On 23 Jul 2002 at 14:19, R. Thomas Leonard wrote: > I'm on a mission to determine bacterial viability as well as quantify > bacteria using Molecular Probes' BacLight viability kit. Using an EPICS > Elite, I have routinely found bacterial counts to be 10% of those <> > Why such a disparity in counts? My conclusion is that the instrument simply > can't detect the smaller organisms in the population (of E. coli). The Elite can detect bacteria - either that or I've been dreaming up my data for the last 8 years.... Does your Elite just have a 488 laser? We find that much better signal resolution is achieved if we use the gated-amp set up supplied with the second laser option and we use these electronics even when just doing 488 work. Using this setup together with the default FSC mask (the one with just a thin bar and tiny rectangle down the middle) we get almost no noise and plenty of signal with E. coli and M. luteus. If you don't have the gated-amp setup available you could use a 'stain everything' stain and use that as your trigger rather than FSC. You could also (microscopically) check your samples and sheath fluid for background particles. I use filtered (0.22um) water for making media and sheath fluid etc. Hope that helps, Hazel -- Hazel Davey HLR@aber.ac.uk http://pcfcij.dbs.aber.ac.uk/ Sefydliad y Gwyddorau Biolegol, Prifysgol Cymru, Aberystwyth Inst. Biological Sciences, University of Wales, Aberystwyth http://www.nspcc.org.uk/donate-4-free/donate-mainhome.asp
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