[Chlamydomonas] Re: Counting chlamy

bob via chlamy%40net.bio.net (by bbx107 from excite.XXXX.com)
Mon Jun 4 00:21:50 EST 2007

On Thu, 31 May 2007 22:51:34 -0700 (PDT), jgalazka
<jgalazka from berkeley.edu> wrote:

>I am just beginning to work with Chlamy, and have had trouble getting
>consistent cell counts.  My current protocol consists of removing a sample
>from my culture, spiking it with 10% Lugol's solution, and then counting
>with a hemacytometer.  When performing a growth curve, my counts are
>inconsistent, especially at higher cell densities.  This contrasts with OD
>measurements made at 750 nm, which are beautiful.  Any suggestions would be
>greatly appreciated!

Some ideas -- based on bacteria, not Chlamy.

What do you mean "trouble getting consistent cell counts"?

Cell counts and OD measure different things. They should give you
different growth curves. At least with bacteria, there are predictable
differences in cell size during growth curve. (At high densities, one
expects the cells to be smaller, so the cell count goes on further
than the OD curve.)

How many cells do you count? The statistical error is the square root
of the count. So if you count 9 cells, you have a standard deviation
of 3, which is 33%. And that assumes perfect technique. In the real
world it can only be worse. 

Do you know how to seat the cover slip? How to count cells on the


bob bruner
bbruner at berkeley dot edu

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