Re: Bacterial Analysis

From: Mario Roederer (roederer@drmr.com)
Date: Wed Jul 24 2002 - 14:21:21 EST


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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