Bacteria counting

Susanne Beckert susanne.beckert at medizin.uni-ulm.de
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
gram+
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
suspension,
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 "http://transgalactic.com/index.shtml". 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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