Hi, Another issue is to make sure you filter EVERYTHING with a 0.22 um filter. And also, not all filters are created equal. I have found that the little syringe top filters are pretty good. When I decided to get "smart" one time and filter 250 ml in one of those screwtop disposable filters with the cup on top it took 2 days to figure out that the "filtered" solution had a ton of junk in it. -Dave -------Original Message------- From: Mario Roederer Date: Thursday, July 25, 2002 01:43:52 PM To: cyto-inbox Subject: Re: Bacterial Analysis Your operators should threshold (trigger) on log side scatter. If they are triggering on FS (as is customary), then most bacteria won't come close to being seen. You might also just trigger on fluorescence, and see if the counts are closer. By triggering on fluorescence, you'll also get an idea of how low to set the side scatter (log) threshold to catch all the events. You will likely have a lot of background (noise) events. Consider running a medium blank and decreasing the log SS trigger threshold until you have about 50 counts/sec (i.e., noise at 50/sec). Then run the bacteria, and see what it looks like--you can then increase the threshold until you are sure you aren't losing real events. Then, at that threshold, run blank medium again and see what the background event count is like. You should have no problems seeing all of the bacteria. mr .
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