Bacteria counting

Susanne Beckert susanne.beckert at
Mon Feb 14 03:23:19 EST 2000

Thanks for all the replies I recieved to my original questions! This
newsgroup is not as dreadful as some believe ;-)
Easiest thing to try will be some DAPI staining probably. And decoulorizing
dead bacteria with ethanol (_Afonso Souza_). Another interesting advice:
counting bacteria by conductivity (_Des OConnor_). Ever tried it / reference
or is it handmade technique to be developed by myself?
I was asked for a resume - here it goes.

des.oconnor wrote:
You cant count bacteria by ELISA But which dye would be the best to enter
cells?  ( I Think its called VITAL BLUE or Vital Orange)
You considered trying inmpedance techniques or simply correlating
conductivity measurments with cfu/mass.

Eoin Brodie wrote:
just a thought - try Viagram stain from molecular probes - if you
have an epiflourescent microscope that is? This will show
Gram+/Gram- and viable/non-viable.

Michael P. Kolotila wrote:
 There are a number of vital stains to determine viability.  Molecular
Probes has a number of them.  Check their catalog or give them a call.
Unfortunately, I do not have a catalog with their number.  They are in
Washington state if memory serves.

Karen Heaton wrote:
If all you want to do is to count the total number of bacteria in a
i suggest that you stain them with DAPI.  Cells will appear blue under
excitation by UV light.

YinSuo Zhao wrote:
Regarding the measure of OD, One instrument is accurate, fast,
duplicate very well, i.e. "Microbiology Reader Bioscreen", the WWW of which
is "". The Bioscreen can assay the
growth curve of 200 samples at once. I've done a lot with the Bioscreen.

Original question: Susanne Beckert wrote:

> Hello all,
> we are looking for a convenient method to count bacteria other than OD
> (too inaccurate) or cfu counting (too time consuming). I looked for
> special cell stains in the molecular probes catalogue. We dont have a
> flow cytometer at hand but probably an elisa plate reader able to
> messure fluorescence. But which dye would be the best to enter gram+
> cells?
> Is there even a dye that will distinguish dead from living cells? OK,
> there is e.g. sytox green, that exclusively enters dead cells but I need
> it vice versa. And it can not be a stain that needs a certain time to
> react (like tetrazolium salts) because bacteria would divide in that
> time.
> Any experience with such stains? Or is there a completely different,
> accurate and time saving method for counting bacteria I am not aware of?
> We have to count lots of samples and counting cfu on plates for hours is
> really a waste of time.
> Thanks for any suggestions.
> Susanne

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