distinguishing living and dead cells

Julie Paquin jpaqui2 at PO-BOX.MCGILL.CA
Thu Jan 21 23:03:42 EST 1999

Hi there,

    It would be helpful if you could tell us the type of treatment those
bacterial cells were under.  If the treatment really breaks open the cell
membrane, releasing all the bacterial content, yes they will have different
density or molecular weight than the living cells.  If I understand well,
you would like to separate the living cells from all the dead cells.  I
think that you could try to separate those through chromatography, like
Percoll step gradients to be precise.  I don't know if you ever heard about
this but briefly how it works is that you pour  gels of different density
into a tube and you just pour your liquid media through and you centrifuge
the tube to separate the different component in your sample.  The dead and
living cells will separate on the basis of their molecular weight and size,
thus the molecules will separate into distinct bands and the bigger the
molecule, the faster it will stop migrating.  I've done it with to separate
chloroplasts from plant material so I'm sure it is feasible to separate dead
from living cells but you would have to look for the details.  Also if your
separation requires to keep the media intact, well this technique would
obviously not work cause you loose all our media.

    So I hope I could help

            Julie +ADs-)

+AD4APg- Hi,
+AD4APg- After a processing to inactivatea specific bacterial population (e.g. S.
+AD4APg-aureus)  in any kind of liquid media, how can you seperate dead and living
+AD4APg- Assume that the treatment destroys the cell membrane. In addition, in
+AD4APg-your liquid media not every bacterial cell is not treated equally meaning
+AD4APg-treatment is not homogenous throughout the system thus. you have not
+AD4APg-injured, and death cells. In this case some cell organells will go out
+AD4APg-media from the injured and death cells and the density of that cells would
+AD4APg-different than the one that has not been destroyed. But I am not sure if
+AD4APg-density difference will help me?
+AD4APg- Thanks
+AD4APg- Gulsun
+AD4-I am at all sure I understand your statements and questions. AFAIK, you can
+AD4-not separate dead from living cells from a liquid medium, since all
+AD4-dead or alive tend to have very similar density. Was that your query?
+AD4-However, you can do +ACI-viable counts+ACI- from a liquid culture by plating known
+AD4-dilutions of the same on an appropriate plate.
+AD4-Dr. Hiranya Sankar Roychowdhury
+AD4-New Mexico State University
+AD4-Las Cruces, NM 88003
+AD4-Ph. (505) 646-5785

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