Natural Science Forum / Biology / Botany / March 2004

Dear Martha  The convential way would be to count cell numbers on a
haemocytometer slide, however that is tedious.  Another and more
adventurous way is to measure either visble absorption 615nm or
fluorescence of the  phycocyanin. This has the advantage of being able
to separate the bg cells from green cells in a mixed suspension if that
is pertinent to your study..  In a cell suspension the light entering a
cuvette is scattered everywhere so one needs to insert a diffusing disc
of etched glass or oiled paper (opalescent glass is the best) to
recollect the light and transmit to the photocell of the
spectrophotometer.  If you do a visible scan of an algal suspension you
will not get any sense out of it until you insert a diffusing glass in
front of the  collecting phototube. If you simply want algal biomass and
don't need to separate different types, use an haematocrit tube as used
for blood determinations. Spin at standard time and speed and calibrate
the  length of sedimented cells against some biomass measurement
Hope this is of some use.

Warwick Silvester
Dept of Biological Sciences
University of Waikato
Hamilton
New Zealand
Ph  07 838 4316
Fax 07 838 4324
E-mail  w.silvester@waikato.ac.nz

-----Original Message-----
From: mmphillips@stkate.edu [mailto:mmphillips@stkate.edu]
Sent: Wednesday, 3 March 2004 4:35 a.m.
To: plant-ed@net.bio.net
Subject: Measuring Growth of Anabaena

Dear Plant-Ed:

We do independent research projects for our General Biology lab and I've
got a student group who wants to do a project on eutrophication using
Anabaena.  We've struggled before with how to quantify growth with
Anabaena and haven't found a good method.  Do you have any suggestions?

Thanks,
Martha

Martha M. Phillips, Ph.D
Biology Department
The College of St. Catherine
2004 Randolph Avenue
St. Paul, MN 55105
651-690-6630
mmphillips@stkate.edu

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You might do a simple assay for chlorophyll as a proxy for cell
number.  Extract the cells in acetone or methanol, spin down debris,
and measure spectrophotometrically.  In combination with Warwick's
suggestion, you could construct a calibration curve of cell number
(hemocytometer) vs. chlorophyll - but that is probably more than you
need, although it might be informative for the students to see the
relationship.
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