks were solid charcol and agar on the bottom (maybe 2mm thick) and the top was liquid (8-9mm). To solve it I microwaved the flasks for a few seconds to reliquify the bottom, swirled them around and put them in the fridge. Worked perfectly, 0% contaminated.

Turns out the problem was that I left the flasks in the pressure cooker to long. they cooled to slowly and the charcol and agar settled out of solution. Everyother time since I open the cooker as soon as its safe and put a fan on the cooling flasks. I get nice homogenous flasks now.

Kyle

Hi Kyle,
Thanks for the guess. Unfortunately, I don't think that's the problem. I dumped out the liquid and everything came out. There was no agar on the bottom (I'm familiar with that problem too!) that "fell out". I swished the flasks around a bit, moving everything in the jar, and I put them in the fridge... We'll see by morning if that fixes the problem.

Best,
Ross

Interesting! I had that same problem for the very first time with a new batch of M551 Malmgren last week. I fiddled with it and decided that the recent lot must have a problem with agar (I reheated and stirred briskly and so forth and couldnt get anything more than slightly lumpy. I added an additional 1% agar to the medium and it gelled fine (but still very slightly squooshy). Since I am doing daughter flasks with these that is fine since Cyp roots tend to grow on top at label agar. I suspect the latest lot has perhaps 2% or so less agar than usual.

Ron